adapter: make WAIT FOR roll back on timeout - #38621
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WAIT FOR currently forces a cut-over when the controller handles an expired deadline while the target remains unhydrated. Use the safer ROLLBACK action instead while preserving cut-over when the target hydrates. Users can still request a forced cut-over explicitly with ON TIMEOUT COMMIT.
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Motivation
ALTER CLUSTER ... WITH (WAIT FOR ...)currently forces a cut-over when itstimeout is processed while the target replicas remain unhydrated. This differs
from the safer
ROLLBACKdefault used byWAIT UNTIL READYand can introduceunexpected downtime.
Description
Make
WAIT FORuseROLLBACKwhen its deadline is processed while the targetremains unhydrated. A hydrated target still cuts over. Users who need a forced
cut-over can request it explicitly with
WAIT UNTIL READY (..., ON TIMEOUT = 'COMMIT').Update the user and design documentation to describe the safe timeout behavior.
Tests that intentionally require a forced cut-over now spell out
ON TIMEOUT COMMIT. The cluster-controller testdrive coverage verifies that anunhydrated
WAIT FORtarget times out and leaves the realized cluster shapeunchanged.
This changes a private-preview SQL option.
Verification
The existing cluster reconfiguration tests were updated to cover the new timeout
action and preserve explicit forced cut-over scenarios. Documentation build and
link validation covers the updated user pages.