Swaroop Jagadish created HELIX-249:
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Summary: Allow participants to "Reject state transitions"
Key: HELIX-249
URL: https://issues.apache.org/jira/browse/HELIX-249
Project: Apache Helix
Issue Type: New Feature
Reporter: Swaroop Jagadish
Assignee: Swaroop Jagadish
Priority: Minor
There are situations in which a participant will not be able to honor the state
transition directive from the controller (e.g: Bad configuration etc.).
Currently, if the state transition handler throws an exception, it enters the
"error" state. This can be a problem in scenarios where the participant runs
internal consistency checks (i.e. no partition should be in error state) to
decide whether it should disable itself.
For well known error conditions (bad configuration etc.), we should allow the
participant to reject the state transition. For all unexpected errors, the
participant can still go into an error state.
We need to figure out the exact mechanism for rejecting a state transition -
one mechanism could be to be to throw a special type of exception. The client
library then requests a rejection by recording a flag in the currentstate. The
controller can still decide to send the participant into an error state or
re-evaluate system state based on the rejection.
Let me know if this makes sense
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