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