[pgpool-hackers: 1308] Re: [pgpool -C option] need more description?

[Huong Dangminh]

Hi Ishii-san,

Thanks for prompt response,

> -----Original Message-----
> From: Tatsuo Ishii [mailto:ishii at postgresql.org]
> Sent: Wednesday, January 06, 2016 1:21 PM
> To: Dangminh Huong(ダンＭ フーン) <huo-dangminh at ys.jp.nec.com>
> Cc: ishii at postgresql.org; pgpool-hackers at pgpool.net; Yanagisawa
> Hiroshi(柳澤 博) <hir-yanagisawa at ut.jp.nec.com>
> Subject: Re: [pgpool-hackers: 1303] Re: [pgpool -C option] need more
> description?
> 
> > Hi Ishii-san,
> >
> > Thanks for prompt response,
> >
> >> -----Original Message-----
> >> From: Tatsuo Ishii [mailto:ishii at postgresql.org]
> >> Sent: Wednesday, January 06, 2016 8:31 AM
> >> To: Dangminh Huong(ダンＭ フーン) <huo-dangminh at ys.jp.nec.com>;
> >> Yanagisawa Hiroshi(柳澤 博) <hir-yanagisawa at ut.jp.nec.com>
> >> Cc: pgpool-hackers at pgpool.net
> >> Subject: Re: [pgpool-hackers: 1303] Re: [pgpool -C option] need more
> >> description?
> >>
> >> I appeared that the implementation of -c or --clear-cache is quite
> >> confusing. It does exactly the same thing as -C or --clear-oidmaps. So
> >> there's no point to have both of options at all.  Moreover -c or
> >> --clear-cache is not shown when pgpool --help is requested. Apparently
> >> -c or --clear-cache is useless, and I doubt if we need to have this in
> >> 3.5.
> >
> > I think clear oidmaps should be processed along with clear cache.
> 
> No, it's not possible at the moment because pgpool-II cannot
> distinguish its own cache entries from other entries registered by
> certain applications on the memcached server. If we could assume that
> the memcached server is dedicated to pgpool-II, just blowing up all of
> the cache entries on the memcached server is enough, but that is too
> simple assumption I guess.
> 

Before clear oidmaps, invalidate only cache entries in oid files 
but not flush out all cache entries in memcached server is also 
a solution sir?
It could take a decrease in performance when pgpool start.

Blowing up all of cache entries by adding -c option also a good idea.

Best regards,
---
Dang Minh Huong
NEC Solution Innovators, Ltd.
http://www.nec-solutioninnovators.co.jp/en/

> > So, remove -C option and add -c option with clear both of oidmaps
> > and cache is also a solution in V3.5?
> >
> > Best regards,
> > ---
> > Dang Minh Huong
> > NEC Solution Innovators, Ltd.
> > http://www.nec-solutioninnovators.co.jp/en/
> >
> >>
> >> Best regards,
> >> --
> >> Tatsuo Ishii
> >> SRA OSS, Inc. Japan
> >> English: http://www.sraoss.co.jp/index_en.php
> >> Japanese:http://www.sraoss.co.jp
> >>
> >> >> Hi all,
> >> >>
> >> >> I think below case is depended on the way of using
> >> >> but is it need to be added more detail at pgpool -C option?
> >> >> something like "But not clear related cache in memcached server."?
> >> >>
> >> >> When memcached is using in "In Memory Cached" mode, pgpool
> >> >> start with -C option does not clear related cache in cache
> >> >> server.
> >> >> Obviously it lead to get the old query result by SELECT
> >> >> as below.
> >> >
> >> > Sounds a fair complaint. Will fix.
> >> >
> >> > Best regards,
> >> > --
> >> > Tatsuo Ishii
> >> > SRA OSS, Inc. Japan
> >> > English: http://www.sraoss.co.jp/index_en.php
> >> > Japanese:http://www.sraoss.co.jp
> >> >
> >> >> ===
> >> >>
> >> >> testdb=# select * from testtbl;   -- create cache
> >> >>  id
> >> >> ----
> >> >>   1
> >> >> (1 row)
> >> >>
> >> >> testdb=# \q
> >> >> ]$ pgpool stop
> >> >> ]$ pgpool -C -d -n > /var/log/pgpool/log 2>&1 & # start with -C option
> >> >> ]$ psql -p 9999
> >> >> psql (9.4.4)
> >> >> Type "help" for help.
> >> >>
> >> >> testdb=# insert into testtbl values(1);
> >> >> INSERT 0 1
> >> >> testdb=# select * from testtbl;  -- old query result from cache server
> >> >>  id
> >> >> ----
> >> >>   1
> >> >> (1 row)
> >> >>
> >> >> ===
> >> >>
> >> >> Best regards,
> >> >> ---
> >> >> Dang Minh Huong
> >> >> NEC Solution Innovators, Ltd.
> >> >> http://www.nec-solutioninnovators.co.jp/en/
> >> >>
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> >