1. Cassandra 0.7

2. Features
• Live schema modification
• Secondary indexes
• Hadoop OutputFormat
• (Very) large rows
• up to 2 billion columns
• NetworkTopologyStrategy

3. Operations
• efficient Streaming
• Per-ColumnFamily settings of memtable
thresholds
• Much more (optional) metadata about
columns

4. Operations backports
• 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)
• Tombstone removal in minor compaction (0.6.6)

5. Compatiblity
• Fully backwards-compatible with 0.6 data
• Some Thrift API changes
• String row keys become byte[]
• keyspace is set once per connection
• Requires drain + cluster restart

6. Features

7. Live schema changes
• Details: http://www.riptano.com/blog/live-
schema-updates-cassandra-07

8. Data model tradeoffs
• Twitter: “Fifteen months ago, it took two
weeks to perform ALTER TABLE on the
statuses [tweets] table.”

9. A static ColumnFamily

11. A dynamic ColumnFamily

12. SELECT * FROM tweets
WHERE user_id IN (SELECT follower FROM followers WHERE user_id = ?)
followers timeline
?
?
tweets

13. SuperColumns = full denormalization

14. A little deeper
• http://twissandra.com
• http://github.com/jhermes/twissjava

15. Secondary indexes

16. A static ColumnFamily

17. demo time

18. Hadoop OutputFormat
job.setOutputFormatClass(ColumnFamilyOutputFormat.class);
ConfigHelper.setOutputColumnFamily(job.getConfiguration(), KS, CF);
...
public void reduce(Text word, Iterable<IntWritable> values, Context
context)
{
int sum = 0;
for (IntWritable val : values)
sum += val.get();
context.write(outputKey,
Collections.singletonList(getMutation(word, sum)));
}

19. Large rows
• 0.6: smaller of {2GB, memory limit}
• 0.7: 2 billion columns
• in_memory_compaction_limit_in_mb

20. NetworkTopologyStrategy
• RackAwareStrategy is tuned for 3 replicas
and 2 data centers
• renamed to OldNetworkTopologyStrategy
• NTS allows configuring replicas per data
center, per Keyspace
• ignores replication_factor directive

21. Operations

22. Efficient Streaming

23. W A
F
(A-L]
T
L

24. W A
F
(A-F]
(A-F]
T
(F-L]
L

25. W A
F
Data
T
L
Index
Filter

26. W A
F
T
L
Index
Filter

27. Per-CF memtable thresholds
• Easier tuning for large numbers of ColumnFamilies

28. Column Metadata
• 0.6: comparator, subcomparator
• 0.7: default_validation_class,
column_metadata

29. Native code
• JNA introduced in 0.6.5 for mlockall
• Extended to hard links in 0.6.6 for
snapshots
• 0.7.1: posix_fadvise / fcntl for writes

30. Flow Control (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)

31. Flow control in 0.5
• Why backpressure doesn’t fit Cassandra

32. Dynamic snitch
public void sortByProximity(List<InetAddress> addresses);

33. Everything else

34. 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: even more speed (fix nagle + delayed
acks, zero-copy reads, ...)

35. Thrift: the libpq of Cassandra
• OOMs on malformed packets
• Python Unicode string issues
• PHP support is buggy and maintainerless

36. Client support from Riptano
• Hector
• Building JPA/JDO layer on top
• pycassa
• phpcassa
• Soon: cassandra gem

37. After 0.7.0
• Distributed counters
• IndexOperator.GT
• Entity groups
• 1.0?