I'm using New Relic in conjunction with W3 Total Cache on a WordPress site of mine. I've got my own dedicated server as well which the site resides on.
New Relic seems to be working fine, however, when I try to integrate it with W3 Total Cache it causes a 501 bad gateway error to appear when trying to access the site in any web browser.
I've narrowed the problem down to the .htaccess file. W3 Total Cache is inserting this code in my .htaccess file whenever New Relic is enabled...
php_value newrelic.appname 'PR Tech'
That code is what is causing the 501 bad gateway errors all throughout my site. When I remove that code and disable New Relic via W3 Total Cache everything works just as it should.
I've read the New Relic documentation here... https://newrelic.com/docs/php/per-directory-settings
That article states that the code that W3 Total Cache is inserting in the .htaccess file is indeed correct. So, I'm not sure what's going on here and was hoping maybe someone had some sort of idea.