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https://issues.apache.org/jira/browse/IGNITE-17261?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Alexander Lapin resolved IGNITE-17261.
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Resolution: Duplicate
> Implement a coordinator path write intent resolution logic for RO reads
> -----------------------------------------------------------------------
>
> Key: IGNITE-17261
> URL: https://issues.apache.org/jira/browse/IGNITE-17261
> Project: Ignite
> Issue Type: Improvement
> Reporter: Alexander Lapin
> Priority: Major
> Labels: ignite-3, transaction3_ro
> Attachments: Screenshot from 2022-07-06 17-00-26.png
>
>
> Because of lock-free nature, RO reads might interact with writeIntents,
> meaning that such intents should be either evaluated as committed, aborted or
> pending. In order to perform writeIntent resolution it's required to
> * If PartitionReplicaListener read a write intent then it checks a local txn
> state map for committed or aborted state - allow read if the state is
> committed and commitTs <= readTs.
> * If not possible, PartitionReplicaListener send TxStateReq to coordinator
> by ReplicaService. - this initiates the {*}coordinator path{*}. Coordinator
> address is fetched from the [txn state
> map|https://docs.google.com/document/d/1PndaylEfK7CPUN7Kv9RYPKASN299s2qlbnMA5xIOFXo/edit#heading=h.wx3zf7jlf156].
> * If a coordinator path was not able to resolve the intent, one of the
> following has happened - the coordinator is dead or txn state is not
> available in the cache. Calculate a commit partition and send the TxStateReq
> to its primary replica - this initiates the {*}commit partition path{*}.
> * Retry commit partition path until a success or timeout.
> On receiving TxStateReq in ReplicaManager on the coordinator:
> * ReplicaManager reads txn state map. If the local txn is finished, return
> the response with the outcome: commit or abort. The txn state is stored in a
> local cache (https://issues.apache.org/jira/browse/IGNITE-17638)
> * If the local txn is finishing (txState == Finishing) waiting for finish
> state replication, wait with timeout for outcome and return response with the
> outcome: commit or abort. txState become Finishing in TxManager on creating
> TxFinishReplicaRequest. TxManager has a txn state map. We can use future for
> concurrency and atomic operations on txn state map.
> * If the outcome is commit, additional timestamp check is required: a commit
> timestamp must be <= readTs. If the condition is not held, the outcome is
> changed to abort.
> * If local txn is active (txState != [finishing, commit, abort]), adjust the
> txn coordinator node HLC according to readTs to make sure the txn commit
> timestamp is above the read timestamp. The read timestamp must be installed
> before txn is started to commit, so commit timestamp is assigned after the
> read timestamp.
> * If txn state is not found in a local cache and txn is not active, return
> NULL.
>
> There's an open question about MvPartitionStorage api feature:
> https://issues.apache.org/jira/browse/IGNITE-17627
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