Zookeeper

ClickHouse Coordinates a Cluster-Wide Backup with ZooKeeper

Oct 23, 2026 22 min read Jay Hubbert

A cluster-wide backup is a ZooKeeper-coordinated election: one owner per data file, a stage barrier between phases, and a consensus loop over metadata.

Clickhouse Backups Zookeeper Distributed Internals

ClickHouse Keeper Carries a Tree Digest in Every Raft Log Entry

Oct 23, 2026 14 min read Jay Hubbert

Keeper puts a digest of its node tree inside every Raft log entry; a follower whose recomputed digest disagrees with the leader’s kills itself.

Clickhouse Keeper Raft Zookeeper Internals

ClickHouse Runs Distributed DDL Through a ZooKeeper Task Queue

Oct 23, 2026 16 min read Jay Hubbert

Distributed DDL is a ZooKeeper queue of sequential entries plus a per-host finished directory that the initiator lists to collect results.

Clickhouse Distributed Zookeeper Ddl Internals

How ClickHouse Replicates MergeTree: A ZooKeeper Log and a Hash Deduplication

Oct 22, 2026 16 min read Jay Hubbert

Replication is a ZooKeeper log plus a content-hash deduplication check that rides along with the block-number allocation.

Clickhouse Replication Internals Zookeeper Distributed