Random errors with PHP-FPM

[markopolojarvi@…]

We are having a bizarre problem with our server setup, and I traced to self-compiled nginx. Previously we used the official Docker image for nginx + PHP-FPM setup and everything worked perfectly. Due to some new requirements, we needed to use the substitution module which meant that we needed to compile nginx ourselves. Everything seems to work fine in our test environment but in the production we start to get huge amount of random E_WARNINGs from PHP. These errors don't make any sense and they are things like 'array_filter() expects parameter 1 to be array, null given' or 'implode(): Invalid arguments passed'.

We initially suspected that the problem was caused by the substitution module but the problem persists even without it. So something is going wrong in the compilation because if I swap pre-compiled nginx from apt, everything works.

I don't know nginx in depth so I'm running out of ideas how to debug this.

Here's the build configuration (copied from apt nginx):

 --prefix=/etc/nginx \
 --sbin-path=/usr/sbin/nginx \
 --modules-path=/usr/lib/nginx/modules \
 --conf-path=/etc/nginx/nginx.conf \
 --error-log-path=/var/log/nginx/error.log \
 --http-log-path=/var/log/nginx/access.log \
 --pid-path=/var/run/nginx.pid \
 --lock-path=/var/run/nginx.lock \
 --http-client-body-temp-path=/var/cache/nginx/client_temp \
 --http-proxy-temp-path=/var/cache/nginx/proxy_temp \
 --http-fastcgi-temp-path=/var/cache/nginx/fastcgi_temp \
 --http-uwsgi-temp-path=/var/cache/nginx/uwsgi_temp \
 --http-scgi-temp-path=/var/cache/nginx/scgi_temp \
 --user=nginx \
 --group=nginx \
 --with-compat \
 --with-file-aio \
 --with-threads \
 --with-http_addition_module \
 --with-http_auth_request_module \
 --with-http_dav_module \
 --with-http_flv_module \
 --with-http_gunzip_module \
 --with-http_gzip_static_module \
 --with-http_mp4_module \
 --with-http_random_index_module \
 --with-http_realip_module \
 --with-http_secure_link_module \
 --with-http_slice_module \
 --with-http_ssl_module \
 --with-http_stub_status_module \
 --with-http_sub_module \
 --with-http_v2_module \
 --with-mail \
 --with-mail_ssl_module \
 --with-stream \
 --with-stream_realip_module \
 --with-stream_ssl_module \
 --with-stream_ssl_preread_module \
 --with-cc-opt='-g -O2 -fdebug-prefix-map=/data/builder/debuild/nginx-1.15.5/debian/debuild-base/nginx-1.15.5=. -specs=/usr/share/dpkg/no-pie-compile.specs -fstack-protector-strong -Wformat -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -fPIC' \
 --with-ld-opt='-specs=/usr/share/dpkg/no-pie-link.specs -Wl,-z,relro -Wl,-z,now -Wl,--as-needed -pie'

[Maxim Dounin]

PHP-FPM is a completely separate daemon, and nginx talks to it only via a network connection configured. If you see errors and warnings from PHP-FPM, this is likely something to do with PHP-FPM, not nginx.

The most likely cause at least somehow related to nginx I can think of is a different nginx configuration and/or defaults compared to your previous setup, resulting in different fastcgi parameters being sent to PHP-FPM, and incorrect PHP scripts being used due to this (or something like this).

In either case, this doesn't look like a bug in nginx. For questions, consider using ​support options available.