Read repair is triggered during a read request. Consider a keyspace with replication factor 3. You send a write request to the cluster. The coordinator node will forward the write request to three relevant replica nodes. Suppose you read the same data with consistency QUORUM or TWO, and the coordinator node forwards the request to node 1 and 2. The coordinator node will then merge results from nodes 1 and 2 before returning them to the client. It will also trigger a background read repair on node 3, if enabled. This read repair ensures that the data on node 3 is in sync with nodes 1 and 2. In read repair, Cassandra sends a digest request to each replica not directly involved in the read. Cassandra compares all replicas and writes ...
Read repair
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