Data Change Protocol
Data Change Protocol (DCP) is a high-performance streaming protocol that communicates the state of the data using an ordered change log with sequence numbers. It is a generic protocol designed for keeping a consumer of the Data Service up to date.
DCP is robust and resilient in the face of transitory errors. For example, if a stream is interrupted, DCP resumes from exactly the point of its last successful update once connectivity resumes. DCP provides version histories and rollbacks that provide a snapshot of the data. Snapshots can be used to create a brand new replica or catch up an interrupted or partially built node.
Couchbase Server leverages DCP internally and externally for several different purposes. Within Couchbase Server, DCP is used to create replicas of data within and between clusters, maintain indexes (both local and global), backups, etc. DCP also feeds most Connector Guides, which are integrations with external systems such as Hadoop, Kafka or Elasticsearch. Some of these connectors leverage DCP directly or connect to Couchbase Server’s XDCR functionality to keep the external systems in sync by acting like Couchbase Server nodes.