MSMQ - Wait for Message

Declaration

<AMMSMQ ACTION="wait_message" REMOTEMACHINE="text" 
QUEUENAME="text" RESULTDATASET="text" MESSAGELABEL="text" 
TIMEOUT="number" RESULTVARIABLE="text" ENCODING="text (options)" 
REMOVEMESSAGE="YES/NO" />

Description: Suspends task execution and waits for a specified message to exist in the selected queue. Upon arrival, the message is retrieved and task execution continues. A dataset is populated with specific information about the message and a variable is populated with the message text.

IMPORTANT: MSMQ activities are performed using the Microsoft Message Queuing engine, therefore, MSMQ must be installed on the computer that will run such operations. MSMQ software comes bundled with all Microsoft Windows operating systems from Windows 2000 up to, and including Windows 8, however, it is not installed by default.

Practical Usage

The Retrieve message activity throws an error if the specified message does not exist in the queue. Use this activity before the Retrieve message activity to allow the task to wait at the current step until a message arrives.

General Parameters

Property

Type

Required

Default

Markup

Description

Local computer

        

If enabled, specifies that this activity will be performed on the local computer (enabled by default). This is a visual mode parameter used only during design time, therefore, contains no markup.

Another computer

Text

No

(Empty)

  1. REMOTEMACHINE="CompName"

  2. REMOTEMACHINE="xxx.xxx.xxx.xxx

If enabled, specifies the host name or IP address of the remote computer that this activity will be performed on. When this parameter is enabled, the Local computer parameter is ignored.

Message queue

Text

Yes

(Empty)

QUEUENAME=

"HostName\QueueName"

The name of the message queue to retrieve message from. The message queue name consists of the compute name, an optional PRIVATE$ keyword that indicates whether it is a private queue and the name of the queue.

Public queue example: ComputerName\QueueName

Private queue example: ComputerName\PRIVATE$\QueueName

Message body type

Text (options)

No

Text

NULL

Indicates whether the message contents should be retrieved as text populated into a variable or saved to a specific text file. Different parameters become active depending on which option is selected. The available options are:

  • Text (default): Message will be in text format and saved to a variable.

  • File: Message will be saved directly to a text file.

Timeout (minutes)

Number

No

5

TIMEOUT="7"

The maximum number of minutes that this activity will wait for the specified message to arrive before throwing a time out error.

Remove message from queue

Yes/No

No

No

REMOVEMESSAGE="YES"

If set to YES, specifies that the message being retrieved will be removed from the queue upon arrival. This parameter is set to NO by default.

Populate dataset with message information

Text

No

(Empty)

RESULTDATASET="theDataset"

The name of a dataset to create and populate with information regarding the message to wait for. More information regarding this parameter can be found below under Datasets.

Encoding

Text (options)

No

UTF8

  1. ENCODING="UTF8"

  2. ENCODING="UTF7"

  3. ENCODING="ASCII"

The character encoding method to use. This parameter is only available if the Message body type parameter is set to Text. The available options are:

  • UTF8 (Default)

  • UTF7

  • ASCII

Populate variable with message text

Text

Yes if message is saved to variable

(Empty)

RESULTVARIABLE="theVar"

Indicates an existing variable in which to populate the contents of the message body. This parameter is only available if the Message body type parameter is set to Text.

File

Text

Yes if message is saved to file

(Empty)

MESSAGEFILE=

"c:\temp\Message.txt"

The path and file name of the text file in which to save the body of the message. If the file does not exist. It will be created at runtime. This parameter is only available if the Message body type parameter is set to File.

Overwrite if exists

Yes/No

No

No

OVERWRITE="YES"

Specifies that if a file with the same name already exists, it will be overwritten with the new message body. This parameter is only available if the Message body type parameter is set to File.

Description tab - A custom description can be provided on the Description tab to convey additional information or share special notes about a task step.

Error Causes tab - Specify how this step should behave upon the occurrence of an error. (Refer to Task Builder > Error Causes Tab for details.)

On Error tab - Specify what AWE should do if this step encounters an error as defined on the Error Causes tab. (Refer to Task Builder > On Error Tab for details.)

Datasets

The sample AML code below can be copied and pasted directly into the Steps panel of the Task Builder.

A dataset is a multiple column, multiple row container object. This activity creates and populates a dataset containing a specific set of fields. The table below describes these fields (assuming the dataset name assigned was theDataset).

Name

Type

Return Value

theDataset.Label

Text

Returns the label text included with the message.

theDataset.ID

Text

Returns the message ID, which is a 20-byte Message Queuing-generated identifier.

theDataset.LookupID

Text

Returns the Lookup ID, which is a 64-bit ID that is assigned to the message when it is placed in the queue.

theDataset.SentTime

Date/Time

Returns the date/time when the message was sent.

theDataset.ArriveTime

Date/Time

Returns the date/time when the message was retrieved.

theDataset.Priority

Text

Returns the message priority.

theDataset.SourceMachine

Text

Returns the machine name where the message originated from.

Example

The sample AML code below can be copied and pasted directly into the Steps panel of the Task Builder.

Description: A simple task that creates a queue, sends message to that queue, waits for the message, retrieves the message and purges the queue.

<!-- Create variable --><AMVARIABLE NAME="theVar" />
<!-- Create private queue -->
<AMMSMQ PRIVATE="YES" NAME="myPrivateQueue" 
RESULTDATASET="privateQueueData" />
<!-- Send message to queue -->
<AMMSMQ ACTIVITY="send_message" 
QUEUENAME="vmwinvx64\Private$\myPrivateQueue" MESSAGELABEL="Support" 
MESSAGEFILE="C:\Users\techsupport\Desktop\cd.txt" />
<!-- Wait for message -->
<AMMSMQ ACTIVITY="wait_for_message" 
QUEUENAME="vmwinvx64\Private$\myPrivateQueue" RESULTDATASET="data" 
MESSAGELABEL="Support" RESULTVARIABLE="theVar" />
<!-- Retrieve message -->
<AMMSMQ ACTIVITY="retrieve_message" 
QUEUENAME="vmwinvx64\Private$\myPrivateQueue" RESULTDATASET="data" 
MESSAGEFILE="C:\Users\techsupport\Desktop\rt.txt" OVERWRITEFILE="YES" 
REMOVEMESSAGE="YES" />
<!-- Purge queue -->
<AMMSMQ ACTIVITY="delete_queue" 
QUEUENAME="vmwinvx64\Private$\myPrivateQueue" />