When doing Apache graceful restart, Web Agent reports error "PID Cache error"
Article ID: 7127
Updated On:
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Issue/Introduction
We're running a Web Agent on Apache, and when we restart Apache server
with the command :
service reload myinstance
then the Web Agent reports errors :
error.log :
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Info] [CA WebAgent IPC]
[31025] [CSmSem::getSem] Attempted to attach to non-existent semaphore with key 0xXXXXXX
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Info] [CA WebAgent IPC]
[31025] [CSmSem::getSem] Attempted to attach to non-existent semaphore with key 0xXXXXXX
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Info] [CA WebAgent IPC]
[31025] [CSmSem::getSem] Created semaphore 30081042 using key 0xXXXXXX
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Error] [CA WebAgent IPC]
[31025] [CSmSharedSegment::smalloc] Error allocating shared memory segment using key 0xXXXXXX -
File exists (17)
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Info] [CA WebAgent IPC]
[31025] [CSmSem::SemRm] Removed semaphore 30081042
May 23 14:19:36 myhost [23/May/2017:14:19:36] [Error] SiteMinder Agent
May 23 14:19:36 myhost PID Cache error.
May 23 14:19:36 myhost Failed to initialize PID Cache
May 23 14:19:40 myhost nm: '/{webserver_home}/bin/httpd': No such file
May 23 14:19:40 myhost [Tue May 23 14:19:40 2017] [warn] Siteminder Web Agent:
restart not supported.
Why do we have the Notice "nm: '/{webserver_home}/bin/httpd': No such file"
and Warning "Siteminder Web Agent: restart not supported." ?
Environment
Web Agent 12.52SP1CR10 build 2813 on Apache 2.4.43 64bit RedHat 7.8;
Cause
When you ran nm -A against /usr/sbin/httpd and /usr/sbin/httpd.worker
on the RedHat Apache and you get the message :
"no symols".
To illustrate it :
[root@localhost /opt]# nm -A /{webserver_home}/bin/httpd
nm: /{webserver_home}/bin/httpd: no symbols
[root@localhost /opt]# nm -A /{webserver_home}/bin/httpd.worker
nm: /{webserver_home}/bin/httpd.worker: no symbols
For the Agent to be able to support graceful restart, symbols should
be available. If no symbol is available, then you'll see the message
"nm: '/{webserver_home}/bin/httpd': No such file"
If symbols are available from the httpd binary, but the symbol
"restart_pending" is not found, then the warning message
"Siteminder Web Agent: restart not supported"
will appear. Out of the box Web Agent does this check for start, stop,
restart and gracefull options for the apachectl commands.
Resolution
Compile your own Apache or get an Apache version which binaries will
show symbols and the "restart_pending" symbols, in order to have the
LLAWP to not shutdown if a restart or graceful is option is send to
the apachectl command. If restart_pending symbol is not present, the
LLAWP process will shutdown and start over.
The commands
nm -A /{webserver_home}/bin/httpd
nm -A /{webserver_home}/bin/httpd .worker
should return symbols and "restart_pending" one.
Note that this applies up to Apache 2.4.27 Version. For higher Apache
version please refer to the following KD :
WebAgent does not support restart with Apache 2.4
https://knowledge.broadcom.com/external/article?articleId=205981
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