ActiveMQ–Discovery

• From the book
• Discovery
• is a process of detecting remote broker services.
• Clients usually want to discover all available brokers.
• Brokers usually want to find other available brokers so that they can establish a network of brokers.

Apache ActiveMQ ™ – Discovery

This document is a little bit old, because it was using maven 1.

• Discovery Agents
• ActiveMQ uses an abstraction called a Discovery Agent to detect remote services such as remote brokers. We can use discovery for JMS clients to auto-detect a Message Broker to connect to, or to provide Networks of Brokers
• Two kinds of discovery agent
• Multicast
• Zeroconfig
• LDAP Discovery
• Trying out discovery

Apache ActiveMQ ™ -- Discovery Transport Reference

• 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.
• Note that to be able to use Discovery to find brokers, the brokers need to have the multicast discovery agent enabled on the broker.
• <transportConnector … discoveryUri=”multicast://default” />
• discovery:(discoveryAgentURI)?transportOptions
• discovery:discoveryAgentURI
• Example URI:
• discovery:(multicast://default)?initialReconnnectDelay=100

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)