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Receiver checks

duplicate-receiver

Level: error

Two receivers share the same name. Alertmanager uses the first definition and silently ignores the second, which is almost never intentional.

receivers:
  - name: team-slack
    slack_configs:
      - channel: '#alerts'
  - name: team-slack          # duplicate!
    slack_configs:
      - channel: '#incidents'

receivers:
  - name: team-slack
    slack_configs:
      - channel: '#alerts'
  - name: team-slack-incidents   # unique name
    slack_configs:
      - channel: '#incidents'

empty-receiver

Level: warn (info if it's the default receiver)

A receiver has no integration configured — no slack_configs, pagerduty_configs, webhook_configs, etc. Alerts routed here will be silently dropped.

Using an empty receiver as the default (to blackhole low-priority alerts) is intentional and triggers info instead of warn.

receivers:
  - name: default
    slack_configs: [...]
  - name: pager               # no integrations — alerts dropped!

receivers:
  - name: default
    slack_configs: [...]
  - name: pager
    pagerduty_configs:
      - routing_key: 'your-key'

route:
  receiver: null              # default catch-all blackhole
receivers:
  - name: null                # empty by design — INFO, not WARN

email-no-smarthost

Level: error

An email_configs entry has no smarthost and global.smtp_smarthost is not set. Alertmanager cannot send emails without knowing the SMTP server address.

receivers:
  - name: team
    email_configs:
      - to: 'team@example.com'
        from: 'alertmanager@example.com'
        # missing smarthost!

receivers:
  - name: team
    email_configs:
      - to: 'team@example.com'
        from: 'alertmanager@example.com'
        smarthost: 'smtp.example.com:587'

global:
  smtp_smarthost: 'smtp.example.com:587'
  smtp_from: 'alertmanager@example.com'

receivers:
  - name: team
    email_configs:
      - to: 'team@example.com'

webhook-no-url

Level: error

A webhook_configs entry has no url or url_file. Alertmanager cannot deliver alerts without a target URL — they fail silently.

receivers:
  - name: team
    webhook_configs:
      - send_resolved: true   # missing url!

receivers:
  - name: team
    webhook_configs:
      - url: 'http://my-service/webhook'
        send_resolved: true

pagerduty-no-routing-key

Level: error

A pagerduty_configs entry has no routing_key or routing_key_file. PagerDuty requires an integration key to accept events.

receivers:
  - name: pager
    pagerduty_configs:
      - severity: critical   # missing routing_key!

receivers:
  - name: pager
    pagerduty_configs:
      - routing_key: 'your-pagerduty-integration-key'
        severity: critical

slack-no-api-url

Level: error

A slack_configs entry has no api_url or api_url_file, and global.slack_api_url is not set. Slack requires an incoming webhook URL to receive messages.

receivers:
  - name: team
    slack_configs:
      - channel: '#alerts'   # missing api_url!

receivers:
  - name: team
    slack_configs:
      - api_url: 'https://hooks.slack.com/services/...'
        channel: '#alerts'

global:
  slack_api_url: 'https://hooks.slack.com/services/...'
receivers:
  - name: team
    slack_configs:
      - channel: '#alerts'

opsgenie-no-api-key

Level: error

An opsgenie_configs entry has no api_key or api_key_file, and global.opsgenie_api_key is not set. OpsGenie requires an API key to accept alerts.

receivers:
  - name: team
    opsgenie_configs:
      - priority: P1   # missing api_key!

receivers:
  - name: team
    opsgenie_configs:
      - api_key: 'your-opsgenie-api-key'
        priority: P1

global:
  opsgenie_api_key: 'your-opsgenie-api-key'

msteams-no-webhook-url

Level: error

An msteams_configs entry has no webhook_url or webhook_url_file. MS Teams requires an incoming webhook URL to receive messages.

receivers:
  - name: team
    msteams_configs:
      - title: 'Alert'   # missing webhook_url!

receivers:
  - name: team
    msteams_configs:
      - webhook_url: 'https://outlook.office.com/webhook/...'
        title: 'Alert'

template-file-missing

Level: error (warn for globs)

A path in templates: does not exist on disk. Alertmanager loads template files at startup — a missing literal path causes startup failure; a glob that matches no files silently loads no templates.

This check only runs when linting a file (not stdin) and resolves paths relative to the config file's directory.

Tip

If your templates live at a runtime path (e.g. /etc/alertmanager/templates/) that isn't present in CI, add template-file-missing to your .amlint.yml ignore list.

templates:
  - /etc/alertmanager/templates/custom.tmpl   # file does not exist

templates:
  - templates/*.tmpl   # no files match this pattern

templates:
  - templates/custom.tmpl   # file exists in the repo alongside the config
# or use a glob that actually matches:
templates:
  - templates/*.tmpl        # and ensure at least one .tmpl file is present

unused-receiver

Level: info

A receiver is defined but never referenced by any route. It may be leftover from a previous config version.

route:
  receiver: default
receivers:
  - name: default
    slack_configs: [...]
  - name: old-pager           # never used in any route
    pagerduty_configs: [...]

# Remove the unused receiver, or add a route that uses it