Do not ignore shard not-available exceptions in replication #28571
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The shard not-available exceptions are currently ignored in the replication as the best effort avoids failing not-yet-ready shards. However these exceptions can also happen from fully active shards. If this is the case, we may have skipped important failures from replicas. Since elastic#28049, only fully initialized shards are received write requests. This restriction allows us to handle all exceptions in the replication. There is a side-effect with this change. If a replica retries its peer recovery second time after being tracked in the replication group, it can receive replication requests even though it's not-yet-ready. That shard may be failed and allocated to another node even though it has a good lucene index on that node. This PR does not change the way we report replication errors to users, hence the shard not-available exceptions won't be reported as before.
dnhatn
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Thanks @ywelsch for your quick review. |
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The shard not-available exceptions are currently ignored in the replication as the best effort avoids failing not-yet-ready shards. However these exceptions can also happen from fully active shards. If this is the case, we may have skipped important failures from replicas. Since #28049, only fully initialized shards are received write requests. This restriction allows us to handle all exceptions in the replication. There is a side-effect with this change. If a replica retries its peer recovery second time after being tracked in the replication group, it can receive replication requests even though it's not-yet-ready. That shard may be failed and allocated to another node even though it has a good lucene index on that node. This PR does not change the way we report replication errors to users, hence the shard not-available exceptions won't be reported as before. Relates #28049 Relates #28534
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Apr 27, 2018
Since elastic#28049, only fully initialized shards are received write requests. This enhancement allows us to handle all exceptions. In elastic#28571, we started strictly handling shard not-available exceptions and tried to keep the way we report replication errors to users by only reporting if the error is not shard-not-available exceptions. However, since then we unintentionally always log warn for all exception. This change restores to the previous behavior to log warn only if an exception is not a shard not-available exception.
dnhatn
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Apr 27, 2018
Since #28049, only fully initialized shards are received write requests. This enhancement allows us to handle all exceptions. In #28571, we started strictly handling shard-not-available exceptions and tried to keep the way we report replication errors to users by only reporting if the error is not shard-not-available exceptions. However, since then we unintentionally always log warn for all exception. This change restores to the previous behavior which logs warn only if an exception is not a shard-not-available exception. Relates #28049 Relates #28571
dnhatn
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Apr 27, 2018
Since #28049, only fully initialized shards are received write requests. This enhancement allows us to handle all exceptions. In #28571, we started strictly handling shard-not-available exceptions and tried to keep the way we report replication errors to users by only reporting if the error is not shard-not-available exceptions. However, since then we unintentionally always log warn for all exception. This change restores to the previous behavior which logs warn only if an exception is not a shard-not-available exception. Relates #28049 Relates #28571
dnhatn
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Apr 27, 2018
Since #28049, only fully initialized shards are received write requests. This enhancement allows us to handle all exceptions. In #28571, we started strictly handling shard-not-available exceptions and tried to keep the way we report replication errors to users by only reporting if the error is not shard-not-available exceptions. However, since then we unintentionally always log warn for all exception. This change restores to the previous behavior which logs warn only if an exception is not a shard-not-available exception. Relates #28049 Relates #28571
ywelsch
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Jun 11, 2018
Swallowing these exceptions is dangerous as they can result in replicas going out-of-sync with the primary. Follow-up to #28571
ywelsch
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Jun 11, 2018
Swallowing these exceptions is dangerous as they can result in replicas going out-of-sync with the primary. Follow-up to #28571
ywelsch
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Jun 11, 2018
Swallowing these exceptions is dangerous as they can result in replicas going out-of-sync with the primary. Follow-up to #28571
dnhatn
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Sep 11, 2018
We fail to notify the resync listener if the resync replication hits a shard unavailable exception. Moreover, we no longer need to swallow these unavailable exceptions. Relates elastic#28571 Closes elastic#33613
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The shard not-available exceptions are currently ignored in the
replication as the best effort avoids failing not-yet-ready shards.
However these exceptions can also happen from fully active shards. If
this is the case, we may have skipped important failures from replicas.
Since #28049, only fully initialized shards are received write requests.
This restriction allows us to handle all exceptions in the replication.
There is a side-effect with this change. If a replica retries its peer
recovery second time after being tracked in the replication group, it
can receive replication requests even though it's not-yet-ready. That
shard may be failed and allocated to another node even though it has a
good lucene index on that node.
This PR does not change the way we report replication errors to users,
hence the shard not-available exceptions won't be reported as before.
Relates #28049
Relates #28534