1This directory contains all Redis dependencies, except for the libc that 2should be provided by the operating system. 3 4* **Jemalloc** is our memory allocator, used as replacement for libc malloc on Linux by default. It has good performances and excellent fragmentation behavior. This component is upgraded from time to time. 5* **geohash-int** is inside the dependencies directory but is actually part of the Redis project, since it is our private fork (heavily modified) of a library initially developed for Ardb, which is in turn a fork of Redis. 6* **hiredis** is the official C client library for Redis. It is used by redis-cli, redis-benchmark and Redis Sentinel. It is part of the Redis official ecosystem but is developed externally from the Redis repository, so we just upgrade it as needed. 7* **linenoise** is a readline replacement. It is developed by the same authors of Redis but is managed as a separated project and updated as needed. 8* **lua** is Lua 5.1 with minor changes for security and additional libraries. 9 10How to upgrade the above dependencies 11=== 12 13Jemalloc 14--- 15 16Jemalloc is modified with changes that allow us to implement the Redis 17active defragmentation logic. However this feature of Redis is not mandatory 18and Redis is able to understand if the Jemalloc version it is compiled 19against supports such Redis-specific modifications. So in theory, if you 20are not interested in the active defragmentation, you can replace Jemalloc 21just following tose steps: 22 231. Remove the jemalloc directory. 242. Substitute it with the new jemalloc source tree. 253. Edit the Makefile localted in the same directory as the README you are 26 reading, and change the --with-version in the Jemalloc configure script 27 options with the version you are using. This is required because otherwise 28 Jemalloc configuration script is broken and will not work nested in another 29 git repository. 30 31However note that we change Jemalloc settings via the `configure` script of Jemalloc using the `--with-lg-quantum` option, setting it to the value of 3 instead of 4. This provides us with more size classes that better suit the Redis data structures, in order to gain memory efficiency. 32 33If you want to upgrade Jemalloc while also providing support for 34active defragmentation, in addition to the above steps you need to perform 35the following additional steps: 36 375. In Jemalloc three, file `include/jemalloc/jemalloc_macros.h.in`, make sure 38 to add `#define JEMALLOC_FRAG_HINT`. 396. Implement the function `je_get_defrag_hint()` inside `src/jemalloc.c`. You 40 can see how it is implemented in the current Jemalloc source tree shipped 41 with Redis, and rewrite it according to the new Jemalloc internals, if they 42 changed, otherwise you could just copy the old implementation if you are 43 upgrading just to a similar version of Jemalloc. 44 45Geohash 46--- 47 48This is never upgraded since it's part of the Redis project. If there are changes to merge from Ardb there is the need to manually check differences, but at this point the source code is pretty different. 49 50Hiredis 51--- 52 53Hiredis uses the SDS string library, that must be the same version used inside Redis itself. Hiredis is also very critical for Sentinel. Historically Redis often used forked versions of hiredis in a way or the other. In order to upgrade it is advised to take a lot of care: 54 551. Check with diff if hiredis API changed and what impact it could have in Redis. 562. Make sure thet the SDS library inside Hiredis and inside Redis are compatible. 573. After the upgrade, run the Redis Sentinel test. 584. Check manually that redis-cli and redis-benchmark behave as expecteed, since we have no tests for CLI utilities currently. 59 60Linenoise 61--- 62 63Linenoise is rarely upgraded as needed. The upgrade process is trivial since 64Redis uses a non modified version of linenoise, so to upgrade just do the 65following: 66 671. Remove the linenoise directory. 682. Substitute it with the new linenoise source tree. 69 70Lua 71--- 72 73We use Lua 5.1 and no upgrade is planned currently, since we don't want to break 74Lua scripts for new Lua features: in the context of Redis Lua scripts the 75capabilities of 5.1 are usually more than enough, the release is rock solid, 76and we definitely don't want to break old scripts. 77 78So upgrading of Lua is up to the Redis project maintainers and should be a 79manual procedure performed by taking a diff between the different versions. 80 81Currently we have at least the following differences between official Lua 5.1 82and our version: 83 841. Makefile is modified to allow a different compiler than GCC. 852. We have the implementation source code, and directly link to the following external libraries: `lua_cjson.o`, `lua_struct.o`, `lua_cmsgpack.o` and `lua_bit.o`. 863. There is a security fix in `ldo.c`, line 498: The check for `LUA_SIGNATURE[0]` is removed in order toa void direct bytecode execution. 87 88 89