--- title: "Setting Up Message Handlers" slug: "setting-up-messaging-overview" description: "This document shows how to set up Decisions to work with a messaging system. The included example discusses how to setup RabbitMQ. The Decisions Messaging system is built on plugins and can be extended via the SDK. " updated: 2025-06-17T18:37:09Z published: 2025-06-17T18:37:09Z --- > ## Documentation Index > Fetch the complete documentation index at: https://documentation.decisions.com/llms.txt > Use this file to discover all available pages before exploring further. # Setting Up Message Handlers ## Setting up a Listener/Message Handler Message Handlers in Clustered EnvironmentIn a clustered environment, users must configure the Message Handler on only one node. All the other nodes in the cluster automatically inherit the configuration. To subscribe to messages in a queue, a **Message Handler Flow** needs to be configured. This will be used to interpret and run actions on messages received from the queue. The desired Message Queue module must be installed and a dependency to that module needs to be made in the Project the Handler Flow will be created in. The following example will demonstrate how to pull messages from a configured [RabbitMQ](/v9/docs/rabbitmq-message-services). A similar process will be involved for other message queues. 1. From a Project, go to **Manage > Jobs & Events > Messaging > Queue Handlers**. Click the ADD MESSAGE HANDLER action and then Create New. 2. Navigate to the **Properties Panel**for the Flow. Under the **SETTINGS** category, you will see that the drop-down menu under **Behavior Type**has the type******Message****Queue****Handler****Flow**. Choosing this Flow behavior provides three additional Flow Inputs; Message, Handler Id, and Headers. The Message Input contains the Payload (Byte[]), Id (String), and MessageDateTime (DateTime) Inputs.![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/image-1750185068710.png) 3. From**Toolbox,**navigate to **DATA > TEXT**and attach a **Get String From UTF 8 Bytes**step to the **Start**step. 4. On the Properties panel under INPUTS, click **Unknown**and select **Flow Data**. Click **Message**, select **Payload**, and click DONE. RabbitMQ Messages are typically encoded in UTF8. Other messengers may use Base 64, Ascii, or a different UTF decoding step to help decode the Payload. ![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/image-1750185184644.png) 5. Attach a **Show****Popup** step from **Toolbox > FAVORITE STEPS** to the workspace. Map **GetStringFromUTF8Bytes1_Output**to **Message**, and **Constant**map the desired **Subject**. This is merely to demonstrate the the message is being received and is not required for functionality. ![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/image-1750185329739.png) 6. Click **Save**to save changes to****the Flow. --- ## Subscribing to a Queue The messaging system Queue will need to be configured in order for Decisions to subscribe to it. 1. If a Queue has not been added, navigate to****the desired**Project > Manage > Jobs & Events > Message Queues**. Click ADD RABBIT QUEUE from the **Global****Action****Bar**. 2. From the **Add Rabbit Queue**window, define the Message Queue parameters and click **SAVE**. ![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2025-01-13_11h05_09.png) --- ## Connect Processing Flow to Queue The following demonstrates a **Message Queue Handler.** The setting options can be overridden to specify different servers or queues by navigating to **[Project Name] > Manage** **> Jobs and Events > Messaging > Queues**, creating a message queue, and selecting the **Override Server Info** option. 1. Navigate to the desired**Project > Manage****> Jobs and Events > Message Queue Handlers**. Click **ADD MESSAGE HANDLER**. 2. From the **Add Message Handler** window, define the desired **Handler****Name**, select the desired **Message****Handling**behavior, define the **Active****Flow****Count**, create or pick the **Message****Handler****Flow**, then select the **Message****Queue**. Click **SAVE.**  ![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/2025-01-13_11h06_10.png) | Configuration Options | Description | | --- | --- | | Handler Name | Name to display in Decisions. | | Message Handling | Sets the Message Handling mode to lease the message (lock), lease the message temporarily (lock with auto timeout), remove it after processing (pop), or use it but leave it on the Queue (peek). | | | Lease | Receives a message from the queue. Decisions will send an acknowledgment to the queue once the message has completed processing. | | | Lease w/ Expire | Shares the same behavior as leased, with the addition of sending not acknowledged signals. There are two ways for messages can time out: The Message Handler Flow throws an exception or the communication between Decisions and the message server is broken. | | | Get | Retrieves a message from the queue. The message will be processed, and no acknowledgment will be sent to the queue. | | | Get and Remove | Retrieves and removes a message from the queue without sending an acknowledgment. | | Active Flow Count | The maximum number of simultaneous Messages that Decisions will process. | | PICK HANDLER FLOW | The Flow is used to process Messages that appear in the Queue. | | Message Queue | The Queue for the Handler to listen on was configured in System Settings. | ### Thread Fine-Tuning Starting in v9.4 users are able to configure how many threads are created to handle message queues. They can also specify how long those threads should exist when they are idle. This can help increase performance by dismissing unneeded threads. The settings are found when first creating a Message Handler or when editing its registration entity. ![](https://cdn.document360.io/6ef8bcc1-6489-4486-9ad1-83acff7e5df0/Images/Documentation/Screenshot%202024-10-22%20154123.png) 1. Checking the Fine-Tune Thread Behavior option will bring up the setting for configuring the maximum number of threads to create field. It will also cause the Stop Threads When Idle option to appear. 2. Checking the Stop Threads When Idle option opens up the options for idle threads and the sliders to choose how long the thread can remain idle. | Setting | Description | | --- | --- | | Max. Number of New Threads to Create When Busy | Sets the maximum number of threads that will be created when the Message Queue is running. Default value is 5. | | Number of Idle Threads to Keep Alive | Threads go into an idle state after they handle a Message as they wait for the next message. This will limit how many threads will remain in an idle state. Otherwise threads will terminate based on the amount of time set. | --- ## Feature Changes | Description | Version | Release | Developer Task | | --- | --- | --- | --- | | Added in settings to manage message queue thread. | [9.4](https://documentation.decisions.com/v99/docs/version-94x-release-notes) | October 2024 | [DT-039962] | | Right clicking on a message queue folder will only show relevant actions now. | [9.4](https://documentation.decisions.com/v99/docs/version-94x-release-notes) | October 2024 | [DT-039961] | For further information on Modules, visit the [Decisions Forum](https://community.decisions.com/categories/Modules).