[mistwang]

if 503 error is due to consistent PHP process crash, you can add environment variable

LSAPI_ALLOW_CORE_DUMP

to lsphp5 external app configuration to let PHP dump a core file.
http://www.litespeedtech.com/php-litespeed-sapi.html

then check the core file with
gdb /usr/local/lsws/fcgi-bin/lsphp5 core_file_name
bt

It lists the stack call backs when PHP crashes, you can get some clue from it.


Latest 4.0.13 build reduce some 503 error for busy site. you can do a manual upgrade.