Xinyu Tan created RATIS-1874:
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Summary: Add notifyLeaderReady function in IStateMachine
Key: RATIS-1874
URL: https://issues.apache.org/jira/browse/RATIS-1874
Project: Ratis
Issue Type: Improvement
Reporter: Xinyu Tan
Assignee: Xinyu Tan
In a highly available metadata service built on top of Ratis, such as IoTDB's
confignode, the Leader node launches more modules compared to the Follower
node. These additional modules include functionalities like load balancing and
others.
Currently, we employ the "notifyLeaderChange" callback to prompt the Leader to
initiate the corresponding modules like load balancing. However, within this
callback, the leader's state machine might not have fully recovered,
potentially leading to the retrieval of outdated data when directly reading
from certain modules.
One approach in this scenario would involve utilizing a linearizable read
interface along with implementing corresponding retry logic (such as timeouts
or waiting until a leader is elected). However, such modifications would result
in significant changes to our codebase. Therefore, we are inclined to opt for
an alternative solution – adding a "notifyLeaderReady" interface to the
"StateMachine". This interface would be invoked only when the Leader's state
machine applies the first log entry of its current term. This adjustment would
ensure the accurate recovery of certain modules.
[~szetszwo] What's your opinion?
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