PostgreSQL 支持動態跟蹤, 可以通過dtrace或者systemtap工具統計相關探針的信息. 安裝systemtap yum install systemtap kernel-debuginfo kernel-devel 將安裝以下包 systemtap-devel-1.8-6.el5 systemtap-client-1.8-6.el5 systemtap-runtime-1.8-6.el5 后面將使用的stap命令 [root@db-172-16-3-39 ~]# rpm -qf /usr/bin/stap systemtap-devel-1.8-6.el5 systemtap-client-1.8-6.el5檢查stap是否正常 [root@db-172-16-3-39 ~]# stap stap: /usr/lib64/libelf.so.1: version `ELFUTILS_1.5' not found (required by stap) stap: /usr/lib64/libdw.so.1: version `ELFUTILS_0.148' not found (required by stap) stap: /usr/lib64/libdw.so.1: version `ELFUTILS_0.138' not found (required by stap) stap: /usr/lib64/libdw.so.1: version `ELFUTILS_0.142' not found (required by stap) stap: /usr/lib64/libdw.so.1: version `ELFUTILS_0.143' not found (required by stap) stap: /usr/lib64/libdw.so.1: version `ELFUTILS_0.149' not found (required by stap) 這個錯誤的原因是庫文件版本不正確, 用來老版本, 使用eu-readelf查看stap文件的兩個環境變量, 如下 : [root@db-172-16-3-39 ~]# eu-readelf -d /usr/bin/stap|grep -E "RPATH|RUNPATH"RPATH Library rpath: [/usr/lib64/systemtap]RUNPATH Library runpath: [/usr/lib64/systemtap] 將路徑加入到LD_LIBRARY_PATH中. [root@db-172-16-3-39 ~]# export LD_LIBRARY_PATH=/usr/lib64/systemtap:$LD_LIBRARY_PATH stap現在正常了 [root@db-172-16-3-39 ~]# stap A script must be specified. Systemtap translator/driver (version 1.8/0.152 non-git sources) Copyright (C) 2005-2012 Red Hat, Inc. and others This is free software; see the source for copying conditions. enabled features: AVAHI LIBRPM LIBSQLITE3 NSS BOOST_SHARED_PTR TR1_UNORDERED_MAP NLS Usage: stap [options] FILE Run script in file.or: stap [options] - Run script on stdin.or: stap [options] -e SCRIPT Run given script.or: stap [options] -l PROBE List matching probes.or: stap [options] -L PROBE List matching probes and local variables. 測試 : [root@db-172-16-3-39 pg94]# vi tps.d probe begin {printf("hello\n")exit() } [root@db-172-16-3-39 pg94]# stap tps.d Checking "/lib/modules/2.6.18-274.el5/build/.config" failed with error: No such file or directory Incorrect version or missing kernel-devel package, use: yum install kernel-devel-2.6.18-274.el5.x86_64 這個錯誤是由于未安裝當前正在運行的kernel對應的kernel-devel包. [root@db-172-16-3-39 pg94]# rpm -qa|grep kernel kernel-headers-2.6.18-274.el5 kernel-xen-devel-2.6.18-274.el5 kernel-xen-2.6.18-274.el5 kernel-2.6.18-274.el5 [root@db-172-16-3-39 ~]# uname -a Linux db-172-16-3-39.sky-mobi.com 2.6.18-274.el5 #1 SMP Fri Jul 22 04:43:29 EDT 2011 x86_64 x86_64 x86_64 GNU/Linux安裝對應的kernel-devel版本. yum install kernel-devel-2.6.18-274.el5.x86_64 如果yum源中沒有這個版本的kernel-devel包, 可以去安裝光盤中找一找. 或者同時更新內核版本至新版本.yum install -y kernel.x86_64 kernel-devel.x86_64 Package kernel-2.6.18-348.12.1.el5.x86_64 already installed and latest version Package kernel-devel-2.6.18-348.12.1.el5.x86_64 already installed and latest version vi /boot/grub/grub.conf default=0 timeout=5 splashimage=(hd0,0)/boot/grub/splash.xpm.gz hiddenmenu title CentOS (2.6.18-348.12.1.el5)root (hd0,0)kernel /boot/vmlinuz-2.6.18-348.12.1.el5 ro root=LABEL=/ rhgb quietinitrd /boot/initrd-2.6.18-348.12.1.el5.img 重啟服務器 現在stap工作正常了 : [root@db-172-16-3-39 postgresql-5e3e8e4]# stap -ve 'probe begin { log("hello world") exit() }' Pass 1: parsed user script and 85 library script(s) using 146788virt/23676res/3000shr/21384data kb, in 170usr/0sys/173real ms. Pass 2: analyzed script: 1 probe(s), 2 function(s), 0 embed(s), 0 global(s) using 147316virt/24396res/3224shr/21912data kb, in 10usr/0sys/6real ms. Pass 3: using cached /root/.systemtap/cache/3b/stap_3b2eaec778ce9832b394535505dde575_838.c Pass 4: using cached /root/.systemtap/cache/3b/stap_3b2eaec778ce9832b394535505dde575_838.ko Pass 5: starting run. hello world Pass 5: run completed in 0usr/20sys/306real ms. stap調試好后, 就可以用來跟蹤postgresql了. PostgreSQL編譯時必須開啟dtrace支持. 開啟dtrace后, 數據庫將啟用代碼中的探針或跟蹤點. PostgreSQL內建探針參考如下 : src/backend/utils/probes.d http://www.postgresql.org/docs/devel/static/dynamic-trace.html 檢查你的PostgreSQL是否開啟了dtrace支持, 如下 : pg94@db-172-16-3-39-> pg_config --configure '--prefix=/home/pg94/pgsql9.4devel' '--with-pgport=2999' '--with-perl' '--with-tcl' '--with-python' '--with-openssl' '--with-pam' '--without-ldap' '--with-libxml' '--with-libxslt' '--enable-thread-safety' '--with-wal-blocksize=16' '--enable-dtrace' 如果沒有--enable-dtrace, 那么需要重新編譯一下你的PostgreSQL軟件.stap測試腳本1. [root@db-172-16-3-39 pg94]# cat postgresql-query.stp global query_time, query_summaryprobe process("/home/pg94/pgsql9.4devel/bin/postgres").mark("query__start") {query_time[tid(), $arg1] = gettimeofday_us(); }probe process("/home/pg94/pgsql9.4devel/bin/postgres").mark("query__done") {p = tid()t = query_time[p, $arg1]; delete query_time[p, $arg1]if (t) {query_summary[p] <<< (gettimeofday_us() - t);} }probe end {printf("\ntid count min(us) avg(us) max(us)\n");foreach (p in query_summary) {printf("%d %d %d %d %d\n", p, @count(query_summary[p]),@min(query_summary[p]), @avg(query_summary[p]), @max(query_summary[p]));} } 執行stap : [root@db-172-16-3-39 pg94]# stap postgresql-query.stp 執行以下SQL : [root@db-172-16-3-39 pg94]# stap postgresql-query.stp digoal=# begin; BEGIN digoal=# select * from test for update;id ----12345678910 (10 rows) digoal=# end; COMMIT digoal=# select txid_current();txid_current --------------5969062 (1 row) 結束stap, 輸出 : [root@db-172-16-3-39 pg94]# stap postgresql-query.stp 按鍵Ctrl+C, 輸出 : tid count min(us) avg(us) max(us) 17112 4 46 3794 14885 這個tid對應PostgreSQL background process [root@db-172-16-3-39 pg94]# ps -ewf|grep 17112 pg94 17112 17005 0 15:15 ? 00:00:00 postgres: postgres digoal [local] idle digoal=# select pg_backend_pid();pg_backend_pid ----------------17112 (1 row)[小結] 1. 安裝systemtap注意 : -- 需要安裝kernel相關, 并且版本要一致, 啟動的kernel版本也要一致 : kernel kernel-debuginfo kernel-devel kernel-debuginfo的安裝要用到debug源. [root@db-172-16-3-39 pg94]# cd /etc/yum.repos.d/ [root@db-172-16-3-39 yum.repos.d]# ll total 36 -rw-r--r-- 1 root root 1926 Aug 29 2011 CentOS-Base.repo -rw-r--r-- 1 root root 631 Aug 29 2011 CentOS-Debuginfo.repo -rw-r--r-- 1 root root 626 Aug 29 2011 CentOS-Media.repo -rw-r--r-- 1 root root 5390 Aug 29 2011 CentOS-Vault.repo [root@db-172-16-3-39 yum.repos.d]# cat CentOS-Debuginfo.repo # CentOS-Base.repo # # The mirror system uses the connecting IP address of the client and the # update status of each mirror to pick mirrors that are updated to and # geographically close to the client. You should use this for CentOS updates # unless you are manually picking other mirrors. ## All debug packages from all the various CentOS-5 releases # are merged into a single repo, split by BaseArch # # Note: packages in the debuginfo repo are currently not signed #[debug] name=CentOS-5 - Debuginfo baseurl=http://debuginfo.centos.org/5/$basearch/ gpgcheck=0 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-CentOS-5 enabled=0 這里用到的源名為debug. yum --enablerepo=debug list kernel-debuginfo yum --enablerepo=debug install kernel-debuginfo 安裝細節參考此文 : http://pic.dhe.ibm.com/infocenter/lnxinfo/v3r0m0/topic/liaai.systemTap/liaaisystap_pdf.pdf2. postgresql編譯時必須加上--enable-dtrace參數, 否則stap時會出現類似以下錯誤. [root@db-172-16-3-39 pg93]# stap test.stp semantic error: while resolving probe point: identifier 'process' at test.stp:3:7source: probe process("/opt/pgsql9.3beta2/bin/postgres").mark("lock__wait__start")^semantic error: no match semantic error: while resolving probe point: identifier 'process' at :8:7source: probe process("/opt/pgsql9.3beta2/bin/postgres").mark("lock__wait__done")^semantic error: while resolving probe point: identifier 'process' at :17:7source: probe process("/opt/pgsql9.3beta2/bin/postgres").mark("lwlock__wait__start")^semantic error: while resolving probe point: identifier 'process' at :22:7source: probe process("/opt/pgsql9.3beta2/bin/postgres").mark("lwlock__wait__done")^semantic error: while resolving probe point: identifier 'process' at :32:7source: probe process("/opt/pgsql9.3beta2/bin/postgres").mark("lwlock__condacquire__fail")^Pass 2: analysis failed. Try again with another '--vp 01' option. 3. 允許stap需要root權限, 或者將用戶加入stapdev或者stapsys, 以及stapusr組. 如果普通用戶不加入這兩個組, 執行stap將報錯 : pg93@db-172-16-3-39-> stap -ve 'probe begin { log("hello world") exit() }' You are trying to run systemtap as a normal user. You should either be root, or be part of the group "stapusr" and possibly one of the groups "stapsys" or "stapdev". Systemtap translator/driver (version 1.8/0.152 non-git sources) 加完組后正常 # usermod -G stapdev,stapusr pg94 pg94@db-172-16-3-39-> stap -ve 'probe begin { log("hello world") exit() }' Pass 1: parsed user script and 85 library script(s) using 148892virt/23772res/3068shr/21396data kb, in 160usr/10sys/172real ms. Pass 2: analyzed script: 1 probe(s), 2 function(s), 0 embed(s), 0 global(s) using 149420virt/24492res/3292shr/21924data kb, in 10usr/0sys/6real ms. Pass 3: translated to C into "/tmp/stapcqtmUe/stap_758dbd41826239e5e3211a815f6bfc58_838_src.c" using 149420virt/24760res/3540shr/21924data kb, in 0usr/0sys/0real ms. Pass 4: compiled C into "stap_758dbd41826239e5e3211a815f6bfc58_838.ko" in 910usr/110sys/1028real ms. Pass 5: starting run. hello world

?http://blog.163.com/digoal@126/blog/static/16387704020137140265557/

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