Using Slack Channel IDs vs Names in Notification Policies

When setting up Slack notifications in Spacelift notification policies, you must use Slack channel IDs rather than human-readable channel names in the channel_id field.

Why Channel IDs Are Required

Slack's API expects the channel_id field to contain the actual Slack channel ID (for example, C0123456789), not the human-readable channel name (like my-team-alerts). When a channel name is provided instead of an ID, Slack cannot consistently resolve it, leading to intermittent "channel not found" errors.

Channel names are also mutable - they can change at any time, which would break your notification workflow. Channel IDs remain stable and provide reliable delivery.

Best Practice: Mapping Names to IDs

You can maintain human-readable stack labels while still using channel IDs in your policy. Here's the recommended approach:

1. Keep using readable channel names in your stack labels (e.g., slack:team-alerts)

2. In your notification policy, maintain a mapping that converts these names to their corresponding Slack channel IDs

3. The policy automatically converts the label's name into the correct ID

This gives you the best of both worlds: clear, readable labels and stable, reliable Slack notifications.

Example Policy Structure

Here's how you might structure your policy to handle the name-to-ID conversion:

package spacelift

# Mapping of human-readable names to Slack channel IDs
channel_mapping := {
    "team-alerts": "C0123456789",
    "dev-notifications": "C9876543210",
    "qa-updates": "C5555555555"
}

slack_channels[slack_channel_name] {
    label := input.run_updated.stack.labels[_]
    startswith(label, "slack:")
    slack_channel_name := split(label, ":")[1]
}

slack[{"channel_id": channel_id}] {
    run := input.run_updated.run
    run.type == "TRACKED"
    
    channel_name = slack_channels[_]
    channel_id = channel_mapping[channel_name]
}

This approach ensures consistent notification delivery while keeping your stack labels human-readable and maintainable.