[pgpool-hackers: 2899] Re: Pgpool-II 3.8: allow to specify load balance weight ratio for load balance parameters

[Tatsuo Ishii]

Thank you for the patch!

I have looked into the patch and here are some feedbacks.

1) git apply makes complainings.

t-ishii at localhost: git apply ~/load_balance_ratio_v1.diff 
/home/t-ishii/load_balance_ratio_v1.diff:101: trailing whitespace.
			<xref linkend="guc-database-redirect-preference-list">, when multiple database 
/home/t-ishii/load_balance_ratio_v1.diff:142: trailing whitespace.
         node for a particular database connection at a specified load balance ratio. 
/home/t-ishii/load_balance_ratio_v1.diff:237: trailing whitespace.
			<xref linkend="guc-database-redirect-preference-list">, when multiple database 
/home/t-ishii/load_balance_ratio_v1.diff:324: trailing whitespace.
			/* 
warning: 4 lines add whitespace errors.

2) Compiler warnings.

In file included from protocol/child.c:60:0:
protocol/child.c: In function ‘select_load_balancing_node’:
protocol/child.c:1743:18: warning: too many arguments for format [-Wformat-extra-args]
        errdetail("app_name: %s index is %d dbnode is %s", app_name, index_app,
                  ^
../src/include/utils/elog.h:195:14: note: in definition of macro ‘ereport_domain’
    errfinish rest; \
              ^
protocol/child.c:1741:5: note: in expansion of macro ‘ereport’
     ereport(DEBUG1,
     ^
protocol/child.c:1794:7: warning: ‘no_load_balance_node_id’ may be used uninitialized in this function [-Wmaybe-uninitialized]
    if (i == no_load_balance_node_id)
       ^

3) Subtle comment typos.

		 * If the wight is bigger than random rate then send to suggested_node_id.
		 * If the wight is less than random rate then choose load balance node from other nodes.

"wight" should be "weight", perhaps?

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

From: Bo Peng <pengbo at sraoss.co.jp>
Subject: [pgpool-hackers: 2897] Re: Pgpool-II 3.8: allow to specify load balance weight ratio for load balance parameters
Date: Mon, 30 Jul 2018 11:49:12 +0900
Message-ID: <20180730114912.41c0cb8237871fb5a62b8d46 at sraoss.co.jp>

> Hi,
> 
> I added a new feature to allow to specify load balance weight ratio for 
> database_redirect_preference_list and app_name_redirect_preference_list 
> parameters. Attached is the first patch.
> 
> You can specify the list of "database-name:node id(ratio)" pairs to 
> send SELECT queries to a particular backend node for a particular 
> database connection at a specified load balance ratio. 
> This load balance ratio specifies a value between 0 and 1, 
> and the default is 1.0. 
> 
> For example, by specifying "test:1(0.5)", 
> Pgpool-II will redirect 50% SELECT queries to the backend node of ID 1 
> for the connection to "test" database. And the other 50% SELECT queries
> will be sent to other backend nodes.
> 
> Example: 
> 
> If you spacify like below:
> 
>    database_redirect_preference_list = 'postgres:primary,mydb[01]:1(0.3),mydb2:standby'
> 
> It means,
> 
> - Route all SELECT queries on postgres database to the primary backend node.
> 
> - Route 30% SELECT queries on mydb0 or on mydb1 databases to backend node of ID. 
>   The other 70% SELECT queries will be sent to other backend nodes.
> 
> - Route all SELECT queries on mydb2 database to standby backend nodes. 
> 
> 
> The notion of app_name_redirect_preference_list is same as the database_redirect_preference_list. 
> 
> 
> On Thu, 14 Dec 2017 14:08:03 +0900 (JST)
> Tatsuo Ishii <ishii at sraoss.co.jp> wrote:
> 
>> > Currently we can specify load balance condition by using,
>> > database_redirect_preference_list, and
>> > app_name_redirect_preference_list like:
>> > 
>> > postgres:primary
>> > 
>> > This means, if connected database is postgres, every SELECTs will be
>> > redirected to primary.
>> > 
>> > It would be nice if we could specify load balance ratio like:
>> > 
>> > postgres:primary(0.3)
>> > 
>> > which redirects 30% of SELECTs to primary (that is, other 70% of
>> > SELECTs will be redirected to the load balance node). If the primary
>> > node is also the load balance node, 100% of SELCTs will be redirected
>> > to the primary.
>> > 
>> > Other example is:
>> > 
>> > postgres:primary(0.0)
>> > 
>> > which never redirects SELECTs to the primary. This is useful if user
>> > never wants to redirect SELECTs on the primary. Actually we cannot do
>> > this for now if a primary node changes time to time.
>> 
>> Sorry I was wrong. This is possible today too by
>> "postgres:standby". What we cannot do today is
>> "postgres:primary(0.3)".
>> 
>> > postgres:mydb[0-4]:1(0.3)
>> > 
>> > which redirects 30% of SELECTs to node 1 (that is, other 70% of
>> > SELECTs will be redirected to the load balance node). If node 1 is
>> > also the load balance node, 100% of SELCTs will be redirected to node
>> > 1.
>> > 
>> > I suppose the new specification overrides the current "weight"
>> > parameters for each node.
>> > 
>> > Comments and suggestions are welcome.
>> > --
>> > Tatsuo Ishii
>> > SRA OSS, Inc. Japan
>> > English: http://www.sraoss.co.jp/index_en.php
>> > Japanese:http://www.sraoss.co.jp
>> _______________________________________________
>> pgpool-hackers mailing list
>> pgpool-hackers at pgpool.net
>> http://www.pgpool.net/mailman/listinfo/pgpool-hackers
>> 
> 
> 
> -- 
> Bo Peng <pengbo at sraoss.co.jp>
> SRA OSS, Inc. Japan