CoroSync+Pacemaker实现web高可用
一、简介CoroSync最初只是用来演示OpenAIS集群框架接口规范的一个应用，可以说CoroSync是OpenAIS的一部分，但后面的发展明显超越了官方最初的设想，越来越多的厂商尝试使用CoroSync作为集群解决方案。如Redhat的RHCS集群套件就是基于CoroSync实现。
CoroSync只提供了message layer，而没有直接提供CRM，一般使用Pacemaker进行资源管理。 CoroSync和Pacemaker的配合使用有2种方式：①Pacemaker以插件形式使用②Pacemaker独立的守护进程 本文Pacemaker以插件的形式运行。
二、配置web高可用 0、前提 ①时间同步、ssh互信、hosts域名通信 （略）
②安装httpd服务，开机不启动
③关闭NetworkManager，开启不启动，开启network服务
1、安装CoroSync、Pacemaker、crmsh
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# yuminstall corosync pacemaker
CoroSync的软件包组成：
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# rpm -ql corosync
/etc/corosync #CoroSync的配置文件目录
/etc/corosync/corosync.conf.example #CoroSync的配置样例
/etc/corosync/corosync.conf.example.udpu
/etc/corosync/service.d
/etc/corosync/uidgid.d
/etc/dbus-1/system.d/corosync-signals.conf
/etc/rc.d/init.d/corosync #CoroSync的服务脚本
/etc/rc.d/init.d/corosync-notifyd
/usr/bin/corosync-blackbox
/usr/libexec/lcrso
/usr/libexec/lcrso/coroparse.lcrso
/usr/libexec/lcrso/objdb.lcrso
/usr/libexec/lcrso/quorum_testquorum.lcrso
/usr/libexec/lcrso/quorum_votequorum.lcrso
/usr/libexec/lcrso/service_cfg.lcrso
/usr/libexec/lcrso/service_confdb.lcrso
/usr/libexec/lcrso/service_cpg.lcrso
/usr/libexec/lcrso/service_evs.lcrso
/usr/libexec/lcrso/service_pload.lcrso
/usr/libexec/lcrso/vsf_quorum.lcrso
/usr/libexec/lcrso/vsf_ykd.lcrso
/usr/sbin/corosync
/usr/sbin/corosync-cfgtool
/usr/sbin/corosync-cpgtool
/usr/sbin/corosync-fplay
/usr/sbin/corosync-keygen #生成节点message layer通信秘钥
/usr/sbin/corosync-notifyd
/usr/sbin/corosync-objctl
/usr/sbin/corosync-pload
/usr/sbin/corosync-quorumtool
/usr/share/doc/corosync-1.4.1
/var/lib/corosync
/var/log/cluster
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# yuminstall-ycrmsh-1.2.6-4.el6.x86_64.rpmpssh-2.3.1-2.el6.x86_64.rpm ###crmsh依赖于pssh
从pacemaker 1.1.8开始，crm发展成了一个独立项目，叫crmsh。也就是说，我们安装了pacemaker后，并没有crm这个命令，我们要实现对集群资源管理，还需要独立安装crmsh。 2、配置CoroSync
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#cat/etc/corosync/corosync.conf
compatibility: whitetank ##是否兼容旧版本
totem {
version: 2 ##版本号，无法修改
secauth: off ##安全认证，当使用aisexec时，会非常消耗CPU
threads: 0 ##线程数，根据CPU个数和核心数确定
interface {
ringnumber: 0
bindnetaddr:192.168.192.0##绑定心跳网络IP地址
mcastaddr: 226.94.1.1 ##组播地址
mcastport: 5405 ##组播端口
ttl: 1 ##组播的ttl值
}
}
logging {
fileline: off
to_stderr: no ##是否发送到标准错误输出
to_logfile: yes ##是否记录到文件
to_syslog: yes ##是否记录到syslog
logfile: /var/log/cluster/corosync.log ##日志文件位置
debug: off
timestamp: on ##是否打印时间戳，利于定位错误，但会消耗CPU
logger_subsys {
subsys: AMF
debug: off
}
}
service { ##定义pacemaker以插件的形式启动
ver:0
name: pacemaker
}
aisexec { ##corosync启动的身份，由于corosync需要管理服务，需要root身份
user: root
group:root
}
amf {
mode: disabled
}
3、配置CoroSync的认证(authkey)
使用corosync-keygen生成key时，由于要使用/dev/random生成随机数，因此如果新装的系统操作不多，如果没有足够的熵，可能会出现如下提示：
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# corosync-keygen
Corosync Cluster Engine Authentication key generator.
Gathering 1024 bits for key from /dev/random.
Press keys on your keyboard to generate entropy.
Press keys on your keyboard to generate entropy (bits = 240).
解决办法：在本地随意输入即可，可以通过安装，卸载软件方式解决。
authkey的权限为默认400
4、将配置文件复制到集群节点
5、启动CoroSync
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# service corosync start
Starting Corosync Cluster Engine (corosync): [确定]
# ssh node2 'service corosync start'
Starting Corosync Cluster Engine (corosync): [确定]
检查CoroSync的引擎启动是否成功：
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# grep -e "Corosync Cluster Engine" -e "configuration file" /var/log/messages
Oct 19 19:21:21 node1 corosync: Corosync Cluster Engine ('1.4.1'): started and ready to provide service.
Oct 19 19:21:21 node1 corosync: Successfully read main configuration file '/etc/corosync/corosync.conf'.
查看初始化成员节点通知是否正常发出：
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# grepTOTEM/var/log/messages
Oct 19 19:21:21 node1 corosync: Initializing transport (UDP/IP Multicast).
Oct 19 19:21:21 node1 corosync: Initializing transmit/receive security: libtomcrypt SOBER128/SHA1HMAC (mode 0).
Oct 19 19:21:22 node1 corosync: The network interface is now up.
Oct 19 19:21:23 node1 corosync: Process pause detected for 1264 ms, flushing membership messages.
Oct 19 19:21:23 node1 corosync: A processor joined or left the membership and a new membership was formed.
检查启动过程中是否有错误产生：
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# grep ERROR: /var/log/messages | grep -v unpack_resources
Oct 19 19:21:22 node1 corosync: ERROR: process_ais_conf: You have configured a cluster using the Pacemaker plugin for Corosync. The plugin is not supported in this environment and will be removed very soon.
Oct 19 19:21:22 node1 corosync: ERROR: process_ais_conf:Please see Chapter 8 of 'Clusters from Scratch' (http://www.clusterlabs.org/doc) for details on using Pacemaker with CMAN
查看pacemaker是否正常启动：
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# grep pcmk_startup /var/log/messages
Oct 19 19:21:22 node1 corosync: info: pcmk_startup: CRM: Initialized
Oct 19 19:21:22 node1 corosync: Logging: Initialized pcmk_startup
Oct 19 19:21:22 node1 corosync: info: pcmk_startup: Maximum core file size is: 18446744073709551615
Oct 19 19:21:23 node1 corosync: info: pcmk_startup: Service: 9
Oct 19 19:21:23 node1 corosync: info: pcmk_startup: Local hostname: node1.yu.com
这里可能存在的问题：iptables，selinux
6、配置crmsh实现资源管理
crmsh具有补全命令功能，并且交互式，可随时help查看帮助说明 crmsh简介：
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# crm<--进入crmsh
crm(live)# help ##查看帮助
This is crm shell, a Pacemaker command line interface.
Available commands:
cib manage shadow CIBs ##CIB管理模块
resource resources management ##资源管理模块
configure CRM cluster configuration##CRM配置，包含资源粘性、资源类型、资源约束等
node nodes management##节点管理
options user preferences##用户偏好
history CRM cluster history##CRM 历史
site Geo-cluster support ##地理集群支持
ra resource agents information center ##资源代理配置
status show cluster status ##查看集群状态
help,? show help (help topics for list of topics) ##查看帮助
end,cd,up go back one level ##返回上一级
quit,bye,exit exit the program ##退出
crm(live)# configure <--进入配置模式
crm(live)configure# show ##查看当前配置
node node1.yu.com
node node2.yu.com
property $id="cib-bootstrap-options" \
dc-version="1.1.8-7.el6-394e906" \
cluster-infrastructure="classic openais (with plugin)" \
expected-quorum-votes="2"
crm(live)configure# verify ##检查当前配置语法，由于没有STONITH，所以报错，可关闭
error: unpack_resources: Resource start-up disabled since no STONITH resources have been defined
error: unpack_resources: Either configure some or disable STONITH with the stonith-enabled option
error: unpack_resources: NOTE: Clusters with shared data need STONITH to ensure data integrity
Errors found during check: config not valid
-V may provide more details
crm(live)configure# property stonith-enabled=false ##禁用stonith后再次检查配置，无报错
crm(live)configure# verify
crm(live)configure# commit##提交配置
crm(live)configure# cd
crm(live)# ra <--进入RA（资源代理配置）模式
crm(live)ra# help
This level contains commands which show various information about
the installed resource agents. It is available both at the top
level and at the `configure` level.
Available commands:
classes list classes and providers ##查看RA类型
list list RA for a class (and provider)##查看指定类型（或提供商）的RA
meta,info show meta data for a RA ##查看RA详细信息
providers show providers for a RA and a class##查看指定资源的提供商和类型
help,? show help (help topics for list of topics)
end,cd,up go back one level
quit,bye,exit exit the program
crm(live)ra# classes
lsb
ocf / heartbeat pacemaker redhat
service
stonith
crm(live)ra# list ocf pacemaker
ClusterMon Dummy HealthCPU HealthSMART Stateful SysInfo SystemHealthcontrold o2cb ping pingd
crm(live)ra# info ocf:heartbeat:IPaddr
Manages virtual IPv4 addresses (portable version) (ocf:heartbeat:IPaddr)
This script manages IP alias IP addresses
It can add an IP alias, or remove one.
Parameters (* denotes required, [] the default):
ip* (string): IPv4 address
The IPv4 address to be configured in dotted quad notation, for example
"192.168.192.208".
nic (string, ): Network interface
The base network interface on which the IP address will be brought
online.
……下略……
crm(live)ra# cd
crm(live)# status<--查看集群状态
Last updated: Sun Oct 20 22:06:16 2013
Last change: Sun Oct 20 21:58:46 2013 via cibadmin on node1.yu.com
Stack: classic openais (with plugin)
Current DC: node2.yu.com - partition with quorum
Version: 1.1.8-7.el6-394e906
2 Nodes configured, 2 expected votes
0 Resources configured.
Online: [ node1.yu.com node2.yu.com ]
法定票数问题：
在双节点集群中，由于票数是偶数，当心跳出现问题（脑裂）时，两个节点都将达不到法定票数，默认quorum策略会关闭集群服务，为了避免这种情况，可以增加票数为奇数（如前文的增加ping节点，qdisk），或者调整默认quorum策略为【ignore】。
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crm(live)configure# property no-quorum-policy=ignore
crm(live)configure# show
node node1.yu.com
node node2.yu.com
property $id="cib-bootstrap-options" \
dc-version="1.1.8-7.el6-394e906" \
cluster-infrastructure="classic openais (with plugin)" \
expected-quorum-votes="2" \
stonith-enabled="false" \
no-quorum-policy="ignore"
crm(live)configure# commit
资源来回转移问题：（防止资源转移后，故障点恢复又转移）故障发生时，资源会迁移到正常节点上，但当故障节点恢复后，资源可能再次回到原来节点，这样有时候不一定是好事，例如某些繁忙的场景，来回飘逸就会出现问题，这里通过资源粘性来避免
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crm(live)configure#property default-resource-stickiness=INFINITY
7.配置httpd的高可用样例
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## 配置浮动IP
crm(live)configure# primitive webip ocf:heartbeat:IPaddr params ip=192.168.192.222
crm(live)configure# commit
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##配置httpd
crm(live)configure#primitive web lsb:httpd \
op monitor interval="30s" timeout="20s" on-fail="restart" \
meta target-role="Started"
crm(live)configure# commit
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##资源，默认会平均分配在各个不同的几点，将webip和httpd定义为一个组资源，可以将资源运行于同一个节点
crm(live)configure#group web_srv webip web
crm(live)configure# commit
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# crm
crm(live)# status
Last updated: Sun Apr 12 08:31:35 2015
Last change: Sun Apr 12 08:17:47 2015 via cibadmin on node1.yu.com
Stack: classic openais (with plugin)
Current DC: node1.yu.com - partition with quorum
Version: 1.1.8-7.el6-394e906
2 Nodes configured, 2 expected votes
5 Resources configured.
Online: [ node1.yu.com node2.yu.com ]
Resource Group: web_srv
webip (ocf::heartbeat:IPaddr): Started node2.yu.com
web (lsb:httpd): Started node2.yu.com
至此httpd的HA完成，后文会详细说明，约束的实现。
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