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 |
---|---|
|
Single host, default port, usual for testing |
|
Multi host, default port |
|
Multi host, custom port |
|
Default port and keyspace |
|
Provided Session reference |
|
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
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` if
resultSetConversionStrategy
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:
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 name |
|
|
Primary key columns |
|
Repository name, value used for |
|
|
Key time to live |
|
|
Consistency level used to insert/delete key: |
|
|
Consistency level used to read/check key: |
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 name |
|
|
Primary key columns |
|
|
Exchange Id column |
|
|
Exchange content column |
|
Repository name, value used for |
|
|
Exchange time to live |
|
|
Consistency level used to insert/delete exchange: |
|
|
Consistency level used to read/check exchange: |