Switchwrites: error if no tablets available on target for reverse replication #8142
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sougou
reviewed
May 24, 2021
…e are no tablets available on the target to source data for the reverse flow Signed-off-by: Rohit Nayak <rohit@planetscale.com> Signed-off-by: Rohit Nayak <rohit@planetscale.com>
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Signed-off-by: Rohit Nayak <rohit@planetscale.com>
The case fixed here is the one that caused the user issue recently where they were not able to reverse after detecting an issue after cutover causing an unexpected outage. I agree we should validate for available tablets while creating streams as well. For those use cases though, the workflow would just not start and the error would be visible in Adding other validations will involve some time writing the tests for it, so I would like to move ahead with this for now and implement those later. |
deepthi
approved these changes
Jun 9, 2021
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Description
This PR addresses an edge case while switching writes.
-tablet_typesselected asRDONLYSwitchWritesis called next to switch all traffic to the target, with the-reverse_replication trueflagthe user tries to rollback by reversing the writes.
This PR adds a check on invoking SwitchWrites that there are tablets available to source data from the target keyspace if reverse replication is enabled. Note that this only checks for tablets being available when SwitchWrites is called. If, in this usecase, the RDONLY tablets disappear in the future then the workflow will stop replicating resulting in the same problem as outlined above.
Checklist