Python MapScript via WSGI example

README.md

Overview

Simple example of MapServer MapScript Python via WSGI testing

Environment

• MapServer 6.4.2
• Ubuntu 14.04

Running

python ./mapscript-wsgi.py
# open "http://localhost:8000/?service=WMS&version=1.3.0&request=GetCapabilities"
# open "http://localhost:8000/?service=WMS&version=1.1.1&request=GetMap&layers=CURRENT_CONDITIONS&srs=EPSG:4326&bbox=-180,-90,180,90&format=image/png&width=500&height=300"

apache.conf

WSGIDaemonProcess foo processes=10 threads=1
Alias /ms-wsgi /tmp/foo/mapscript-wsgi.py
<Directory "/tmp/foo">
        AllowOverride None
        Options +ExecCGI -MultiViews +SymLinksIfOwnerMatch
        AddHandler wsgi-script .py
        Order Allow,Deny
        Allow from all
</Directory>

mapscript-wsgi.py

import os
import sys

import mapscript


# List of all environment variable used by MapServer
MAPSERV_ENV = [
  'CONTENT_LENGTH', 'CONTENT_TYPE', 'CURL_CA_BUNDLE', 'HTTP_COOKIE',
  'HTTP_HOST', 'HTTPS', 'HTTP_X_FORWARDED_HOST', 'HTTP_X_FORWARDED_PORT',
  'HTTP_X_FORWARDED_PROTO', 'MS_DEBUGLEVEL', 'MS_ENCRYPTION_KEY',
  'MS_ERRORFILE', 'MS_MAPFILE', 'MS_MAPFILE_PATTERN', 'MS_MAP_NO_PATH',
  'MS_MAP_PATTERN', 'MS_MODE', 'MS_OPENLAYERS_JS_URL', 'MS_TEMPPATH',
  'MS_XMLMAPFILE_XSLT', 'PROJ_LIB', 'QUERY_STRING', 'REMOTE_ADDR',
  'REQUEST_METHOD', 'SCRIPT_NAME', 'SERVER_NAME', 'SERVER_PORT'
]


def application(env, start_response):
    for key in MAPSERV_ENV:
        if key in env:
            os.environ[key] = env[key]
        else:
            os.unsetenv(key)

    mapfile = '/tmp/foo.map'
    mapfile = mapscript.mapObj(mapfile)

    request = mapscript.OWSRequest()
    mapscript.msIO_installStdoutToBuffer()
    request.loadParamsFromURL(env['QUERY_STRING'])

    try:
        status = mapfile.OWSDispatch(request)
    except Exception as err:
        pass

    content_type = mapscript.msIO_stripStdoutBufferContentType()
    result = mapscript.msIO_getStdoutBufferBytes()
    start_response('200 OK', [('Content-type', content_type)])
    return [result]

if __name__ == '__main__':  # run inline using WSGI reference implementation
    from wsgiref.simple_server import make_server
    port = 8001
    if len(sys.argv) > 1:
        port = int(sys.argv[1])
    httpd = make_server('', port, application)
    print('Serving on port %d...' % port)
    httpd.serve_forever()

Notes on my testing of this, for future readers:

• Python 2.x users may receive an error regarding the header, such as:

AssertionError: Header values must be string

• reason is that Python2 does not handle the header correctly (Python3 does handle it nicely). You can force the content-type to bytes, for Python2, by changing line#40 to:

start_response('200 OK', [('Content-type', 'application/octet-stream')])

• For Windows users of Python, <unsetenv> is not available on Windows, so you can remove the <else> statement (on lines 23-24)

Thanks @jmckenna. To add, if you ave using MapServer 7.0.4 or below this patch is required.

Still a useful script! (tested with Python 3.10.0, mod_wsgi 4.9.0, Python MapScript 8.0-dev, in MS4W 5.0-dev) Thanks again!

Actually it's so useful that it will be distributed in MS4W 5.0, why not, saves me coming back here to find it each release to test with ha! thanks again.

Glad you found this useful @jmckenna! And great to see in MS4W moving forward.