v0.1.0

First public release. Put the hammer down. Keep the brakes.

hammerdown is a dependency-free Go CLI control plane for rolling restarts and upgrades across large sharded fleets. Fork it, teach it two verbs (restart a node, fail over a shard), and roll thousands of nodes shard by shard.

Highlights

• Explicit workers: --workers N fleet-wide, --keyspace-workers N per keyspace
• Leader-aware rolls: replicas first, planned failover to a replica already on the target build, then the old primary
• Exact fail-fast: --max-primary-failures / --max-replica-failures drain before the next operation starts
• Stop cleanly: --stop-at, --blackout, Ctrl-C drains; re-run the same command to resume
• Filters you can type at 3 a.m.: --limit 'users/ALL|teams/-80,80-', globs, --skip, role, cell, host, target, canary --shards-per-keyspace 1
• Dry run by default, plus process and shard locks
• Backends: sim (11,000-node simulated fleet) and shell (drive your existing scripts)
• Claude-ready: CLAUDE.md and an add-backend skill

Install

go install github.com/hashjoin/hammerdown/cmd/hammerdown@v0.1.0, or download a binary below and verify it against checksums.txt.

Try it

hammerdown sim init && hammerdown sim stage --to v20.0.1
hammerdown roll --workers 64 --sim-cursed 2 --dry-run=false --yes