1--- 2title: RocksDB 5.6.1 Released! 3layout: post 4author: yiwu 5category: blog 6--- 7 8### Public API Change 9* Scheduling flushes and compactions in the same thread pool is no longer supported by setting `max_background_flushes=0`. Instead, users can achieve this by configuring their high-pri thread pool to have zero threads. See https://github.com/facebook/rocksdb/wiki/Thread-Pool for more details. 10* Replace `Options::max_background_flushes`, `Options::max_background_compactions`, and `Options::base_background_compactions` all with `Options::max_background_jobs`, which automatically decides how many threads to allocate towards flush/compaction. 11* options.delayed_write_rate by default take the value of options.rate_limiter rate. 12* Replace global variable `IOStatsContext iostats_context` with `IOStatsContext* get_iostats_context()`; replace global variable `PerfContext perf_context` with `PerfContext* get_perf_context()`. 13 14### New Features 15* Change ticker/histogram statistics implementations to use core-local storage. This improves aggregation speed compared to our previous thread-local approach, particularly for applications with many threads. See http://rocksdb.org/blog/2017/05/14/core-local-stats.html for more details. 16* Users can pass a cache object to write buffer manager, so that they can cap memory usage for memtable and block cache using one single limit. 17* Flush will be triggered when 7/8 of the limit introduced by write_buffer_manager or db_write_buffer_size is triggered, so that the hard threshold is hard to hit. See https://github.com/facebook/rocksdb/wiki/Write-Buffer-Manager for more details. 18* Introduce WriteOptions.low_pri. If it is true, low priority writes will be throttled if the compaction is behind. See https://github.com/facebook/rocksdb/wiki/Low-Priority-Write for more details. 19* `DB::IngestExternalFile()` now supports ingesting files into a database containing range deletions. 20 21### Bug Fixes 22* Shouldn't ignore return value of fsync() in flush. 23