Discovery Transport Reference
Using ActiveMQ Classic > Configuring Transports > ActiveMQ Classic 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
discovery:(discoveryAgentURI)?transportOptions
or
discovery:discoveryAgentURI
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">
<transportConnectors>
<transportConnector uri="tcp://localhost:0" discoveryUri="multicast://default"/>
</transportConnectors>
...
</broker>
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
discovery:(multicast://default)?initialReconnectDelay=100
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.
