adding prometheus output

docs/examples/prometheus.py

@@ -0,0 +1,71 @@
+import logging
+import time
+import os
+
+from string import maketrans
+from awslimitchecker.checker import AwsLimitChecker
+from prometheus_client import start_http_server, Summary, Gauge
+
+
+REQUEST_TIME = Summary(
+                        'update_processing_seconds',
+                        'Time spent querying aws for limits'
+                    )
+gauges = {}
+trantab = maketrans(' -.', '___')
+
+
+def main():
+    port = int(os.environ.get('ALC_PORT', '8080'))
+    interval = int(os.environ.get('ALC_INTERVAL', '60'))
+    logger = logging.getLogger()
+    logger.setLevel(logging.ERROR)
+
+    checkers = {}
+    for region in ['us-east-1', 'us-east-2', 'us-west-1', 'us-west-2']:
+        checkers[region] = AwsLimitChecker(region=region)
+
+    start_http_server(port)
+    for region, checker in checkers.iteritems():
+        update(checker, region)
+        time.sleep(interval)
+
+
+@REQUEST_TIME.time()
+def update(checker, region):
+    try:
+        checker.find_usage()
+
+        labels = {'region': region}
+        for service, svc_limits in sorted(checker.get_limits().items()):
+            for limit_name, limit in sorted(svc_limits.items()):
+                path = '.'.join([service, limit_name])
+                usage = limit.get_current_usage()
+                metric = limit.get_limit()
+                update_service(path, usage, metric, region)
+    except Exception as e:
+        logging.exception("message")
+
+
+def update_service(path, usage, limit, region):
+    g = gauge(path)
+
+    g.labels(region=region, type='limit').set(limit)
+    for resource in usage:
+        metric_type = 'current'
+        if resource.resource_id:
+            metric_type = resource.resource_id
+        g.labels(region=region, type=metric_type).set(resource.get_value())
+
+
+def gauge(path):
+    path = path.lower().translate(trantab, '()')
+    g = gauges.get(path, None)
+    if g is None:
+        g = Gauge(path, '', ['region', 'type'])
+        gauges[path] = g
+    return g
+
+
+if __name__ == "__main__":
+    main()