About RabbitMQ Message Services
  • 04 Aug 2022
  • 4 Minutes to read
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About RabbitMQ Message Services

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Overview

The Message Queue architecture allows a designed system to handle large client requests by placing them into a queue to process asynchronously. Message Queues can be placed between an application server and a database server. This setup lets the application server send a response to the requesting user and place the request in the Message Queue. The database server can then pick up the request from the Message Queue and process that transaction.

The Rabbit Message Queue (RabbitMQ) is a messaging system for application-to-application communication. The RabbitMQ module adds the capability to the Decisions Messaging Service, which lets users connect to built-in Flow steps to manage a Rabbit MQ. The RabbitMQ module allows users to queue subscribers so that the Flow can work and push messages to Queues using Flow steps. Users can also integrate with RabbitMQ, take in a message, and then convert the message to any type of data for processing.

Prerequisites


Configuration

  1. Navigate to Systems > Jobs and Events. Right-click Message Queues and select Add Rabbit Queue.
      
  2.  On the Add Rabbit Queue dialog window, enter a Display Name and the Queue Name. Configure any other options necessary and click SAVE.
    Configuration OptionsDescription
    DEFINITION

    Display NameDetermines how the Queue's name displays.

    Queue NameThe name of the Queue that the system references.

    Is Durable QueueWhen Decisions create the Queue, this setting keeps the Message permanently. If no one is using the Queue, this setting will reclaim the Message Queue and recreate the Message.

    Auto DeleteInstructs the Message Server to delete the Queue when its last consumer disconnects.

    Override Server InfoAllows the specific server to be set up. This includes the Server IP or Name as well as the Port number.

    Override Virtual HostAllows the ability to set up multiple virtual hosts allowing the user to host Decisions. The Virtual host runs in order to keep the actual production from interference.

    Server IP or NameSpecify the IP address or server name

    Use Default PortAllows the user to enable using the default port

    Use SSLEnables use of SSL

    Override Queue CredentialsProvides the ability to set up a username and password that can be assigned, allowing specific credentials to be required
    QUEUE ARGUMENTS

    Queue TypeSpecifies the queue type (classic, quorum)

    Dead Letter ExchangeThe queue for undelivered or failed messages

    Dead Letter Routing KeyRouting key for dead letter

    Maximum Queue LengthSets the maximum queue length

    Message TTL (msec)Sets the message time-to-live in milliseconds

  3. Navigate to System > Jobs and Events > Message Queues. Right-click on the Message Queue and select Control. Select Test Queue to verify the connection with RabbitMQ. If successful, a dialog popup screen will appear displaying the test result.
    Configuration OptionsDescription
    Disable QueueDisables the queue
    Resync QueueRecreates the Message Queues if necessary and re-synchronizes with the Message Server
    Start QueueStarts processing Messages on the Message Queues (if stopped)
    Stop QueueStops processing Messages on the Message Queues. The Message Server will hold any unprocessed messages.
    Test QueueReads the number of awaiting Messages on the Queue and shows a pop-up with the amount of awaiting Messages

  4. Navigate to System > Jobs and Events > Message Queue Handlers. Click ADD MESSAGE HANDLER.
    Configuration OptionsDescription
    Handler NameName to display in Decisions
    Message HandlingSets 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)

    LeaseTemporarily pulls the message from the queue; The message cannot be pulled while it is leased but will remain in the queue. If the message fails, the lease is removed and made available in the queue. If the message passes, it is removed from the queue. Slightly slower than Get and Remove.

    Lease w/ ExpireThe lease times out, and the message becomes deliverable again in one of two scenarios: the message handler's flow throws an exception.  Decisions sends the message server a NAck (not acknowledged) signal for that message, or the communications channel between Decisions and the message server is broken.

    GetMessages will be pulled from the queue but NOT REMOVED, and the Handler Flow will run. It will not check to see if the Handler Flow failed. Due to Get not removing messages, messages will continue to be read repeatedly until something else removes the message.

    Get and RemoveMessages will be pulled and removed from the queue, and the Handler Flow will run. It will not check to see if the Handler Flow failed. Messages will not be stored in memory if the server shuts down, resulting in data loss. This is quicker than Lease or Lease w/ Expire.
    Active Flow CountThe maximum number of simultaneous Messages that Decisions will process.
    PICK HANDLER FLOWThis Flow is used to process Messages that appear in the Queue.
    Message QueueThe Queue for the Handler to listen to. This is configured in System > Jobs and Events > Message Queues.
    If setting the Message Handler mode to Get or Get and Remove mode, Decisions will auto-ACK every message. If using Lease or Lease w/Expire mode, Decisions will only ACK if the handler's Flow completes successfully. If the Flow throws an exception, Decisions will send a negative ACK (NACK).

For further information on Modules, visit the Decisions Forum.

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