再谈ORACLE CPROCD进程

罗列一下有关oprocd的知识点

oprocd是oracle在rac中引入用来fencing io的

在unix系统下，假设我们没有採用oracle之外的第三方集群软件，才会存在oprocd进程

在linux系统下，仅仅有在10.2.0.4版本号后，才会具有oprocd进程

在window下，不会存在oprocd 进程，可是会存在一个oraFenceService服务，用来实现同样的功能，该服务採用的技术是基于windows的，与oprocd不同

oprocd进程能够执行在两者模式下：fatal和no fatal，在fatal模式下，假设系统hang住，或者其它原因触发oprocd则oprocd进程会自己主动重新启动server。在no fatal模式下，假设系统hang住，或者其它原因触发oprocd进程，则oprocd进程会在日志中记录警告信息，可是不会重新启动系统。

oprocd进程具有两个參数：timeout 指定oprocd进程调用的时间间隔   margin 指定同意的时间偏差，假设时间偏差超过margin，则oprocd进程会重新启动系统或者记录错误信息到日志。

oprocd进程的日志文件位于：/etc/oracle/oprocd  或者 /var/opt/oracle/oprocd

oprocd进程从cssd进程派生而来，而且以root用户身份同意

[root@node2 init.d]# ps -ef | grep oprocd
root      5109 11227  0 20:37 pts/0    00:00:00 grep oprocd
root      5758  4849  0 19:14 ?        00:00:00 /bin/sh /etc/init.d/init.cssd oprocd
root      6084  5758  0 19:14 ?        00:00:00 /u01/app/crs_home/bin/oprocd.bin run -t 1000 -m 10000 -hsi 5:10:50:75:90 -f

假设一个节点被hang住了非常长时间，那么集群中的其它节点会把该节点剔除出去，在这样的情况下，我们须要採取措施重新启动被hang住的节点，以便达到fencing io的目的。oprocd被设置了两个參数：timeout 和margin，进程会每间隔timeout时间被唤醒一次，假设本次被唤醒的时间与上次被唤醒的时间间隔超过timeout+margin，那么oprocd进程会觉得oracle 节点被hang住，因此会自己主动重新启动节点或者将警告信息写入日志。

通常情况下，我们能够将oprocd进程重新启动系统的原因归为四类：

1:：操作系统的调度问题

2：操作系统的存在硬件或者驱动问题

3：系统具有大量负载，导致调度程序无法及时调入oprocd进程

4：oracle bug

Bug 5015469 – OPROCD may reboot the node whenever the system date is moved

backwards.

Fixed in 10.2.0.3+

Fixed in 10.1.0.3 + One off patch for Bug 4206159.

Fixed in 10.2.0.4+

Fixed in 10.2.0.3+

Bug 4206159 – Oprocd is prone to time regression due to current API used (AIX only)

Diagnostic Fixes (VERY NECESSARY IN MOST CASES):

Bug 5137401 – Oprocd logfile is cleared after a reboot

Bug 5037858 – Increase the warning levels if a reboot is approaching

oprocd进程的两个參数：timeout和margin，其默认值在init.cssd 文件里指定，如

[root@node2 init.d]# cat init.cssd | grep ^OPROCD_DEFAULT_
OPROCD_DEFAULT_TIMEOUT=1000
OPROCD_DEFAULT_MARGIN=500
OPROCD_DEFAULT_HISTORGRAM=

因此，默认情况下，假设两次唤醒oprocd进程的时间间隔超过1.5s，oprocd进程就会重新启动系统。这往往是不合适的，假设我们手工改动init.cssd文件里的默认值，须要oracle support才干够。

假设须要突破1.5s的限制，我们能够调用init.cssd来实现目的，通过调用init.cssd能够改动两个參数：reboottime  和 diagwait，假设diagwait> reboottime,那么margin=diagwait-reboottime。在设置diagwait时，须要将集群中全部节点的全部进程停掉，都在能够造成数据损坏，仅仅需在rac中的一个节点改动就可以。建议将diagwait改动为13

[root@node2 bin]# ./crsctl get css reboottime
3
[root@node2 bin]# ./crsctl get css diagwait
13
[root@node2 bin]# ./crsctl set css diagwait 13 -force

在11.2.0.1后，我们不再须要改动diagwait，因此架构已经发生了改变。

在windows下我们也能够改动diagwait，可是与在linux下不同，改动diagwait不会造成上面的变化。

以下再来看一下有关hangcheck_timer的有关信息，hangcheck_timer与oprocd能够实现同样的功能，可是两者之间没有必定的联系

Hangcheck-Timer Module

Hangcheck-Timer Module Requirements for Oracle 9i, 10g, and 11g RAC on Linux

Starting in release 9.2.0.2 and later, Oracle RAC environments required using a new I/O fencing model, named the hangcheck-timer module. This module was implemented to replace the Watchdog module, which provided similar fencing functionality. Hangcheck-timer
was subsequently delivered as part of the standard kernel distribution for Linux kernel releases 2.4 and above.

Hangcheck-timer should be loaded at boot time, and monitors the Linux kernel for long operating system hangs that could affect the reliability of a RAC node.  It runs in kernel mode and uses the Time Stamp Counter (TSC) to catch scheduling delays or node hangs. 
This is done by setting a timer, then checking when the timer fires as to whether it was delayed by more than the allowed margin of error.  If the duration exceeds the allowed time of (hangcheck_tick + hangcheck_margin seconds), the machine is restarted. 
Hangcheck-timer will not cause reboots to occur due to CPU starvation.

 Hangcheck-timer requires three configuration parameters:

    hangcheck_tick - defines how often, in seconds, the hangcheck-timer checks the node for hangs. The default value is 60 seconds.

    hangcheck_margin - defines how much margin is allowed, in seconds, between expected scheduling and real scheduling time. The default value is 180 seconds.

    hangcheck_reboot - determines if the hangcheck-timer restarts the node if the kernel fails to respond within the sum of the hangcheck_tick and hangcheck_margin parameter values. If the value of hangcheck_reboot is equal to or greater than 1, then the hangcheck-timer
module restarts the system. If the hangcheck_reboot parameter is set to zero, then the hangcheck-timer module will not reboot the node, even if a hang is detected.   The default value varies by kernel version.  In the 2.4 kernel, the default is 1.  In 2.6
kernels, the default is 0.

Hangcheck-timer will provide message logging to the system messages log when a failure is detected, and a node restart is initiated by the module:

    When Hangcheck-timer reboots it may leave "Hangcheck: hangcheck is restarting the machine" message in /var/log/messages

    If you see the following message in /var/log/messages:  "Hangcheck: hangcheck value past margin!" this means a reboot was required but was not performed, because hangcheck_reboot was not set to 1.  If this message is seen, you must reload the hangcheck
module as described earlier in this note, with the hangcheck_reboot value set to 1.

Note : Hangheck timer is not required starting with Oracle Clusterware 11gR2