Receive Alert Notifications via Slack

Getting started

Last9 can send alert notifications and resolutions to Slack channels. This document provides step-by-step instructions on how to set up Slack integration with Last9 and start receiving alert notifications.

Setting up an Incoming Webhook in Slack

1. Navigate to Slack API Apps and click Create New App

2. Select From scratch and provide:

   • App Name: A descriptive name (e.g., “Last9 Alerts”)
   • Workspace: Select the workspace where you want to receive alerts

3. Click Create App

4. In your app settings, navigate to Incoming Webhooks in the left sidebar

5. Toggle Activate Incoming Webhooks to On

6. Click Add New Webhook to Workspace

7. Select the channel where you want alert notifications to be posted and click Allow

8. Copy the generated webhook URL. It will look like:

   https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX

Setting up a notification channel in Last9

1. In Notification Channels, click Add to create a new channel

   

2. Provide the following details:

   • Channel Name: A descriptive name to easily identify the channel (e.g., “Slack Production Alerts”)
   • Channel: Select Slack from the dropdown
   • Webhook URL: Paste the Slack webhook URL copied from the previous step
   • Send Resolved: Enable this option if you want to be notified when an alert has been resolved

   

3. Click Test Config to send a test message to your Slack channel and verify the integration is working

   

4. Click Save to enable the channel

Assigning a notification channel to an alert group

1. Navigate to your Alert Group in Alert Studio

2. Click on the notification channel icon to configure notifications

3. Select your Slack channel from the dropdown

Slack Notification Format

Last9 sends rich notifications to Slack that include:

Mentioning users or user groups in Slack alerts

To @-mention a user or user group in a Slack alert, use Slack’s mrkdwn mention syntax inside the alert template:

Find a user ID by clicking the user’s profile in Slack → More → Copy member ID. User group IDs are visible in the URL when editing the group at /admin/user_groups.

Example alert template body

<!subteam^S0123ABCD> :rotating_light: *{{ alert_name }}* — {{ severity }}

Service: `{{ service }}`
Environment: `{{ env }}`
Error: {{ error_message }}
Time: {{ timestamp }}

<{{ dashboard_url }}|Open in Last9>

Using Terraform

You can also create the Slack notification channel using the Last9 Terraform Provider:

resource "last9_notification_channel" "slack" {
  name          = "slack-production-alerts"
  type          = "slack"
  destination   = "https://hooks.slack.com/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX"
  send_resolved = true
}

Troubleshooting

Notifications not appearing in Slack

1. Verify the webhook URL is correct and starts with https://hooks.slack.com/services/
2. Check that the Slack app is still installed in your workspace
3. Ensure the channel selected for the webhook still exists
4. Verify the app has permission to post to the channel

Test message not working

1. Click Test Config to send a test message
2. Check if the test message appears in your Slack channel
3. If it doesn’t appear, verify the webhook URL is correct

Rate limiting

Slack has rate limits for incoming webhooks. If you’re sending a high volume of alerts, some messages may be delayed. Consider consolidating alerts using alert grouping in Last9.

Webhook URL expired or revoked

If your webhook stops working:

1. Navigate to your Slack app settings
2. Go to Incoming Webhooks
3. Check if the webhook is still active
4. If needed, create a new webhook and update the URL in Last9

@user mention not triggering notification

If the mention appears in the alert message but the user is not notified:

1. Verify the mention syntax. Slack requires <@USER_ID> (not @username). Find the user ID via Slack profile → More → Copy member ID.
2. Move the mention to the first line of the alert template body. Mentions buried inside attachment fields or context blocks may render visually but skip notification on some Slack clients (notably mobile).
3. Confirm the user is a member of the channel that the webhook posts to. Mentions of non-members do not generate notifications.
4. For user groups (<!subteam^GROUP_ID>), confirm the group is enabled at /admin/user_groups — disabled groups silently drop mentions.

Please get in touch with us on Discord or Email if you have any questions.