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| -rw-r--r-- | src/mongo/db/repl/README.md | 24 |
1 files changed, 10 insertions, 14 deletions
diff --git a/src/mongo/db/repl/README.md b/src/mongo/db/repl/README.md index 6a4cc0b6a82..0c209ce3089 100644 --- a/src/mongo/db/repl/README.md +++ b/src/mongo/db/repl/README.md @@ -235,18 +235,14 @@ Each node communicates with other nodes at regular intervals to: Each oplog entry is assigned an `OpTime` to describe when it occurred so other nodes can compare how up-to-date they are. -In the old replication protocol, -[PV0](https://docs.mongodb.com/manual/reference/replica-set-protocol-versions/), OpTimes were simply -a timestamp. +OpTimes include a timestamp and a term field. The term field indicates how many elections have +occurred since the replica set started. -In the new protocol, -[PV1](https://docs.mongodb.com/manual/reference/replica-set-protocol-versions/), OpTimes also -include a term field which indicates how many elections have occurred since the replica set started. - -The election protocol is built on top of [Raft](https://raft.github.io/raft.pdf), so it is -guaranteed that two primaries will not be elected in the same term. This helps differentiate ops -that occurred at the same time but from different primaries in the case of a network partition. This -article will only talk about PV1, the new replication protocol. +The election protocol, known as +[protocol version 1 or PV1](https://docs.mongodb.com/manual/reference/replica-set-protocol-versions/), +is built on top of [Raft](https://raft.github.io/raft.pdf), so it is guaranteed that two primaries +will not be elected in the same term. This helps differentiate ops that occurred at the same time +but from different primaries in the case of a network partition. #### Oplog Fetcher Responses @@ -382,9 +378,9 @@ actually sends the `replSetUpdatePosition` command to the sync source. This comm sent every `keepAliveInterval` milliseconds (`(electionTimeout / 2)`) to maintain liveness information about the nodes in the replica set. -In PV1, `replSetUpdatePosition` commands are the primary means of maintaining liveness. Thus, if the -primary cannot communicate directly with every node, but it can communicate with every node through -other nodes, it will still stay primary. +`replSetUpdatePosition` commands are the primary means of maintaining liveness. Thus, if the primary +cannot communicate directly with every node, but it can communicate with every node through other +nodes, it will still stay primary. The `replSetUpdatePosition` command contains the following information: |