[pgpool-general: 3649] Re: Error in pgpool memory cache invalidation.

[Tatsuo Ishii]

Thanks for the report.

I confirm this with pgpool-II 3.4.1. I also found that this does not
happen with 3.3.5 (I tested with shmem).

Here is the test script.
-------------------------------------
drop table t1;
create table t1(i int, j text);
insert into t1 values(1, 'aaa');
select * from t1;
select * from t1;
update t1 set j = 'bbb' where i = 1;
select * from t1;
-------------------------------------

Will look into this...

Best regards,
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese:http://www.sraoss.co.jp

> Looks like only part of this email ended up in the mailing list , not
> sure how. Resending again - hope it works this time.
> 
> pgpool doesn't seem to be invalidating caches properly. See the
> example test case below
> 
> psql -U ruser -d mydb -h 127.0.0.1 -p 9999
> Password for user ruser:
> psql (9.4.1)
> Type "help" for help.
> 
> mydb=> select comments from users where id=1;
>  comments
> ----------
>  boooo
> (1 row)
> 
> # comes from cache
> mydb=> select comments from users where id=1;
>  comments
> ----------
>  boooo
> (1 row)
> 
> # works
> mydb=> update users set comments='hello' where id=1;
> UPDATE 1
> mydb=> select comments from users where id=1;
>  comments
> ----------
>  hello
> (1 row)
> 
> # stale
> mydb=> update users set comments='hello world' where id=1;
> UPDATE 1
> mydb=> select comments from users where id=1;
>  comments
> ----------
>  hello
> (1 row)
> 
> # also stale
> mydb=> update users set comments='booo' where id=1;
> UPDATE 1
> mydb=> select comments from users where id=1;
>  comments
> ----------
>  hello
> (1 row)
> 
> 
> From the second write onwards, the cache is not invalidated and stale
> value is being served. Is it a bug or am I doing something wrong? This
> happens with both cache backends (memcache and shmem but test logs are
> from memcache backend)
> 
> Test setup is postgresql-9.4 and memcached 1.4.21 and pgpool-3.4.2. my
> configs and logs from test are here
> 
> https://gist.github.com/dbalan/d635993a3e532a083751
> 
> Regards,
> --------
> DHANANJAY | Infrastructure Engineer
> Plivo, Inc. 340 Pine St, San Francisco - 94104, USA
> Web: www.plivo.com | Twitter: @plivo, @notmycommit
> DHANANJAY | Infrastructure Engineer
> Plivo, Inc. 340 Pine St, San Francisco - 94104, USA
> Web: www.plivo.com | Twitter: @plivo, @notmycommit
> 
> Free Incoming SMS for All US Short Codes – Get One Today!
> 
> 
> 
> 
> On Tue, Apr 21, 2015 at 12:33 PM, Dhananjay Balan <dhananjay at plivo.com> wrote:
>> pgpool doesn't seem to be invalidating caches properly. See the
>> example test case below
>>
>> psql -U ruser -d mydb -h 127.0.0.1 -p 9999
>> Password for user ruser:
>> psql (9.4.1)
>> Type "help" for help.
>>
>> mydb=> select comments from users where id=1;
>>  comments
>> ----------
>>  boooo
>> (1 row)
>>
>> # comes from cache
>> mydb=> select comments from users where id=1;
>>  comments
>> ----------
>>  boooo
>> (1 row)
>>
>> # works
>> mydb=> update users set comments='hello' where id=1;
>> UPDATE 1
>> mydb=> select comments from users where id=1;
>>  comments
>> ----------
>>  hello
>> (1 row)
>>
>> # stale
>> mydb=> update users set comments='hello world' where id=1;
>> UPDATE 1
>> mydb=> select comments from users where id=1;
>>  comments
>> ----------
>>  hello
>> (1 row)
>>
>> # also stale
>> mydb=> update users set comments='booo' where id=1;
>> UPDATE 1
>> mydb=> select comments from users where id=1;
>>  comments
>> ----------
>>  hello
>> (1 row)
>>
>>
>> From the second write onwards, the cache is not invalidated and stale
>> value is being served. Is it a bug or am I doing something wrong? This
>> happens with both cache backends (memcache and shmem but test logs are
>> from memcache backend)
>>
>> Test setup is postgresql-9.4 and memcached 1.4.21 and pgpool-3.4.2. my
>> configs and logs from test are here
>>
>> https://gist.github.com/dbalan/d635993a3e532a083751
>>
>> Regards,
>> --------
>> DHANANJAY | Infrastructure Engineer
>> Plivo, Inc. 340 Pine St, San Francisco - 94104, USA
>> Web: www.plivo.com | Twitter: @plivo, @notmycommit
> _______________________________________________
> pgpool-general mailing list
> pgpool-general at pgpool.net
> http://www.pgpool.net/mailman/listinfo/pgpool-general