This section describes how to configure the JMS inbound protocol with ActiveMQ.
Configuring with ActiveMQ
Follow the instructions below to set up and configure Apache ActiveMQ as the JMS server:
- Download and set up Apache ActiveMQ. For more information, see the ActiveMQ getting started guide.
Set up WSO2 EI. For information on getting the WSO2 EI set up, see Installation Guide.
ActiveMQ should be up and running before starting WSO2 EI.
- Copy the following client libraries from the
<AMQ_HOME>/libdirectory to the
ActiveMQ 5.8.0 and above
Earlier version of ActiveMQ
- Next, configure the inbound listener in the ESB.
Configuring the JMS inbound listener
Following is a sample JMS inbound listener configuration:
The sample configuration above does not address the problem of transient failures of the ActiveMQ message broker. For example, if we consider a scenario where the ActiveMQ broker goes down for some reason and comes back up after a while, the ESB profile of WSO2 EI will not reconnect to ActiveMQ but instead it will throw errors when requests are sent to the ESB profile until it is restarted.
In order to tackle this issue you need to specify the following as the
java.naming.provider.url parameter value.
Setting this as the value for the
java.naming.provider.url parameter will make sure that re-connection takes place when ActiveMQ is up and running. The failover prefix is associated with the failover transport of ActiveMQ. For more information, see Failover Transport.
Now you have an instances of ActiveMQ and the inbound endpoint of the ESB profile configured, up and running.
Setting up delayed delivery
This explains how you can set up delayed delivery in the broker.
Setting up delayed delivery for topics
When a topic has one or more subscriptions and when you need to apply a global delay to all the subscriptions of it, you can set it up in the broker by defining global policies.
Setting up delayed delivery for subscribers
The client who connects can override the global policies you set up for topics. When configuring the
java.naming.provider.url parameter in the JMS Inbound Endpoint, you can pass the re-delivery policy property as a query String. For a detailed description on the policy properties, go to Apache ActiveMQ Documentation.
For example, when configuring a Script mediator, if you need to rollback the message four times upon an error with a one second delay, set the
java.naming.provider.url property as follows.
redeliveryDelay property specifies the re-delivery delay in milliseconds and the
maximumRedeliveries property defines the number of times the retry should occur. For more information on these properties, go to Apache ActiveMQ Documentation.
In ActiveMQ 5.9.0, although the broker properly identifies the re-delivery times, the broker does not delay the messages as expected. Thus, it will not enforce even the global level delay.
The final Inbound Endpoint configuration with the re-delivery delay and number of times you defined will be as follows:
Enforcing a delay per message
There are not an out of the box feature available in ActiveMQ to enforce delay per message. The re-delivery policies are defined by the Initial Context Factory when it establishes the connection and it does not happen on a per message basis.
However, before rolling back, you can enforce a delay using the Script mediator in the error sequence as follows.
Then, the sample sequence is as follows.
The Script mediator holds the end of the sequence for the defined number of times before it reaches the end. The
rollback() operation occurs once the sequence ends. Hence, this holds onto the rollback operation for a specified period of time. Further, this re-delivers the message only after the specified duration.
Therefore, in the above example, the
java.lang.Thread.sleep(10000) property schedules the message back after 10 seconds.
There is no grantee that the re-scheduling will occur as soon as the defined time period in the sleep(..) operation ends. Also, it considers the delay of any re-deliveries. For example, if the re-delivery delay is x seconds and the sleep time is y seconds, then the overall time for the message to get re-delivered is x+y seconds.
Also you can use the filter mediator and switch mediator to do the filtering as shown in the example below, when you need to define re-delivery intervals based on the message error condition dynamically.