Camel Cassandra Component
Available as of Camel 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
:
<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.
Endpoint Options
Option | Default | Description |
---|---|---|
| Cluster name | |
| Session authentication | |
| CQL query. Can be overriden with a message header. | |
|
| |
|
| Use prepared statement (default) or not |
| ALL | How is ResultSet converted transformed into message body |
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
orRegularStatement
): CQL query either as a plain String or built using theQueryBuilder
.
Outgoing Message
The Camel Cassandra endpoint produces one or many a Cassandra Row objects depending on the resultSetConversionStrategy
:
List<Row>
ifresultSetConversionStrategy
isALL
orLIMIT_[0-9]+
- Single
Row
ifresultSetConversionStrategy
isONE
- Anything else, if
resultSetConversionStrategy
is a custom implementation of theResultSetConversionStrategy
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:
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:
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 … |