From: | "shiy(dot)fnst(at)fujitsu(dot)com" <shiy(dot)fnst(at)fujitsu(dot)com> |
---|---|
To: | "houzj(dot)fnst(at)fujitsu(dot)com" <houzj(dot)fnst(at)fujitsu(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
Cc: | Ajin Cherian <itsajin(at)gmail(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, "osumi(dot)takamichi(at)fujitsu(dot)com" <osumi(dot)takamichi(at)fujitsu(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Rahila Syed <rahila(dot)syed(at)2ndquadrant(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Craig Ringer <craig(at)2ndquadrant(dot)com> |
Subject: | RE: logical replication empty transactions |
Date: | 2022-03-24 03:33:23 |
Message-ID: | OSZPR01MB6310C805D34716CB0590F2DAFD199@OSZPR01MB6310.jpnprd01.prod.outlook.com |
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Lists: | pgsql-hackers |
On Thursday, March 24, 2022 11:19 AM Hou, Zhijie/侯 志杰 <houzj(dot)fnst(at)fujitsu(dot)com> wrote:
>
> Attach the new version patch which include the following changes:
>
> - Fix a typo
> - Change the requestreply flag of the newly added WalSndKeepalive to false,
> because the subscriber can judge whether it's necessary to post a reply
> based
> on the received LSN.
> - Add a testcase to make sure there is no data in subscriber side when the
> transaction is skipped.
> - Change the name of flag skipped_empty_xact to skipped_xact which seems
> more
> understandable.
> - Merge Amit's suggested changes.
>
Hi,
This patch skips sending BEGIN/COMMIT messages for empty transactions and saves
network bandwidth. So I tried to do a test to see how does it affect bandwidth.
This test refers to the previous test by Peter[1]. I temporarily modified the
code in worker.c to log the length of the data received by the subscriber (after
calling walrcv_receive()). At the conclusion of the test run, the logs are
processed to extract the numbers.
The number of transactions is fixed (1000), and I tested different mixes of
empty and not-empty transactions sent - 0%, 25%, 50%, 100%. The patch will send
keepalive message when skipping empty transaction in synchronous replication
mode, so I tested both synchronous replication and asynchronous replication.
The results are as follows, and attach the bar chart.
Sync replication - size of sending data
--------------------------------------------------------------------
0% 25% 50% 75% 100%
HEAD 335211 281655 223661 170271 115108
patched 335217 256617 173878 98095 18108
Async replication - size of sending data
--------------------------------------------------------------------
0% 25% 50% 75% 100%
HEAD 339379 285835 236343 184227 115000
patched 335077 260953 180022 113333 18126
The details of the test is also attached.
Summary of result:
In both synchronous replication mode and asynchronous replication mode, as more
empty transactions, the improvement is more obvious. Even if when there is no
empty transaction, I can't see any overhead.
Regards,
Shi yu
Attachment | Content-Type | Size |
---|---|---|
image/png | 47.2 KB | |
details.txt | text/plain | 1.4 KB |
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