@concile/fleet

Multi-node fleet mode for Concile: run several concile serve nodes against one Postgres database, with a lease-elected writer, read/sync nodes serving from embedded replicas, and sharded write scale-out.

License

Source-available under the Concile Commercial License (see the LICENSE file in this package). In the current phase it is free to use in production — no license key is required. It may not be copied, modified, or distributed as part of a product or service that competes with Concile, and it does not convert to an open-source license.

What it provides

• Lease-based writer election with live failover. Nodes boot symmetrically; a Postgres lease decides which node is the writer. If the writer dies or wedges, a sync node acquires the expired lease and promotes itself — no manual intervention. The failover clock scales from a single lease-TTL knob (CONCILE_FLEET_LEASE_TTL_MS, default 15000 ms).
• Sync/read nodes with embedded replicas. Non-writer nodes tail the commit log into a local SQLite replica and serve queries and reactive subscriptions from it, forwarding mutations to the current writer with read-your-own-writes catch-up.
• Group commit. Batches concurrent commits into fewer Postgres flushes for higher write throughput (enabled via CONCILE_GROUP_COMMIT).
• Sharded write scale-out. Writes are partitioned across per-shard leases (shard count from CONCILE_FLEET_SHARDS, persisted at first boot and immutable after), with a balancer distributing shard ownership across nodes and an offline reshard path (reshardFleet) for changing the count on a stopped deployment.
• Fencing. A node that loses its lease fails closed (FencedError) rather than continuing to write.

Usage

Install alongside concile in the project you deploy:

bun add concile @concile/fleet

Fleet mode is activated per node by concile serve --fleet. The CLI has no static dependency on this package — when --fleet is passed it loads @concile/fleet via dynamic import at runtime and fails fast with an actionable message if the package is not installed.

Each fleet node needs a Postgres URL and the URL other nodes can reach it at:

concile serve --fleet \
  --database-url postgres://user:pass@db-host:5432/concile \
  --advertise-url http://this-node:3000

CONCILE_FLEET=1, CONCILE_DATABASE_URL, and env equivalents of the flags are also honored (flags win). Start additional nodes with the same --database-url and their own --advertise-url; roles (writer vs sync) are decided at boot and re-decided on failover.

Part of Concile — docs at https://concile-six.vercel.app/docs