AggregateReply node

Use the AggregateReply node to mark the end of an aggregation fan-in. This node collects replies and combines them into a single compound message.

Information about the state of in-flight messages is held on storage queues that are controlled by IBM® MQ. If you are using aggregation on an integration server that is managed by an integration node, you must install IBM MQ on the same computer as your integration node in order to use the capabilities that are provided by the AggregateReply node. The storage queues that hold the state information are owned by the queue manager that is associated with the integration node.

If you are using aggregation on an independent integration server, you can use a remote default queue manager to control the system queues, without the need to install IBM MQ on the same machine as the integration server. Interactions between an independent integration server and IBM MQ can use a client connection to a remote queue manager, by using a default policy setting. For more information about using a remote default queue manager, see Using a remote default queue manager and Configuring an integration server to use a remote default queue manager.

For more information about the queues that are required by the AggregateReply node, see Configuring the storage of events for aggregation nodes.

This topic contains the following sections:

Purpose

Aggregation is an extension of the request/reply application model. It combines the generation and fan-out of a number of related requests with the fan-in of the corresponding replies, and compiles those replies into a single aggregated reply message.

The aggregation function is provided by the following three nodes:

  • The AggregateControl node marks the beginning of a fan-out of requests that are part of an aggregation. It sends a control message that is used by the AggregateReply node to match the different requests that have been made. The information that is propagated from the Control terminal includes the integration server identifier, the aggregate name property, and the timeout property. The aggregation information that is added to the message Environment by the AggregateControl node must not be changed.
  • The AggregateRequest node records the fact that the request messages have been sent. It also collects information that helps the AggregateReply node to construct the aggregated reply message. The information that is added to the message Environment by the AggregateRequest must be preserved, otherwise the aggregation fails.
  • The AggregateReply node marks the end of an aggregation fan-in. It collects replies and combines them into a single aggregated reply message.

The AggregateReply node is contained in the Routing drawer of the palette, and is represented in the IBM App Connect Enterprise Toolkit by the following icon:

AggregateReply node icon

When incoming messages are stored by the AggregateReply node before all responses for the aggregation are received, the persistence of the message determines whether the message is retained across a restart.

If, during an aggregation, one or more of the response messages are not received by the AggregateReply node, the normal timeout or unknown message processing deals with the responses that have been received already.

The MQMD.Expiry value of each AggregateReply message is set to -1 in the compound output message. This value is set because the MQMD.Expiry value has no meaning once the reply message is no longer on the IBM MQ Transport and has been stored by the integration server during the aggregation process.

Terminals and properties

When you have put an instance of the AggregateReply node into a message flow, you can configure it; see Configuring a message flow node. The properties of the node are displayed in the Properties view. All mandatory properties for which you must enter a value (those that do not have a default value defined) are marked with an asterisk.

The AggregateReply node terminals are described in the following table.

Terminal Description
In The input terminal that accepts a message for processing by the node.
Failure The output terminal to which the message is routed if a failure is detected during processing.
Unknown The output terminal to which messages are routed when they cannot be identified as valid reply messages.
Out The output terminal to which the compound message is routed when processing completes successfully.
Timeout The output terminal to which the incomplete compound message is routed when the timeout interval that is specified in the corresponding AggregateControl node has expired.
Catch The output terminal to which the message is routed if an exception is thrown downstream and then caught by this node.

The following tables describe the node properties. The column headed M indicates whether the property is mandatory (marked with an asterisk if you must enter a value when no default is defined); the column headed C indicates whether the property is configurable (you can change the value when you add the message flow to the BAR file to deploy it).

The Description properties of the AggregateReply node are described in the following table.

Property M C Default Description
Node name No No The node type (AggregateReply) The name of the node.
Short Description No No   A brief description of the node.
Long Description No No   Text that describes the purpose of the node in the message flow.

The AggregateReply node Basic properties are described in the following table.

Property M C Default Description mqsiapplybaroverride command property
Aggregate Name Yes Yes   A name that is used to associate the fan-in message flow with the fan-out message flow. This value must be contextually unique within an integration server.

This name is also used to identify an Aggregation policy (if one exists) to be used by the node (see Aggregation policy). Specify the name of the policy project and the policy in the format {policyProjectName}:PolicyName.

 aggregateName
Unknown Message Timeout No No 0 The amount of time, in seconds, for which messages that cannot be identified as replies are held before they are propagated to the Unknown terminal.

The default value is zero; if you accept this default value, the timeout is disabled, and unknown messages are propagated to the Unknown terminal upon receipt.

 
Transaction Mode Yes No Selected This property defines the transactional characteristics of this message:
  • If you select the check box (the default), the subsequent message flow is under transaction control. This setting remains true for messages that derive from the output message and are produced by an MQOutput node, unless the MQOutput node explicitly overrides the transaction status. No other node can change the transactional characteristics of the output message.
  • If you clear the check box, the subsequent message flow is not under transaction control. This setting remains true for messages that derive from the output message and are produced by an MQOutput node, unless the MQOutput node has specified that the message must be put under sync point.
 
The Monitoring properties of the node are described in the following table.
Property M C Default Description
Events No No None Events that you have defined for the node are displayed on this tab. By default, no monitoring events are defined on any node in a message flow. Use Add, Edit, and Delete to create, change or delete monitoring events for the node.

You can enable and disable events that are shown here by selecting or clearing the Enabled check box.