JGroups raft

Since Camel 2.24

JGroups-raft is a Raft implementation in JGroups. The jgroups-raft: component provides interoperability between camel and a JGroups-raft clusters.

Maven users will need to add the following dependency to their pom.xml for this component.

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

URI format

jgroups-raft:clusterName[?options]

Where clusterName represents the name of the JGroups-raft cluster the component should connect to.

Options

The JGroups raft component supports 5 options, which are listed below.

Name Description Default Type

raftHandle (common)

RaftHandle to use.

RaftHandle

stateMachine (common)

StateMachine to use.

NopStateMachine

StateMachine

raftId (common)

Required Unique raftId to use.

String

channelProperties (common)

Specifies configuration properties of the RaftHandle JChannel used by the endpoint (ignored if raftHandle ref is provided).

raft.xml

String

resolveProperty Placeholders (advanced)

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

boolean

The JGroups raft endpoint is configured using URI syntax:

jgroups-raft:clusterName

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

clusterName

Required The name of the JGroupsraft cluster the component should connect to.

String

Query Parameters (5 parameters):

Name Description Default Type

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

enableRoleChangeEvents (consumer)

If set to true, the consumer endpoint will receive roleChange event as well (not just connecting and/or using the state machine). By default it is set to false.

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

synchronous (advanced)

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

false

boolean

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-jgroups-raft-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 11 options, which are listed below.

Name Description Default Type

camel.component.jgroups-raft.channel-properties

Specifies configuration properties of the RaftHandle JChannel used by the endpoint (ignored if raftHandle ref is provided).

raft.xml

String

camel.component.jgroups-raft.enabled

Enable jgroups-raft component

true

Boolean

camel.component.jgroups-raft.raft-handle

RaftHandle to use. The option is a org.jgroups.raft.RaftHandle type.

String

camel.component.jgroups-raft.raft-id

Unique raftId to use.

String

camel.component.jgroups-raft.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

camel.component.jgroups-raft.state-machine

StateMachine to use. The option is a org.jgroups.protocols.raft.StateMachine type.

String

camel.component.jgroups.raft.cluster.service.enabled

Sets if the jgroups raft cluster service should be enabled or not, default is false.

false

Boolean

camel.component.jgroups.raft.cluster.service.id

Cluster Service ID

String

camel.component.jgroups.raft.cluster.service.jgroups-raft-cluster-name

JGroups Cluster name

String

camel.component.jgroups.raft.cluster.service.jgroups-raft-config

JGrups-raft configuration File name

String

camel.component.jgroups.raft.cluster.service.raft-id

JGroups-raft ID

String

Headers

Header Constant Since version Description

JGROUPSRAFT_COMMIT_INDEX

JGroupsRaftEndpoint.HEADER_JGROUPSRAFT_COMMIT_INDEX

2.24.0

Consumer : The commit index (int).

JGROUPSRAFT_CURRENT_TERM

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_CURRENT_TERM

2.24.0

Consumer : The current raft term (int).

JGROUPSRAFT_IS_LEADER

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_IS_LEADER

2.24.0

Consumer: Whether the node is the Raft Leader or not (boolean).

JGROUPSRAFT_LAST_APPLIED

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_LAST_APPLIED

2.24.0

Consumer: The index of the last log entry that was appended to the log (int).

JGROUPSRAFT_LEADER_ADDRESS

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_LEADER_ADDRESS

2.24.0

Consumer: The Address ot Raft Leader or not (org.jgroups.Address).

JGROUPSRAFT_LOG_SIZE

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_LOG_SIZE

2.24.0

Consumer: The Raft log size in number of entries (int).

JGROUPSRAFT_LOG_SIZE_BYTE

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_LOG_SIZE_BYTE

2.24.0

Consumer: The Raft log size in bytes (int).

JGROUPSRAFT_RAFT_ID

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_RAFT_ID

2.24.0

Consumer: The Raft id of the node (String).

JGROUPSRAFT_EVENT_TYPE

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_EVENT_TYPE

2.24.0

Consumer: The event type, one of org.apache.camel.component.jgroups.raft.JGroupsRaftEventType ENUM.

JGROUPSRAFT_SET_OFFSET

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_SET_OFFSET

2.24.0

Producer: Offset to use in the byte[] buffer to be set().

JGROUPSRAFT_SET_LENGTH

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_SET_LENGTH

2.24.0

Producer: Length to use in the byte[] buffer to be set().

JGROUPSRAFT_SET_TIMEOUT

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_SET_TIMEOUT

2.24.0

Producer: Timeout to be used in set() operation.

JGROUPSRAFT_SET_TIMEUNIT

JGroupsRaftEndpoint.`HEADER_JGROUPSRAFT_SET_TIMEUNIT

2.24.0

Producer: Timeunit to be used in set() operation.

Usage

Using jgroups-raft component with enableRoleChangeEvents=true on the consumer side of the route will capture change in JGrups-raft role and forward them to the Camel route. JGroups-raft consumer processes incoming messages asynchronously.

// Capture raft role changes from cluster named
// 'clusterName' and send them to Camel route.
from("jgroups-raft:clusterName?enableRoleChangeEvents=true").to("seda:queue");

Using jgroups-raft component on the producer side of the route will use the body of the camel exchange (which must be a byte[]) to perform a setX() operation on the raftHandle associated with the endpoint..

// perform a setX() operation to the cluster named 'clusterName' shared state machine
from("direct:start").to("jgroups-raft:clusterName");

Examples

Receive cluster view change notifications

The snippet below demonstrates how to create the consumer endpoint listening to the change role events. By default this option is off.

...
from("jgroups-raft:clusterName?enableRoleChangeEvents=true").to(mock:mockEndpoint);
...

Keeping singleton route within the cluster

The snippet below demonstrates how to keep the singleton consumer route in the cluster of Camel Contexts. As soon as the master node dies, one of the slaves will be elected as a new master and started. In this particular example we want to keep singleton Jetty instance listening for the requests on address` http://localhost:8080/orders`.

JGroupsRaftClusterService service = new JGroupsRaftClusterService();
service.setId("raftId");
service.setRaftId("raftId");
service.setJgroupsClusterName("clusterName");
...
context.addService(service);

from("master:mycluster:jetty:http://localhost:8080/orders").to("jms:orders");
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