Crate crdt_migrate 

crdt-migrate

Transparent schema migrations for crdt-kit.

When your data schema evolves between versions, crdt-migrate ensures that persisted data is automatically and transparently migrated — no downtime, no manual intervention, no data loss.

How It Works

1. Every serialized CRDT is wrapped in a version envelope (3-byte header).
2. When data is loaded, the envelope version is compared to the current version.
3. If they differ, a chain of migration steps runs automatically.
4. Optionally, the migrated data is written back to storage.

Key Concepts

• Lazy migration: Data is migrated on read, not eagerly on startup.
• Deterministic: Two devices migrating the same data produce identical results.
• Linear chain: Migrations run v1→v2→v3→…→current, never skipping steps.
• Compiled in: All migrations are embedded in the binary at compile time.

Structs

MigrationConfig

Configuration for the migration engine.

MigrationEngine

The migration engine that runs a chain of migration steps.

VersionedEnvelope

A version envelope wrapping serialized CRDT data.

Enums

CrdtType

Identifies the type of CRDT stored in the envelope.

MigrationError

Error during migration.

Constants

ENVELOPE_HEADER_SIZE

Size of the version envelope header in bytes.

MAGIC_BYTE

Magic byte identifying crdt-kit serialized data.

Traits

MigrationStep

A single migration step that transforms data from one version to the next.

Schema

Trait for types with a versioned schema.

Attribute Macros

crdt_schema

Attribute macro that generates schema + versioning impls for a struct.

migration

Attribute macro that wraps a migration function into a MigrationStep.