Manage etcd with lavinmqctl

[annieblomgren]

Related to #1350

Summary

• Adds lavinmqctl list_in_sync_replicas command that queries etcd directly (no LavinMQ HTTP API required)
• Outputs a table with node_id, address, and role (leader/follower) for each in-sync replica
• Adds lavinmqctl list_etcd_members command that queries the etcd MemberList API directly
• Outputs a table with name, peer_urls, client_urls, and learner status for each etcd member
• Adds --etcd-endpoints and --etcd-prefix global options (also read from LAVINMQ_CLUSTERING_ETCD_ENDPOINTS / LAVINMQ_CLUSTERING_ETCD_PREFIX env vars)
• Adds election_leader and member_list methods to Etcd class

How it works

Node addresses are discovered by calling get_prefix("{prefix}/leader/") — etcd stores each campaigning node's advertised URI under {prefix}/leader/{hex_lease_id}, where the hex lease ID converts to the base-36 node ID via hex.to_i64(16).to_s(36).

list_etcd_members calls /v3/cluster/member/list directly, giving operators visibility into the etcd layer that LavinMQ clustering depends on. Since etcd quorum loss means LavinMQ loses leader election and ISR tracking, this command helps with:

• Verifying all expected etcd members have joined the cluster
• Checking which client_urls to use for --clustering-etcd-endpoints
• Spotting stuck learners that haven't been promoted to full voting members
• Identifying when the cluster is at risk (e.g. a 3-node cluster down to 2 members is one failure away from losing quorum)

Test plan

• Start a multi-node LavinMQ cluster with etcd
• Run lavinmqctl --etcd-endpoints=<host:port> list_in_sync_replicas
• Verify all in-sync nodes appear with correct addresses and roles
• Run lavinmqctl --etcd-endpoints=<host:port> list_etcd_members
• Verify all etcd members appear with correct names, peer/client URLs and learner status
• Run against a single-instance LavinMQ and verify error message: "Is LavinMQ running in a cluster?"

🤖 Generated with Claude Code

[claude]

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[github-actions]

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[Loofeit]

Added lavinmqctl list_etcd_members command