Scylla release: version 1.5 RC1
The Scylla team is pleased to announce the release of Scylla 1.5 RC1, the first Release Candidate toward Scylla 1.5. From now on only critical bugs (showstoppers) will be fixed in branch-1.5. We will continue to fix bugs and add features on the master branch.
Scylla is an open source, Apache-Cassandra-compatible NoSQL database, with superior performance and consistently low latency.
Scylla 1.5 focused on stability, bug fix and workload conditioning.
Scylla 1.5 takes another step into workload conditioning, Scylla ability to self-tune to better handle various user workload. In this release, Scylla is capable of automatically reducing the rate of requests it accepts if the disk is not fast enough to write back memtables and commitlog entries. The rate is automatically determined to be the highest rate possible that still allow the resources to keep up.
Noteworthy bug fix
- Range scans, often used by analytics tool like Spark, issue unnecessary parallel queries making them needlessly slow #1863 (this fix will be part of 1.4.2 as well)
- when the ‘nodetool compact’ command is issued, in some circumstances, sstable file descriptors may stay open after deletion (by compaction), causing the disk space to run out #1840
- nodetool info returns a negative cache capacity value #1801
- snapshot operation may not release all of its memory back to Scylla, eventually causing an out of memory and exit #1831
- CQL: Using SELECT DISTINCT queries with paging can return duplicate results #1822
- Histogram and moving average metrics returning wrong values which propagate to REST, JMX API like org.apache.cassandra.metrics.Write.Latency #1832, #1836,#1837
- Scylla may not start on large machine (with many cores) when a column family has many sstables #1812
- CQL: Selecting the same column twice will trigger an assert #1367
- High 99th percentile latency of Ubuntu installations during compaction
- Relatively high 99th percentile latency during compaction #1794
- Relatively high latencies on Ubuntu caused by different default clock configuration #1794
- Concurrent reads and writes to the same partition may cause slowly leak. When running with cache disabled (not recommended) can cause a crash #1753
Noteworthy new and updated metrics in Scylla 1.5
database_total_operations_requests_blocked_memory– a new monotonic counter of replica writes which were delayed due to too much dirty (unflushed) memory. Typically that is caused by disk not keeping up with the write rate. Helps in correlating increased write latency with this cause of stall.
commitlog_total_operations_requests_blocked_memory– total over time amount of requests blocked in the commitlog write path due to insufficient disk speed. Part of workload conditioning.
commitlog_queue_length_pending_allocations– the amount of requests currently blocked in the commitlog write path due to insufficient disk speed. Part of workload conditioning.
The following metrics was made obsolete by the workload conditioning