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https://issues.apache.org/jira/browse/IGNITE-20116?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17775837#comment-17775837
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Roman Puchkovskiy commented on IGNITE-20116:
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The patch looks good to me
> Linearize storage updates with safeTime adjustment rules
> --------------------------------------------------------
>
> Key: IGNITE-20116
> URL: https://issues.apache.org/jira/browse/IGNITE-20116
> Project: Ignite
> Issue Type: Bug
> Reporter: Alexander Lapin
> Assignee: Alexander Lapin
> Priority: Blocker
> Labels: ignite-3, transactions
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> h3. Motivation
> The logic of setting safeTime explicitly prohibits setting a larger time
> ahead of a smaller one. In other words, all data updates within storages
> should be strictly ordered by the safeTime associated with such updates.
> Currently it's not true:
> * We associate update and safe time during update command creation (see
> org.apache.ignite.internal.table.distributed.replicator.PartitionReplicaListener)
> {code:java}
> UpdateCommandBuilder bldr = MSG_FACTORY.updateCommand()
> ...
> .safeTimeLong(hybridClock.nowLong()); {code}
> * However, neither applying a given command locally nor sending it to the
> raft isn't linearized with associated safeTime value. In other words, it's
> possible that we will assign t0 to the cmd0 and t1 to the cmd1 but will apply
> cmd1 prior to cmd0 locally.
> Simply speaking, we lack some sort of synchronization here.
> h3. Definition of Done
> * It's required to linearize updates application to preserve guarantees of
> the monotonicity of a safeTime's adjustment.
> h3. Implementation Notes
> Different options are possible:
> # We may reject a command that is associated with safeTime < already applied
> one. Such approach requires
> ## To resend the command with new safeTime in case of 1pc.
> ## Adjust local safeTime, and resend command with new safe time in case of
> 2pc.
> # Add proper synchronization both on client and server side.
> # Send pending safeTime instances with each command. More details below:
> Let’s assume that there were two updateCommands cmd1(safeTime: t1) and
> cmd2(safeTime: t2). Let’s also assume that cmd2 was send prior to cmd2
> (meaning that it was reordered). In that case, assuming that cmd2 has both t1
> and t2 within its data bag, it will wait for cmd1 to bring it data in a queue
> or formally it will wait previous commands to apply themselves.
>
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