Apache 2.4 httpd in Docker doesn't start when loading proxy module

Question

I'm building a Apache2.4 stack with Docker. During configuration, the server doesn't start:

apache-php-fpm-docker_apache_1 exited with code 1

Found out this happens after adding the following line to load a module:

LoadModule proxy_module modules/mod_proxy.so

I think that I did something wrong, but how can I get the error message to see what's the problem?

What I already tried

Running httpd -hI saw the following option:

-e level : show startup errors of level (see LogLevel)

So I tried ENTRYPOINT httpd -k start -e debug and see now some logs, but not errors. And the webserver doesn't start, not even when the errors were fixed.

Full apache config

Listen 80
ServerRoot "/usr/local/apache2"
DocumentRoot "/usr/local/apache2/htdocs"
ServerName localhost
LogLevel warn

LoadModule mpm_event_module modules/mod_mpm_event.so
LoadModule authn_file_module modules/mod_authn_file.so
LoadModule authn_core_module modules/mod_authn_core.so
LoadModule authz_host_module modules/mod_authz_host.so
LoadModule authz_groupfile_module modules/mod_authz_groupfile.so
LoadModule authz_user_module modules/mod_authz_user.so
LoadModule authz_core_module modules/mod_authz_core.so
LoadModule access_compat_module modules/mod_access_compat.so
LoadModule auth_basic_module modules/mod_auth_basic.so
LoadModule reqtimeout_module modules/mod_reqtimeout.so
LoadModule filter_module modules/mod_filter.so
LoadModule mime_module modules/mod_mime.so
LoadModule log_config_module modules/mod_log_config.so
LoadModule env_module modules/mod_env.so
LoadModule headers_module modules/mod_headers.so
LoadModule setenvif_module modules/mod_setenvif.so
LoadModule version_module modules/mod_version.so
LoadModule unixd_module modules/mod_unixd.so
LoadModule status_module modules/mod_status.so
LoadModule autoindex_module modules/mod_autoindex.so
LoadModule dir_module modules/mod_dir.so
LoadModule alias_module modules/mod_alias.so

#LoadModule proxy_module modules/mod_proxy.so
#LoadModule proxy_fcgi_module modules/mod_proxy_fcgi.so

<IfModule mime_module>
    TypesConfig conf/mime.types
    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz
</IfModule>

<Directory />
    AllowOverride none
    Require all denied
</Directory>

<Files ".ht*">
    Require all denied
</Files>

#ProxyPassMatch ^/(.*\.php(/.*)?)$ fcgi://php:9000/usr/local/apache2/htdocs/$1
<Directory "/usr/local/apache2/htdocs">
    Options Indexes FollowSymlinks
    AllowOverride None
    Require all granted
</Directory>

Docker Compose

version: "2.4"
services: 
  apache:
    image: httpd:2.4
    volumes:
      - ./apache/httpd.conf:/usr/local/apache2/conf/httpd.conf
      - ./src:/usr/local/apache2/htdocs
    ports:
      - 80:80

  php:
    image: php:7.3-fpm
    volumes_from:
      - apache

Answer 1

First, add ErrorLog /proc/self/fd/2 to your http.conf to enable the error log.

Then, I saw the error log of your situation:

shubuntu1@shubuntu1:~/aa$ docker run -idt -v ${PWD}/httpd.conf:/usr/local/apache2/conf/httpd.conf -p 9000:80 httpd:2.4
fd0d0b45bd8e25e5ce8219d6b96e5b446307d7a76bf7e3eecb47e23d93b04368
shubuntu1@shubuntu1:~/aa$ docker ps -a
CONTAINER ID        IMAGE               COMMAND              CREATED             STATUS                    PORTS               NAMES
fd0d0b45bd8e        httpd:2.4           "httpd-foreground"   3 seconds ago       Exited (1) 1 second ago                       agitated_edison
shubuntu1@shubuntu1:~/aa$ docker logs agitated_edison
[Wed Jun 19 08:45:20.774433 2019] [core:emerg] [pid 1:tid 139720185319488] (22)Invalid argument: AH00024: Couldn't set permissions on the proxy mutex; check User and Group directives
[Wed Jun 19 08:45:20.774495 2019] [proxy:crit] [pid 1:tid 139720185319488] (22)Invalid argument: AH02478: failed to create proxy mutex
AH00016: Configuration Failed

From the error log: it seems failure when create proxy mutex for proxy_module. So, I add next to httpd.conf, then everything works:

<IfModule unixd_module>
User daemon
Group daemon
</IfModule>