Add more Raft status metrics for Prometheus and Grafana dashboard

[Copilot]

Expands the existing Prometheus metrics exporter with additional Raft status gauges sourced from the already-polled raft.Raft.Stats() map — no extra RPC calls.

New metrics

Metric	Description
elastickv_raft_term	Current Raft term — increments on each leader election
elastickv_raft_last_log_index	Last written log entry index — useful for cross-node replication lag
elastickv_raft_last_snapshot_index	Most recent snapshot index
elastickv_raft_fsm_pending	Commands queued to FSM but not yet applied — backpressure indicator
elastickv_raft_num_peers	Other voting members in the cluster, excluding this node

All metrics carry the same group, node_id, and node_address labels as existing Raft gauges.

Grafana dashboard

A new dashboard monitoring/grafana/dashboards/elastickv-raft-status.json is included for visualising Raft health at a glance:

Row	Panels
Cluster Overview	Raft Term · Voting Peers · Member Count · FSM Pending (stat, color-coded)
Leader & State	Current Leader per Group · Node Local State · Cluster Members (tables)
Index Progress	last log / commit / applied / snapshot index over time (time series)
Replication Health	Replication Lag (last_log_index − applied_index) · Last Leader Contact in seconds (time series)

The dashboard includes a group template variable for filtering by Raft group and auto-refreshes every 10 seconds.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add metrics output for prometheus</issue_title>
<issue_description></issue_description>

<agent_instructions>add more raft status metrics</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Add metrics output for prometheus #65

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[bootjp]

@copilot fix golangci-lint and ai require document add

[Copilot]

@copilot fix golangci-lint and ai require document add

Fixed in 71eedf1:

• golangci-lint: Removed extra alignment spaces from the RaftMetrics struct fields (the gci formatter requires standard gofmt alignment, not manual column alignment).
• Doc comments: Added a type-level doc comment to RaftMetrics and per-field comments describing each gauge's purpose, including all five new fields (term, lastLogIndex, lastSnapshotIndex, fsmPending, numPeers).

golangci-lint run ./monitoring/... now reports 0 issues.

[bootjp]

@copilot Raftの状態を確認するGrafanaダッシュボードのJSONを作ってください

[Copilot]

@copilot Raftの状態を確認するGrafanaダッシュボードのJSONを作ってください

Added monitoring/grafana/dashboards/elastickv-raft-status.json in commit 7755874.

The dashboard has 4 rows:

Row	Panels
Cluster Overview	Raft Term · Voting Peers · Member Count · FSM Pending (stat, color-coded)
Leader & State	Current Leader per Group · Node Local State · Cluster Members (tables)
Index Progress	last log / commit / applied / snapshot index over time (time series)
Replication Health	Replication Lag (last log − applied entries) · Last Leader Contact in seconds (time series)

A group template variable is included so you can filter by Raft group, and the dashboard auto-refreshes every 10 seconds.