The Consul agent collects various runtime metrics about the performance of different libraries and subsystems. These metrics are aggregated on a ten second interval and are retained for one minute.
When telemetry is being streamed to an external metrics store, the interval is defined to
be that store's flush interval. Otherwise, the interval can be assumed to be 10 seconds
when retrieving metrics from the built-in store using the above described signals.
## Agent Health
These metrics are used to monitor the health of specific Consul agents.
<tableclass="table table-bordered table-striped">
<tr>
<th>Metric</th>
<th>Description</th>
<th>Unit</th>
<th>Type</th>
</tr>
<tr>
<td>`consul.runtime.num_goroutines`</td>
<td>This tracks the number of running goroutines and is a general load pressure indicator. This may burst from time to time but should return to a steady state value.</td>
<td>number of goroutines</td>
<td>gauge</td>
</tr>
<tr>
<td>`consul.runtime.alloc_bytes`</td>
<td>This measures the number of bytes allocated by the Consul process. This may burst from time to time but should return to a steady state value.</td>
<td>bytes</td>
<td>gauge</td>
</tr>
<tr>
<td>`consul.runtime.heap_objects`</td>
<td>This measures the number of objects allocated on the heap and is a general memory pressure indicator. This may burst from time to time but should return to a steady state value.</td>
<td>number of objects</td>
<td>gauge</td>
</tr>
</table>
## Server Health
These metrics are used to monitor the health of the Consul servers.
<tableclass="table table-bordered table-striped">
<tr>
<th>Metric</th>
<th>Description</th>
<th>Unit</th>
<th>Type</th>
</tr>
<tr>
<td>`consul.raft.state.leader`</td>
<td>This increments whenever a Consul server becomes a leader. If there are frequent leadership changes this may be indication that the servers are overloaded and aren't meeting the soft real-time requirements for Raft, or that there are networking problems between the servers.</td>
<td>leadership transitions / interval</td>
<td>counter</td>
</tr>
<tr>
<td>`consul.raft.state.candidate`</td>
<td>This increments whenever a Consul server starts an election. If this increments without a leadership change occurring it could indicate that a single server is overloaded or is experiencing network connectivity issues.</td>
<td>election attempts / interval</td>
<td>counter</td>
</tr>
<tr>
<td>`consul.raft.apply`</td>
<td>This counts the number of Raft transactions occurring over the interval, which is a general indicator of the write load on the Consul servers.</td>
<td>raft transactions / interval</td>
<td>counter</td>
</tr>
<tr>
<td>`consul.raft.commitTime`</td>
<td>This measures the time it takes to commit a new entry to the Raft log on the leader.</td>
<td>ms</td>
<td>timer</td>
</tr>
<tr>
<td>`consul.raft.leader.dispatchLog`</td>
<td>This measures the time it takes for the leader to write log entries to disk.</td>
<td>ms</td>
<td>timer</td>
</tr>
<tr>
<td>`consul.raft.replication.appendEntries`</td>
<td>This measures the time it takes to replicate log entries to followers. This is a general indicator of the load pressure on the Consul servers, as well as the performance of the communication between the servers.</td>
<td>This will only be emitted by the Raft leader and measures the time since the leader was last able to contact the follower nodes when checking its leader lease. It can be used as a measure for how stable the Raft timing is and how close the leader is to timing out its lease.<br><br>The lease timeout is 500 ms times the [`raft_multiplier` configuration](/docs/agent/options.html#raft_multiplier), so this telemetry value should not be getting close to that configured value, otherwise the Raft timing is marginal and might need to be tuned, or more powerful servers might be needed. See the [Server Performance](/docs/guides/performance.html) guide for more details.</td>
These metrics give insight into the health of the cluster as a whole.
<tableclass="table table-bordered table-striped">
<tr>
<th>Metric</th>
<th>Description</th>
<th>Unit</th>
<th>Type</th>
</tr>
<tr>
<td>`consul.memberlist.msg.suspect`</td>
<td>This increments when an agent suspects another as failed when executing random probes as part of the gossip protocol. These can be an indicator of overloaded agents, network problems, or configuration errors where agents can not connect to each other on the [required ports](/docs/agent/options.html#ports).</td>
<td>suspect messages received / interval</td>
<td>counter</td>
</tr>
<tr>
<td>`consul.serf.member.flap`</td>
<td>Available in Consul 0.7 and later, this increments when an agent is marked dead and then recovers within a short time period. This can be an indicator of overloaded agents, network problems, or configuration errors where agents can not connect to each other on the [required ports](/docs/agent/options.html#ports).</td>
<td>This increments when an agent processes an [event](/docs/commands/event.html). Consul uses events internally so there may be additional events showing in telemetry. There are also a per-event counters emitted as `consul.serf.events.<event name>`.</td>
<td>Available in Consul 0.7.1 and later, this increments when an agent serves a DNS query based on information from a server that is more than 5 seconds out of date.</td>
<td>This tracks how long it takes to service the given HTTP request for the given verb and path. Paths do not include details like service or key names, for these an underscore will be present as a placeholder (eg. `consul.http.GET.v1.kv._`)</td>
