upstream sent unexpected FastCGI record: 3 while reading response header from upstream

Tue Mar 14 22:01:45 UTC 2017

I am getting random "upstream sent unexpected FastCGI record: 3 while
reading response header from upstream" while using Nginx with PHP7. So far I
was waiting for bug https://bugs.php.net/bug.php?id=67583 to be fixed by PHP
which they now have but I still get this error.

Everything works fine for few days and then suddenly I start getting this
error. How can I debug this in detail? Is there a way I could see or log
response from PHP (FastCGI) when this error occurs?

Posted at Nginx Forum: https://forum.nginx.org/read.php?2,272936,272936#msg-272936