Merge pull request #457 from Adnuntius/jp_fix_prometheus_metrics

fix issue with prometheus

Author: rdunklau

pghoard/monitoring/prometheus.py

@@ -38,8 +38,8 @@ def get_metrics(self):
     def _update(self, metric, value, tags):
         ts = str(int(time.time())) + "000"
 
-        metric = metric.replace(".", "_")
-        tags = {**self._tags, **tags}
+        metric = metric.replace(".", "_").replace("-", "_")
+        tags = {**self._tags, **tags} if tags else {**self._tags}
         tag_list = []
         for k in sorted(tags.keys()):
             tag_list.append("{}=\"{}\"".format(k, tags[k]))