MQInput node

Use the MQInput node to receive messages from clients that connect to the broker by using the WebSphere® MQ Enterprise Transport, and that use the MQI and AMI application programming interfaces.

This topic contains the following sections:

Purpose

The MQInput node receives a message from a WebSphere MQ message queue that is defined on the broker's queue manager. The node uses MQGET to read a message from a specified queue, and establishes the processing environment for the message. If appropriate, you can define the input queue as a WebSphere MQ clustered queue or shared queue.

Message flows that handle messages that are received across WebSphere MQ connections must always start with an MQInput node. You can set the properties of the MQInput node to control the way in which messages are received, by causing appropriate MQGET options to be set. For example, you can indicate that a message is to be processed under transaction control. You can also request that data conversion is performed on receipt of every input message.

If you include an output node in a message flow that starts with an MQInput node, the output node can be any one of the supported output nodes, including user-defined output nodes; you do not need to include an MQOutput node. You can create a message flow that receives messages from WebSphere MQ clients and generates messages for clients that use any of the supported transports to connect to the broker, because you can configure the message flow to request that the broker provides any conversion that is necessary.

If you create a message flow to use as a subflow, you cannot use a standard input node; you must use an Input node as the first node to create an In terminal for the subflow.

If your message flow does not receive messages across WebSphere MQ connections, you can choose one of the supported input nodes.

The MQInput node is contained in the WebSphere MQ drawer of the palette, and is represented in the workbench by the following icon:

MQInput node icon

Using the MQInput node in a message flow

Look at the following sample to see how to use the MQInput node:

You can view samples only when you use the information center that is integrated with the Message Brokers Toolkit.

Connecting the terminals

The MQInput node routes each message that it retrieves successfully to the Out terminal. If this action fails, the message is retried. If the backout count is exceeded (as defined by the BackoutThreshold attribute of the input queue), the message is routed to the Failure terminal; you can connect nodes to this terminal to handle this condition. If you have not connected the Failure terminal, the message is written to the backout queue.

If the message is caught by this node after an exception has been thrown further on in the message flow, the message is routed to the Catch terminal. If you have not connected the Catch terminal, the message loops continually through the node until the problem is resolved.

You must define a backout queue or a dead-letter queue (DLQ) to prevent the message from looping continually through the node.

Configuring for coordinated transactions

When you include an MQInput node in a message flow, the value that you set for Transaction mode defines whether messages are received under sync point:
  • If you set the property to Automatic, the message is received under sync point if the incoming message is marked as persistent; otherwise, it is not received under sync point. Any message that is sent subsequently by an output node is put under sync point, as determined by the incoming persistence property, unless the output node has overridden this explicitly.
  • If you set the property to Yes (the default), the message is received under sync point; that is, within a WebSphere MQ unit of work. Any messages that are sent subsequently by an output node in the same instance of the message flow are put under sync point, unless the output node has overridden this explicitly.
  • If you set the property to No, the message is not received under sync point. Any messages that are sent subsequently by an output node in the message flow are not put under sync point, unless an individual output node has specified that the message must be put under sync point.
The MQOutput node is the only output node that you can configure to override this option.

MQGET buffer size

The MQGET buffer size is implemented internally by the broker and you cannot change it. The following description is provided for information only. You must not rely on it when you develop your message flows, because the internal implementation might change.

When the MQInput node initializes, it sets the size of the default buffer for the first MQGET to 4 KB. The MQInput node monitors the size of messages and increases or reduces the size of the buffer:

  1. If an MQGET fails because the message is larger than the size of the buffer, the node immediately increases the size of the buffer to accommodate the message, issues the MQGET again, and zeros a message count.
  2. When 10 messages have been counted since the increase in the size of the buffer, the node compares the size of the largest of the 10 messages with the size of the buffer. If the size of the largest message is less than 75% of the size of the buffer, the buffer is reduced to the size of the largest of the 10 messages. If an MQGET fails during the 10 messages because the message is larger than the size of the buffer, the node takes action 1.

For example, if the first message that the node receives is 20 MB, and the next 10 messages are each 14 MB, the size of the buffer is increased from 4 KB to 20 MB and remains at 20 MB for 10 messages. However, after the 10th message the size of the buffer is reduced to 14 MB.

Terminals and properties

When you have put an MQInput node into a message flow, you can configure the node; see Configuring a message flow node. The properties of the node are displayed in the Properties view. To display the properties of the node in the Properties dialog, either double-click the node, or right-click the node and click Properties. All mandatory properties that do not have a default value defined are marked with an asterisk.

The terminals of the MQInput node are described in the following table.

Terminal Description
Failure The output terminal to which the message is routed if an error occurs. Even if the Validation property is set, messages propagated to this terminal are not validated.
Out The output terminal to which the message is routed if it is successfully retrieved from the WebSphere MQ queue.
Catch The output terminal to which the message is routed if an exception is thrown downstream and 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 MQInput node are described in the following table.

Property M C Default Description
Node name No No The node type, MQInput 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 Basic properties of the MQInput node are described in the following table.

Property M C Default Description
Queue name Yes Yes   The name of the WebSphere MQ input queue from which this node retrieves messages (using MQGET) for processing by this message flow. You must predefine this WebSphere MQ queue to the queue manager that hosts the broker to which the message flow is deployed.

The Advanced properties of the MQInput node are described in the following table. Set these properties to determine how the message is processed, such as its transactional characteristics. Many of these properties map to options on the MQGET call.

Property M C Default Description
Transaction mode Yes No Yes This property controls whether the incoming message is received under sync point. Valid values are Automatic, Yes, and No.
  • If you select Automatic, the incoming message is received under sync point if it is marked persistent, otherwise it is not received under sync point. The transactionality of any derived messages that are sent subsequently by an output node is determined by the incoming persistence property, unless the output node has overridden transactionality explicitly.
  • If you select Yes, the incoming message is received under sync point. Any derived messages that are sent subsequently by an output node in the same instance of the message flow are sent transactionally, unless the output node has overridden transactionality explicitly.
  • If you select No, the incoming message is not received under sync point. Any derived messages that are sent subsequently by an output node in the message flow are sent non-transactionally, unless the output node has specified that the messages must be put under sync point.
Order mode Yes No Default The order in which messages are retrieved from the input queue and processed. Valid values are Default, By User ID, and By Queue Order. This property has an effect only if the message flow property Additional instances on the Instances tab, is set to greater than zero; that is, if multiple threads read the input queue. Valid values are:
  • Default. Messages are retrieved in the order that is defined by the queue attributes, but this order is not guaranteed because the messages are processed by the message flow.
  • By User ID. Messages that have the same UserIdentifier in the MQMD are retrieved and processed in the order that is defined by the queue attributes; this order is guaranteed to be preserved when the messages are processed. A message that is associated with a particular UserIdentifier that is being processed by one thread, is completely processed before the same thread, or another thread, can start to process another message with the same UserIdentifier. No other ordering is guaranteed to be preserved.
  • Start of changeBy Queue Order. Messages are retrieved and processed by this node in the order that is defined by the queue attributes; this order is guaranteed to be preserved when the messages are processed. This behavior is identical to the behavior that is exhibited if the message flow property Additional instances is set to zero. However, if you set Order mode to By Queue Order then redeploy the message flow, additional instances that are already running are not released. Therefore, when you set Order mode to By Queue Order, either stop and restart the message flow, or run the mqsireload command for the execution group after you redeploy the flow.End of change

Start of changeFor more details about using this option, see Receiving messages in a WebSphere MQ message group.End of change

Logical order Yes No Selected If you select this check box, messages are received in logical order, as defined by WebSphere MQ. This option maps to the MQGMO_LOGICAL_ORDER option of the MQGMO of the MQI.

If you clear the check box, messages that are sent as part of a group are not received in a predetermined order. If a broker expects to receive messages in groups, and you have not selected this check box, either the order of the input messages is not significant, or you must design the message flow to process them appropriately.

You must also select Commit by message group if you want message processing to be committed only after the final message of a group has been received and processed.

More information about the options to which this property maps is available in the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Start of changeFor more details about using this option, see Receiving messages in a WebSphere MQ message group.End of change

All messages available Yes No Cleared Select All messages available if you want message retrieval and processing to be done only when all messages in a single group are available. This property maps to the MQGMO_ALL_MSGS_AVAILABLE option of the MQGMO of the MQI. Clear this check box if message retrieval does not depend on all of the messages in a group being available before processing starts.

More information about the options to which this property maps is available in the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Match message ID No No   A message ID that must match the message ID in the MQMD of the incoming message. Enter a message identifier if you want the input node to receive only messages that contain a matching message identifier value in the MsgId field of the MQMD.

Enter an even number of hexadecimal digits (characters 0 to 9, A to F, and a to f are valid) up to a maximum of 48 digits. If the matching message identifier that you enter is shorter than the size of the MsgId field, Match message ID is padded on the right with X'00' characters. This property maps to the MQMO_MATCH_MSG_ID option of the MQGMO of the MQI.

Leave this property blank if you do not want the input node to check that the message ID matches.

More information about the options to which this property maps is available in the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Match correlation ID No No   A correlation ID that must match the correlation ID in the MQMD of the incoming message. Enter a message identifier if you want the input node to receive only messages that contain a matching correlation identifier value in the CorrelId field of the MQMD.

Enter an even number of hexadecimal digits (characters 0 to 9, A to F, and a to f are valid) up to a maximum of 48 digits. If the ID that you enter is shorter than the size of the CorrelId field, it is padded on the right with X'00' characters. This property maps to the MQMO_MATCH_CORREL_ID option of the MQGMO of the MQI.

Leave this property blank if you do not want the input node to check that the CorrelID matches.

More information about the options to which this property maps is available in the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Convert Yes No Cleared If you select this check box, WebSphere MQ converts data in the message to be received, in conformance with the CodedCharSetId and Encoding values set in the MQMD. Select Convert if you want WebSphere MQ to perform data conversion on the message when it is retrieved from the queue. This option is useful if you are handling messages in the BLOB domain, or are using a user-defined parser. Do not select this option if you are parsing messages with the XML or MRM domains, because the parser does the conversion.

WebSphere MQ converts the incoming message to the encoding and coded character set that is specified in the MQMD that the input node supplies on the MQGET call to retrieve the message from the input queue. The broker uses the MQGMO_CONVERT option on the MQGET call; typical rules for WebSphere MQ conversion apply. The values that you specify in the Convert encoding and Convert coded character set ID options are used in the MsgDesc Encoding and CCSID fields in the MQGET call. WebSphere MQ can convert the incoming message only if the MQMD Format field is a built-in WebSphere MQ value that identifies character data, or if a data conversion exit exists in WebSphere MQ.

This property maps to the MQGMO_CONVERT option of the MQGMO of the MQI.

Clear the check box if you do not want WebSphere MQ to convert the message.

If you select this check box, you can also specify:

  • Convert encoding. Enter the number that represents the encoding to which you want to convert numeric data in the message body. Valid values include:
    • Windows platform 546 for DOS and all Windows® systems
    • Linux platformUNIX platform 273 for all Linux® and UNIX® systems
    • z/OS platform 785 for z/OS® systems
    The encoding is used only in the following circumstances:
    • If a user-defined WebSphere MQ data conversion exit uses the encoding.
    • If the built-in WebSphere MQ conversion exit uses the encoding to convert messages in any of the predefined WebSphere MQ formats.
    If you specify an incorrect value, no conversion is done.
  • Convert coded character set ID. Enter the value that represents the character set identifier to which you want to convert character data in the message body.

    If you specify an incorrect value, no conversion is done.

For more information about WebSphere MQ data conversion, and why you might choose to use this option, see the Application Programming Guide section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page. For further information about the values that you can specify for Convert encoding and Convert coded character set ID, see the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Convert encoding No No   The representation used for numeric values in the message data, expressed as an integer value. This property is valid only if you have selected Convert.
Convert coded character set ID No No   The coded character set identifier of character data in the message data, expressed as an integer value. This property is valid only if you have selected Convert.
Commit by message group Yes No Cleared This property controls when a transaction is committed when processing messages that are part of a message group. If you select the check box, the transaction is committed when the message group has been processed. If you leave this check box cleared, a commit is performed after each message has been propagated completely through the message flow.

This property is relevant only if you have selected Logical order.

Set the Order mode property to By Queue Order if the messages in a group must be retrieved and processed in the order in which they are displayed on the queue.

z/OS serialization token No No   On z/OS only: A user-defined token for serialized application support. The value that is specified must conform to the rules for a valid ConnTag in the WebSphere MQ MQCNO structure. Enter a serialization token if you want to use the serialized access to shared resources that is provided by WebSphere MQ.

The value that you provide for the serialization token must conform to the rules described in the Application Programming Reference section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

For more information about serialization and queue sharing on z/OS, see the Concepts and Planning Guide section of the WebSphere MQ Version 6 information center online, or the Version 5.3 book on the WebSphere MQ library Web page.

Topic No Yes   The default topic for the input message. You can associate a message with a publish/subscribe topic by using this property. You can enter any characters as the topic name. When messages pass through the MQInput node, they take on whatever topic name you have entered. (If you are using publish/subscribe, you can subscribe to a topic and see any messages that passed through the MQInput node and were published under that topic name.) If the incoming message has an MQRFH2 header, you do not need to set a value for the Topic property because the value can be obtained from the <psc> folder in the MQRFH2 header; for example:
<psc><Topic>stockquote</Topic></psc>
If you set a Topic property value, and that value differs from the <Topic> value in the MQRFH2 header, the value in the MQRFH2 header takes precedence.
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Last updated : 2009-01-07 15:39:42

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