Cassandra CQL Component

Available as of Camel version 2.15

Apache Cassandra is an open source NoSQL database designed to handle large amounts on commodity hardware. Like Amazon’s DynamoDB, Cassandra has a peer-to-peer and master-less architecture to avoid single point of failure and garanty high availability. Like Google’s BigTable, Cassandra data is structured using column families which can be accessed through the Thrift RPC API or a SQL-like API called CQL.

This component aims at integrating Cassandra 2.0+ using the CQL3 API (not the Thrift API). It’s based on Cassandra Java Driver provided by DataStax.

Maven users will need to add the following dependency to their pom.xml:

pom.xml

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-cassandraql</artifactId>
    <version>x.y.z</version>
    <!-- use the same version as your Camel core version -->
</dependency>

URI format

The endpoint can initiate the Cassandra connection or use an existing one.

URI Description

cql:localhost/keyspace

Single host, default port, usual for testing

cql:host1,host2/keyspace

Multi host, default port

cql:host1,host2:9042/keyspace

Multi host, custom port

cql:host1,host2

Default port and keyspace

cql:bean:sessionRef

Provided Session reference

cql:bean:clusterRef/keyspace

Provided Cluster reference

To fine tune the Cassandra connection (SSL options, pooling options, load balancing policy, retry policy, reconnection policy…​), create your own Cluster instance and give it to the Camel endpoint.

Cassandra Options

The Cassandra CQL component has no options.

The Cassandra CQL endpoint is configured using URI syntax:

cql:beanRef:hosts:port/keyspace

with the following path and query parameters:

Path Parameters (4 parameters):

Name Description Default Type

beanRef

beanRef is defined using bean:id

String

hosts

Hostname(s) cassansdra server(s). Multiple hosts can be separated by comma.

String

port

Port number of cassansdra server(s)

Integer

keyspace

Keyspace to use

String

Query Parameters (14 parameters):

Name Description Default Type

cluster (common)

To use the Cluster instance (you would normally not use this option)

Cluster

clusterName (common)

Cluster name

String

consistencyLevel (common)

Consistency level to use

ConsistencyLevel

cql (common)

CQL query to perform. Can be overridden with the message header with key CamelCqlQuery.

String

loadBalancingPolicy (common)

To use a specific LoadBalancingPolicy

String

password (common)

Password for session authentication

String

prepareStatements (common)

Whether to use PreparedStatements or regular Statements

true

boolean

resultSetConversionStrategy (common)

To use a custom class that implements logic for converting ResultSet into message body ALL ONE LIMIT_10 LIMIT_100…​

String

session (common)

To use the Session instance (you would normally not use this option)

Session

username (common)

Username for session authentication

String

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler which mean any exceptions occurred while the consumer is trying to pickup incoming messages or the likes will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer)

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this options is not in use. By default the consumer will deal with exceptions that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer)

Sets the exchange pattern when the consumer creates an exchange.

ExchangePattern

synchronous (advanced)

Sets whether synchronous processing should be strictly used or Camel is allowed to use asynchronous processing (if supported).

false

boolean

Messages

Incoming Message

The Camel Cassandra endpoint expects a bunch of simple objects (Object or Object[] or Collection<Object>) which will be bound to the CQL statement as query parameters. If message body is null or empty, then  CQL query will be executed without binding parameters.

Headers:

  • CamelCqlQuery (optional, String or RegularStatement): CQL query either as a plain String or built using the QueryBuilder.

Outgoing Message

The Camel Cassandra endpoint produces one or many a Cassandra Row objects depending on the resultSetConversionStrategy:

 
  • List<Row> if resultSetConversionStrategy is ALL or LIMIT_[0-9]+

  • Single` Row` if resultSetConversionStrategy is ONE

  • Anything else, if resultSetConversionStrategy is a custom implementation of the ResultSetConversionStrategy

Repositories

Cassandra can be used to store message keys or messages for the idempotent and aggregation EIP.

Cassandra might not be the best tool for queuing use cases yet, read Cassandra anti-patterns queues and queue like datasets. It’s advised to use LeveledCompaction and a small GC grace setting for these tables to allow tombstoned rows to be removed quickly.

Idempotent repository

The NamedCassandraIdempotentRepository stores messages keys in a Cassandra table like this:

CAMEL_IDEMPOTENT.cql

CREATE TABLE CAMEL_IDEMPOTENT (
  NAME varchar,   -- Repository name
  KEY varchar,    -- Message key
  PRIMARY KEY (NAME, KEY)
) WITH compaction = {'class':'LeveledCompactionStrategy'}
  AND gc_grace_seconds = 86400;

This repository implementation uses lightweight transactions (also known as Compare and Set) and requires Cassandra 2.0.7+.

Alternatively, the CassandraIdempotentRepository does not have a NAME column and can be extended to use a different data model.

Option Default Description

table

CAMEL_IDEMPOTENT

Table name

pkColumns

NAME,` KEY`

Primary key columns

name

Repository name, value used for NAME column

ttl

Key time to live

writeConsistencyLevel

Consistency level used to insert/delete key: ANY, ONE, TWO, QUORUM, LOCAL_QUORUM

readConsistencyLevel

Consistency level used to read/check key: ONE, TWO, QUORUM, LOCAL_QUORUM

Aggregation repository

The NamedCassandraAggregationRepository stores exchanges by correlation key in a Cassandra table like this:

CAMEL_AGGREGATION.cql

CREATE TABLE CAMEL_AGGREGATION (
  NAME varchar,        -- Repository name
  KEY varchar,         -- Correlation id
  EXCHANGE_ID varchar, -- Exchange id
  EXCHANGE blob,       -- Serialized exchange
  PRIMARY KEY (NAME, KEY)
) WITH compaction = {'class':'LeveledCompactionStrategy'}
  AND gc_grace_seconds = 86400;

Alternatively, the CassandraAggregationRepository does not have a NAME column and can be extended to use a different data model.

Option Default Description

table

CAMEL_AGGREGATION

Table name

pkColumns

NAME,KEY

Primary key columns

exchangeIdColumn

EXCHANGE_ID

Exchange Id column

exchangeColumn

EXCHANGE

Exchange content column

name

Repository name, value used for NAME column

ttl

Exchange time to live

writeConsistencyLevel

Consistency level used to insert/delete exchange: ANY, ONE, TWO, QUORUM, LOCAL_QUORUM

readConsistencyLevel

Consistency level used to read/check exchange: ONE, TWO, QUORUM, LOCAL_QUORUM