Slack

Notification

Synopsis

Sends alert notifications to Slack channels using incoming webhooks, supporting message attachments with customizable colors, additional fields, and branding options.

Schema

- slack:
    webhook_url: <string>
    title: <string>
    message: <string>
    username: <string>
    icon_url: <string>
    icon_emoji: <string>
    channel: <string>
    color: <string>
    fields: <field[]>
    description: <text>
    if: <script>
    ignore_failure: <boolean>
    on_failure: <processor[]>
    on_success: <processor[]>
    tag: <string>

Configuration

Field	Required	Default	Description
`webhook_url`	N	`${SLACK_WEBHOOK_URL}`	Slack incoming webhook URL
`title`	Y	-	Message title displayed prominently
`message`	Y	-	Main message body text
`username`	N	`VirtualMetric`	Bot username displayed in Slack
`icon_url`	N	VirtualMetric icon	URL to image used as bot avatar
`icon_emoji`	N	-	Emoji to use as bot avatar (overrides icon_url)
`channel`	N	-	Channel to post to (overrides webhook default)
`color`	N	`#47BEFF`	Attachment color: `good`, `warning`, `danger`, `info`, or hex code
`fields`	N	-	Array of field objects with `title`, `value`, and `short` fields
`description`	N	-	Explanatory note
`if`	N	-	Condition to run
`ignore_failure`	N	`false`	See Handling Failures
`on_failure`	N	-	See Handling Failures
`on_success`	N	-	See Handling Success
`tag`	N	-	Identifier

Details

The slack processor sends notifications to Slack channels using incoming webhooks.

Webhook Setup: Create an incoming webhook in Slack:

Go to your Slack workspace's App Directory
Search for "Incoming Webhooks" and add it
Choose a channel and create the webhook
Copy the webhook URL

Colors: Visual severity indicators for the message attachment sidebar:

good / green / success: Green (#26A65B)
warning / yellow: Orange (#FFB655)
danger / red / error / critical: Red (#FB4946)
info / blue: Blue (#47BEFF) - default
Custom hex codes (e.g., #FF5733) for brand colors

Fields: Structured data displayed in the attachment:

fields:
  - title: "Server"
    value: "{{ .hostname }}"
    short: true
  - title: "CPU"
    value: "{{ .cpu_usage }}%"
    short: true

Set short: true to display fields side-by-side.

Channel Override: The channel field overrides the webhook's default channel. Use #channel-name for public channels or @username for direct messages.

Template Support: All string fields support Go template syntax with event field interpolation using {{ .field_name }}.

For integration patterns with schema validation, see Schema Drift Detection.

Examples

Basic Alert

Sending a simple alert notification...

{
  "alert_name": "High CPU Usage",
  "server": "prod-server-01",
  "cpu_usage": "95%"
}

- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    title: "Alert: {{ .alert_name }}"
    message: "CPU usage is at {{ .cpu_usage }} on server {{ .server }}"
    color: "danger"

Red-colored alert posted to Slack...

With Fields

Including structured data as fields...

{
  "alert_name": "Schema Drift Detected",
  "schema": "ASimNetworkSessionLogs",
  "missing": "3 required fields"
}

- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    title: "{{ .alert_name }}"
    message: "Schema validation failed"
    color: "warning"
    fields:
      - title: "Schema"
        value: "{{ .schema }}"
        short: true
      - title: "Missing Fields"
        value: "{{ .missing }}"
        short: true

Fields displayed side-by-side in attachment...

Custom Username and Channel

Overriding bot identity and target channel...

{
  "bot_name": "AlertBot",
  "channel": "#alerts"
}

- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    username: "{{ .bot_name }}"
    channel: "{{ .channel }}"
    title: "System Alert"
    message: "This is a test alert"
    color: "info"

Message posted as AlertBot to #alerts channel...

Color Options

Using different severity colors...

# Success - green sidebar
- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    title: "Deployment Complete"
    message: "Version 2.0 deployed successfully"
    color: "good"

# Warning - orange sidebar
- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    title: "High Memory Usage"
    message: "Memory usage at 85%"
    color: "warning"

# Danger - red sidebar
- slack:
    webhook_url: "${SLACK_WEBHOOK_URL}"
    title: "Service Down"
    message: "API service not responding"
    color: "danger"

Colors indicate severity at a glance...

Schema Drift Alert

Alerting on schema validation failures...

processors:
  - check_schema:
      schema: "ASimNetworkSessionLogs"
      target_field: "schema_check"
      on_missing:
        - slack:
            webhook_url: "${SLACK_WEBHOOK_URL}"
            title: "Schema Validation Failed: ASimNetworkSessionLogs"
            message: "Schema validation detected missing required fields"
            color: "danger"
            fields:
              - title: "Schema"
                value: "ASimNetworkSessionLogs"
                short: true
              - title: "Valid"
                value: "{{ .schema_check.is_valid }}"
                short: true

Alert triggered automatically when schema drift detected...

Synopsis​

Schema​

Configuration​

Details​

Examples​

Basic Alert​

With Fields​

Custom Username and Channel​

Color Options​

Schema Drift Alert​