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)

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

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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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