I want to run a small apache app inside a heroku dyno. It's alongside a js app, which calls out to the php service for a small number of its requests.

The supervisord config for this service is:

[program:pdf-service]
command=apachectl -D FOREGROUND
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
redirect_stderr=true

The Dockerfile that builds the image does:

COPY pdf /var/www/html
COPY pdf/apache2/ports.conf /etc/apache2/ports.conf 
COPY pdf/apache2/apache2.conf /etc/apache2/apache2.conf

This all works fine when I run it locally (i.e. build the docker container and then run it).

However, when I deploy to heroku, I get an error:

INFO spawned: 'pdf-service' with pid 9
chown: changing ownership of '/var/lock/apache2.A4FPKqG8rS': Operation not permitted
exited: pdf-service (exit status 1; not expected)

Does anyone know why this might be happening / how I can avoid it?

Alternatively, can I spin up the php service in its own container and then call it from the js without using private spaces? I think this isn't possible as dynos can't communicate with each other.