Asynchronous parallel processing

To reduce the overall processing time of an aggregation you can call multiple services concurrently, instead of processing each service in series.

A branched aggregation block such as shown in Figure 1 will not, by default, be processed in parallel.

Figure 1. Branched aggregation block

To enable multiple service invocations to occur before the processing of response messages you must complete the following steps:

Specify the Invocation style property on each Service Invoke mediation primitive to be Async, as shown in Figure 2.
Figure 2. Service invoke mediation primitive property details
If the mediation flow component is configured to run under a Global Transaction, ensure that the component Reference that is associated with the Service Invoke mediation primitive has a qualifier for Asynchronous invocation that is set to Call, as shown in Figure 3.
Figure 3. Setting the Asynchronous invocation qualifier

If a global Transaction is configured, and the Asynchronous invocation setting is Commit, then request messages are never sent, because the service request cannot be sent until the transaction commits.
An additional step of configuration is required when the aggregation block processes in Iterate mode. Using the Fan Out mediation primitive you can specify the number of concurrent unprocessed requests that can be made before the response messages are processed. By specifying an integer value in the Check for asynchronous responses after X messages have been fired field, as shown in Figure 4, the runtime completes the processing of X requests and then processes the response messages before further iterations are processed. This way you can restrict the number of parallel requests being processed by back-end services, such as the Payroll and HR services. To process all entries within the array before the handling of any response messages, select Check for asynchronous responses after all messages have been fired.
Figure 4. Setting the number of requests that should be processed

By using the Invocation style and Asynchronous invocation settings both Payroll and HR services are called before either of the response messages being processed.