Thread: [HACKERS] Re: [BUGS] Problem in using pgbench's --connect(-C) and --rate=rate(-Rrate) options together.

Repost from bugs.

-- 
Fabien.

---------- Forwarded message ----------
Date: Wed, 25 Jan 2017 18:59:45 +0100 (CET)
From: Fabien COELHO <coelho@cri.ensmp.fr>
To: nuko yokohama <nuko.yokohama@gmail.com>
Cc: PostgreSQL Bugs List <pgsql-bugs@postgresql.org>
Subject: Re: [BUGS] Problem in using pgbench's --connect(-C) and --rate=rate(-R
     rate) options together.


>> It operates normally when only the -C option or only the -R option is 
>> specified.
>> 
>> In the PostgreSQL document, It is not described that "these two options can 
>> not be specified at the same time ". Is this a problem of pgbench?
> 
> Yes, indeed there is. Thanks for the report. Option -C is seldom used and 
> tested.

The problem is already fixed in head. Looking at git log, it was unclear to 
guess which change fixed that... After another reading, I got it in one, it has 
been fixed by Heikki restructuring patch 
12788ae49e1933f463bc59a6efe46c4a01701b76 which has no vocation to be 
backpatched to prior versions...

The bug is that prior to --rate doCustom was always disconnect/reconnect 
without exiting, but with rate it returns if it has to wait. However threadRun 
test whether there is a connection before recalling doCustom, so it was never 
called.

This is exactly the kind of unmanageable state combination that refactoring has 
cleaned up.

Attached a small patch which fixes the issue, I think, in 9.6.
Fixing it raised another issue wrt to some stats under -C, that I fixed as 
well.

-- 
Fabien.
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On 1/25/17 2:58 PM, Fabien COELHO wrote:
> 
> Repost from bugs.

This patch does not apply at cccbdde:

$ patch -p1 < ../other/pgbench-CR-bug-1.patch
(Stripping trailing CRs from patch.)
patching file src/bin/pgbench/pgbench.c
Hunk #1 FAILED at 1967.
Hunk #2 succeeded at 4180 with fuzz 2 (offset -164 lines).

Marked as "Waiting for Author".

-- 
-David
david@pgmasters.net

Hello David,

>> Repost from bugs.
>
> This patch does not apply at cccbdde:

Indeed. It should not. The fix is for the 9.6 branch. The issue has been 
fixed by some heavy but very welcome restructuring in master.

> Marked as "Waiting for Author".

I put it back to "Needs review".

-- 
Fabien.

On 3/17/17 2:08 AM, Fabien COELHO wrote:
> 
> Hello David,
> 
>>> Repost from bugs.
>>
>> This patch does not apply at cccbdde:
> 
> Indeed. It should not. The fix is for the 9.6 branch. The issue has been
> fixed by some heavy but very welcome restructuring in master.

Whoops, sorry about that!

>> Marked as "Waiting for Author".
> 
> I put it back to "Needs review".

Beena, do you know when you'll have time to review?

Thanks,
-- 
-David
david@pgmasters.net

Hi, the patch looks good except why do you remove initialization of is_throttled?
Suppose, just a typo?
 --- a/src/bin/pgbench/pgbench.c
+++ b/src/bin/pgbench/pgbench.c
@@ -1967,7 +1967,6 @@ top:        st->listen = false;        st->sleeping = false;        st->throttling = false;
-       st->is_throttled = false;        memset(st->prepared, 0, sizeof(st->prepared));    }


-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
  WWW: http://www.sigaev.ru/
 

Hello Teodor,

> Hi, the patch looks good except why do you remove initialization of 
> is_throttled? Suppose, just a typo?

No, it is really needed so that the lag measure is correct.

Without the is_throttled change:
 sh> ./pgbench -T 3 -R 10 -C -S -P 1 starting vacuum...end. progress: 1.0 s, 9.0 tps, lat 8.278 ms stddev 9.134, lag
2049638230412146.250ms progress: 2.0 s, 12.0 tps, lat 4.897 ms stddev 3.961, lag 2.219 ms transaction type: <builtin:
selectonly> scaling factor: 1 query mode: simple number of clients: 1 number of threads: 1 duration: 3 s number of
transactionsactually processed: 33 latency average = 5.602 ms latency stddev = 5.820 ms rate limit schedule lag: avg
558992244657859.500(max 18446744073709264.000) ms tps = 11.024559 (including connections establishing) tps = 12.183456
(excludingconnections establishing)
 

With the is_throttled change:
 ./pgbench -T 3 -R 10 -C -S -P 1 starting vacuum...end. progress: 1.0 s, 11.0 tps, lat 3.742 ms stddev 2.161, lag 1.658
msprogress: 2.0 s, 7.0 tps, lat 2.985 ms stddev 0.496, lag 0.276 ms transaction type: <builtin: select only> scaling
factor:1 query mode: simple number of clients: 1 number of threads: 1 duration: 3 s number of transactions actually
processed:25 latency average = 3.312 ms latency stddev = 1.518 ms rate limit schedule lag: avg 0.894 (max 7.031) ms tps
=8.398353 (including connections establishing) tps = 9.069456 (excluding connections establishing)
 

-- 
Fabien.

> No, it is really needed so that the lag measure is correct.
Thank you, pushed

-- 
Teodor Sigaev                                   E-mail: teodor@sigaev.ru
  WWW: http://www.sigaev.ru/