File watch sensor to utilize trigger with parameters

CHANGELOG.rst

@@ -41,6 +41,9 @@ in development
   ``TRIGGER_*`` RBAC permission constants (improvement)
 * Implement RBAC for webhooks get all and get one API endpoint. (improvement)
 * Add webhook payload to the Jinja render context when rendering Jinja variable inside rule criteria section
+* Switch file_watch_sensor in Linux pack to use trigger type with parameters. Now you can add a
+  rule with `file_path` and sensor will pick up the `file_path` from the rule. A sample rule
+  is provided in contrib/examples/rules/sample_rule_file_watch.yaml. (improvement)
 
 2.2.1 - April 3, 2017
 ---------------------

contrib/examples/rules/sample_rule_file_watch.yaml

@@ -0,0 +1,17 @@
+---
+name: sample_rule_file_watch
+pack: "examples"
+description: Sample rule custom trigger type - add a file to be watched by file_watch_sensor in linux pack.
+enabled: false
+
+trigger:
+  parameters:
+    file_path: /var/log/dmesg
+  type: linux.file_watch.file_path
+
+criteria: {}
+
+action:
+  parameters:
+    cmd: echo "{{trigger}}"
+  ref: core.local

contrib/linux/config.yaml

@@ -1,2 +0,0 @@
-file_watch_sensor:
-  file_paths:

contrib/linux/sensors/file_watch_sensor.py

@@ -9,17 +9,14 @@ class FileWatchSensor(Sensor):
     def __init__(self, sensor_service, config=None):
         super(FileWatchSensor, self).__init__(sensor_service=sensor_service,
                                               config=config)
-        self._config = self._config['file_watch_sensor']
-
-        self._file_paths = self._config.get('file_paths', [])
         self._trigger_ref = 'linux.file_watch.line'
+        self._logger = self._sensor_service.get_logger(__name__)
+
+        self._file_paths = []  # stores a list of file paths we are monitoring
         self._tail = None
 
     def setup(self):
-        if not self._file_paths:
-            raise ValueError('No file_paths configured to monitor')
-
-        self._tail = Tail(filenames=self._file_paths)
+        self._tail = Tail(filenames=[])
         self._tail.handler = self._handle_line
         self._tail.should_run = True
 
@@ -36,13 +33,29 @@ def cleanup(self):
                 pass
 
     def add_trigger(self, trigger):
-        pass
+        file_path = trigger['parameters'].get('file_path', None)
+
+        if not file_path:
+            self._logger.error('Received trigger type without "file_path" field.')
+            return
+
+        self._tail.add_file(filename=file_path)
+
+        self._logger.info('Added file "%s"' % (file_path))
 
     def update_trigger(self, trigger):
         pass
 
     def remove_trigger(self, trigger):
-        pass
+        file_path = trigger['parameters'].get('file_path', None)
+
+        if not file_path:
+            self._logger.error('Received trigger type without "file_path" field.')
+            return
+
+        self._tail.remove_file(filename=file_path)
+
+        self._logger.info('Removed file "%s"' % (file_path))
 
     def _handle_line(self, file_path, line):
         trigger = self._trigger_ref

contrib/linux/sensors/file_watch_sensor.yaml

@@ -4,8 +4,21 @@
   entry_point: "file_watch_sensor.py"
   description: "Sensor which monitors files for new lines"
   trigger_types:
+    -
+      name: "file_watch.file_path"
+      pack: "linux"
+      description: "Trigger which represents a file path to be monitored"
+      parameters_schema:
+        type: "object"
+        properties:
+          file_path:  # User ``st2`` should have permissions to be able to read this file.
+            description: "Path to the file to monitor"
+            type: "string"
+            required: true
+        additionalProperties: false
     -
       name: "file_watch.line"
+      pack: "linux"
       description: "Trigger which indicates a new line has been detected"
       payload_schema:
         type: "object"