Cassandra CQL resource adaptor configuration

The Cassandra CQL resource adaptor has configuration properties related to:

  1. The Cassandra database to connect to — hosts and keyspace

  2. Configuration options of the Cassandra cluster — protocol version, port, query consistency level and so on

  3. Connecting to the Cassandra database — policies for connecting and re-connecting to the database

  4. Cache of prepared statements — cache size and entry expiry configuration

  5. Processing asynchronous responses — threads used for processing asynchronous responses and submitting events to the SLEE

  6. Optional switches related to debugging — options that may be useful for debugging

The Cassandra database to connect to

These configuration options define the initial set of hosts the resource adaptor entity should connect to and the keyspace it should use. There is one keyspace per resource adaptor entity. If your application requires several keyspaces, then you must create one resource adaptor entity for each keyspace. These properties may be actively changed (i.e whilst the ra entity is active).

Name Type Default Description

cassandraHosts

String

localhost

Comma separated list of hostname/ip address for the hosts in the cassandra cluster. The default value is 'localhost'

keyspace

String

The keyspace this RA entity should 'connect' to. There is no default, so this property must be defined.

These configuration options define general properties of the connection made to the Cassandra cluster. They may be actively changed (i.e whilst the ra entity is active) and will have an impact on the next time the resource adaptor needs to re-connect to the cassandra cluster.

Name Type Default Description

policy.protocol.version

String

use-default

The binary protocol version to use. Possible values are: V1, V2, V3 (the default).

policy.protocol.compression

String

use-default

The compression method to use with the binary protocol. Possible values are:

  • NONE — the default

  • SNAPPY — use the Snappy library for frame compression

  • LZ4 — use the LZ4 library for frame compression

policy.protocol.usessl

Boolean

false

If SSL should be used.

Note This property is currently ignored and will be enabled in a future release.

policy.protocol.port

Integer

9042

The port to connect to the cassandra database

policy.query.consistency

String

use-default

The default query consistency level. The default value is ONE.

policy.query.serialconsistency

String

use-default

The default serial consistency level for conditional updates. The default value is SERIAL

policy.query.fetchsize

Integer

5000

The default fetch size (the number of rows) to use for SELECT queries. Allowable values are 1 …​ Integer.MAX_VALUE
Note

The configuration options policy.query.consistency, policy.query.serialconsistency and policy.query.fetchsize represent the default values the resource adaptor will use if per query values are not provided. For example, you can set the consistency level of a statement to a value other than the default by using CassandraStatement.setConsistencyLevel(CassandraConsistencyLevel consistency)
Note

Possible consistency levels (from Apache Cassandra™ 2.0 — Configuring data consistency) are:

  • ALL — A write must be written to the commit log and memtable on all replica nodes in the cluster for that partition.

  • EACH_QUORUM — Strong consistency. A write must be written to the commit log and memtable on a quorum of replica nodes in all data centers.

  • QUORUM — A write must be written to the commit log and memtable on a quorum of replica nodes.

  • LOCAL_QUORUM — Strong consistency. A write must be written to the commit log and memtable on a quorum of replica nodes in the same data center as the coordinator node. Avoids latency of inter-data center communication.

  • ONE — A write must be written to the commit log and memtable of at least one replica node.

  • TWO — A write must be written to the commit log and memtable of at least two replica nodes.

  • THREE — A write must be written to the commit log and memtable of at least three replica nodes.

  • LOCAL_ONE — A write must be sent to, and successfully acknowledged by, at least one replica node in the local data center.

  • ANY — A write must be written to at least one node. If all replica nodes for the given partition key are down, the write can still succeed after a hinted handoff has been written. If all replica nodes are down at write time, an ANY write is not readable until the replica nodes for that partition have recovered.

  • SERIAL — Achieves linearizable consistency for lightweight transactions by preventing unconditional updates.

  • LOCAL_SERIAL — Same as SERIAL but confined to the data center. A write must be written conditionally to the commit log and memtable on a quorum of replica nodes in the same data center.

For more details, refer to Cassandra documentation:

Connecting to the Cassandra database

These properties dictate how the Cassandra CQL resource adaptor directs the DataStax driver to connect to the Cassandra cluster. These properties may be actively changed (i.e whilst the ra entity is active) and will have an impact on the next time the resource adaptor needs to re-connect to the cassandra cluster.

Name Type Default Description

reconnectionPolicy

String

constant

The two policies available for connection/re-connection (reconnectionPolicy) are:

  • constant — the driver attempts to connect with a fixed period. The connectToCassandraDelay property is the period (measured in seconds).

  • exponential — the driver attempts to connect with an increasing period from 1s up to 32s.

connectToCassandraDelay

Integer

10

How long (s) between attempts to connect to the Cassandra DB. Acceptable values are 5s to 60s.
Note

The reconnectionPolicy, as the name suggests, is related to the resource adaptor re-connecting to a database that it had previously connected. Connection attempts for the initial connection are always constant with a period of connectToCassandraDelay

Cache of prepared statements

The resource adaptor manages a cache of prepared statements, implemented as a LoadingCache<String, PreparedCassandraStatement> from the Guava library (guava-libraries — CachesExplained).

Tip See section Preparing statements for more information on preparing statements using the Cassandra CQL resource adaptor API.

The cache is cleared when the resource adaptor entity is deactivated. The size of the cache, and the cache entry expiry behaviour is controlled by the statementCache.maxSize and statementCache.expireAfterAccessT properties. These properties may be actively changed (i.e whilst the ra entity is active). Entries in the cache are preserved when properties of the cache are changed.

Name Type Default Description

statementCache.maxSize

Integer

100

Maximum number of entries in the prepared statement cache

statementCache.expireAfterAccessT

Integer

10

Time (s) after which a statement is removed from the cache since it was last used

Processing asynchronous responses

The resource adaptor receives asynchronous responses from the DataStax driver and delivers them as events into the Rhino TAS. This function is implemented using a standard java ThreadPoolExecutor. The ThreadPoolExecutor encapsulates a thread pool and a task queue. The following properties define the configuration of this ThreadPoolExecutor and should be set to suit the expected rate of asynchrounous responses.

Name Type Default Description

responseExecutor.corePoolSize

Integer

1

Number of threads available at all times

responseExecutor.maxPoolSize

Integer

5

Maximum number of threads

responseExecutor.nonCoreThreadKeepAliveT

Integer

60

How long (s) to keep non-core threads if they are idle

responseExecutor.queueCapacity

Integer

500

The maximum results to queue waiting for a result executor thread

These properties may be actively changed (i.e whilst the ra entity is active).

Optional switches for debugging

The resource adaptor will request additional notifications from the Rhino TAS when CassandraSession activities end if the debug.activity.requestendedcallback is true. This behaviour is not required for normal operation of the resource adaptor, but may be useful during application testing scenarios. This property be actively changed (i.e whilst the ra entity is active).

Name Type Default Description

debug.activity.requestendedcallback

Boolean

false

Should the RA request activity ended notification from the slee
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