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-rw-r--r--docs/configuration/service/index.rst1
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diff --git a/docs/configuration/service/eventhandler.rst b/docs/configuration/service/eventhandler.rst
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+.. _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)
diff --git a/docs/configuration/service/index.rst b/docs/configuration/service/index.rst
index 11a1a118..8607490d 100644
--- a/docs/configuration/service/index.rst
+++ b/docs/configuration/service/index.rst
@@ -25,3 +25,4 @@ Service
ssh
tftp-server
webproxy
+ eventhandler