# appcore-sync
[English guide](wiki/guide.en.md) |
[Guia em português](wiki/guide.pt.md) |
[Guide français](wiki/guide.fr.md)
Conservative leader-to-follower replication with versioned wire, log,
snapshots, checkpoints, outbox, receiver and transport contracts.
Identity, protocol, sequence and hash-chain validation are mandatory. This
crate is not RAFT, multi-master consensus or a domain conflict resolver.
File logs, snapshots, checkpoints and outbox records are versioned and bounded.
The receiver validates the complete incoming batch, sequence range and record
sizes before mutating the replication log or checkpoint.
On the next-major development line, `ReplicationLog::len`, `last_index` and
`is_empty` return `SyncResult`. Persistent providers surface observation
failures instead of substituting zero or stale state. Consumers must handle the
result before updating; see
[`release/fallible-replication-log-observations.md`](../../release/fallible-replication-log-observations.md).
The next-major `FileSyncOutbox` uses the explicit
`appcore-sync-outbox-v2` append-only binary journal. Enqueue and acknowledgement
sync one integrity-chained frame; readers scan only a new tail, and bounded
compaction atomically retains pending messages. Only an incomplete final frame
is recoverable. A complete corrupt, V1, unversioned or future-format file fails
closed. Drain the V1 queue before upgrading and the V2 queue before rollback;
see [`release/outbox-v2-migration.md`](../../release/outbox-v2-migration.md).
`HttpSyncTransport` owns a reusable bounded HTTP client. `with_timeout_ms`
keeps the uniform V1 deadline, while `with_timeouts` selects independent
connect/admission, read and write deadlines.
```bash
cargo test -p appcore-sync
```