Apache Error Log Indicates "Segmentation Fault"

When encountering blank white pages that can't be debugged through CakePHP, consulting the Apache error.log may reveal messages indicating child processes exiting with a "Segmentation fault (11)" signal. This error indicates an issue with accessing memory.

Understanding the Segmentation Fault

A segmentation fault occurs when a program attempts to access memory outside of the allocated memory segment. This can happen due to memory corruption, array index out of bounds errors, and other coding defects.

Identifying the Cause

To determine the exact cause of the segmentation fault, it's recommended to attach a debugger (e.g., gdb) to one of the child processes and capture a backtrace when a crash occurs. The backtrace will provide information about the function call stack leading up to the fault.

$ sudo gdb
(gdb) attach 
(gdb) backtrace

Resolving the Segmentation Fault

Once the cause of the fault is known, it can be addressed by fixing the underlying code. This may involve correcting memory allocation, handling array indices correctly, or fixing logic errors.

Configuring Apache to Reduce Crashes

If the crash is hard to reproduce, configuring Apache to use only one child process can help minimize the impact of the error:

StartServers 1
MinSpareServers 1
MaxSpareServers 1

By using a single child process, Apache will avoid the issue of multiple processes accessing memory concurrently and potentially causing segmentation faults. However, this configuration may not be suitable for higher-traffic websites.