Hazelcast Instance

Since Camel 2.7

Only consumer is supported

The Hazelcast instance component is one of Camel Hazelcast Components which allows you to consume join/leave events of the cache instance in the cluster. Hazelcast makes sense in one single "server node", but it’s extremely powerful in a clustered environment.

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The Hazelcast Instance component supports 4 options, which are listed below.

Name Description Default Type

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. 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

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

hazelcastInstance (advanced)

The hazelcast instance reference which can be used for hazelcast endpoint. If you don’t specify the instance reference, camel use the default hazelcast instance from the camel-hazelcast instance.

HazelcastInstance

hazelcastMode (advanced)

The hazelcast mode reference which kind of instance should be used. If you don’t specify the mode, then the node mode will be the default.

node

String

Endpoint Options

The Hazelcast Instance endpoint is configured using URI syntax:

hazelcast-instance:cacheName

With the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

cacheName (consumer)

Required The name of the cache.

String

Query Parameters (7 parameters)

Name Description Default Type

defaultOperation (consumer)

To specify a default operation to use, if no operation header has been provided.

Enum values:

  • put

  • delete

  • get

  • update

  • query

  • getAll

  • clear

  • putIfAbsent

  • addAll

  • removeAll

  • retainAll

  • evict

  • evictAll

  • valueCount

  • containsKey

  • containsValue

  • getKeys

  • removeValue

  • increment

  • decrement

  • setValue

  • destroy

  • compareAndSet

  • getAndAdd

  • add

  • offer

  • peek

  • poll

  • remainingCapacity

  • drainTo

  • removeIf

  • take

  • publish

  • readOnceHead

  • readOnceTail

  • capacity

HazelcastOperation

hazelcastConfigUri (consumer)

Hazelcast configuration file.

String

hazelcastInstance (consumer)

The hazelcast instance reference which can be used for hazelcast endpoint.

HazelcastInstance

hazelcastInstanceName (consumer)

The hazelcast instance reference name which can be used for hazelcast endpoint. If you don’t specify the instance reference, camel use the default hazelcast instance from the camel-hazelcast instance.

String

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions (if possible) occurred while the Camel consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. Important: This is only possible if the 3rd party component allows Camel to be alerted if an exception was thrown. Some components handle this internally only, and therefore bridgeErrorHandler is not possible. In other situations we may improve the Camel component to hook into the 3rd party component and make this possible for future releases. 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 (advanced))

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 (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

ExchangePattern

instance consumer - from("hazelcast-instance:foo")

The instance consumer fires if a new cache instance joins or leaves the cluster.

Here’s a sample:

fromF("hazelcast-%sfoo", HazelcastConstants.INSTANCE_PREFIX)
.log("instance...")
.choice()
    .when(header(HazelcastConstants.LISTENER_ACTION).isEqualTo(HazelcastConstants.ADDED))
        .log("...added")
        .to("mock:added")
    .otherwise()
        .log("...removed")
        .to("mock:removed");

Message Headers

The Hazelcast Instance component supports 5 message header(s), which is/are listed below:

Name Description Default Type

CamelHazelcastListenerAction (consumer)

Constant: LISTENER_ACTION

The type of event - here added and removed.

String

CamelHazelcastListenerType (consumer)

Constant: LISTENER_TYPE

The map consumer.

String

CamelHazelcastListenerTime (consumer)

Constant: LISTENER_TIME

The time of the event in millis.

Long

CamelHazelcastInstanceHost (consumer)

Constant: INSTANCE_HOST

The host name of the instance.

String

CamelHazelcastInstancePort (consumer)

Constant: INSTANCE_PORT

The port number of the instance.

Integer