Add defaults and config parser.

Resolves #4
Resolves #6

README.md

@@ -2,18 +2,22 @@ This application bridges [Prometheus Alertmanager](https://prometheus.io/docs/al
 
 # Usage
 ```
-usage: alertify.py [-h] [-H]
+usage: alertify.py [-h] [-c CONFIG] [-H]
 
 Bridge between Prometheus Alertmanager and Gotify
 
 optional arguments:
   -h, --help            show this help message and exit
-  -H, --healthcheck  Simply exit with 0 for healthy or 1 when unhealthy
+  -c CONFIG, --config CONFIG
+                        path to config YAML. (default: alertify.yaml)
+  -H, --healthcheck     simply exit with 0 for healthy or 1 when unhealthy
 
-Three environment variables are required to be set:
+The following environment variables will override any config or default:
-  * GOTIFY_SERVER: hostname of the Gotify server
+  * LISTEN_PORT   (default: 8080)
-  * GOTIFY_PORT: port of the Gotify server
+  * GOTIFY_SERVER (default: localhost)
-  * GOTIFY_KEY: app token for alertify
+  * GOTIFY_PORT   (default: 80)
+  * GOTIFY_KEY    (default: None)
+  * VERBOSE       (default: False)
 ```
 
 

alertify.py

@@ -5,14 +5,23 @@ Module to act as a Prometheus Exporter for Docker containers with a
 """
 
 import argparse
+import functools
 import http.client
 import json
 import os
 import sys
+from distutils.util import strtobool
 from http.server import HTTPServer, SimpleHTTPRequestHandler
 
-LISTEN_PORT = 8080
+import yaml
-VERBOSE = int(os.environ.get('ALERTIFY_VERBOSE', 0))
+
+DEFAULTS = {
+    'listen_port': int(8080),
+    'gotify_server': str('localhost'),
+    'gotify_port': int(80),
+    'gotify_key': str(),
+    'verbose': bool(False),
+}
 
 
 class HTTPHandler(SimpleHTTPRequestHandler):
@@ -21,6 +30,15 @@ class HTTPHandler(SimpleHTTPRequestHandler):
         for Docker containers with a healthcheck configured
     """
 
+    config = None
+
+    @staticmethod
+    def set_config(config):
+        """
+        Method
+        """
+        HTTPHandler.config = config
+
     # Override built-in method
     # pylint: disable=invalid-name
     def do_GET(self):
@@ -28,7 +46,7 @@ class HTTPHandler(SimpleHTTPRequestHandler):
         Method to handle GET requests
         """
         if self.path == '/healthcheck':
-            if not healthy():
+            if not healthy(self.config):
                 print('ERROR: Check requirements')
                 self._respond(500, 'ERR')
 
@@ -44,6 +62,9 @@ class HTTPHandler(SimpleHTTPRequestHandler):
             self._alerts()
 
     def _respond(self, status, message):
+        """
+        Method to output a simple HTTP status and string to the client
+        """
         self.send_response(int(status) or 500)
         self.end_headers()
         self.wfile.write(bytes(str(message).encode()))
@@ -52,7 +73,7 @@ class HTTPHandler(SimpleHTTPRequestHandler):
         """
         Method to handle the request for alerts
         """
-        if not healthy():
+        if not healthy(self.config):
             print('ERROR: Check requirements')
             self._respond(500, 'Server not configured correctly')
             return
@@ -67,7 +88,7 @@ class HTTPHandler(SimpleHTTPRequestHandler):
             self._respond(400, f'Bad JSON: {error}')
             return
 
-        if VERBOSE:
+        if self.config.get('verbose'):
             print('Received from Alertmanager:')
             print(json.dumps(alert, indent=2))
 
@@ -94,21 +115,20 @@ class HTTPHandler(SimpleHTTPRequestHandler):
             self._respond(400, f'Missing field: {error}')
             return
 
-        if VERBOSE:
+        if self.config.get('verbose'):
             print('Sending to Gotify:')
             print(json.dumps(gotify_msg, indent=2))
-        response = 'Status: {status}, Reason: {reason}'.format(
+
-            **gotify_send(
+        response = gotify_send(
-                os.environ['GOTIFY_SERVER'],
+            self.config.get('gotify_server'),
-                os.environ['GOTIFY_PORT'],
+            self.config.get('gotify_port'),
-                os.environ['GOTIFY_KEY'],
+            self.config.get('gotify_key'),
             gotify_msg
         )
-        )
 
-        if VERBOSE:
+        if self.config.get('verbose'):
-            print(response)
+            print('Status: {status}, Reason: {reason}'.format(**response))
-        self._respond(200, response)
+        self._respond(response['status'], response['reason'])
 
 
 def gotify_send(server, port, authkey, payload):
@@ -122,8 +142,15 @@ def gotify_send(server, port, authkey, payload):
         'Content-type': 'application/json',
     }
 
+    try:
         gotify.request('POST', '/message', json.dumps(payload), headers)
         response = gotify.getresponse()
+    except ConnectionRefusedError as error:
+        print(f'ERROR: {error}')
+        return {
+            'status': error.errno,
+            'reason': error.strerror
+        }
 
     return {
         'status': response.status,
@@ -131,35 +158,73 @@ def gotify_send(server, port, authkey, payload):
     }
 
 
-def healthy():
+def healthy(config):
     """
-    Simple funtion to return if all the requirements are met
+    Simple function to return if all the requirements are met
     """
     return all([
-        'GOTIFY_SERVER' in os.environ,
+        len(config.get('gotify_key', ''))
-        'GOTIFY_PORT' in os.environ,
-        'GOTIFY_KEY' in os.environ,
     ])
 
 
+@functools.lru_cache
+def parse_config(configfile):
+    """
+    Function to parse a configuration file
+    """
+    config = {}
+
+    try:
+        with open(configfile, 'r') as file:
+            parsed = yaml.safe_load(file.read())
+    except FileNotFoundError as error:
+        print(f'WARN: {error}')
+        parsed = {}
+
+    # Iterate over the DEFAULTS dictionary and check for environment variables
+    #   of the same name, then check for any items in the YAML config, otherwise
+    #   use the default values.
+    # Ensure the types are adhered to.
+    for key, val in DEFAULTS.items():
+        config[key] = os.environ.get(key.upper(), parsed.get(key, val))
+        if isinstance(val, bool):
+            config[key] = strtobool(str(config[key]))
+        else:
+            config[key] = type(val)(config[key])
+
+    if config['verbose']:
+        print(f'Config:\n{yaml.dump(config, explicit_start=True, default_flow_style=False)}')
+    return config
+
+
 if __name__ == '__main__':
-    def cli_parse():
+    def parse_cli():
         """
         Function to parse the CLI
         """
+        maxlen = max([len(key) for key in DEFAULTS])
+        defaults = [
+            f'  * {key.upper().ljust(maxlen)} (default: {val if val != "" else "None"})'
+            for key, val in DEFAULTS.items()
+        ]
+
         parser = argparse.ArgumentParser(
             formatter_class=argparse.RawDescriptionHelpFormatter,
             description='Bridge between Prometheus Alertmanager and Gotify\n',
-            epilog='Three environment variables are required to be set:\n'
+            epilog='The following environment variables will override any config or default:\n' +
-                   '  * GOTIFY_SERVER: hostname of the Gotify server\n'
+                   '\n'.join(defaults)
-                   '  * GOTIFY_PORT: port of the Gotify server\n'
+        )
-                   '  * GOTIFY_KEY: app token for alertify'
+
+        parser.add_argument(
+            '-c', '--config',
+            default=f'{os.path.splitext(__file__)[0]}.yaml',
+            help=f'path to config YAML.  (default: {os.path.splitext(__file__)[0]}.yaml)',
         )
 
         parser.add_argument(
             '-H', '--healthcheck',
             action='store_true',
-            help='Simply exit with 0 for healthy or 1 when unhealthy',
+            help='simply exit with 0 for healthy or 1 when unhealthy',
         )
 
         return parser.parse_args()
@@ -168,15 +233,20 @@ if __name__ == '__main__':
         """
         main()
         """
-        args = cli_parse()
+        args = parse_cli()
+        config = parse_config(args.config)
 
         if args.healthcheck:
             # Invert the sense of 'healthy' for Unix CLI usage
-            return not healthy()
+            return not healthy(config)
 
-        print(f'Starting web server on port {LISTEN_PORT}')
+        listen_port = config.get('listen_port')
+
+        print(f'Starting web server on port {listen_port}')
         try:
-            HTTPServer(('', LISTEN_PORT), HTTPHandler).serve_forever()
+            with HTTPServer(('', listen_port), HTTPHandler) as webserver:
+                HTTPHandler.set_config(config)
+                webserver.serve_forever()
         except KeyboardInterrupt:
             print('Exiting')
 

example.yaml

@@ -0,0 +1,6 @@
+---
+# verbose: true
+gotify_server: gotifyserver.example.net
+gotify_key: sOmEsEcReTkEy1
+gotify_port: "80"
+listen_port: "8080"

requirements.txt

@@ -1 +1,2 @@
 # To ensure app dependencies are ported from your virtual environment/host machine into your container, run 'pip freeze > requirements.txt' in the terminal to overwrite this file
+pyyaml