watchdog_node¶

This package provides a ‘watchdog’ node that monitors for specified conditions, and takes a specified action if any condition becomes true.

Usage¶

rosrun watchdog_node watchdog_node _config:=/path/to/config.yaml

where config.yaml is the configuration specifying a list of watchdogs in terms of ‘monitors’ and ‘actions’:

- name: check_battery
  description: Monitors the battery level.
  restart_timeout: 30
  monitors:
      - monitor_type: TopicFieldCondition
        topic: /battery_state/lifePercent
        condition: "{value} < 97"
  actions:
      - action_type: SendEmail
        to_addresses:  [cburbridge@gmail.com]
        from_address: cburbridge@gmail.com
        message: "Warning: robot battery is critically low."
        server: mail-relay.cs.bham.ac.uk
        port: 25
- name: check_scitos_node
  description: Checks the /odom topic, kills scitos node if not published for 20s.
  restart_timeout: 30
  monitors:
      - monitor_type: TopicAlive
        topic: /odom
        max_duration: 20
  actions:
      - action_type: KillNode
        node_name: /scitos_mira

Each watchdog must have the following fields:

name: any name chosen by the user
description: some hopefully useful description string
restart_timeout: how many seconds to wait after this watchdog has fired before restarting the watchdog. If value is -1 then the watchdog will stop running after it has been fired.
monitors: a list of monitors that make up the watchdog. If any one of the monitors fires then the watchdog will fire and stop, restarting after restart_timeout.
actions: a list of actions to take when this watchdog fires.

Monitors¶

The following monitors are available:

- type:  TopicPublished
  description:  This monitor triggers the actions if a message is published on a given topic
  configuration fields:
    -  topic  :  The topic to listen to

- type:  TopicAlive
  description:  This monitor triggers the actions if there are no messages on the given topic for a given period
  configuration fields:
    -  topic  :  The topic to monitor
    -  max_duration  :  The maximum number of seconds to accept not receiving a message

- type:  TopicFieldCondition
  description:  This monitor checks a field in a given topic and triggers the actions when a condition is met.
  configuration fields:
    -  topic  :  The topic & field to watch, eg /topic/field
    -  condition  :  A python expression containing {value} as a place holder for the value of the topic field. For example '{value} < 30'

Actions¶

The following actions are available:

- type:  KillNode
  description:  Sends a specified node a kill signal.
  configuration fields:
    -  node_name  :  The rosgraph name of the node to kill.

- type:  SendEmail
  description:  Sends an email using simple unsecure SMTP.
  configuration fields:
    -  to_addresses  :  A list of email addresses to send to.
    -  from_address  :  The email address to be sent from.
    -  message  :  The message body of the email.
    -  server  :  The SMTP server.
    -  port  :  The port the SMTP server uses.

Developing new actions/monitors¶

Monitors¶

Monitors are classes that derive from the base classes watchdog_node.MonitorType. They must provide name, description and config_keys fields at the class level and implement a start() and stop() method. start() will be called when the monitor is started or restarted following the firing of the watchdog. stop() will be called when the watchdog fires or is shutdown.

In order to signal that the watchdog should fire, the class should call ‘self.set_invalid()`.

TopicPublished provides a straightforward example.

Note that all modules defining monitors need to be imported in monitors/__init__.py

Actions¶

Actions are classes that derive from the base class watchdog_node.ActionType. Similar to monitors they must provide name, description and config_keys fields at the class level. They must also provide a execute(self) method that will be called when the watchdog fires.

KillNode provides a straightforward example.

Note that all modules defining actions need to be imported in actions/__init__.py

Original page: https://github.com/strands-project/strands_apps/blob/indigo-devel/watchdog_node/README.md