Discovery Transport Reference

Using ActiveMQ > Configuring Transports > ActiveMQ Connection URIs > Discovery Transport Reference

The Discovery Transport

The Discovery transport works just like the Failover transport, except that it uses a discovery agent to locate the list of uri to connect to. The Discovery transport is also used by the Fanout transport for discovering brokers to send a fanout message to.

Configuration Syntax




Note that to be able to use Discovery to find brokers, the brokers need to have the multicast discovery agent enabled on the broker.

To configure discovery in a Broker you should use the Xml Configuration. Here is an example of using discovery. Its basically something like the following (see the discoveryUri)

<broker name="foo">
    <transportConnector uri="tcp://localhost:0" discoveryUri="multicast://default"/>

Transport Options

Option Name|Default Value|Description —|—|— reconnectDelay|10|How long to wait for discovery initialReconnectDelay|10|How long to wait before the first reconnect attempt to a discovered url maxReconnectDelay|30000|The maximum amount of time we ever wait between reconnect attempts useExponentialBackOff|true|Should an exponential backoff be used btween reconnect attempts backOffMultiplier|2|The exponent used in the exponential backoff attempts maxReconnectAttempts|0|If not 0, then this is the maximum number of reconnect attempts before an error is sent back to the client group|default|an identifier for the group to partition multi cast traffic among collaborating peers; the group forms part of the shared identity of a discovery datagram (since 5.2)

Example URI

Applying parameters to discovered transports

From 5.4, transport parameters in the URI will also be applied to discovered transports if they are prefixed with discovered.; For example, adding the discovered.connectionTimeout parameter to the URI will apply the parameter to every discovered TCP transport, even though this parameter is not a Discovery transport option.

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