Module resume_token 

MongoDB change stream resume token persistence.

Resume tokens are opaque BSON documents that allow a change stream to be resumed from a specific position. This module provides a pluggable storage trait and two implementations:

• FileResumeTokenStore: Persists to a local file (embedded/test use)
• MongoResumeTokenStore: Persists to a dedicated MongoDB collection (production use, feature-gated behind mongodb-cdc)

Resume Token Semantics

• Track postBatchResumeToken from every getMore response, not just individual event _id fields. This prevents unnecessary oplog re-scanning across empty getMore batches.
• On startup: if a persisted token exists, open with resumeAfter.
• On invalidate events, switch to startAfter (cannot resumeAfter an invalidate token).

Structs

FileResumeTokenStore

File-based resume token store for embedded and test use.

InMemoryResumeTokenStore

In-memory resume token store (no persistence, for testing).

MongoResumeTokenStore

MongoDB-backed resume token store (feature-gated behind mongodb-cdc).

ResumeToken

An opaque resume token from a MongoDB change stream.

Enums

ResumeTokenStoreConfig

Configuration for resume token persistence.

ResumeTokenStoreError

Errors from resume token store operations.

Traits

ResumeTokenStore

Trait for pluggable resume token persistence.