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https://issues.apache.org/jira/browse/HBASE-25913?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17353651#comment-17353651
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Andrew Kyle Purtell edited comment on HBASE-25913 at 5/29/21, 2:19 AM:
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I've put together a JMH based harness, attached to this JIRA. JMH is GPLed so
we cannot include this in the project, but it is fine for standalone work.
Build with Maven, 'mvn clean install'.
Run like:
{noformat}
java -jar ./target/benchmarks.jar BenchHRegionIncrementAdvancingClock -f 0 -t 1
{noformat}
-f 0 is to avoid forks, for some reason JMH doesn't work for me if forking
-t 1 is single thread
I have a lot of work to do yet characterizing performance in real conditions
that matter, but the results so far comport with what you'd expect.
In the meantime some early results are available in this PDF:
[^JMH-HBASE-25913.pdf] All measurements in this document are in nanoseconds.
was (Author: apurtell):
I've put together a JMH based harness, attached to this JIRA. JMH is GPLed so
we cannot include this in the project, but it is fine for standalone work.
Build with Maven, 'mvn clean install'.
Run like:
{noformat}
java -jar ./target/benchmarks.jar BenchHRegionIncrementAdvancingClock -f 0 -t 1
{noformat}
-f 0 is to avoid forks, for some reason JMH doesn't work for me if forking
-t 1 is single thread
I have a lot of work to do yet characterizing performance in real conditions
that matter, but the results so far comport with what you'd expect.
In the meantime some early results are available in this PDF:
[^JMH-HBASE-25913.pdf]
> 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
> Assignee: Andrew Kyle Purtell
> Priority: Major
> Fix For: 3.0.0-alpha-1, 2.5.0
>
> Attachments:
> 0001-HBASE-25913-Introduce-EnvironmentEdge-Clock-and-Cloc.patch,
> JMH-HBASE-25913.pdf, jmh-HBASE-25913.tar.gz
>
>
> 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.
> When processing mutations we substitute the {{Long.MAX_VALUE}} timestamp
> placeholder with a real placeholder just before committing the mutation. The
> current code gets the current time for timestamp substitution while under row
> lock and mvcc. We will simply use {{EnvironmentEdge#currentTimeAdvancing}}
> instead of {{EnvironmentEdge#currentTime}} at this point in the code to
> ensure we have seen the clock tick over. 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 a batch. Count the number of
> mutations, call this M. Acquire all row locks and get the current time. Then,
> wait for at least M milliseconds. Then, set the first mutation timestamp with
> this value and increment by 1 for all remaining. Then, do the rest of
> mutation processing as normal. I don't think this extra waiting to reserve
> the range of timestamps 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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