503 Errors with PHP, Reproducible Easily - question relating to LSAPI_AVOID_FORK
I've been running LiteSpeed (standard edition) for several years now and periodically have had issues with 503 errors. These problems have not often been easily reproducible, and didn't occur that often, so I haven't investigated much.
However, recently I set up a new system and installed phpMyAdmin. I was able to very easily reproduce 503 errors by just logging in to phpMyAdmin and changing the theme back and forth from one theme to the other. When I start doing this, every time, within about 10 attempts, usually less, I get a 503 error.
I tried PHP 5.3.8, 5.3.6, 5.2.17, 5.2.10, 5.2.11 all with the exact same results.
Then I looked at the configuration for another server of mine that I had many 503 issues with in the past with vBulletin.
The setting LSAPI_AVOID_FORK comes into question.
For the phpMyAdmin reproducible test, with LSAPI_AVOID_FORK=0 (the default), I can cause 503 errors as I said, easily and reproducible.
With LSAPI_AVOID_FORK=1, I cannot cause a 503 error in the same manner.
For the vBulletin server, if I have LSAPI_AVOID_FORK=0, I end up with 50-100 503 errors in the logs per day (out of many, many requests), and with LSAPI_AVOID_FORK=1 I end up with about 5-10 per day.
So it seems that LSAPI_AVOID_FORK=0 is causing me problems, but I wonder if there is something else that would be causing this as I haven't found much documentation on LSAPI_AVOID_FORK with regards to 503 errors.
My environment settings for the external app are:
So my question is why does LSAPI_AVOID_FORK reduce the frequency of 503 errors significantly/almost get rid of them completely? And are there any other settings I should be using instead?