Backbeat is the core engine for asynchronous replication, optimized for queuing metadata updates and dispatching work to long-running background tasks, like retries for failed cross-region replication (CRR) attempts. Backbeat maintains job queues for CloudServer. It mediates between the core CloudServer logic and the transient Kafka lists and MongoDB databases where task information is queued. It is also instrumental in garbage collection.

Backbeat provides a REST API with endpoints for healthcheck, cross-region replication (CRR), and metrics.

The Backbeat API provides REST endpoints for these features.

Common Request Headers

All Backbeat API endpoints are addressed through the /_/backbeat/api/ route with endpoints entered as described in the sections linked above.

Accessing the Backbeat API paths is detailed in Setting Up Backbeat Access in Zenko Operation.

The internal routes presented in the following table are required for testing the overall health of Backbeat and to measure the progress of an ongoing replication.

Replication Status

A special status, PROCESSING, supports cross-region replication with a multiple-backend topology. Objects in CRR buckets transition from PENDING to PROCESSING, then to COMPLETED or FAILED.

  • PENDING: CRR to all backends is pending.
  • PROCESSING: At least one backend has completed and is waiting for other backend(s) to finish.
  • COMPLETED: All backends report a completed status.
  • FAILED: At least one backend failed.

Each backend’s replication status is reported as user metadata.

For example, if the site names configured in the replication endpoints are aws-backend-1, aws-backend-2, azure-backend-1, and azure-backend-2, user metadata on the head object may appear as:

aws-backend-1-replication-status: COMPLETED
aws-backend-2-replication-status: PENDING
azure-backend-1-replication-status: COMPLETED
azure-backend-2-replication-status: PENDING

This user metadata is in addition to the object’s replication status, which follows the logic laid out in the bucket config file.