A dead man’s switch

The following Wishbone bootstrap file triggers an action in the case an event is expected but not received within a certain time window. This principle is called a dead man’s switch.

For this setup we will make use of wishbone.module.flow.fresh.


The wishbone_contrib.module.input.httpserver module is an external module and should be installed separately.

Consider following bootstrap file:

    module: wishbone_contrib.module.input.httpserver

    module: wishbone.module.flow.fresh
      timeout: 10
        message: We didn't recieve the expected keepalive signal from agent X.
        message: Agent X says hello.

    module: wishbone.module.output.stdout
      prefix: 'Agent message :'
      colorize: true
      foreground_color: GREEN
      payload: '{{data}}'

    module: wishbone.module.output.stdout
      prefix: 'Agent status :'
      colorize: true
      foreground_color: RED
      payload: '{{data}}'

  - input.outbox             -> dead_mans_switch.inbox
  - dead_mans_switch.outbox  -> agent_messages.inbox
  - dead_mans_switch.timeout -> agent_alarms.inbox

The diagram of this bootstrap file:


The output looks like:

$ wishbone start --config simple.yaml

Instance started in foreground with pid 11971
2017-11-19T15:58:10.4449+00:00 wishbone[11971] informational input: Serving on with a connection poolsize of 1000.
Agent message :hello
2017-11-19T15:58:16.3481+00:00 None[11971] informational input: - - [2017-11-19 16:58:16] "PUT / HTTP/1.1" 200 103 0.000461
Agent message :hello
2017-11-19T15:58:19.3404+00:00 None[11971] informational input: - - [2017-11-19 16:58:19] "PUT / HTTP/1.1" 200 103 0.000323
Agent status :We didn't recieve the expected keepalive signal from agent X.
2017-11-19T15:58:29.4267+00:00 wishbone[11971] informational dead_mans_switch: Timeout of 10 seconds expired.  Generated timeout event.

Whenever data is submitted into Wishbone’s webserver echo hello|curl -XPUT -d @- http://localhost:19283/ the timeout window resets and the message gets submitted to the agent_messages module instance.

When data is not submitted withint the predefined window of 10s then an internal event is generated and send to the agent_alarms output module.