Add raft metrics (#621)

Add raft saturation metrics

Author: jonathanfrappier

content/vault/v1.20.x/content/docs/internals/telemetry/metrics/all.mdx

@@ -474,6 +474,10 @@ alphabetic order by name.
 
 @include 'telemetry-metrics/vault/raft-storage/transaction.mdx'
 
+@include 'telemetry-metrics/vault/raft/thread/fsm/saturation.mdx'
+
+@include 'telemetry-metrics/vault/raft/thread/main/saturation.mdx'
+
 @include 'telemetry-metrics/vault/raft-wal/head-truncations.mdx'
 
 @include 'telemetry-metrics/vault/raft-wal/tail-truncations.mdx'

content/vault/v1.20.x/content/docs/internals/telemetry/metrics/raft.mdx

@@ -168,6 +168,12 @@ Vault [integrated storage](/vault/docs/configuration/storage/raft).
 
 @include 'telemetry-metrics/vault/raft-storage/transaction.mdx'
 
+## Thread saturation metrics
+
+@include 'telemetry-metrics/vault/raft/thread/main/saturation.mdx'
+
+@include 'telemetry-metrics/vault/raft/thread/fsm/saturation.mdx'
+
 ## Write-ahead logging (WAL) metrics
 
 @include 'telemetry-metrics/vault/raft-wal/head-truncations.mdx'

content/vault/v1.20.x/content/partials/telemetry-metrics/vault/raft/thread/fsm/saturation.mdx

@@ -0,0 +1,8 @@
+### vault.raft.thread.fsm.saturation ((#vault-raft-thread-fsm-saturation))
+
+Metric type | Value       | Description
+----------- | ----------- | -----------
+gauge       | percentage  | Approximate proportion of time the raft FSM goroutine could not accept new work
+
+High saturation of the raft goroutines can increase latency in the rest of the
+system and cause cluster instability.

content/vault/v1.20.x/content/partials/telemetry-metrics/vault/raft/thread/main/saturation.mdx

@@ -0,0 +1,8 @@
+### vault.raft.thread.main.saturation ((#vault-raft-thread-main-saturation))
+
+Metric type | Value       | Description
+----------- | ----------- | -----------
+gauge       | percentage  | Approximate proportion of time the main raft goroutine could not accept new work
+
+High saturation of the raft goroutines can increase latency in the rest of the
+system and cause cluster instability.