* cluster: add alertmanager_cluster_messages_queued metric
* cluster: add metrics for sent messages
This change adds 2 new metrics:
- alertmanager_cluster_messages_sent_total
- alertmanager_cluster_messages_sent_size_total
* Fix marshaling for entries being broadcast
Individual notifications logs and silences being broadcast to the other
peers need to be encoded using the same length-delimited format as when
doing full-state synchronization.
* main: fix argument order for cluster.Join()
cluster.Join() was called with the push/pull and gossip interval
parameters being swapped one for another.
TestStateMerge() was skipped because of a typo. Fixing the name revealed
that the test itself needed to be updated following the switch to the
memberlist library.
This adds metrics that look like this:
```
alertmanager_alerts{state="active"} 6
alertmanager_alerts{state="suppressed"} 0
alertmanager_silences{state="active"} 1
alertmanager_silences{state="expired"} 1
alertmanager_silences{state="pending"} 0
```
This can be used to monitor alertmanager's usage and validate that
alertmanagers in a mesh have a similar number of silences and alerts.
* silences: avoid deadlock
Calling gossip.GossipBroadcast() will cause a deadlock if
there is a currently executing OnBroadcast* function.
See #982
* silence_test: better unit test to detect deadlocks
This commit adds an implementation of a silence storage that can
share store and modify silences, share state via a mesh network,
write and load snapshots, and be dynamically queried.
All data formats are based on protocol buffers.
