A write request's journey in ZooKeeper

gistfile1.txt

               client → write request → zk_server_1
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                           write request is sent to the leader
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             leader fans out a transaction proposal to all followers
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            ↓                ↓                           ↓                 ↓
       follower 1        follower 2                  follower 3         follower 4
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               followers, non-synchronously, acknowledge the proposal
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 when the leader gets a sufficient number of acks (from a "majority") it fans out COMMIT msgs to followers
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            ↓                ↓                           ↓                 ↓
       follower 1        follower 2                  follower 3         follower 4
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   followers will then apply the write which triggers watches, that in turn will flow to listening clients...