Chapter 6. Network Connections

AMQ Interconnect provides listeners that accept client connections. A client connecting to a router listener uses the same methods that it would use to connect to a broker. From the client’s perspective, the router connection and link establishment are identical to broker connection and link establishment.

Several types of listeners are defined by their role.

You can configure AMQ Interconnect to create outbound connections to messaging brokers or other AMQP entities using connectors. A connector is defined with the network address of the broker and the name or names of the resources that are available in that broker. When a router connects to a broker through a connector, it uses the same methods a normal messaging client would use when connecting to the broker.

Several types of connectors are defined by their role.

When a router connects to a broker, the broker might provide backup connection data that the router can use if the primary connection fails. If the primary connection fails, the router attempts to reconnect by using a combination of the primary and — if provided — backup connections in round-robin fashion until the connection is successful. For more information about viewing the backup connection data provided by the broker, see Section 10.3.2.2, “Managing Connectors”.

In AMQ Interconnect, a connector attempts to maintain an open network transport connection to the configured remote host and port. If the connection cannot be established, the connector will continually retry until the connection is established. If an established connection is lost, the connector shall immediately attempt to re-establish the connection.

Connection Failover is a mechanism by which the remote host can provide alternate connection information for the connector to use in the event the established connection is lost. In this case, rather than attempting to re-establish the connection to the same host, the connector shall try the alternate hosts as well. This is useful in the case where the remote host is formed by a cluster or array of servers providing the same service.

AMQ Interconnect can participate in Connection Failover as both a client (initiator of transport connections) and a server (recipient of transport connections). In the client role, connectors shall always honor the failover lists provided by connected servers. As a server, a listener may be configured to provide a failover list to the clients that connect to it.

Listener attribute failoverUrls is an optional component that contains a comma-separated list of URLs to be used as backups for this listener. Each URL is of the form:

[(amqp|amqps|ws|wss)://]host_or_ip[:port]

[(amqp|amqps|ws|wss)://]host_or_ip[:port]

When a client establishes a connection to this listener, it will be provided with this list of backup URLs to be used in the event that this connection is lost.

As an example, a listener may be configured like this:

listener {
    host: primary.domain.com
    port: amqp
    failoverUrls: secondary.domain.com:20000, tertiary.domain.com
    .
    .
    .
}

listener {
    host: primary.domain.com
    port: amqp
    failoverUrls: secondary.domain.com:20000, tertiary.domain.com
    .
    .
    .
}