Message Queues

A message queue provides a buffer that temporarily stores messages and dispatches them to their consuming service. The messages are usually small, and can be things like requests, replies or error messages, etc.

Typically in Agnost, a message queue is used to execute your message handler functions asynchronously. For example, you can submit a message to a queue to send a welcome email to a new user immediately after they sign up. Or you can submit a delay message to a message queue to send a reminder email to a user after 24 hours.

Submit message to a queue

You can submit messages to the queue using the submitMessage method.

info

It submits a message to the specified message queue to execute the handler function.

• After the message is submitted, the handler function defined in your message queue configuration is invoked if there is no delay. If there is a delay, then the message waits for the specified delay duration and then is sent to the handler function for processing.
• This handler function processes the input message and performs necessary tasks defined in its business logic.

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The delay amount can only be used in Message Brokers that support it. In the case of RabbitMQ, if you use the Default Message Broker of the cluster, the necessary configurations are already made to handle delayed messages. If you bring your own external RabbitMQ instance and add it as a resource and would like to use the delayed messages functionality, you need to make sure that Delayed Message Exchange plugin has been installed to your instance.

Javascript

const queueName = "default";
const messageBody = {
  name: "Rooby",
  email: "[email protected]",
};

// Submit a message to a `default` queue for asychronous processing, no delay, process the message immediately
const result = await agnost
  .queue(queueName)
  .submitMessage(messageBody);

// Process the message after 24 hours (e.g., 60 x 60 x 24 * 1000 = 86400000 milliseconds)
const result2 = await agnost
  .queue(queueName)
  .submitMessage(messageBody, 86400000);

Example response

{
  "trackingId": "6237ae0f45aba7a695579b8f",
  "queueId": "que-9zbw5d04wcom",
  "queueName": "default",
  "submittedAt": "2022-03-20T22:43:27.485Z",
  "status": "pending"
}

Parameters

Here you can find parameters for the submitMessage method.

#	Name	Data type	Required	Description
1	message	Object	No	The message payload (JSON object) that will be submitted to the message queue.
2	delay	Number	No	The number of milliseconds to delay the messages in queue before dispacthing them to their consuming service.

info

• If successful, it returns information about the submitted message, including the trackingId of the submitted message.

• You can use trackingId to check the processing status of your message by calling getMessageStatus method.

Get message status

You can retrieve the status of a message using the getMessageStatus method.

Javascript

const queueName = "default";
const trackingId = "6237ae0f45aba7a695579b8f";

// Get the status of submitted message whether it has been completed processing or not
const result= await agnost
  .queue(queueName)
  .getMessageStatus(trackingId);

Example response

{
  "trackingId": "6237ae0f45aba7a695579b8f",
  "queueId": "que-9zbw5d04wcom",
  "queueName": "default",
  "submittedAt": "2022-03-20T22:54:31.676Z",
  "status": "completed",
  "startedAt": "2022-03-20T22:54:31.697Z",
  "completedAt": "2022-03-20T22:54:31.723Z"
}

Parameters

Here you can find parameters for the getMessageStatus method.

#	Name	Data type	Required	Description
1	trackingId	String	Yes	The tracking id of the submitted message.

info

Please note that only the last 7 days message metadata is stored in the database. If you ty to get the message status of a message that has been submitted to the queue before this period, null will be returned.