背景

我一直以來都比較推薦plproxy這個PostgreSQL代理軟件, 因為它小巧靈活好用, 效率高.

最近朋友邀請我給他們做個分布式的方案, 所以又把plproxy翻出來了.

本文講一講在單節點中如何快速的部署plproxy環境.

環境

PostgreSQL 9.3.1 plproxy 2.x

plrpoxy節點

hostaddr 172.16.3.150 port 1921 user proxy password proxy dbname proxy schema digoal // 這個schema名和數據節點一致, 可以省去寫plproxy language target的步驟.

數據節點

hostaddr 172.16.3.150 port 1921 user digoal // plproxy將使用digoal用戶連接數據節點. password digoal dbname db0 schema digoal dbname db1 schema digoal dbname db2 schema digoal dbname db3 schema digoal

部署plproxy

首先在http://git.postgresql.org/gitweb/?p=plproxy.git;a=summary下載plproxy.

tar -zxvf plproxy-d703683.tar.gz mv plproxy-d703683 /opt/soft_bak/postgresql-9.3.1/contrib cd /opt/soft_bak/postgresql-9.3.1/contrib/plproxy-d703683 [root@db-172-16-3-150 plproxy-d703683]# export PATH=/home/pg93/pgsql9.3.1/bin:$PATH [root@db-172-16-3-150 plproxy-d703683]# which pg_config [root@db-172-16-3-150 plproxy-d703683]# gmake clean [root@db-172-16-3-150 plproxy-d703683]# gmake [root@db-172-16-3-150 plproxy-d703683]# gmake install

創建proxy庫, proxy角色, 在proxy庫創建plproxy extension.

pg93@db-172-16-3-150-> psql psql (9.3.1) Type "help" for help. postgres=# create role proxy nosuperuser login encrypted password 'proxy'; CREATE ROLE digoal=# create database proxy; CREATE DATABASE digoal=# \c proxy You are now connected to database "proxy" as user "postgres". proxy=# create extension plproxy; CREATE EXTENSION

調整proxy庫權限

proxy=# grant all on database proxy to proxy; GRANT proxy=# \c proxy proxy You are now connected to database "proxy" as user "digoal".

創建digoal schema, 目的是和數據節點的schema匹配, 這樣的話可以省去在代理函數中寫target強行指定schema.

proxy=> create schema digoal; CREATE SCHEMA

創建節點數據庫

proxy=> \c postgres postgres You are now connected to database "postgres" as user "postgres". postgres=# create role digoal nosuperuser login encrypted password 'digoal'; postgres=# create database db0; postgres=# create database db1; postgres=# create database db2; postgres=# create database db3;

調整權限, 賦予給后面將要給user mapping中配置的option user權限.

postgres=# grant all on database db0 to digoal; postgres=# grant all on database db1 to digoal; postgres=# grant all on database db2 to digoal; postgres=# grant all on database db3 to digoal;

使用超級用戶在proxy數據庫中創建server.

proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# CREATE SERVER cluster_srv1 FOREIGN DATA WRAPPER plproxy options (connection_lifetime '1800', p0 'dbname=db0 hostaddr=172.16.3.150 port=1921 application_name=test', p1 'dbname=db1 hostaddr=172.16.3.150 port=1921', p2 'dbname=db2 hostaddr=172.16.3.150 port=1921', p3 'dbname=db3 hostaddr=172.16.3.150 port=1921');

創建server時可以使用libpq中的選項. 例如本例使用了application_name.

將server權限賦予給proxy用戶.

proxy=# grant usage on FOREIGN server cluster_srv1 to proxy; GRANT

配置proxy用戶的連接cluster_srv1的選項.

proxy=# create user mapping for proxy server cluster_srv1 options (user 'digoal'); CREATE USER MAPPING

用戶proxy連接到cluster_srv1時使用digoal用戶連接, 這里不需要配置password, 因為我們將使用trust認證.

修改數據節點的pg_hba.conf

從proxy節點使用digoal用戶連接數據庫db0, db1, db2, db3使用trust認證.

vi $PGDATA/pg_hba.conf host db0 digoal 172.16.3.150/32 trust host db1 digoal 172.16.3.150/32 trust host db2 digoal 172.16.3.150/32 trust host db3 digoal 172.16.3.150/32 trust pg_ctl reload

在plproxy節點創建代理函數

使用超級用戶創建plproxy函數, 然后把函數權限賦予給proxy權限.

proxy=# CREATE OR REPLACE FUNCTION digoal.dy(sql text) RETURNS SETOF record LANGUAGE plproxy STRICT AS $function$ cluster 'cluster_srv1'; run on all; $function$; proxy=# grant execute on function digoal.dy(text) to proxy; GRANT

在數據節點創建實體函數

proxy=# \c db0 digoal db0=# CREATE OR REPLACE FUNCTION digoal.dy(sql text) RETURNS SETOF record LANGUAGE plpgsql STRICT AS $function$ declare rec record; begin for rec in execute sql loop return next rec; end loop; return; end; $function$; db0=# \c db1 digoal ... db1=# \c db2 digoal ... db2=# \c db3 digoal ...

在proxy節點中就可以訪問數據節點了。

例如查詢這個動態SQL.

proxy=> select * from digoal.dy('select count(*) from pg_class') as t(i int8); i ----- 293 293 293 293 (4 rows) proxy=> select sum(i) from digoal.dy('select count(*) from pg_class') as t(i int8); sum ------ 1172 (1 row)

plproxy節點測試

一. 修改foreign server測試, 觀察連接將重置.

前面那個會話不要斷開, 在另一個會話中觀察proxy發起的連接到數據節點的連接.

postgres=# select * from pg_stat_activity where usename='digoal'; datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_sta rt | xact_start | query_start | state_change | waiting | state | q uery -------+---------+------+----------+---------+------------------+--------------+-----------------+-------------+-------------------- -----------+------------+-------------------------------+-------------------------------+---------+-------+------------------------- ---------------------------- 91246 | db0 | 8171 | 91250 | digoal | test | 172.16.3.150 | | 47937 | 2013-11-22 17:23:26 .138425+08 | | 2013-11-22 17:27:05.539286+08 | 2013-11-22 17:27:05.539745+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91247 | db1 | 8172 | 91250 | digoal | | 172.16.3.150 | | 47938 | 2013-11-22 17:23:26 .138688+08 | | 2013-11-22 17:27:05.53938+08 | 2013-11-22 17:27:05.539874+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91248 | db2 | 8173 | 91250 | digoal | | 172.16.3.150 | | 47939 | 2013-11-22 17:23:26 .138957+08 | | 2013-11-22 17:27:05.53938+08 | 2013-11-22 17:27:05.539841+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91249 | db3 | 8174 | 91250 | digoal | | 172.16.3.150 | | 47940 | 2013-11-22 17:23:26 .139178+08 | | 2013-11-22 17:27:05.539366+08 | 2013-11-22 17:27:05.539793+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) (4 rows)

再次在proxy的同一會話中查詢時, 這些會話會復用, 不會斷開. 前面已經講了plproxy是使用長連接的.

如果修改了server, 那么這些連接會斷開, 重新連接. 所以不需要擔心修改server帶來的連接cache問題.

postgres=# \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# alter server cluster_srv1 options (set p1 'dbname=db1 hostaddr=172.16.3.150 port=1921 application_name=abc'); ALTER SERVER

再次在proxy的同一會話中查詢后, 我們發現4個連接都變了, 說明alter server后, 如果再次發起plproxy函數的查詢請求, 那么proxy會重置連接.

proxy=> select sum(i) from digoal.dy('select count(*) from pg_class') as t(i int8); sum ------ 1172 (1 row)

在另一會話的查詢結果 :

proxy=# select * from pg_stat_activity where usename='digoal'; datid | datname | pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_sta rt | xact_start | query_start | state_change | waiting | state | q uery -------+---------+------+----------+---------+------------------+--------------+-----------------+-------------+-------------------- -----------+------------+-------------------------------+-------------------------------+---------+-------+------------------------- ---------------------------- 91246 | db0 | 8245 | 91250 | digoal | test | 172.16.3.150 | | 47941 | 2013-11-22 17:30:36 .933077+08 | | 2013-11-22 17:30:36.936784+08 | 2013-11-22 17:30:36.938837+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91248 | db2 | 8247 | 91250 | digoal | | 172.16.3.150 | | 47943 | 2013-11-22 17:30:36 .933502+08 | | 2013-11-22 17:30:36.936783+08 | 2013-11-22 17:30:36.938981+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91249 | db3 | 8248 | 91250 | digoal | | 172.16.3.150 | | 47944 | 2013-11-22 17:30:36 .933731+08 | | 2013-11-22 17:30:36.937147+08 | 2013-11-22 17:30:36.939015+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) 91247 | db1 | 8246 | 91250 | digoal | abc | 172.16.3.150 | | 47942 | 2013-11-22 17:30:36 .933288+08 | | 2013-11-22 17:30:36.93757+08 | 2013-11-22 17:30:36.939299+08 | f | idle | select i::int8 from digo al.dy($1::text) as (i int8) (4 rows)

二. run on 的幾種形式, 表示數據路由方法.

在數據節點創建測試表.

proxy=# \c db0 digoal db0=> create table t(id int); CREATE TABLE db0=> \c db1 You are now connected to database "db1" as user "digoal". db1=> create table t(id int); CREATE TABLE db1=> \c db2 You are now connected to database "db2" as user "digoal". db2=> create table t(id int); CREATE TABLE db2=> \c db3 You are now connected to database "db3" as user "digoal". db3=> create table t(id int); CREATE TABLE

在數據節點創建插入數據的實體函數, 每個節點返回不一樣的數字.

\c db0 digoal db0=> create or replace function digoal.f_test4() returns int as $$declare begin insert into t(id) values (1); return 0; end; $$language plpgsql strict; db1=> create or replace function digoal.f_test4() returns int as $$declare begin insert into t(id) values (1); return 1; end; $$language plpgsql strict; db2=> create or replace function digoal.f_test4() returns int as $$declare begin insert into t(id) values (1); return 2; end; $$language plpgsql strict; db3=> create or replace function digoal.f_test4() returns int as $$declare begin insert into t(id) values (1); return 3; end; $$language plpgsql strict;

在proxy節點創建代理函數, 并且將執行權限賦予給proxy用戶.

proxy=> \c proxy postgres create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on 0; -- 在指定的數據節點上運行, 本例可以設置為0到3, 順序和創建的server中的配置順序一致. p0, p1, p2, p3 $$language plproxy strict; proxy=# grant execute on function digoal.f_test4() to proxy; GRANT proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select * from digoal.f_test4(); f_test4 --------- 0 (1 row)

如果run on 的數字改成0-3以外的數字, 運行時將報錯, 符合預期.

proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on 4; $$language plproxy strict; CREATE FUNCTION proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select * from digoal.f_test4(); ERROR: PL/Proxy function digoal.f_test4(0): part number out of range

run on any表示隨機的選擇一個數據節點運行.

proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on any; $$language plproxy strict; CREATE FUNCTION proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select * from digoal.f_test4(); f_test4 --------- 0 (1 row) proxy=> select * from digoal.f_test4(); f_test4 --------- 3 (1 row) proxy=> select * from digoal.f_test4(); f_test4 --------- 2 (1 row) proxy=> select * from digoal.f_test4(); f_test4 --------- 3 (1 row)

run on function() 則使用函數結果的hash值計算得到運行節點.

proxy=> create or replace function digoal.f(int) returns int as $$select $1; $$language sql strict; CREATE FUNCTION proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on digoal.f(10); $$language plproxy strict; CREATE FUNCTION proxy=> select digoal.f_test4(); f_test4 --------- 2 (1 row) proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on digoal.f(11); $$language plproxy strict; CREATE FUNCTION proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select digoal.f_test4(); f_test4 --------- 3 (1 row) proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on digoal.f(-11); $$language plproxy strict; CREATE FUNCTION proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select digoal.f_test4(); f_test4 --------- 1 (1 row)

run on all表示所有數據節點運行. 代理函數必須使用returns setof返回.

proxy=> \c proxy postgres You are now connected to database "proxy" as user "postgres". proxy=# create or replace function digoal.f_test4() returns int as $$cluster 'cluster_srv1'; run on all; $$language plproxy strict; ERROR: PL/Proxy function digoal.f_test4(0): RUN ON ALL requires set-returning function proxy=# drop function digoal.f_test4(); DROP FUNCTION proxy=# create or replace function digoal.f_test4() returns setof int as $$cluster 'cluster_srv1'; run on all; $$language plproxy strict; CREATE FUNCTION proxy=# grant execute on function digoal.f_test4() to proxy; GRANT proxy=# \c proxy proxy You are now connected to database "proxy" as user "proxy". proxy=> select digoal.f_test4(); f_test4 --------- 0 1 2 3 (4 rows)

注意事項

1. 設計時需要注意
plproxy函數所在的schema盡量和數據節點上實際函數的schema一致.

否則需要在plproxy函數中使用target指定 schema.functionname;

2. 數據節點的個數請保持2^n,

這么做有利于后期的節點擴展, 例如2個節點擴展到4個節點時, 數據不需要發生跨節點的重分布.

例如

mod(x,2)=0 那么mod(x,4)=0或2 mod(x,2)=1 那么mod(x,4)=1或3

比較適合位運算的分布算法.

當然我們也可以使用一致性哈希的設計思路，參考

《一致性哈希在分布式數據庫中的應用探索》
https://yq.aliyun.com/articles/57954

3. 如果業務為短連接的形式, 那么需要1層連接池, 在應用程序和plproxy數據庫之間. 而不是plproxy和數據節點之間.

在應用程序和plproxy之間加連接池后, 其實對于plproxy來說就是長連接了, 所以在plproxy和數據節點之間也就不需要連接池了.

4. 長連接不需要連接池, 因為plproxy和數據節點之間的連接是長連接.

5. plproxy語法非常簡潔，而且函數調用徹底避免了事務的問題

connect, cluster, run, select, split, target.

6. 關于連接密碼

出于安全考慮, 建議在任何配置中不要出現明文密碼, 所以最好是plproxy服務器到數據節點是trust驗證, 保護好plproxy即可.

假設plproxy在172.16.3.2上. 數據節點有4個, 庫名和用戶名都為digoal. 那么在4個節點上配置pg_hba.conf如下.

node0 host digoal digoal 172.16.3.2/32 trust node1 host digoal digoal 172.16.3.2/32 trust node2 host digoal digoal 172.16.3.2/32 trust node3 host digoal digoal 172.16.3.2/32 trust

7. run 詳解:

run on <NR>, <NR>是數字常量, 范圍是0 到 nodes-1; 例如有4個節點 run on 0; (run on 4則報錯). run on ANY, run on function(...), 這里用到的函數返回結果必須是int2, int4 或 int8. run on ALL, 這種的plproxy函數必須是returns setof..., 實體函數沒有setof的要求.

8. 一個plproxy中只能出現一條connect語句, 符合預期, 否則報錯.

digoal=# create or replace function f_test3() returns setof int8 as $$connect 'hostaddr=172.16.3.150 dbname=db0 user=digoal port=1921'; connect 'hostaddr=172.16.3.150 dbname=db1 user=digoal port=1921'; select count(*) from pg_class; $$language plproxy strict; ERROR: PL/Proxy function postgres.f_test3(0): Compile error at line 2: Only one CONNECT statement allowed

9. 不要把plproxy語言的權限賦予給普通用戶, 因為開放了trust認證, 如果再開放plproxy語言的權限是非常危險的.

正確的做法是使用超級用戶創建plproxy函數, 然后把函數的執行權限賦予給普通用戶.

千萬不要這樣省事 :

update pg_language set lanpltrusted='t' where lanname='plproxy';

10. 如果有全局唯一的序列需求, 可以將序列的步調調整一下, 每個數據節點使用不同的初始值.
例如

db0=# create sequence seq1 increment by 4 start with 0; CREATE SEQUENCE db1=# create sequence seq1 increment by 4 start with 1; db2=# create sequence seq1 increment by 4 start with 2; db3=# create sequence seq1 increment by 4 start with 3;

考慮到擴容, 可以將步調調比較大, 例如1024. 那么可以容納1024個節點.

參考

1. http://kaiv.wordpress.com/2007/07/27/postgresql-cluster-partitioning-with-plproxy-part-i/

2. http://kaiv.wordpress.com/2007/09/02/postgresql-cluster-partitioning-with-plproxy-part-ii/

3. http://blog.163.com/digoal@126/blog/static/163877040201041111304328/

4. http://blog.163.com/digoal@126/blog/static/1638770402010411113114315/

5. http://blog.163.com/digoal@126/blog/static/163877040201192535630895/

6. http://www.postgresql.org/docs/9.3/static/libpq-connect.html#LIBPQ-CONNSTRING

7. http://git.postgresql.org/gitweb/?p=plproxy.git;a=summary

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