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Event Source for Slack

This event source uses the Slack Events API through a bot user to ingest events into TriggerMesh.


  • A Slack user that can manage applications is required to configure the source.

Create the Slack Source Integration

Deploy the Slack source in 3 steps:

  1. Deploy the Slack source, retrieve exposed endpoint at TriggerMesh.
  2. Configure Slack App to send events to the Slack Source endpoint.
  3. (optional) Modify the Slack Source to add Signing Secret and AppID from the configured App.

Deploy Slack Source

Create an instance of the Slack Source at TriggerMesh as part of a Bridge.

  • name is an internal identifier inside the bridge.
  • broker where messages should be sent to.

Save the source, fill the rest of the bridge fields and press Submit Bridge. The Slack source creates a service, navigate to Functions/Services and copy the URL for the exposed service.

Configure Slack Events API App

  1. Create a new [Slack App][slack-app]

Slack app

  1. From Basic Information, Features and functionality, select Event Subscriptions

Features and functionality

  1. Slide the Enable Events selector to on and write the Slack source exposed URL at the Request URL box. A request with a verification challenge will be sent and when the Slack source adapter answer it will be validated and a green check will be shown.

Request URL verified

  1. At the Subscribe to bot events section select the bot events that will be sent on behalf of this integration and then press Save Changes at the bottom of the page.. Refer to Slack documentation on which ones to use, as a hint the we think these 3 could be useful for different scenarios:

  2. app_mention will send an event when the App is mentioned.

  3. will send an event when sending a direct message to the App.
  4. message.channels an event will be sent for each message at a channel where the App is invited.


  1. At Install App section click on Install App to Workspace

Install to workspace

  1. (Optional)Return to the application's Basic Information and take note of App ID and Signing Secret

    Retrieve info

You will now have a working integration. Any Slack action that matches the configured event subscription will be sent to the Slack Source and from there to the sink.

Secure the Slack Source (optional)

Create a new secret at TriggerMesh and add a key named signingSecret containing the value retrieved at the previous step.

Signing secret

Go back to the bridge and edit the source:

  • Signing secret set to the created secret.
  • App ID is also optional and will filter for the App ID in case the endpoint is used for multiple integrations.


The Slack source creates a cloud event for each Slack event sent on behalf of the integration. Slack events are wrapped in a structure that is used for CloudEvents categorization, while the wrapped event is sent as the payload.

Cloud Event header example:

CloudEvent Description Example
type fixed value
source Team ID (Slack workspace) TA1J7JEBS
subject Event type message
time Event wrapper time 2020-06-21T09:44:35Z
id Event wrapper ID Ev01656P5WP3

Cloud Event data example:

  "blocks": [
      "block_id": "ws9ME",
      "elements": [
          "elements": [
              "text": "waving hello ",
              "type": "text"
              "type": "user",
              "user_id": "U015NKH6R6G"
          "type": "rich_text_section"
      "type": "rich_text"
  "channel": "C01112A09FT",
  "channel_type": "channel",
  "client_msg_id": "9fc2ed3e-c823-4dcf-be6b-4d788ab0beea",
  "event_ts": "1592732675.009400",
  "team": "TA1J7JEBS",
  "text": "waving hello \u003c@U015NKH6R6G\u003e",
  "ts": "1592732675.009400",
  "type": "message",
  "user": "UT8LFLXR8"