Template engine for configuration files

A new mechanism that allows generating Apache and Nginx configuration files. The mechanism is based on a template that enables to use logical branches and parameter setting, allowing for more flexible creation and modification configuration parameters of a web-server.

With this mechanism, you can use the required parameters in order to configure Apache and Nginx. Besides, after you add user parameters into the configuration file, other operations that the template engine performs, won't modify them.

This article will walk you through the steps you need to perform to start using a template engine, describe its general functions and syntax.

How to start?

The template engine will be used by default to generate configuration files of the "WWW-domains" module.

General principles

In the WWW-domains module every function has a corresponding configuration file template. E.g., web-domain creation/edit function has a corresponding template in the /usr/local/mgr5/etc/templates/default/apache2-vhosts.template file for Apache configuration file, and /usr/local/mgr5/etc/templates/default/nginx-vhosts.template for Nginx.

Files with configuration templates can be re-defined by user parameters. Copy a file with template into the /usr/local/mgr5/etc/templates directory with the same name. If the /usr/local/mgr5/etc/templates directory contains a template file, the template in the /usr/local/mgr5/etc/templates/default/ directory will be ignored. When the panel updates, files in the /usr/local/mgr5/etc/templates/default/ directory will be overwritten, that's why you should make changes in /usr/local/mgr5/etc/templates/.

The table below shows correspondence between a file with a template, and a function to call in the WWW-domains module.

Syntax

All template sections must locate between tags {% and %}. E.g. a variable should look like this: {% $VARIABLE_NAME %}.

Variables

A variable name should meet the following requirements:

• user upper-case letters
• start with $
• have the same name as the parameter passed to the session by the control panel.

If a configuration string in template contains a variable that is not present in the session, the string will be ignored. Let's consider an example where the template will create the VirtualHost section for the Apache configuration file. In the example below, we will use the {%$LISTEN_ON %} variable where an address and port are kept: 192.168.0.1:80.

  <VirtualHost {% $LISTEN_ON %}
  >
</VirtualHost>

As a result, the VirtualHost section will be created in the configuration file:

  <VirtualHost 192.168.0.1:80
  >
</VirtualHost>

Conditions

A condition is the main selection tool. It will choose, what parameter to add or delete depending on variable during condition check. Conditions should start with the if statement and end with endif. Let's consider a simple condition containing only if.

{% if $VARIABLE_NAME == VALUE %}
    ParameterName ParameterValue;
{% endif %}

If a result of this condition is true, every parameter located between if and endif will be added into the configuration file (if that parameter is not present). If the result is false, every parameter between if and endif will be deleted from the configuration file.

Advanced conditions

You can create an advanced condition containing else. Parameters located between else and endif will be added into the configuration file if a result of the if statement is false or deleted from the configuration file if it is true. Let's consider an example where parameter will be added or deleted depending on the Apache version:

  <VirtualHost {% $LISTEN_ON %}
  >
{% if $APACHEITK == ON %}
    AssignUserID owner group
{% else %}
    SuexecUserGroup owner group
{% endif %}
</VirtualHost>

The VirtualHost section will be created in the configuration file, if ApacheITK is used, the AssignUserID owner group parameter will be added into VirtualHost, and the SuexecUserGroup owner group parameter will be deleted from VirtualHost, if it was present in that section. The following example shows what parameters the configuration file will contain if ApacheITK is used:

  <VirtualHost 192.168.0.1:80
  >
    AssignUserID owner group
</VirtualHost>

If another version of Apache is used, the configuration file will contain the following parameters:

  <VirtualHost 192.168.0.1:80
  >
    SuexecUserGroup owner group
</VirtualHost>

Conditions for multiple selections

A condition can be enlarged with the elif statement. It can be used if one of the variables have different values, which should be processed. E.g. when creating or editing a web-domain, ISPmanager enables to choose a PHP mode. Let's consider such a situation, and suppose that we have created a web-domain with "PHP as Apache" enabled. Our configuration file looks like that:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
    ServerAlias www.domain.ru
    <FilesMatch "\.ph(p[3-5]?|tml)$"
  >
        SetHandler application/x-httpd-php
    </FilesMatch>
    <FilesMatch "\.phps$"
  >
        SetHandler application/x-httpd-php-source
    </FilesMatch>
</VirtualHost>

We edited web-domain parameters and set PHP as CGI. The template below enables to add or delete the FilesMatch subsection depending on a selected PHP mode.

  <VirtualHost {% $LISTEN_ON %}
  >
{% if $PHP_MODE == MODULE_APACHE %}
    <FilesMatch "\.ph(p[3-5]?|tml)$"
  >
        SetHandler application/x-httpd-php
    </FilesMatch>
    <FilesMatch "\.phps$"
  >
        SetHandler application/x-httpd-php-source
    </FilesMatch>
{% elif $PHP_MODE == CGI %}
    <FilesMatch "\.ph(p[3-5]?|tml)$"
  >
        SetHandler application/x-httpd-php5
    </FilesMatch>
{% endif %}
</VirtualHost>

The VirtualHost section won't be created in the configuration file, as it is already present. All the changes will be made in existing VirtualHost. Based on conditions from our example, the result of the if statement will be false, therefore, all parameters between if and elif will be deleted from VirtualHost. Parameters between elif and endif will be added into VirtualHost. The configuration file will look like that:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
    ServerAlias www.domain.ru
    <FilesMatch "\.ph(p[3-5]?|tml)$"
  >
        SetHandler application/x-httpd-php5
    </FilesMatch>
</VirtualHost>

Table of comparison operators

The following comparison operators can be used in conditions:

String commenting

You can use {#} to comment strings in the configuration file template. Everything that you add after comment will be ignored by the template engine. Example:

  <VirtualHost {% $LISTEN_ON %}
  >
    ServerName {% $NAME %} {#} Comment 
    {#} ServerAlias {% $ALIASES %}
</VirtualHost>

The configuration file will then look like that:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
</VirtualHost>

Template import

Other templates can be imported into the configuration file template. Use the import construction. E.g.:

  <VirtualHost {% $LISTEN_ON %}
  >
    {% import /path/to/template/apache-params.template %}
</VirtualHost>

Enter an absolute path to a template you want to import.

Parameters that identify sections

Every type of configuration file has certain parameters that are used by the template engine to identify sections. E.g. for the Nginx configuration file, server_name and ssl are selected as key parameters. Therefore, when something should be added or deleted from the configuration file without a control panel, the template engine "knows" exactly where to perform the operation. However, if you are trying to modify those parameters in the configuration file, they are likely not to be added into a required section but will be applied in a new section.

Searching for a modified parameter by key values

There are additional tags — [% and %]. They can contain only variables, such as [% $VARIABLE_NAME %]. This expression is interpreted as a common variable but plays a specific role in parameter search. These tags define values that won't be used during the search process. Let's consider the following example:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
    ServerAlias www.domain.ru
</VirtualHost>

Use the template:

  <VirtualHost {% $LISTEN_ON %}
  >
{% if $ERROR == on %}
    ErrorDocument {% $CODE %} [% $URI %]
{% endif %}
</VirtualHost>

If the $ERROR variable is on, the ErrorDocument parameter with variables $CODE and $URI will be added into VirtualHost. The $CODE and $URI values are specified in the control panel on the error page creation form. During that process, the $ERROR variable is set to on, therefore the condition is met, and our configuration file looks like that:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
    ServerAlias www.domain.ru
    ErrorDocument 404 /404.php
</VirtualHost>

Then, we decided in the configuration file change the path from /404.php into /404.html. We have the following configuration file:

  <VirtualHost 192.168.0.1:80
  >
    ServerName domain.ru
    ServerAlias www.domain.ru
    ErrorDocument 404 /404.html
</VirtualHost>

In this case, the ErrorDocument parameter differs from the one specified in the control panel. If we decide to delete the error page from the control panel, the template engine won't find a required parameter in the configuration file and won't delete it. But in the template the $URI value is canceled, the search will be made by the ErrorDocument 404 string. Deleting of an error page will set the $ERROR variable to off, therefore the condition used in the template, won't be met. Only ErrorDocument 404 will be used to search for our parameter, thus it will be found and deleted in the configuration file.

Standard variables

Every function you call uses its own set of parameters that are passed to a session. The following list contains standard variables for each WWW-domain management function.

Creating/Editing WWW-domain

The table below contains a list of variables regardless a web-servers type.

Apache variables

Nginx variables

Error pages

Redirects

Access

Parameters on your server may vary depending on applications, plug-ins, etc that you use. A current set of parameters of the function that you call, can be found in the /usr/local/mgr5/var/ispmgr.log log file. Function call is shown in green. You can also view parameters that were passed, in the console of your web-browser after the form is sent to server.

Example

Let's consider a situation when we need to generate different parameters of the configuration files depending on account template type that was used for user creation. In our example, we will use only two types of user templates: for CMS «1C-Bitrix» and web-framework «Django». First, we need to create user templates. Log in to ispmanager → "Settings" → "Templates", and create a new template named «Bitrix». You can enter any values in the «Limits» tab. In the «Access» tab select the Can use PHP as Apache checkbox, domain encoding - UTF-8, and PHP mode - Apache. Create a template for Django. Name - Django, enter any limits and access permissions, "Default values" - set the same values as in your previous template.

If you want to manage your site with «1C-Bitrix», in the apache2-vhost.template template you need to define additional parameters. If you want to use Django, you need to install the «mod_wsgi» module for Apache. If you run Debian, execute the command to install the module:

# apt-get install libapache2-mod-wsgi

If you run CentOS, execute the command:

# yum install mod_wsgi

In order to handle requests, we will need a web-interface for the «mod_wsgi» module. A source code of the interface can be found on the Internet in topics related to «Django». In our example, we will define only the interface name — django.wsgi that you should put to the WWW-domain root directory.

Create a configuration file template. Copy the /usr/local/mgr5/etc/templates/default/apache2-vhosts.template template into the /usr/local/mgr5/etc/templates/ directory, as described in General principles, and add parameters at the end of:

{% if $PRESET == Bitrix %}
    php_admin_value mbstring.func_overload 2
    php_admin_value mbstring.internal_encoding UTF-8
    php_admin_value opcache.revalidate_freq 0
    php_admin_value display_errors on
{% elif $PRESET == Django %}
    WSGIScriptAlias / {% $DOCROOT %}/django.wsgi
    WSGIDaemonProcess [% $NAME %] processes=2 maximum-requests=5 threads=1
    WSGIProcessGroup {% $NAME %}
{% endif %}

VirtualHost template will look like this:

  <VirtualHost {% $LISTEN_ON %}
  >
	ServerName {% $NAME %}
	ServerAlias {% $ALIASES %}
	DocumentRoot {% $DOCROOT %}
	ServerAdmin {% $EMAIL %}
	DirectoryIndex {% $DIRINDEX %}
	AddDefaultCharset {% $CHARSET %}
{% if $APACHEITK == on %}
	AssignUserID {% $OWNER %} {% $OWNER_GROUP %}
{% else %}
	SuexecUserGroup {% $OWNER %} {% $OWNER_GROUP %}
{% endif %}
{% if $LOG_ACCESS == on %}
	CustomLog {% $ACCESS_LOG_PATH %} combined
{% else %}
	CustomLog /dev/null combined
{% endif %}
{% if $LOG_ERROR == on %}
	ErrorLog {% $ERROR_LOG_PATH %}
{% else %}
	ErrorLog /dev/null
{% endif %}
{% if $CGI == on %}
	ScriptAlias /cgi-bin/ {% $CGI_EXT_PATH %}
{% endif %}
{% if $INCLUDE %}
	Include {% $INCLUDE %}
{% endif %}
{% if $PHP == on and $FILES_MATCH == on %}
	<FilesMatch "\.ph(p[3-5]?|tml)$"
  >
		SetHandler {% $PHP_HANDLER %}
{% if $APACHE_FCGID == on %}
		FCGIWrapper {% $PHP_BIN_WRAPPER %}
		Options ExecCGI
{% endif %}
	</FilesMatch>
{% endif %}
{% if $PHP_MODE == php_mode_mod %}
	<FilesMatch "\.phps$"
  >
		SetHandler application/x-httpd-php-source
	</FilesMatch>
{% if $INCLUDE_PHP %}
	Include {% $INCLUDE_PHP %}
{% endif %}
	php_admin_value sendmail_path "/usr/sbin/sendmail -t -i -f {% $EMAIL %}"
	php_admin_value upload_tmp_dir "{% $MOD_TMP_PATH %}"
	php_admin_value session.save_path "{% $MOD_TMP_PATH %}"
{% if $OPEN_BASEDIR != / %}
	php_admin_value open_basedir "{% $OPEN_BASEDIR %}"
{% endif %}
{% elif $PHP_MODE == php_mode_cgi %}
	ScriptAlias /php-bin/ {% $PHP_BIN_DIR %}
	AddHandler application/x-httpd-php5 .php .php3 .php4 .php5 .phtml
	Action application/x-httpd-php5 /php-bin/php
{% elif $PHP_MODE == php_mode_fcgi_apache and $APACHE_FCGID != on %}
	AddType application/x-httpd-fastphp .php .php3 .php4 .php5 .phtml
	Alias /php-fcgi/ {% $PHP_BIN_DIR %}
{% endif %}
{% if $VIRTUAL_DOCROOT == on %}
	VirtualDocumentRoot {% $VIRTUAL_DOCROOT_PATH %}
{% endif %}
{% if $PRESET == Bitrix %}
    php_admin_value mbstring.func_overload 2
    php_admin_value mbstring.internal_encoding UTF-8
    php_admin_value opcache.revalidate_freq 0
    php_admin_value display_errors on
{% elif $PRESET == Django %}
    WSGIScriptAlias / {% $DOCROOT %}/django.wsgi
    WSGIDaemonProcess [% $NAME %] processes=2 maximum-requests=5 threads=1
    WSGIProcessGroup {% $NAME %}
{% endif %}
</VirtualHost>

When creating a WWW-domain, depending on a user template that was used for user creation, configuration data will be generated for «1C-Bitrix» or «Django».