1. Cassandra Native
Protocol Drivers
Tyler Hobbs, C* and C* driver engineer

2. About Me
CHART TITLE GOES HERE
Thrift drivers: pycassa, phpcassa,
telephus, and others
DataStax python driver (native
protocol)
Cassandra Engineer

3. Thrift Drivers
CHART TITLE GOES HERE
RPC Framework, machine generated

4. Thrift Drivers
Problems?
● Backwards & forwards compatibility
● Too many connections
● No standard interface
● Thrift overhead
● Cluster state must be polled

5. Problems & Solutions
Backwards/Forwards Compatibility
● Possible with Thrift, but easier with a
query language (CQL)
● Separately versioned query language
and protocol

6. Problems & Solutions
Too Many Connections
Operation pipelining with the native
protocol

7. Problems & Solutions
Operation Pipelining
● 127 in-flight ops per connection
● Improves throughput (not latency)
● Out-of-order processing
● Async, event-loop driven

8. Problems & Solutions
No Standard Interface
● Query language
● Standard policies for load balancing,
connection management, and
retries/failure handling
● More similar to standard RDMBS drivers

9. Problems & Solutions
Thrift Overhead
Custom protocol, prepared statements

10. Problems & Solutions
Cluster State Must be Polled
“Control connection,” register for
pushed notifications

11. New Driver API
Sync/Async Operations
result = session.execute(“SELECT * FROM foo”)

12. New Driver API
Sync/Async Operations
future = session.execute_async(“SELECT * FROM foo”)
…
result = future.result()

13. New Driver API
Sync/Async Operations
session.execute_async(query).add_callbacks(
callback=process_data,
errback=log_error
)

14. New Driver Architecture
Connection Pooling
● Min/max conns per remote, local nodes
● Use least busy conn
● Open and close conns as needed

15. New Driver Architecture
What happens during Operations?
● Nodes to query are picked by
LoadBalancingPolicy
● Failures are handled by RetryPolicy
● On errors, nodes are marked down by
ConvictionPolicy

16. New Driver Architecture
Load Balancing Policies
● RoundRobin
● DcAwareRoundRobin
● TokenAware wrapper
● Custom

17. New Driver Architecture
What happens during Operations?
● Nodes to query are picked by
LoadBalancingPolicy
● Failures are handled by RetryPolicy
● On errors, nodes are marked down by
ConvictionPolicy

18. New Driver Architecture
Retry Policies
● Operation type
● Consistency level
● Number (and type) of responses
● Type of failure
● Retry, raise error, or ignore error

19. New Driver Architecture
What happens during Operations?
● Nodes to query are picked by
LoadBalancingPolicy
● Failures are handled by RetryPolicy
● On errors, nodes are marked down by
ConvictionPolicy, reconnect with
ReconnectionPolicy

20. New Driver Architecture
Reconnection Policy
● Schedule for attempting reconnects to
down nodes
● Constant and Exponential backoff

21. New Driver Architecture
Policy Defaults
● RoundRobin load balancing (not token
or DC aware)
● Retry at most once (in a small number
of cases)
● Mark node down after one failure
● Exponential backoff on reconnection
attempts

22. New Driver Architecture
Prepared Statements
● Prepared against all nodes
● Cache
● Re-preparation
prepared = session.prepare(“SELECT foo FROM bar WHERE id=?”)
result = session.execute(prepared, [user_id1])

23. New Driver Architecture
Control Connection
● Listens for pushed updates to cluster
state and schema
● Marks nodes up and down
● Auto discovers nodes in cluster
● Updates schema metadata

24. New Driver Architecture
Metrics
● Count timeouts, connection errors, and
other errors
● Open connection stats
● Operation latency histogram

25. New Driver Architecture
Cursors
● No more manual paging over large
queries
● Works across multiple nodes
●
Paging state provided by client

26. New Driver Architecture
Quick Python Benchmark
● 3 nodes (local, ccm), one conn per host
● 50k individual inserts, single threaded
● Pycassa: ~1200 ops/sec
● DataStax python driver (sync,
blocking): ~950 ops/sec
● DataStax python driver (future
batching): ~3000 ops/sec
● DataStax python driver (callback
chaining): ~7300 ops/sec

27. New Driver Architecture
Languages Supported
● Java – 1.0 released
●
in Spring 2013
Simple object mapper under
development
● C# - 1.0 released in Summer 2013
●
LINQ integration
● Python – Beta since Summer 2013, 1.0
coming soon
●
Basic mapper available through
cqlengine
● C++ - Currently in Alpha state
● Ruby, JS, PHP – planned, but no
development so far

28. New Driver Architecture
Languages Supported
github.com/datastax

29. Questions?
@tylhobbs
thobbs on #cassandra, #datastaxdrivers