Slack Listener Use Case

In this Article

Use Case: Using Slack Snap Pack To Design an Event Listener for Slack Workspace

In any enterprise ecosystem, receiving notifications is critical to carry out your daily tasks. Emails are no longer the preferred method of receiving notifications, especially when the notifications involve time-critical issues. Managers usually run on a time crunch; to fasten the decision-making process and deliver results, they can configure an Event Listener in their Slack workspace to cut through the clutter and get notified on items that need their immediate attention. This use case demonstrates how we can use the Slack Snap Pack to route events that are important to the manager into a custom channel created for this purpose.


In a real business case scenario, checking for all messages on the Slack Channel is time-consuming and owing to the the hectic schedule of managers leaves them with little time to go through all the messages posted on Slack. However they cannot miss on important updates that require their attention. 


Using Slack integration for your organization allows you to set up notifications to send messages to a Slack private channel or a specific user on Slack. We can efficiently automate the process of listening to Slack events, configuring the events, and receiving alerts on your Slack Channel upon the trigger of events. This Pipeline demonstrates how we can automate the process of receiving alerts on the private channel when these events are triggered.

Parent Pipeline - Slack ListenerChild Pipeline - Process Event

Download the Slack Listener and Process Events Pipelines. 

Understanding the Slack Pipeline


  • Create an app in your Slack Workspace that listens to the Slack instance.
  • Set the required scopes for the app. In this Use Case we set the Bot and User Token scopes to perform the following actions:
    • Add read channels, read messages, and read users.
    • Add write messages and read channels.

Building this Pipeline involves the following key steps:

  1. Create a Private Channel in Sack.
  2. Subscribe to the Slack events.
  3. Create a Child Pipeline.

Create a Private Channel in Slack

Create a private (custom) channel named #my_alerts, and add the necessary stakeholders who should receive alerts for the given events.

Subscribe to Slack Events

We want to configure the following two events and receive alerts on the private channel when these events occur:

  • Event 1: When a new member joins the Slack channel.
  • Event 2: When a SWAT ticket is posted in the channel.

To subscribe events in Slack:

  1. Navigate to—Slack Apps page.

  2. Click Event Subscriptions in the left navigation pane.

  3. Enable the toggle for Enable Events.

  4. Subscribe to the events you want to listen.
    • Bot events: Whenever a bot performs the operation of adding a user to channel, we want to receive an alert.
    • User events: Whenever a user posts a message to public channel, private channel, individual user or multiple users or group of users, we want to receive an alert.

  5. Provide the URL of the triggered task of the Parent Pipeline in the Request URL field.
    To provide the Request URL in Slack app, you need to configure a Pipeline with a Mapper Snap and create a triggered task.

Create a Parent Pipeline 

First, we configure the Mapper Snap with an expression to determine if the object is a challenge or an event.


This expression includes three elements: Token, Challenge and Type.

  • If the element is a challenge, the Snap sends the JSON response containing the challenge.
  • If the element is an event, the Snap checks whether it is Retry, because most often the Pipeline might take more time to process events. Hence, if the Slack application does not get response in three seconds, the Snap retriggers the Pipeline.
  • If it is a retry, the Snap sends the JSON object without processing it. If it is a not a retry, the Snap sends the event for further processing.

Next, we create a a
triggered task for the Parent Pipeline. From the Triggered task dialog window, we copy the Cloud URL and HTTP Header (token) and paste it in Request URL field in the Slack app for verification.

You must append the bearer token to the URL. 

Once the Slack app receives the challenge from the Parent Pipeline, the URL is verified. After the URL is verified which usually takes three seconds, the request triggers the Parent Pipeline and it receives the challenge as response.

The Redirect URL should correspond to the same URL used for event subscription for the Slack app to function with the Slack Snap Pack.

Now we continue with the Parent Pipeline configuration to listen to 
the Slack events and process the events as per the requirement.

We configure the Router Snap with expressions that evaluate whether the input view contains a challenge or an event and routes the outputs appropriately.

If the input is a challenge, the Pipeline processes and sends the response. If the input is an event, the Router Snap routes the output to the Pipeline Execute Snap that runs the child Pipeline to process the event in the Process_Event Pipeline.

Next we use the Join Snap to join both the output views of Pipeline Execute and Mapper Snaps using left outer join to get a unified output.

Create a Child Pipeline to Process Events

We configure the child Pipeline to perform the following two operations:

  1. Determine the type of event and route the flow appropriately.
      • Event 1: When a new member joins the Slack channel.
      • Event 2: When a user posts a SWAT message in the channel.

        You can configure the Pipeline to process more events based on your need.

  1. Join the output views from the Slack User Operations and Channel Operations Snaps to route the final output to the Parent Pipeline.

First, we configure the Router Snap to determine the type of event, whether it is a new member joining the channel (event 1) or a message posted in the channel (event 2).

If it is a message event, we want to check if the message contains the key word SWAT. Hence, we configure the Filter Snap as follows:

If the message contains SWAT, we intend to send the alert to the #my_alerts channel. So, we configure the Send Channel Message Snap with relevant Slack message as follows:

On running the Pipeline, the relevant SWAT message is sent to #my_alerts channel as follows:

If the event is a new member joining the channel we take this approach. We take a copy of the output from the Router Snap to extract user and channel information when a member joins a channel, and  configure the following Snaps:

User Operations SnapChannel Operations Snap

We configure the Mapper Snap to extract the name of the user and map it to the channel.

Next, we join the inputs from the Slack User Operations and Channel Operations Snaps using the Outer join of Join Snap to get an user alert.

We configure the Slack Send Message Snap to send alerts to #my_alerts channel.

On running the Pipeline, the relevant new user alert is sent to #my_alerts channel as follows:

Finally, we configure the Join Snap to get a single output from the two output views. This output is the output of the Pipeline Execute Snap in the Parent Pipeline.


  File Modified

File Use_Case_Slack_Listener.slp

Jun 10, 2021 by Kalpana Malladi

File Use_Case_Process_Event.slp

Jun 10, 2021 by Kalpana Malladi