TODO.md

Leader Election Implementation — TODO

Completed Steps

Step 1: Create src/services/leaderElection.js

• Implement Redis lease-based distributed lock
• tryAcquire() — SET key value NX PX
• renew() — Lua script for atomic check-and-renew
• release() — Lua script for atomic conditional DEL
• isLeader() — check if current instance holds lease
• getCurrentLeader() — get current lease holder from Redis
• Periodic renewal loop (start/stop)
• Clear logging on state transitions

Step 2: Update src/config.js

• Add INSTANCE_ID env var (default: auto-generated from hostname + random suffix)
• Add LEASE_TTL_MS env var (default: 15000)
• Add LEASE_RENEW_INTERVAL_MS env var (default: 5000)
• Export leaderElection config section

Step 3: Create src/jobs/leaderAwareJob.js

• Factory that wraps job modules
• Only activates underlying job when leader
• Reacts to leadership transitions (acquire/renew/release)
• Graceful lease release on stop
• Extended getHealth() with leadership info
• Clear logging: "acting as follower" / "acquired leader lease"

Step 4: Update src/index.js

• Import leader election service and leader-aware job wrapper
• Create leader election instances for price_refresh, webhook_retry, airdrop_expiry
• Wrap all three background jobs with leader-aware wrapper
• Use wrapped jobs in startServer()
• Use wrapped jobs in shutdown() (await stop for graceful lease release)
• Update health endpoint to include leadership state per job
• Add leader_election section to health response
• Clean up duplicate/broken code

Step 5: Update README.md

• Document leader-election mechanism
• Document failover timing (TTL + renewal gap)
• New env vars table entries
• How to verify which replica holds the lock

Step 6: Create tests in test/leaderElection.test.js

• Test file created with comprehensive test suite