xref: /f-stack/app/redis-5.0.5/redis.conf (revision 572c4311)
1# Redis configuration file example.
2#
3# Note that in order to read the configuration file, Redis must be
4# started with the file path as first argument:
5#
6# ./redis-server /path/to/redis.conf
7
8# Note on units: when memory size is needed, it is possible to specify
9# it in the usual form of 1k 5GB 4M and so forth:
10#
11# 1k => 1000 bytes
12# 1kb => 1024 bytes
13# 1m => 1000000 bytes
14# 1mb => 1024*1024 bytes
15# 1g => 1000000000 bytes
16# 1gb => 1024*1024*1024 bytes
17#
18# units are case insensitive so 1GB 1Gb 1gB are all the same.
19
20################################## INCLUDES ###################################
21
22# Include one or more other config files here.  This is useful if you
23# have a standard template that goes to all Redis servers but also need
24# to customize a few per-server settings.  Include files can include
25# other files, so use this wisely.
26#
27# Notice option "include" won't be rewritten by command "CONFIG REWRITE"
28# from admin or Redis Sentinel. Since Redis always uses the last processed
29# line as value of a configuration directive, you'd better put includes
30# at the beginning of this file to avoid overwriting config change at runtime.
31#
32# If instead you are interested in using includes to override configuration
33# options, it is better to use include as the last line.
34#
35# include /path/to/local.conf
36# include /path/to/other.conf
37
38################################## MODULES #####################################
39
40# Load modules at startup. If the server is not able to load modules
41# it will abort. It is possible to use multiple loadmodule directives.
42#
43# loadmodule /path/to/my_module.so
44# loadmodule /path/to/other_module.so
45
46################################## NETWORK #####################################
47
48# By default, if no "bind" configuration directive is specified, Redis listens
49# for connections from all the network interfaces available on the server.
50# It is possible to listen to just one or multiple selected interfaces using
51# the "bind" configuration directive, followed by one or more IP addresses.
52#
53# Examples:
54#
55# bind 192.168.1.100 10.0.0.1
56# bind 127.0.0.1 ::1
57#
58# ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the
59# internet, binding to all the interfaces is dangerous and will expose the
60# instance to everybody on the internet. So by default we uncomment the
61# following bind directive, that will force Redis to listen only into
62# the IPv4 loopback interface address (this means Redis will be able to
63# accept connections only from clients running into the same computer it
64# is running).
65#
66# IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES
67# JUST COMMENT THE FOLLOWING LINE.
68# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
69bind 0.0.0.0
70
71# Protected mode is a layer of security protection, in order to avoid that
72# Redis instances left open on the internet are accessed and exploited.
73#
74# When protected mode is on and if:
75#
76# 1) The server is not binding explicitly to a set of addresses using the
77#    "bind" directive.
78# 2) No password is configured.
79#
80# The server only accepts connections from clients connecting from the
81# IPv4 and IPv6 loopback addresses 127.0.0.1 and ::1, and from Unix domain
82# sockets.
83#
84# By default protected mode is enabled. You should disable it only if
85# you are sure you want clients from other hosts to connect to Redis
86# even if no authentication is configured, nor a specific set of interfaces
87# are explicitly listed using the "bind" directive.
88protected-mode no
89
90# Accept connections on the specified port, default is 6379 (IANA #815344).
91# If port 0 is specified Redis will not listen on a TCP socket.
92port 6379
93
94# TCP listen() backlog.
95#
96# In high requests-per-second environments you need an high backlog in order
97# to avoid slow clients connections issues. Note that the Linux kernel
98# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
99# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
100# in order to get the desired effect.
101tcp-backlog 511
102
103# Unix socket.
104#
105# Specify the path for the Unix socket that will be used to listen for
106# incoming connections. There is no default, so Redis will not listen
107# on a unix socket when not specified.
108#
109# unixsocket /tmp/redis.sock
110# unixsocketperm 700
111
112# Close the connection after a client is idle for N seconds (0 to disable)
113timeout 0
114
115# TCP keepalive.
116#
117# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
118# of communication. This is useful for two reasons:
119#
120# 1) Detect dead peers.
121# 2) Take the connection alive from the point of view of network
122#    equipment in the middle.
123#
124# On Linux, the specified value (in seconds) is the period used to send ACKs.
125# Note that to close the connection the double of the time is needed.
126# On other kernels the period depends on the kernel configuration.
127#
128# A reasonable value for this option is 300 seconds, which is the new
129# Redis default starting with Redis 3.2.1.
130tcp-keepalive 300
131
132################################# GENERAL #####################################
133
134# By default Redis does not run as a daemon. Use 'yes' if you need it.
135# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
136daemonize no
137
138# If you run Redis from upstart or systemd, Redis can interact with your
139# supervision tree. Options:
140#   supervised no      - no supervision interaction
141#   supervised upstart - signal upstart by putting Redis into SIGSTOP mode
142#   supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET
143#   supervised auto    - detect upstart or systemd method based on
144#                        UPSTART_JOB or NOTIFY_SOCKET environment variables
145# Note: these supervision methods only signal "process is ready."
146#       They do not enable continuous liveness pings back to your supervisor.
147supervised no
148
149# If a pid file is specified, Redis writes it where specified at startup
150# and removes it at exit.
151#
152# When the server runs non daemonized, no pid file is created if none is
153# specified in the configuration. When the server is daemonized, the pid file
154# is used even if not specified, defaulting to "/var/run/redis.pid".
155#
156# Creating a pid file is best effort: if Redis is not able to create it
157# nothing bad happens, the server will start and run normally.
158pidfile /var/run/redis_6379.pid
159
160# Specify the server verbosity level.
161# This can be one of:
162# debug (a lot of information, useful for development/testing)
163# verbose (many rarely useful info, but not a mess like the debug level)
164# notice (moderately verbose, what you want in production probably)
165# warning (only very important / critical messages are logged)
166loglevel notice
167
168# Specify the log file name. Also the empty string can be used to force
169# Redis to log on the standard output. Note that if you use standard
170# output for logging but daemonize, logs will be sent to /dev/null
171logfile ""
172
173# To enable logging to the system logger, just set 'syslog-enabled' to yes,
174# and optionally update the other syslog parameters to suit your needs.
175# syslog-enabled no
176
177# Specify the syslog identity.
178# syslog-ident redis
179
180# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
181# syslog-facility local0
182
183# Set the number of databases. The default database is DB 0, you can select
184# a different one on a per-connection basis using SELECT <dbid> where
185# dbid is a number between 0 and 'databases'-1
186databases 16
187
188# By default Redis shows an ASCII art logo only when started to log to the
189# standard output and if the standard output is a TTY. Basically this means
190# that normally a logo is displayed only in interactive sessions.
191#
192# However it is possible to force the pre-4.0 behavior and always show a
193# ASCII art logo in startup logs by setting the following option to yes.
194always-show-logo yes
195
196################################ SNAPSHOTTING  ################################
197#
198# Save the DB on disk:
199#
200#   save <seconds> <changes>
201#
202#   Will save the DB if both the given number of seconds and the given
203#   number of write operations against the DB occurred.
204#
205#   In the example below the behaviour will be to save:
206#   after 900 sec (15 min) if at least 1 key changed
207#   after 300 sec (5 min) if at least 10 keys changed
208#   after 60 sec if at least 10000 keys changed
209#
210#   Note: you can disable saving completely by commenting out all "save" lines.
211#
212#   It is also possible to remove all the previously configured save
213#   points by adding a save directive with a single empty string argument
214#   like in the following example:
215#
216#   save ""
217
218save 900 1
219save 300 10
220save 60 10000
221
222# By default Redis will stop accepting writes if RDB snapshots are enabled
223# (at least one save point) and the latest background save failed.
224# This will make the user aware (in a hard way) that data is not persisting
225# on disk properly, otherwise chances are that no one will notice and some
226# disaster will happen.
227#
228# If the background saving process will start working again Redis will
229# automatically allow writes again.
230#
231# However if you have setup your proper monitoring of the Redis server
232# and persistence, you may want to disable this feature so that Redis will
233# continue to work as usual even if there are problems with disk,
234# permissions, and so forth.
235stop-writes-on-bgsave-error yes
236
237# Compress string objects using LZF when dump .rdb databases?
238# For default that's set to 'yes' as it's almost always a win.
239# If you want to save some CPU in the saving child set it to 'no' but
240# the dataset will likely be bigger if you have compressible values or keys.
241rdbcompression yes
242
243# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
244# This makes the format more resistant to corruption but there is a performance
245# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
246# for maximum performances.
247#
248# RDB files created with checksum disabled have a checksum of zero that will
249# tell the loading code to skip the check.
250rdbchecksum yes
251
252# The filename where to dump the DB
253dbfilename dump.rdb
254
255# The working directory.
256#
257# The DB will be written inside this directory, with the filename specified
258# above using the 'dbfilename' configuration directive.
259#
260# The Append Only File will also be created inside this directory.
261#
262# Note that you must specify a directory here, not a file name.
263dir ./
264
265################################# REPLICATION #################################
266
267# Master-Replica replication. Use replicaof to make a Redis instance a copy of
268# another Redis server. A few things to understand ASAP about Redis replication.
269#
270#   +------------------+      +---------------+
271#   |      Master      | ---> |    Replica    |
272#   | (receive writes) |      |  (exact copy) |
273#   +------------------+      +---------------+
274#
275# 1) Redis replication is asynchronous, but you can configure a master to
276#    stop accepting writes if it appears to be not connected with at least
277#    a given number of replicas.
278# 2) Redis replicas are able to perform a partial resynchronization with the
279#    master if the replication link is lost for a relatively small amount of
280#    time. You may want to configure the replication backlog size (see the next
281#    sections of this file) with a sensible value depending on your needs.
282# 3) Replication is automatic and does not need user intervention. After a
283#    network partition replicas automatically try to reconnect to masters
284#    and resynchronize with them.
285#
286# replicaof <masterip> <masterport>
287
288# If the master is password protected (using the "requirepass" configuration
289# directive below) it is possible to tell the replica to authenticate before
290# starting the replication synchronization process, otherwise the master will
291# refuse the replica request.
292#
293# masterauth <master-password>
294
295# When a replica loses its connection with the master, or when the replication
296# is still in progress, the replica can act in two different ways:
297#
298# 1) if replica-serve-stale-data is set to 'yes' (the default) the replica will
299#    still reply to client requests, possibly with out of date data, or the
300#    data set may just be empty if this is the first synchronization.
301#
302# 2) if replica-serve-stale-data is set to 'no' the replica will reply with
303#    an error "SYNC with master in progress" to all the kind of commands
304#    but to INFO, replicaOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG,
305#    SUBSCRIBE, UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB,
306#    COMMAND, POST, HOST: and LATENCY.
307#
308replica-serve-stale-data yes
309
310# You can configure a replica instance to accept writes or not. Writing against
311# a replica instance may be useful to store some ephemeral data (because data
312# written on a replica will be easily deleted after resync with the master) but
313# may also cause problems if clients are writing to it because of a
314# misconfiguration.
315#
316# Since Redis 2.6 by default replicas are read-only.
317#
318# Note: read only replicas are not designed to be exposed to untrusted clients
319# on the internet. It's just a protection layer against misuse of the instance.
320# Still a read only replica exports by default all the administrative commands
321# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
322# security of read only replicas using 'rename-command' to shadow all the
323# administrative / dangerous commands.
324replica-read-only yes
325
326# Replication SYNC strategy: disk or socket.
327#
328# -------------------------------------------------------
329# WARNING: DISKLESS REPLICATION IS EXPERIMENTAL CURRENTLY
330# -------------------------------------------------------
331#
332# New replicas and reconnecting replicas that are not able to continue the replication
333# process just receiving differences, need to do what is called a "full
334# synchronization". An RDB file is transmitted from the master to the replicas.
335# The transmission can happen in two different ways:
336#
337# 1) Disk-backed: The Redis master creates a new process that writes the RDB
338#                 file on disk. Later the file is transferred by the parent
339#                 process to the replicas incrementally.
340# 2) Diskless: The Redis master creates a new process that directly writes the
341#              RDB file to replica sockets, without touching the disk at all.
342#
343# With disk-backed replication, while the RDB file is generated, more replicas
344# can be queued and served with the RDB file as soon as the current child producing
345# the RDB file finishes its work. With diskless replication instead once
346# the transfer starts, new replicas arriving will be queued and a new transfer
347# will start when the current one terminates.
348#
349# When diskless replication is used, the master waits a configurable amount of
350# time (in seconds) before starting the transfer in the hope that multiple replicas
351# will arrive and the transfer can be parallelized.
352#
353# With slow disks and fast (large bandwidth) networks, diskless replication
354# works better.
355repl-diskless-sync no
356
357# When diskless replication is enabled, it is possible to configure the delay
358# the server waits in order to spawn the child that transfers the RDB via socket
359# to the replicas.
360#
361# This is important since once the transfer starts, it is not possible to serve
362# new replicas arriving, that will be queued for the next RDB transfer, so the server
363# waits a delay in order to let more replicas arrive.
364#
365# The delay is specified in seconds, and by default is 5 seconds. To disable
366# it entirely just set it to 0 seconds and the transfer will start ASAP.
367repl-diskless-sync-delay 5
368
369# Replicas send PINGs to server in a predefined interval. It's possible to change
370# this interval with the repl_ping_replica_period option. The default value is 10
371# seconds.
372#
373# repl-ping-replica-period 10
374
375# The following option sets the replication timeout for:
376#
377# 1) Bulk transfer I/O during SYNC, from the point of view of replica.
378# 2) Master timeout from the point of view of replicas (data, pings).
379# 3) Replica timeout from the point of view of masters (REPLCONF ACK pings).
380#
381# It is important to make sure that this value is greater than the value
382# specified for repl-ping-replica-period otherwise a timeout will be detected
383# every time there is low traffic between the master and the replica.
384#
385# repl-timeout 60
386
387# Disable TCP_NODELAY on the replica socket after SYNC?
388#
389# If you select "yes" Redis will use a smaller number of TCP packets and
390# less bandwidth to send data to replicas. But this can add a delay for
391# the data to appear on the replica side, up to 40 milliseconds with
392# Linux kernels using a default configuration.
393#
394# If you select "no" the delay for data to appear on the replica side will
395# be reduced but more bandwidth will be used for replication.
396#
397# By default we optimize for low latency, but in very high traffic conditions
398# or when the master and replicas are many hops away, turning this to "yes" may
399# be a good idea.
400repl-disable-tcp-nodelay no
401
402# Set the replication backlog size. The backlog is a buffer that accumulates
403# replica data when replicas are disconnected for some time, so that when a replica
404# wants to reconnect again, often a full resync is not needed, but a partial
405# resync is enough, just passing the portion of data the replica missed while
406# disconnected.
407#
408# The bigger the replication backlog, the longer the time the replica can be
409# disconnected and later be able to perform a partial resynchronization.
410#
411# The backlog is only allocated once there is at least a replica connected.
412#
413# repl-backlog-size 1mb
414
415# After a master has no longer connected replicas for some time, the backlog
416# will be freed. The following option configures the amount of seconds that
417# need to elapse, starting from the time the last replica disconnected, for
418# the backlog buffer to be freed.
419#
420# Note that replicas never free the backlog for timeout, since they may be
421# promoted to masters later, and should be able to correctly "partially
422# resynchronize" with the replicas: hence they should always accumulate backlog.
423#
424# A value of 0 means to never release the backlog.
425#
426# repl-backlog-ttl 3600
427
428# The replica priority is an integer number published by Redis in the INFO output.
429# It is used by Redis Sentinel in order to select a replica to promote into a
430# master if the master is no longer working correctly.
431#
432# A replica with a low priority number is considered better for promotion, so
433# for instance if there are three replicas with priority 10, 100, 25 Sentinel will
434# pick the one with priority 10, that is the lowest.
435#
436# However a special priority of 0 marks the replica as not able to perform the
437# role of master, so a replica with priority of 0 will never be selected by
438# Redis Sentinel for promotion.
439#
440# By default the priority is 100.
441replica-priority 100
442
443# It is possible for a master to stop accepting writes if there are less than
444# N replicas connected, having a lag less or equal than M seconds.
445#
446# The N replicas need to be in "online" state.
447#
448# The lag in seconds, that must be <= the specified value, is calculated from
449# the last ping received from the replica, that is usually sent every second.
450#
451# This option does not GUARANTEE that N replicas will accept the write, but
452# will limit the window of exposure for lost writes in case not enough replicas
453# are available, to the specified number of seconds.
454#
455# For example to require at least 3 replicas with a lag <= 10 seconds use:
456#
457# min-replicas-to-write 3
458# min-replicas-max-lag 10
459#
460# Setting one or the other to 0 disables the feature.
461#
462# By default min-replicas-to-write is set to 0 (feature disabled) and
463# min-replicas-max-lag is set to 10.
464
465# A Redis master is able to list the address and port of the attached
466# replicas in different ways. For example the "INFO replication" section
467# offers this information, which is used, among other tools, by
468# Redis Sentinel in order to discover replica instances.
469# Another place where this info is available is in the output of the
470# "ROLE" command of a master.
471#
472# The listed IP and address normally reported by a replica is obtained
473# in the following way:
474#
475#   IP: The address is auto detected by checking the peer address
476#   of the socket used by the replica to connect with the master.
477#
478#   Port: The port is communicated by the replica during the replication
479#   handshake, and is normally the port that the replica is using to
480#   listen for connections.
481#
482# However when port forwarding or Network Address Translation (NAT) is
483# used, the replica may be actually reachable via different IP and port
484# pairs. The following two options can be used by a replica in order to
485# report to its master a specific set of IP and port, so that both INFO
486# and ROLE will report those values.
487#
488# There is no need to use both the options if you need to override just
489# the port or the IP address.
490#
491# replica-announce-ip 5.5.5.5
492# replica-announce-port 1234
493
494################################## SECURITY ###################################
495
496# Require clients to issue AUTH <PASSWORD> before processing any other
497# commands.  This might be useful in environments in which you do not trust
498# others with access to the host running redis-server.
499#
500# This should stay commented out for backward compatibility and because most
501# people do not need auth (e.g. they run their own servers).
502#
503# Warning: since Redis is pretty fast an outside user can try up to
504# 150k passwords per second against a good box. This means that you should
505# use a very strong password otherwise it will be very easy to break.
506#
507# requirepass foobared
508
509# Command renaming.
510#
511# It is possible to change the name of dangerous commands in a shared
512# environment. For instance the CONFIG command may be renamed into something
513# hard to guess so that it will still be available for internal-use tools
514# but not available for general clients.
515#
516# Example:
517#
518# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
519#
520# It is also possible to completely kill a command by renaming it into
521# an empty string:
522#
523# rename-command CONFIG ""
524#
525# Please note that changing the name of commands that are logged into the
526# AOF file or transmitted to replicas may cause problems.
527
528################################### CLIENTS ####################################
529
530# Set the max number of connected clients at the same time. By default
531# this limit is set to 10000 clients, however if the Redis server is not
532# able to configure the process file limit to allow for the specified limit
533# the max number of allowed clients is set to the current file limit
534# minus 32 (as Redis reserves a few file descriptors for internal uses).
535#
536# Once the limit is reached Redis will close all the new connections sending
537# an error 'max number of clients reached'.
538#
539# maxclients 10000
540
541############################## MEMORY MANAGEMENT ################################
542
543# Set a memory usage limit to the specified amount of bytes.
544# When the memory limit is reached Redis will try to remove keys
545# according to the eviction policy selected (see maxmemory-policy).
546#
547# If Redis can't remove keys according to the policy, or if the policy is
548# set to 'noeviction', Redis will start to reply with errors to commands
549# that would use more memory, like SET, LPUSH, and so on, and will continue
550# to reply to read-only commands like GET.
551#
552# This option is usually useful when using Redis as an LRU or LFU cache, or to
553# set a hard memory limit for an instance (using the 'noeviction' policy).
554#
555# WARNING: If you have replicas attached to an instance with maxmemory on,
556# the size of the output buffers needed to feed the replicas are subtracted
557# from the used memory count, so that network problems / resyncs will
558# not trigger a loop where keys are evicted, and in turn the output
559# buffer of replicas is full with DELs of keys evicted triggering the deletion
560# of more keys, and so forth until the database is completely emptied.
561#
562# In short... if you have replicas attached it is suggested that you set a lower
563# limit for maxmemory so that there is some free RAM on the system for replica
564# output buffers (but this is not needed if the policy is 'noeviction').
565#
566# maxmemory <bytes>
567
568# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
569# is reached. You can select among five behaviors:
570#
571# volatile-lru -> Evict using approximated LRU among the keys with an expire set.
572# allkeys-lru -> Evict any key using approximated LRU.
573# volatile-lfu -> Evict using approximated LFU among the keys with an expire set.
574# allkeys-lfu -> Evict any key using approximated LFU.
575# volatile-random -> Remove a random key among the ones with an expire set.
576# allkeys-random -> Remove a random key, any key.
577# volatile-ttl -> Remove the key with the nearest expire time (minor TTL)
578# noeviction -> Don't evict anything, just return an error on write operations.
579#
580# LRU means Least Recently Used
581# LFU means Least Frequently Used
582#
583# Both LRU, LFU and volatile-ttl are implemented using approximated
584# randomized algorithms.
585#
586# Note: with any of the above policies, Redis will return an error on write
587#       operations, when there are no suitable keys for eviction.
588#
589#       At the date of writing these commands are: set setnx setex append
590#       incr decr rpush lpush rpushx lpushx linsert lset rpoplpush sadd
591#       sinter sinterstore sunion sunionstore sdiff sdiffstore zadd zincrby
592#       zunionstore zinterstore hset hsetnx hmset hincrby incrby decrby
593#       getset mset msetnx exec sort
594#
595# The default is:
596#
597# maxmemory-policy noeviction
598
599# LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated
600# algorithms (in order to save memory), so you can tune it for speed or
601# accuracy. For default Redis will check five keys and pick the one that was
602# used less recently, you can change the sample size using the following
603# configuration directive.
604#
605# The default of 5 produces good enough results. 10 Approximates very closely
606# true LRU but costs more CPU. 3 is faster but not very accurate.
607#
608# maxmemory-samples 5
609
610# Starting from Redis 5, by default a replica will ignore its maxmemory setting
611# (unless it is promoted to master after a failover or manually). It means
612# that the eviction of keys will be just handled by the master, sending the
613# DEL commands to the replica as keys evict in the master side.
614#
615# This behavior ensures that masters and replicas stay consistent, and is usually
616# what you want, however if your replica is writable, or you want the replica to have
617# a different memory setting, and you are sure all the writes performed to the
618# replica are idempotent, then you may change this default (but be sure to understand
619# what you are doing).
620#
621# Note that since the replica by default does not evict, it may end using more
622# memory than the one set via maxmemory (there are certain buffers that may
623# be larger on the replica, or data structures may sometimes take more memory and so
624# forth). So make sure you monitor your replicas and make sure they have enough
625# memory to never hit a real out-of-memory condition before the master hits
626# the configured maxmemory setting.
627#
628# replica-ignore-maxmemory yes
629
630############################# LAZY FREEING ####################################
631
632# Redis has two primitives to delete keys. One is called DEL and is a blocking
633# deletion of the object. It means that the server stops processing new commands
634# in order to reclaim all the memory associated with an object in a synchronous
635# way. If the key deleted is associated with a small object, the time needed
636# in order to execute the DEL command is very small and comparable to most other
637# O(1) or O(log_N) commands in Redis. However if the key is associated with an
638# aggregated value containing millions of elements, the server can block for
639# a long time (even seconds) in order to complete the operation.
640#
641# For the above reasons Redis also offers non blocking deletion primitives
642# such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and
643# FLUSHDB commands, in order to reclaim memory in background. Those commands
644# are executed in constant time. Another thread will incrementally free the
645# object in the background as fast as possible.
646#
647# DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled.
648# It's up to the design of the application to understand when it is a good
649# idea to use one or the other. However the Redis server sometimes has to
650# delete keys or flush the whole database as a side effect of other operations.
651# Specifically Redis deletes objects independently of a user call in the
652# following scenarios:
653#
654# 1) On eviction, because of the maxmemory and maxmemory policy configurations,
655#    in order to make room for new data, without going over the specified
656#    memory limit.
657# 2) Because of expire: when a key with an associated time to live (see the
658#    EXPIRE command) must be deleted from memory.
659# 3) Because of a side effect of a command that stores data on a key that may
660#    already exist. For example the RENAME command may delete the old key
661#    content when it is replaced with another one. Similarly SUNIONSTORE
662#    or SORT with STORE option may delete existing keys. The SET command
663#    itself removes any old content of the specified key in order to replace
664#    it with the specified string.
665# 4) During replication, when a replica performs a full resynchronization with
666#    its master, the content of the whole database is removed in order to
667#    load the RDB file just transferred.
668#
669# In all the above cases the default is to delete objects in a blocking way,
670# like if DEL was called. However you can configure each case specifically
671# in order to instead release memory in a non-blocking way like if UNLINK
672# was called, using the following configuration directives:
673
674lazyfree-lazy-eviction no
675lazyfree-lazy-expire no
676lazyfree-lazy-server-del no
677replica-lazy-flush no
678
679############################## APPEND ONLY MODE ###############################
680
681# By default Redis asynchronously dumps the dataset on disk. This mode is
682# good enough in many applications, but an issue with the Redis process or
683# a power outage may result into a few minutes of writes lost (depending on
684# the configured save points).
685#
686# The Append Only File is an alternative persistence mode that provides
687# much better durability. For instance using the default data fsync policy
688# (see later in the config file) Redis can lose just one second of writes in a
689# dramatic event like a server power outage, or a single write if something
690# wrong with the Redis process itself happens, but the operating system is
691# still running correctly.
692#
693# AOF and RDB persistence can be enabled at the same time without problems.
694# If the AOF is enabled on startup Redis will load the AOF, that is the file
695# with the better durability guarantees.
696#
697# Please check http://redis.io/topics/persistence for more information.
698
699appendonly no
700
701# The name of the append only file (default: "appendonly.aof")
702
703appendfilename "appendonly.aof"
704
705# The fsync() call tells the Operating System to actually write data on disk
706# instead of waiting for more data in the output buffer. Some OS will really flush
707# data on disk, some other OS will just try to do it ASAP.
708#
709# Redis supports three different modes:
710#
711# no: don't fsync, just let the OS flush the data when it wants. Faster.
712# always: fsync after every write to the append only log. Slow, Safest.
713# everysec: fsync only one time every second. Compromise.
714#
715# The default is "everysec", as that's usually the right compromise between
716# speed and data safety. It's up to you to understand if you can relax this to
717# "no" that will let the operating system flush the output buffer when
718# it wants, for better performances (but if you can live with the idea of
719# some data loss consider the default persistence mode that's snapshotting),
720# or on the contrary, use "always" that's very slow but a bit safer than
721# everysec.
722#
723# More details please check the following article:
724# http://antirez.com/post/redis-persistence-demystified.html
725#
726# If unsure, use "everysec".
727
728# appendfsync always
729appendfsync everysec
730# appendfsync no
731
732# When the AOF fsync policy is set to always or everysec, and a background
733# saving process (a background save or AOF log background rewriting) is
734# performing a lot of I/O against the disk, in some Linux configurations
735# Redis may block too long on the fsync() call. Note that there is no fix for
736# this currently, as even performing fsync in a different thread will block
737# our synchronous write(2) call.
738#
739# In order to mitigate this problem it's possible to use the following option
740# that will prevent fsync() from being called in the main process while a
741# BGSAVE or BGREWRITEAOF is in progress.
742#
743# This means that while another child is saving, the durability of Redis is
744# the same as "appendfsync none". In practical terms, this means that it is
745# possible to lose up to 30 seconds of log in the worst scenario (with the
746# default Linux settings).
747#
748# If you have latency problems turn this to "yes". Otherwise leave it as
749# "no" that is the safest pick from the point of view of durability.
750
751no-appendfsync-on-rewrite no
752
753# Automatic rewrite of the append only file.
754# Redis is able to automatically rewrite the log file implicitly calling
755# BGREWRITEAOF when the AOF log size grows by the specified percentage.
756#
757# This is how it works: Redis remembers the size of the AOF file after the
758# latest rewrite (if no rewrite has happened since the restart, the size of
759# the AOF at startup is used).
760#
761# This base size is compared to the current size. If the current size is
762# bigger than the specified percentage, the rewrite is triggered. Also
763# you need to specify a minimal size for the AOF file to be rewritten, this
764# is useful to avoid rewriting the AOF file even if the percentage increase
765# is reached but it is still pretty small.
766#
767# Specify a percentage of zero in order to disable the automatic AOF
768# rewrite feature.
769
770auto-aof-rewrite-percentage 100
771auto-aof-rewrite-min-size 64mb
772
773# An AOF file may be found to be truncated at the end during the Redis
774# startup process, when the AOF data gets loaded back into memory.
775# This may happen when the system where Redis is running
776# crashes, especially when an ext4 filesystem is mounted without the
777# data=ordered option (however this can't happen when Redis itself
778# crashes or aborts but the operating system still works correctly).
779#
780# Redis can either exit with an error when this happens, or load as much
781# data as possible (the default now) and start if the AOF file is found
782# to be truncated at the end. The following option controls this behavior.
783#
784# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
785# the Redis server starts emitting a log to inform the user of the event.
786# Otherwise if the option is set to no, the server aborts with an error
787# and refuses to start. When the option is set to no, the user requires
788# to fix the AOF file using the "redis-check-aof" utility before to restart
789# the server.
790#
791# Note that if the AOF file will be found to be corrupted in the middle
792# the server will still exit with an error. This option only applies when
793# Redis will try to read more data from the AOF file but not enough bytes
794# will be found.
795aof-load-truncated yes
796
797# When rewriting the AOF file, Redis is able to use an RDB preamble in the
798# AOF file for faster rewrites and recoveries. When this option is turned
799# on the rewritten AOF file is composed of two different stanzas:
800#
801#   [RDB file][AOF tail]
802#
803# When loading Redis recognizes that the AOF file starts with the "REDIS"
804# string and loads the prefixed RDB file, and continues loading the AOF
805# tail.
806aof-use-rdb-preamble yes
807
808################################ LUA SCRIPTING  ###############################
809
810# Max execution time of a Lua script in milliseconds.
811#
812# If the maximum execution time is reached Redis will log that a script is
813# still in execution after the maximum allowed time and will start to
814# reply to queries with an error.
815#
816# When a long running script exceeds the maximum execution time only the
817# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
818# used to stop a script that did not yet called write commands. The second
819# is the only way to shut down the server in the case a write command was
820# already issued by the script but the user doesn't want to wait for the natural
821# termination of the script.
822#
823# Set it to 0 or a negative value for unlimited execution without warnings.
824lua-time-limit 5000
825
826################################ REDIS CLUSTER  ###############################
827
828# Normal Redis instances can't be part of a Redis Cluster; only nodes that are
829# started as cluster nodes can. In order to start a Redis instance as a
830# cluster node enable the cluster support uncommenting the following:
831#
832# cluster-enabled yes
833
834# Every cluster node has a cluster configuration file. This file is not
835# intended to be edited by hand. It is created and updated by Redis nodes.
836# Every Redis Cluster node requires a different cluster configuration file.
837# Make sure that instances running in the same system do not have
838# overlapping cluster configuration file names.
839#
840# cluster-config-file nodes-6379.conf
841
842# Cluster node timeout is the amount of milliseconds a node must be unreachable
843# for it to be considered in failure state.
844# Most other internal time limits are multiple of the node timeout.
845#
846# cluster-node-timeout 15000
847
848# A replica of a failing master will avoid to start a failover if its data
849# looks too old.
850#
851# There is no simple way for a replica to actually have an exact measure of
852# its "data age", so the following two checks are performed:
853#
854# 1) If there are multiple replicas able to failover, they exchange messages
855#    in order to try to give an advantage to the replica with the best
856#    replication offset (more data from the master processed).
857#    Replicas will try to get their rank by offset, and apply to the start
858#    of the failover a delay proportional to their rank.
859#
860# 2) Every single replica computes the time of the last interaction with
861#    its master. This can be the last ping or command received (if the master
862#    is still in the "connected" state), or the time that elapsed since the
863#    disconnection with the master (if the replication link is currently down).
864#    If the last interaction is too old, the replica will not try to failover
865#    at all.
866#
867# The point "2" can be tuned by user. Specifically a replica will not perform
868# the failover if, since the last interaction with the master, the time
869# elapsed is greater than:
870#
871#   (node-timeout * replica-validity-factor) + repl-ping-replica-period
872#
873# So for example if node-timeout is 30 seconds, and the replica-validity-factor
874# is 10, and assuming a default repl-ping-replica-period of 10 seconds, the
875# replica will not try to failover if it was not able to talk with the master
876# for longer than 310 seconds.
877#
878# A large replica-validity-factor may allow replicas with too old data to failover
879# a master, while a too small value may prevent the cluster from being able to
880# elect a replica at all.
881#
882# For maximum availability, it is possible to set the replica-validity-factor
883# to a value of 0, which means, that replicas will always try to failover the
884# master regardless of the last time they interacted with the master.
885# (However they'll always try to apply a delay proportional to their
886# offset rank).
887#
888# Zero is the only value able to guarantee that when all the partitions heal
889# the cluster will always be able to continue.
890#
891# cluster-replica-validity-factor 10
892
893# Cluster replicas are able to migrate to orphaned masters, that are masters
894# that are left without working replicas. This improves the cluster ability
895# to resist to failures as otherwise an orphaned master can't be failed over
896# in case of failure if it has no working replicas.
897#
898# Replicas migrate to orphaned masters only if there are still at least a
899# given number of other working replicas for their old master. This number
900# is the "migration barrier". A migration barrier of 1 means that a replica
901# will migrate only if there is at least 1 other working replica for its master
902# and so forth. It usually reflects the number of replicas you want for every
903# master in your cluster.
904#
905# Default is 1 (replicas migrate only if their masters remain with at least
906# one replica). To disable migration just set it to a very large value.
907# A value of 0 can be set but is useful only for debugging and dangerous
908# in production.
909#
910# cluster-migration-barrier 1
911
912# By default Redis Cluster nodes stop accepting queries if they detect there
913# is at least an hash slot uncovered (no available node is serving it).
914# This way if the cluster is partially down (for example a range of hash slots
915# are no longer covered) all the cluster becomes, eventually, unavailable.
916# It automatically returns available as soon as all the slots are covered again.
917#
918# However sometimes you want the subset of the cluster which is working,
919# to continue to accept queries for the part of the key space that is still
920# covered. In order to do so, just set the cluster-require-full-coverage
921# option to no.
922#
923# cluster-require-full-coverage yes
924
925# This option, when set to yes, prevents replicas from trying to failover its
926# master during master failures. However the master can still perform a
927# manual failover, if forced to do so.
928#
929# This is useful in different scenarios, especially in the case of multiple
930# data center operations, where we want one side to never be promoted if not
931# in the case of a total DC failure.
932#
933# cluster-replica-no-failover no
934
935# In order to setup your cluster make sure to read the documentation
936# available at http://redis.io web site.
937
938########################## CLUSTER DOCKER/NAT support  ########################
939
940# In certain deployments, Redis Cluster nodes address discovery fails, because
941# addresses are NAT-ted or because ports are forwarded (the typical case is
942# Docker and other containers).
943#
944# In order to make Redis Cluster working in such environments, a static
945# configuration where each node knows its public address is needed. The
946# following two options are used for this scope, and are:
947#
948# * cluster-announce-ip
949# * cluster-announce-port
950# * cluster-announce-bus-port
951#
952# Each instruct the node about its address, client port, and cluster message
953# bus port. The information is then published in the header of the bus packets
954# so that other nodes will be able to correctly map the address of the node
955# publishing the information.
956#
957# If the above options are not used, the normal Redis Cluster auto-detection
958# will be used instead.
959#
960# Note that when remapped, the bus port may not be at the fixed offset of
961# clients port + 10000, so you can specify any port and bus-port depending
962# on how they get remapped. If the bus-port is not set, a fixed offset of
963# 10000 will be used as usually.
964#
965# Example:
966#
967# cluster-announce-ip 10.1.1.5
968# cluster-announce-port 6379
969# cluster-announce-bus-port 6380
970
971################################## SLOW LOG ###################################
972
973# The Redis Slow Log is a system to log queries that exceeded a specified
974# execution time. The execution time does not include the I/O operations
975# like talking with the client, sending the reply and so forth,
976# but just the time needed to actually execute the command (this is the only
977# stage of command execution where the thread is blocked and can not serve
978# other requests in the meantime).
979#
980# You can configure the slow log with two parameters: one tells Redis
981# what is the execution time, in microseconds, to exceed in order for the
982# command to get logged, and the other parameter is the length of the
983# slow log. When a new command is logged the oldest one is removed from the
984# queue of logged commands.
985
986# The following time is expressed in microseconds, so 1000000 is equivalent
987# to one second. Note that a negative number disables the slow log, while
988# a value of zero forces the logging of every command.
989slowlog-log-slower-than 10000
990
991# There is no limit to this length. Just be aware that it will consume memory.
992# You can reclaim memory used by the slow log with SLOWLOG RESET.
993slowlog-max-len 128
994
995################################ LATENCY MONITOR ##############################
996
997# The Redis latency monitoring subsystem samples different operations
998# at runtime in order to collect data related to possible sources of
999# latency of a Redis instance.
1000#
1001# Via the LATENCY command this information is available to the user that can
1002# print graphs and obtain reports.
1003#
1004# The system only logs operations that were performed in a time equal or
1005# greater than the amount of milliseconds specified via the
1006# latency-monitor-threshold configuration directive. When its value is set
1007# to zero, the latency monitor is turned off.
1008#
1009# By default latency monitoring is disabled since it is mostly not needed
1010# if you don't have latency issues, and collecting data has a performance
1011# impact, that while very small, can be measured under big load. Latency
1012# monitoring can easily be enabled at runtime using the command
1013# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
1014latency-monitor-threshold 0
1015
1016############################# EVENT NOTIFICATION ##############################
1017
1018# Redis can notify Pub/Sub clients about events happening in the key space.
1019# This feature is documented at http://redis.io/topics/notifications
1020#
1021# For instance if keyspace events notification is enabled, and a client
1022# performs a DEL operation on key "foo" stored in the Database 0, two
1023# messages will be published via Pub/Sub:
1024#
1025# PUBLISH __keyspace@0__:foo del
1026# PUBLISH __keyevent@0__:del foo
1027#
1028# It is possible to select the events that Redis will notify among a set
1029# of classes. Every class is identified by a single character:
1030#
1031#  K     Keyspace events, published with __keyspace@<db>__ prefix.
1032#  E     Keyevent events, published with __keyevent@<db>__ prefix.
1033#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
1034#  $     String commands
1035#  l     List commands
1036#  s     Set commands
1037#  h     Hash commands
1038#  z     Sorted set commands
1039#  x     Expired events (events generated every time a key expires)
1040#  e     Evicted events (events generated when a key is evicted for maxmemory)
1041#  A     Alias for g$lshzxe, so that the "AKE" string means all the events.
1042#
1043#  The "notify-keyspace-events" takes as argument a string that is composed
1044#  of zero or multiple characters. The empty string means that notifications
1045#  are disabled.
1046#
1047#  Example: to enable list and generic events, from the point of view of the
1048#           event name, use:
1049#
1050#  notify-keyspace-events Elg
1051#
1052#  Example 2: to get the stream of the expired keys subscribing to channel
1053#             name __keyevent@0__:expired use:
1054#
1055#  notify-keyspace-events Ex
1056#
1057#  By default all notifications are disabled because most users don't need
1058#  this feature and the feature has some overhead. Note that if you don't
1059#  specify at least one of K or E, no events will be delivered.
1060notify-keyspace-events ""
1061
1062############################### ADVANCED CONFIG ###############################
1063
1064# Hashes are encoded using a memory efficient data structure when they have a
1065# small number of entries, and the biggest entry does not exceed a given
1066# threshold. These thresholds can be configured using the following directives.
1067hash-max-ziplist-entries 512
1068hash-max-ziplist-value 64
1069
1070# Lists are also encoded in a special way to save a lot of space.
1071# The number of entries allowed per internal list node can be specified
1072# as a fixed maximum size or a maximum number of elements.
1073# For a fixed maximum size, use -5 through -1, meaning:
1074# -5: max size: 64 Kb  <-- not recommended for normal workloads
1075# -4: max size: 32 Kb  <-- not recommended
1076# -3: max size: 16 Kb  <-- probably not recommended
1077# -2: max size: 8 Kb   <-- good
1078# -1: max size: 4 Kb   <-- good
1079# Positive numbers mean store up to _exactly_ that number of elements
1080# per list node.
1081# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size),
1082# but if your use case is unique, adjust the settings as necessary.
1083list-max-ziplist-size -2
1084
1085# Lists may also be compressed.
1086# Compress depth is the number of quicklist ziplist nodes from *each* side of
1087# the list to *exclude* from compression.  The head and tail of the list
1088# are always uncompressed for fast push/pop operations.  Settings are:
1089# 0: disable all list compression
1090# 1: depth 1 means "don't start compressing until after 1 node into the list,
1091#    going from either the head or tail"
1092#    So: [head]->node->node->...->node->[tail]
1093#    [head], [tail] will always be uncompressed; inner nodes will compress.
1094# 2: [head]->[next]->node->node->...->node->[prev]->[tail]
1095#    2 here means: don't compress head or head->next or tail->prev or tail,
1096#    but compress all nodes between them.
1097# 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail]
1098# etc.
1099list-compress-depth 0
1100
1101# Sets have a special encoding in just one case: when a set is composed
1102# of just strings that happen to be integers in radix 10 in the range
1103# of 64 bit signed integers.
1104# The following configuration setting sets the limit in the size of the
1105# set in order to use this special memory saving encoding.
1106set-max-intset-entries 512
1107
1108# Similarly to hashes and lists, sorted sets are also specially encoded in
1109# order to save a lot of space. This encoding is only used when the length and
1110# elements of a sorted set are below the following limits:
1111zset-max-ziplist-entries 128
1112zset-max-ziplist-value 64
1113
1114# HyperLogLog sparse representation bytes limit. The limit includes the
1115# 16 bytes header. When an HyperLogLog using the sparse representation crosses
1116# this limit, it is converted into the dense representation.
1117#
1118# A value greater than 16000 is totally useless, since at that point the
1119# dense representation is more memory efficient.
1120#
1121# The suggested value is ~ 3000 in order to have the benefits of
1122# the space efficient encoding without slowing down too much PFADD,
1123# which is O(N) with the sparse encoding. The value can be raised to
1124# ~ 10000 when CPU is not a concern, but space is, and the data set is
1125# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
1126hll-sparse-max-bytes 3000
1127
1128# Streams macro node max size / items. The stream data structure is a radix
1129# tree of big nodes that encode multiple items inside. Using this configuration
1130# it is possible to configure how big a single node can be in bytes, and the
1131# maximum number of items it may contain before switching to a new node when
1132# appending new stream entries. If any of the following settings are set to
1133# zero, the limit is ignored, so for instance it is possible to set just a
1134# max entires limit by setting max-bytes to 0 and max-entries to the desired
1135# value.
1136stream-node-max-bytes 4096
1137stream-node-max-entries 100
1138
1139# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
1140# order to help rehashing the main Redis hash table (the one mapping top-level
1141# keys to values). The hash table implementation Redis uses (see dict.c)
1142# performs a lazy rehashing: the more operation you run into a hash table
1143# that is rehashing, the more rehashing "steps" are performed, so if the
1144# server is idle the rehashing is never complete and some more memory is used
1145# by the hash table.
1146#
1147# The default is to use this millisecond 10 times every second in order to
1148# actively rehash the main dictionaries, freeing memory when possible.
1149#
1150# If unsure:
1151# use "activerehashing no" if you have hard latency requirements and it is
1152# not a good thing in your environment that Redis can reply from time to time
1153# to queries with 2 milliseconds delay.
1154#
1155# use "activerehashing yes" if you don't have such hard requirements but
1156# want to free memory asap when possible.
1157activerehashing yes
1158
1159# The client output buffer limits can be used to force disconnection of clients
1160# that are not reading data from the server fast enough for some reason (a
1161# common reason is that a Pub/Sub client can't consume messages as fast as the
1162# publisher can produce them).
1163#
1164# The limit can be set differently for the three different classes of clients:
1165#
1166# normal -> normal clients including MONITOR clients
1167# replica  -> replica clients
1168# pubsub -> clients subscribed to at least one pubsub channel or pattern
1169#
1170# The syntax of every client-output-buffer-limit directive is the following:
1171#
1172# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
1173#
1174# A client is immediately disconnected once the hard limit is reached, or if
1175# the soft limit is reached and remains reached for the specified number of
1176# seconds (continuously).
1177# So for instance if the hard limit is 32 megabytes and the soft limit is
1178# 16 megabytes / 10 seconds, the client will get disconnected immediately
1179# if the size of the output buffers reach 32 megabytes, but will also get
1180# disconnected if the client reaches 16 megabytes and continuously overcomes
1181# the limit for 10 seconds.
1182#
1183# By default normal clients are not limited because they don't receive data
1184# without asking (in a push way), but just after a request, so only
1185# asynchronous clients may create a scenario where data is requested faster
1186# than it can read.
1187#
1188# Instead there is a default limit for pubsub and replica clients, since
1189# subscribers and replicas receive data in a push fashion.
1190#
1191# Both the hard or the soft limit can be disabled by setting them to zero.
1192client-output-buffer-limit normal 0 0 0
1193client-output-buffer-limit replica 256mb 64mb 60
1194client-output-buffer-limit pubsub 32mb 8mb 60
1195
1196# Client query buffers accumulate new commands. They are limited to a fixed
1197# amount by default in order to avoid that a protocol desynchronization (for
1198# instance due to a bug in the client) will lead to unbound memory usage in
1199# the query buffer. However you can configure it here if you have very special
1200# needs, such us huge multi/exec requests or alike.
1201#
1202# client-query-buffer-limit 1gb
1203
1204# In the Redis protocol, bulk requests, that are, elements representing single
1205# strings, are normally limited ot 512 mb. However you can change this limit
1206# here.
1207#
1208# proto-max-bulk-len 512mb
1209
1210# Redis calls an internal function to perform many background tasks, like
1211# closing connections of clients in timeout, purging expired keys that are
1212# never requested, and so forth.
1213#
1214# Not all tasks are performed with the same frequency, but Redis checks for
1215# tasks to perform according to the specified "hz" value.
1216#
1217# By default "hz" is set to 10. Raising the value will use more CPU when
1218# Redis is idle, but at the same time will make Redis more responsive when
1219# there are many keys expiring at the same time, and timeouts may be
1220# handled with more precision.
1221#
1222# The range is between 1 and 500, however a value over 100 is usually not
1223# a good idea. Most users should use the default of 10 and raise this up to
1224# 100 only in environments where very low latency is required.
1225hz 10
1226
1227# Normally it is useful to have an HZ value which is proportional to the
1228# number of clients connected. This is useful in order, for instance, to
1229# avoid too many clients are processed for each background task invocation
1230# in order to avoid latency spikes.
1231#
1232# Since the default HZ value by default is conservatively set to 10, Redis
1233# offers, and enables by default, the ability to use an adaptive HZ value
1234# which will temporary raise when there are many connected clients.
1235#
1236# When dynamic HZ is enabled, the actual configured HZ will be used as
1237# as a baseline, but multiples of the configured HZ value will be actually
1238# used as needed once more clients are connected. In this way an idle
1239# instance will use very little CPU time while a busy instance will be
1240# more responsive.
1241dynamic-hz yes
1242
1243# When a child rewrites the AOF file, if the following option is enabled
1244# the file will be fsync-ed every 32 MB of data generated. This is useful
1245# in order to commit the file to the disk more incrementally and avoid
1246# big latency spikes.
1247aof-rewrite-incremental-fsync yes
1248
1249# When redis saves RDB file, if the following option is enabled
1250# the file will be fsync-ed every 32 MB of data generated. This is useful
1251# in order to commit the file to the disk more incrementally and avoid
1252# big latency spikes.
1253rdb-save-incremental-fsync yes
1254
1255# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good
1256# idea to start with the default settings and only change them after investigating
1257# how to improve the performances and how the keys LFU change over time, which
1258# is possible to inspect via the OBJECT FREQ command.
1259#
1260# There are two tunable parameters in the Redis LFU implementation: the
1261# counter logarithm factor and the counter decay time. It is important to
1262# understand what the two parameters mean before changing them.
1263#
1264# The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis
1265# uses a probabilistic increment with logarithmic behavior. Given the value
1266# of the old counter, when a key is accessed, the counter is incremented in
1267# this way:
1268#
1269# 1. A random number R between 0 and 1 is extracted.
1270# 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1).
1271# 3. The counter is incremented only if R < P.
1272#
1273# The default lfu-log-factor is 10. This is a table of how the frequency
1274# counter changes with a different number of accesses with different
1275# logarithmic factors:
1276#
1277# +--------+------------+------------+------------+------------+------------+
1278# | factor | 100 hits   | 1000 hits  | 100K hits  | 1M hits    | 10M hits   |
1279# +--------+------------+------------+------------+------------+------------+
1280# | 0      | 104        | 255        | 255        | 255        | 255        |
1281# +--------+------------+------------+------------+------------+------------+
1282# | 1      | 18         | 49         | 255        | 255        | 255        |
1283# +--------+------------+------------+------------+------------+------------+
1284# | 10     | 10         | 18         | 142        | 255        | 255        |
1285# +--------+------------+------------+------------+------------+------------+
1286# | 100    | 8          | 11         | 49         | 143        | 255        |
1287# +--------+------------+------------+------------+------------+------------+
1288#
1289# NOTE: The above table was obtained by running the following commands:
1290#
1291#   redis-benchmark -n 1000000 incr foo
1292#   redis-cli object freq foo
1293#
1294# NOTE 2: The counter initial value is 5 in order to give new objects a chance
1295# to accumulate hits.
1296#
1297# The counter decay time is the time, in minutes, that must elapse in order
1298# for the key counter to be divided by two (or decremented if it has a value
1299# less <= 10).
1300#
1301# The default value for the lfu-decay-time is 1. A Special value of 0 means to
1302# decay the counter every time it happens to be scanned.
1303#
1304# lfu-log-factor 10
1305# lfu-decay-time 1
1306
1307########################### ACTIVE DEFRAGMENTATION #######################
1308#
1309# WARNING THIS FEATURE IS EXPERIMENTAL. However it was stress tested
1310# even in production and manually tested by multiple engineers for some
1311# time.
1312#
1313# What is active defragmentation?
1314# -------------------------------
1315#
1316# Active (online) defragmentation allows a Redis server to compact the
1317# spaces left between small allocations and deallocations of data in memory,
1318# thus allowing to reclaim back memory.
1319#
1320# Fragmentation is a natural process that happens with every allocator (but
1321# less so with Jemalloc, fortunately) and certain workloads. Normally a server
1322# restart is needed in order to lower the fragmentation, or at least to flush
1323# away all the data and create it again. However thanks to this feature
1324# implemented by Oran Agra for Redis 4.0 this process can happen at runtime
1325# in an "hot" way, while the server is running.
1326#
1327# Basically when the fragmentation is over a certain level (see the
1328# configuration options below) Redis will start to create new copies of the
1329# values in contiguous memory regions by exploiting certain specific Jemalloc
1330# features (in order to understand if an allocation is causing fragmentation
1331# and to allocate it in a better place), and at the same time, will release the
1332# old copies of the data. This process, repeated incrementally for all the keys
1333# will cause the fragmentation to drop back to normal values.
1334#
1335# Important things to understand:
1336#
1337# 1. This feature is disabled by default, and only works if you compiled Redis
1338#    to use the copy of Jemalloc we ship with the source code of Redis.
1339#    This is the default with Linux builds.
1340#
1341# 2. You never need to enable this feature if you don't have fragmentation
1342#    issues.
1343#
1344# 3. Once you experience fragmentation, you can enable this feature when
1345#    needed with the command "CONFIG SET activedefrag yes".
1346#
1347# The configuration parameters are able to fine tune the behavior of the
1348# defragmentation process. If you are not sure about what they mean it is
1349# a good idea to leave the defaults untouched.
1350
1351# Enabled active defragmentation
1352# activedefrag yes
1353
1354# Minimum amount of fragmentation waste to start active defrag
1355# active-defrag-ignore-bytes 100mb
1356
1357# Minimum percentage of fragmentation to start active defrag
1358# active-defrag-threshold-lower 10
1359
1360# Maximum percentage of fragmentation at which we use maximum effort
1361# active-defrag-threshold-upper 100
1362
1363# Minimal effort for defrag in CPU percentage
1364# active-defrag-cycle-min 5
1365
1366# Maximal effort for defrag in CPU percentage
1367# active-defrag-cycle-max 75
1368
1369# Maximum number of set/hash/zset/list fields that will be processed from
1370# the main dictionary scan
1371# active-defrag-max-scan-fields 1000
1372
1373