State of Cassandra, August 2010

Professional Cassandra support and services Tuesday, August 10, 2010

Cassandra: Present & Future Jonathan Ellis @spyced Tuesday, August 10, 2010

Cassandra 0.6 & 0.7 Jonathan Ellis @spyced Tuesday, August 10, 2010

Quiet change of policy • 0.5.1 was bug ﬁxes only • Too early to be strict about bugﬁx-only policy in stable branch, especially w/ 0.7 being longer/more break-y • Maybe after 1.0? Tuesday, August 10, 2010

1500 mails sent 1125 750 375 0 Jan Feb Apr May Jun Jul (0.5) (0.5.1) Mar (0.6, 0.6.1) (0.6.2) (0.6.3) (0.6.4) Tuesday, August 10, 2010

Lots of bug ﬁxes • 85 issues marked Resolved/Fixed in 0.6 branch after 0.6 released Tuesday, August 10, 2010

Runtime conﬁguration • concurrent reads, writes (0.6.2) • making it easier to bandage your foot after you shoot it • PhiConvictThreshold (0.6.2) Tuesday, August 10, 2010

Performance • JVM GC defaults (0.6.2) • Faster commitlog (0.6.2) • Faster range slice, Hadoop jobs (0.6.1, 2) • Better parallelization of multiget (0.6.4) • UTF8Type, UUIDType optimizations (0.6.5) Tuesday, August 10, 2010

Bulletprooﬁng • HH disable (0.6.2) • compaction priority (0.6.3) • HH hourly scan (0.6.3) • JMX metrics for row-level bloom ﬁlters (0.6.3) • Flow control (0.6.4, 5) • HH paging (0.6.5) • Dynamic snitch (0.6.5) Tuesday, August 10, 2010

Hinted Handoff • 0.6.0: send hints to natural replicas • 0.6.0: ﬁx row-level concurrency bottleneck • 0.6.2: option to disable entirely • 0.6.3: remove hourly scan • 0.6.4: lower priority • 0.6.5: paging of large hinted rows • 0.7.0: large rows Tuesday, August 10, 2010

Why keep HH around? https://www.cloudkick.com/blog/2010/jan/12/visual-ec2-latency/ Tuesday, August 10, 2010

Compaction priority -XX:+UseThreadPriorities -XX:ThreadPriorityPolicy=42 -Dcassandra.compaction.priority=1 Extended to HH in 0.6.4 Tuesday, August 10, 2010

http://www.javamex.com/tutorials/threads/priority_what.shtml Tuesday, August 10, 2010

JMX for bloom ﬁlters • o.a.c.db:ColumnFamilyStores • getBloomFilterFalsePositives • [not in nodetool yet] Tuesday, August 10, 2010

Flow control in 0.5 • Why backpressure doesn’t ﬁt Cassandra Tuesday, August 10, 2010

Flow Control in 0.6.4 • Replica nodes drop hopeless requests on the ﬂoor • Coordinator node is unaffected • TimedOutException signals client to back off • Requires enough memory to buffer RPCTimeout’s worth of requests • (In the short term, you’re still screwed) Tuesday, August 10, 2010

Flow Control, 0.6.4 IncomingTcpConnection Message Deserializer Uncapped Read Mutation Capped at 4096 Tuesday, August 10, 2010

IncomingTcpConnection Message Deserializer Read Gossip Mutation Tuesday, August 10, 2010

Flow Control, 0.6.5 IncomingTcpConnection Read Gossip Mutation Uncapped Tuesday, August 10, 2010

Dynamic snitch • sortByProximity Tuesday, August 10, 2010

Open problems • Linux/mmap/swap unholy trio (0.6.5) • Memory fragmentation (0.6.5?) • Compaction effect on caches (0.7.1?) Tuesday, August 10, 2010

mmap and swap • The problem • Mitigations • mmap_index_only • swappiness=0 • turn off swap • mlockall at startup (Xms=Xmx) Tuesday, August 10, 2010

GC Fragmentation • Culprit of infamous CASSANDRA-1014? • Mitigation: tune with much larger new generation / tenuring threshold? Tuesday, August 10, 2010

Compaction and caches • Compactions wrecks the OS fs cache • Wrecks Cassandra key cache, too • (but not row cache) Tuesday, August 10, 2010

0.7 Tuesday, August 10, 2010

New in 0.7 • live schema changes • large rows • secondary indexes • efﬁcient Streaming • DatacenterStrategy Tuesday, August 10, 2010

Live schema changes • Details: http://www.riptano.com/blog/live- schema-updates-cassandra-07 Tuesday, August 10, 2010

Large rows • 0.6: smaller of {2GB, memory limit} • 0.7: in_memory_compaction_limit_in_mb Tuesday, August 10, 2010

Secondary indexes Tuesday, August 10, 2010

Streaming in 0.6 W A F (A-L] T L Tuesday, August 10, 2010

W A F (A-F] (A-F] T (F-L] L Tuesday, August 10, 2010

W A F Data T L Index Filter Tuesday, August 10, 2010

Streaming in 0.7 W A F T L Index Filter Tuesday, August 10, 2010

DatacenterStrategy • RackAwareStrategy is tuned for 3 replicas and 2 data centers • DS allows conﬁguring replicas per data center, per Keyspace Tuesday, August 10, 2010

Minor features in 0.7 • read_repair_chance • per-keyspace request scheduling • Hadoop OutputFormat • Per CF what used to be global (gc_grace_seconds, memtable thresholds) Tuesday, August 10, 2010

0.7 API changes • String keys become byte[] • Thrift keyspace argument moved to set_keyspace • i64 timestamp becomes Clock • SlicePredicate for _count methods Tuesday, August 10, 2010

0.7 performance • Reads roughly 100% faster, thanks largely to removing String creation • Row-cached reads up to 8x faster after optimizations by tjake and jbellis • Optimizations for reads of large rows • 0.7.1? ~20% improvement everywhere from Thrift optimizations Tuesday, August 10, 2010

Thrift • OOMs on malformed packets • Python Unicode string issues • PHP support is buggy and maintainerless Tuesday, August 10, 2010

After 0.7.0 • IndexOperator.GT • Triggers / plugins • Avro? • On-disk data format improvements (Compression, heirarchical data?) • Auth Tuesday, August 10, 2010

Questions Tuesday, August 10, 2010

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State of Cassandra, August 2010

by jbellis on Aug 10, 2010

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State of Cassandra, August 2010 — Presentation Transcript