WebSphere Message Brokers
File: ac04750_
Writer: Catherine Tucker

Reference topic

This build: July 31, 2007 21:17:36

AggregateReply node

This topic describes the AggregateReply node.

This topic contains the following sections:

Purpose

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.

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 broker 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 workbench 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 survives 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 WebSphere MQ Transport and has been stored by the broker during the aggregation process.

Using this node in a message flow

Look at the following samples to see how to use this node: You can view samples only when you use the information center that is integrated with the Message Brokers Toolkit.

Configuring the AggregateReply node

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.

Configure the AggregateReply node as follows:

  1. Optional: On the Description tab, enter a short description, a long description, or both. You can also change the name of the node on this tab.
  2. On the Basic tab:
    1. Enter a value for the Aggregate Name. This name is used to associate the fan-in message flow with the fan-out message flow. This value must be contextually unique within a broker. This property is mandatory; you must enter a value.
    2. Enter a value, in seconds, for Unknown Message Timeout. This value specifies the amount of time for which messages that cannot be identified as valid replies are held before being propagated to the unknown terminal.

      If you enter zero, or do not enter a value, the timeout is disabled and unknown messages are propagated to the unknown terminal upon receipt.

    3. Select Transaction Mode to define 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 output 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 output by an MQOutput node, unless the MQOutput node has specified that the message should be put under syncpoint.

Terminals and properties

The AggregateReply node terminals are described in the following table.

Terminal Description
Control The input terminal that accepts control messages that are sent by a corresponding AggregateControl node.

The Control terminal is deprecated in Version 6.0; to use connections to the Control terminal, see Using control messages in aggregation flows.

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 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
Aggregate Name Yes Yes   A name that is used to associate the fan-in message flow with the fan-out message flow. This property is mandatory.
Unknown Message Timeout No No 0 The amount of time for which messages that cannot be identified as replies are held before being propagated to the unknown terminal.

z/OS platform On z/OS, if the Unknown Message Timeout property is not set to zero, set the queue manager parameter EXPRYINT to 5.

Transaction Mode Yes No Selected If the check box is selected, messages that are propagated by this node are put transactionally.
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Copyright IBM Corporation 1999, 2007Copyright IBM Corporation 1999, 2007. All Rights Reserved.
This build: July 31, 2007 21:17:36

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