[jira] [Updated] (HBASE-25913) Introduce EnvironmentEdge.currentTimeAdvancing

["Andrew Kyle Purtell (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HBASE-25913?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Andrew Kyle Purtell updated HBASE-25913:
----------------------------------------
    Description: 
Introduce new {{EnvironmentEdge#currentTimeAdvancing}} which ensures that when the current time is returned, it is the current time in a different clock tick from the last time the {{EnvironmentEdge}} was used to get the current time.

Use {{EnvironmentEdge#currentTimeAdvancing}} wherever we go to substitute a {{Long.MAX_VALUE}} timestamp placeholder with a real placeholder just before committing the mutation. When processing a batch of mutations (doMiniBatchMutation etc) we will call {{currentTimeAdvancing}} only once. This means the client cannot bundle cells with wildcard timestamps into a batch where those cells must be committed with different timestamps. Clients must simply not submit mutations that must be committed with guaranteed distinct timestamps in the same batch. Easy to understand, easy to document, and it aligns with our design philosophy of the client knows best. 

It is not required to handle batches as proposed; we could guarantee a distinct timestamp for every mutation in the batch. Count the number of mutations, call this M. Get the current time. Set the first mutation timestamp with this value and increment by 1 for all remaining. Then, wait for at least M milliseconds. I don't think this is necessary. See reasoning in above paragraph. Mentioned here for sake of discussion.

It will be fine to continue to use {{EnvironmentEdge#currentTime}} everywhere else. In this way we will only potentially spin wait where it matters, and won't suffer serious overheads during batch processing.

  was:Introduce new {{EnvironmentEdge#currentTimeAdvancing}} which ensures that when the current time is returned, it is the current time in a different clock tick from the last time the {{EnvironmentEdge}} was used to get the current time


> Introduce EnvironmentEdge.currentTimeAdvancing
> ----------------------------------------------
>
>                 Key: HBASE-25913
>                 URL: https://issues.apache.org/jira/browse/HBASE-25913
>             Project: HBase
>          Issue Type: Sub-task
>            Reporter: Andrew Kyle Purtell
>            Priority: Major
>             Fix For: 3.0.0-alpha-1, 2.5.0
>
>
> Introduce new {{EnvironmentEdge#currentTimeAdvancing}} which ensures that when the current time is returned, it is the current time in a different clock tick from the last time the {{EnvironmentEdge}} was used to get the current time.
> Use {{EnvironmentEdge#currentTimeAdvancing}} wherever we go to substitute a {{Long.MAX_VALUE}} timestamp placeholder with a real placeholder just before committing the mutation. When processing a batch of mutations (doMiniBatchMutation etc) we will call {{currentTimeAdvancing}} only once. This means the client cannot bundle cells with wildcard timestamps into a batch where those cells must be committed with different timestamps. Clients must simply not submit mutations that must be committed with guaranteed distinct timestamps in the same batch. Easy to understand, easy to document, and it aligns with our design philosophy of the client knows best. 
> It is not required to handle batches as proposed; we could guarantee a distinct timestamp for every mutation in the batch. Count the number of mutations, call this M. Get the current time. Set the first mutation timestamp with this value and increment by 1 for all remaining. Then, wait for at least M milliseconds. I don't think this is necessary. See reasoning in above paragraph. Mentioned here for sake of discussion.
> It will be fine to continue to use {{EnvironmentEdge#currentTime}} everywhere else. In this way we will only potentially spin wait where it matters, and won't suffer serious overheads during batch processing.



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