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Setup: a QGis-2.18 Server (really an embedded MapServer) instance via FastCGI in Apache-2.4.18 on Ubuntu.

If a certain value is set in the query string for the cgi handler, I would like to add another value. To that end, I have added three lines to the top of /etc/apache2/conf-enabled/qgis.conf:

RewriteEngine on RewriteCond "%{QUERY_STRING}" "application/json" [NC] RewriteRule "^/$" "/?OUTPUTFORMAT=GeoJSON" [PT,QSA] ScriptAlias / /usr/lib/cgi-bin/qgis_mapserv.fcgi <Location "/"> SetHandler fcgid-script Require all granted PassEnv QGIS_PROJECT_FILE </Location> FcgidInitialEnv QGIS_LOG_FILE ${QGIS_LOG_FILE} FcgidInitialEnv QGIS_SERVER_LOG_FILE ${QGIS_SERVER_LOG_FILE} FcgidInitialEnv QGIS_DEBUG ${QGIS_DEBUG} FcgidInitialEnv QGIS_SERVER_LOG_LEVEL ${QGIS_SERVER_LOG_LEVEL} FcgidInitialEnv QGIS_PLUGINPATH "${QGIS_PLUGINPATH}" FcgidInitialEnv PGSERVICEFILE ${PGSERVICEFILE} FcgidInitialEnv HOME /var/www

I'm accessing the server like this:

http://myserver.invalid.tld:51081/ ?SERVICE=WFS &VERSION=1.1.0 &REQUEST=GetFeature &OUTPUTFORMAT=application/json &MAXFEATURES=1 &SRSNAME=EPSG:4326 &TYPENAME=feature_type_name &BBOX=8.5985658,56.447691,8.600106,56.448553

I would have expected the effect to be the same as if I had manually appended &OUTPUTFORMAT=GeoJSON at the end of my URL, but I see no difference at all after restarting apache. (Yes, I have run sudo a2enmod rewrite.)

I am unsure how the interaction between rewrite rules and a script alias works, so I'm thinking that one shadows the other? Unfortunately, I also have no idea how to debug this.

The server has one virtual host enabled, which looks like OOTB config to me:

# apache2ctl -S AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 172.17.0.10. Set the 'ServerName' directive globally to suppress this message VirtualHost configuration: *:80 172.17.0.10 (/etc/apache2/sites-enabled/000-default.conf:1) ServerRoot: "/etc/apache2" Main DocumentRoot: "/var/www/html" Main ErrorLog: "/proc/self/fd/2" Mutex default: dir="/var/lock/apache2" mechanism=fcntl Mutex fcgid-pipe: using_defaults Mutex watchdog-callback: using_defaults Mutex rewrite-map: using_defaults Mutex fcgid-proctbl: using_defaults PidFile: "/var/run/apache2/apache2.pid" Define: DUMP_VHOSTS Define: DUMP_RUN_CFG User: name="www-data" id=33 Group: name="www-data" id=33

Here's /etc/apache2/sites-enabled/000-default.conf (comments stripped):

<VirtualHost *:80> ServerAdmin webmaster@localhost DocumentRoot /var/www/html ErrorLog /proc/self/fd/2 CustomLog /proc/self/fd/1 combined </VirtualHost>

And finally apache2.conf (again, comments stripped):

Mutex file:${APACHE_LOCK_DIR} default PidFile ${APACHE_PID_FILE} Timeout 300 KeepAlive On MaxKeepAliveRequests 100 KeepAliveTimeout 5 User ${APACHE_RUN_USER} Group ${APACHE_RUN_GROUP} HostnameLookups Off ErrorLog /proc/self/fd/2 LogLevel warn IncludeOptional mods-enabled/*.load IncludeOptional mods-enabled/*.conf Include ports.conf <Directory /> Options FollowSymLinks AllowOverride None Require all denied </Directory> <Directory /usr/share> AllowOverride None Require all granted </Directory> <Directory /var/www/> Options Indexes FollowSymLinks AllowOverride None Require all granted </Directory> AccessFileName .htaccess <FilesMatch "^\.ht"> Require all denied </FilesMatch> LogFormat "%v:%p %h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" vhost_combined LogFormat "%h %l %u %t \"%r\" %>s %O \"%{Referer}i\" \"%{User-Agent}i\"" combined LogFormat "%h %l %u %t \"%r\" %>s %O" common LogFormat "%{Referer}i -> %U" referer LogFormat "%{User-agent}i" agent IncludeOptional conf-enabled/*.conf IncludeOptional sites-enabled/*.conf

(For bonus points I'd like to replace application/json in the query string with GeoJSON, but if I could get the parameter appended to begin with I'm close to the goal.)

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I would have expected the effect to be the same as if I had manually appended &OUTPUTFORMAT=GeoJSON

Well, that maybe the "problem"; it's not appended. The original query string on the request is appended. The query string (OUTPUTFORMAT=GeoJSON) in the substitution string is at the start of the query string. So, depending on how you are reading/parsing the parameters in the query string, your new setting is probably being overwritten.

To specifically append something to the existing query string you can make use of the QUERY_STRING server variable in the substitution (instead of using the QSA flag). For example:

RewriteCond %{QUERY_STRING} application/json RewriteRule ^/$ /?%{QUERY_STRING}&OUTPUTFORMAT=GeoJSON [PT]

No need to wrap every argument in quotes, unless they contain spaces. Only use the NC flag if you specifically need a case-insensitive match.

Alternatively, to replace the OUTPUTFORMAT=application/json URL parameter in the request, then you can do something like this:

RewriteCond %{QUERY_STRING} (.*)OUTPUTFORMAT=application/json(.*) RewriteRule ^/$ /?%1OUTPUTFORMAT=GeoJSON%2 [PT]

%1 and %2 are backreferences to the captured groups in the preceding CondPattern. ie. Everything before and after the original URL parameter in the query string.

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    Thanks for pointing out that I had misread the docs on what [QSA] does! :o) Your rewriterule with the back references worked like a charm, once we had found the right place to put it. Thanks a bunch. Commented Oct 24, 2017 at 8:36

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