Preparing for problems ahead of ime¶
When customers encounter problem symptoms such as a child process crash or an unresponsive condition with IHS, there is not always enough information available from the first occurrence of the symptom to determine the nature of the problem. Preparation ahead of time can increase the value of the information captured at first failure and reduce the frequency of recreates.
The recommended preparation steps are:
Check for operating system prerequisites¶
An IBM HTTP Server release has the same operating system prerequisites as the release of WebSphere Application Server with which is corresponds. These operating system prerequisites need to be installed on the system with IBM HTTP Server before reporting a problem to IBM support. For all in-service releases of IBM HTTP Server, there is a direct correspondence to a WebSphere Application Server release and its prerequisites.
Check the operating system prerequisites for that release here. First follow the "Software requirements" link for your release, then follow the "Application Server" link.
Installation of IHS diagnostic package on systems with IHS¶
In the event of a child process crash or web server hang on Linux and Unix systems, ihsdiag tools will be used by the administrator on the system where IHS is installed to obtain and format information about the failure. The diagnostic package should be installed ahead of time. The location is not important.
Note that there may be requirements for running ihsdiag tools as root.
These are explained in the documentation for the particular tool (child
process crash; web server
hang; high CPU
condition).
IHS configuration¶
Enabling core dumps on Linux and Unix systems¶
Core dumps are critical information for diagnosing child process crashes.
Most of the configuration required for core dumps is in the realm of the
operating system, but the CoreDumpDirectory directive may need to be
enabled in the IHS configuration file. Core dump configuration issues
are described here.
If a core dump is written at the time of the crash, the information to provide to IBM support is described here. If no core dump was written, review the core dump configuration information to determine the cause. Check the IHS error log for any messages written at startup regarding core dumps, as recent levels of IHS 1.3 and 2.0 report common core dump configuration problems to the error log at startup.
Adding response time to access log¶
When there are concerns about page display time, it is important to know which types of requests are responded to slowly. By recording the response time for every request in the access log, analysis of the access log can provide information about where the problem may lie. The following are potential conclusions which can be made:
all requests are responded to slowly
requests for static files such as images are responded to quickly but requests for dynamic application content are responded to slowly
requests for some application content are responded to slowly, but requests for other application content are responded to quickly
The response time in microseconds can be added to the end of every line of
the access log by adding %D to the end of the format string.
In the following example, a new format called responsetime has been
created with the response time in microseconds at the end of the line, and
the access log uses that format.
LogFormat "%h %l %u %t \"%r\" %>s %b %{RH}e %{WAS}e %D" responsetime
...
CustomLog logs/access_log responsetime
**Note:**Any programs used in your environment to analyze the access log may be impacted by adding this additional field. If there are such programs in use, investigate their requirements before implementing the change.
Enabling standard diagnostic modules¶
IHS 7.0 and later enables available diagnostic modules by default.
Operating system configuration¶
Enabling core dumps on Linux and Unix systems¶
Most of the configuration required for core dumps is in the realm of the operating system. It is described here.
Installation of supporting system tools¶
For some web server problem symptoms, system tools such as debuggers will be used to gather diagnostic information. Instructions for verifying that required tools are already installed are provided here.