Dodemansknop

"Dodemansknop" is 🇳🇱 Dutch 🇳🇱 for "dead man's switch". It is a simple tool to implement such a dead man's switch in your infrastructure with common tools like Prometheus and Alertmanager.

Supported alerting targets

Currently, this supports the following alerting targets:

• Generic Webhooks
• Slack

Support for other targets is planned:

• OpsGenie
• PRs for other targets are welcome

Usage

1. Provide a configuration file. See config.example.yaml for an example.

2. Run Dodemansknop with the configuration file as argument: dodemansknop -config config.yaml:

   $ docker run \
       -p 3030:3030 \
       -v $PWD/config.yaml:/config.yaml \
       ghcr.io/mittwald/dodemansknop:latest --config /config.yaml --listen-addr=0.0.0.0:3030
   

3. Create a Prometheus Alert that continuously fires:

   name: Dodemansknop
   expr: vector(1)
   labels:
     severity: none

4. Configure your Prometheus Alertmanager to route this alert to Dodemansknop:

   route:
     ...
     routes:
     - match:
       alertname: Dodemansknop
       receiver: 'dodemansknop'
       group_wait: 0s
       group_interval: 1m
       repeat_interval: 50s
   receivers:
   - name: 'dodemansknop'
     webhook_configs:
     - url: 'http://dodemansknop/ping/service-id'
       send_resolved: false

How it works

Dodemansknop is a simple HTTP server that listens for HTTP requests on a given port. It expects a request to be made to the path /ping/<service-id>, with <service-id> being a unique identifier for the service that is being monitored.

When a request is received, Dodemansknop will expect to receive continuous requests with the same <service-id> within a given time frame. If no request is received within this time frame (configurable via config file), Dodemansknop will trigger an alert by notifying the configured alerting targets.