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128 lines
4.1 KiB
ReStructuredText
128 lines
4.1 KiB
ReStructuredText
.. _event-handler:
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#############
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Event Handler
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#############
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*********************************
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Event Handler Technology Overview
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*********************************
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Event handler allows you to execute scripts when a string that matches a regex or a regex with
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a service name appears in journald logs. You can pass variables, arguments, and a full matching string to the script.
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******************************
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How to configure Event Handler
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******************************
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`1. Create an event handler`_
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`2. Add regex to the script`_
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`3. Add a full path to the script`_
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`4. Add optional parameters`_
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*********************************
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Event Handler Configuration Steps
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*********************************
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1. Create an event handler
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==========================
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.. cfgcmd:: set service event-handler event <event-handler name>
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This is an optional command because the event handler will be automatically created after any of the next commands.
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2. Add regex to the script
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===========================================
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.. cfgcmd:: set service event-handler event <event-handler name> filter pattern <regex>
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This is a mandatory command. Sets regular expression to match against log string message.
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.. note:: The regular expression matches if and only if the entire string matches the pattern.
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3. Add a full path to the script
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================================
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.. cfgcmd:: set service event-handler event <event-handler name> script path <path to script>
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This is a mandatory command. Sets the full path to the script. The script file must be executable.
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4. Add optional parameters
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==========================
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.. cfgcmd:: set service event-handler event <event-handler name> filter syslog-identifier <sylogid name>
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This is an optional command. Filters log messages by syslog-identifier.
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.. cfgcmd:: set service event-handler event <event-handler name> script environment <env name> value <env value>
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This is an optional command. Adds environment and its value to the script. Use separate commands for each environment.
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One implicit environment exists.
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* ``message``: Full message that has triggered the script.
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.. cfgcmd:: set service event-handler event <event-handler name> script arguments <arguments>
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This is an optional command. Adds arguments to the script. Arguments must be separated by spaces.
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.. note:: We don't recomend to use arguments. Using environments is more preffereble.
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*******
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Example
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*******
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Event handler that monitors the state of interface eth0.
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.. code-block:: none
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set service event-handler event INTERFACE_STATE_DOWN filter pattern '.*eth0.*,RUNNING,.*->.*'
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set service event-handler event INTERFACE_STATE_DOWN filter syslog-identifier 'netplugd'
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set service event-handler event INTERFACE_STATE_DOWN script environment interface_action value 'down'
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set service event-handler event INTERFACE_STATE_DOWN script environment interface_name value 'eth2'
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set service event-handler event INTERFACE_STATE_DOWN script path '/config/scripts/eventhandler.py'
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Event handler script
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.. code-block:: none
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#!/usr/bin/env python3
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#
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# VyOS event-handler script example
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from os import environ
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import subprocess
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from sys import exit
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# Perform actions according to requirements
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def process_event() -> None:
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# Get variables
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message_text = environ.get('message')
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interface_name = environ.get('interface_name')
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interface_action = environ.get('interface_action')
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# Print the message that triggered this script
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print(f'Logged message: {message_text}')
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# Prepare a command to run
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command = f'sudo ip link set {interface_name} {interface_action}'.split()
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# Execute a command
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subprocess.run(command)
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if __name__ == '__main__':
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try:
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# Run script actions and exit
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process_event()
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exit(0)
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except Exception as err:
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# Exit properly in case if something in the script goes wrong
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print(f'Error running script: {err}')
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exit(1)
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