Chapter 73. 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> 73.1. 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. 73.2. Cassandra Options The Cassandra CQL component has no options. The Cassandra CQL endpoint is configured using URI syntax: with the following path and query parameters: 73.2.1. 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 73.2.2. Query Parameters (29 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 sendEmptyMessageWhenIdle (consumer) If the polling consumer did not poll any files, you can enable this option to send an empty message (no body) instead. false boolean exceptionHandler (consumer) To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option 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 pollStrategy (consumer) A pluggable org.apache.camel.PollingConsumerPollingStrategy allowing you to provide your custom implementation to control error handling usually occurred during the poll operation before an Exchange have been created and being routed in Camel. PollingConsumerPoll Strategy synchronous (advanced) Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). false boolean backoffErrorThreshold (scheduler) The number of subsequent error polls (failed due some error) that should happen before the backoffMultipler should kick-in. int backoffIdleThreshold (scheduler) The number of subsequent idle polls that should happen before the backoffMultipler should kick-in. int backoffMultiplier (scheduler) To let the scheduled polling consumer backoff if there has been a number of subsequent idles/errors in a row. The multiplier is then the number of polls that will be skipped before the actual attempt is happening again. When this option is in use then backoffIdleThreshold and/or backoffErrorThreshold must also be configured. int delay (scheduler) Milliseconds before the poll. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour). 500 long greedy (scheduler) If greedy is enabled, then the ScheduledPollConsumer will run immediately again, if the run polled 1 or more messages. false boolean initialDelay (scheduler) Milliseconds before the first poll starts. You can also specify time values using units, such as 60s (60 seconds), 5m30s (5 minutes and 30 seconds), and 1h (1 hour). 1000 long runLoggingLevel (scheduler) The consumer logs a start/complete log line when it polls. This option allows you to configure the logging level for that. TRACE LoggingLevel scheduledExecutorService (scheduler) Allows for configuring a custom/shared thread pool to use for the consumer. By default each consumer has its own single threaded thread pool. ScheduledExecutor Service scheduler (scheduler) To use a cron scheduler from either camel-spring or camel-quartz2 component none ScheduledPollConsumer Scheduler schedulerProperties (scheduler) To configure additional properties when using a custom scheduler or any of the Quartz2, Spring based scheduler. Map startScheduler (scheduler) Whether the scheduler should be auto started. true boolean timeUnit (scheduler) Time unit for initialDelay and delay options. MILLISECONDS TimeUnit useFixedDelay (scheduler) Controls if fixed delay or fixed rate is used. See ScheduledExecutorService in JDK for details. true boolean 73.3. Spring Boot Auto-Configuration The component supports 2 options, which are listed below. Name Description Default Type camel.component.cql.enabled Enable cql component true Boolean camel.component.cql.resolve-property-placeholders Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. true Boolean 73.4. Messages 73.4.1. 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 . 73.4.2. 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 73.5. 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. 73.6. 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 ... 73.7. 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 ... 73.8. Examples To insert something on a table you can use the following code: String CQL = "insert into camel_user(login, first_name, last_name) values (?, ?, ?)"; from("direct:input") .to("cql://localhost/camel_ks?cql=" + CQL); At this point you should be able to insert data by using a list as body Arrays.asList("davsclaus", "Claus", "Ibsen") The same approach can be used for updating or querying the table.

Commands:
<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>
cql:beanRef:hosts:port/keyspace
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;
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;
String CQL = "insert into camel_user(login, first_name, last_name) values (?, ?, ?)"; from("direct:input") .to("cql://localhost/camel_ks?cql=" + CQL);
Arrays.asList("davsclaus", "Claus", "Ibsen")