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"""
SCGI-->WSGI application proxy, "SWAP".
(Originally written by Titus Brown.)
This lets an SCGI front-end like mod_scgi be used to execute WSGI
application objects. To use it, subclass the SWAP class like so::
class TestAppHandler(swap.SWAP):
def __init__(self, *args, **kwargs):
self.prefix = '/canal'
self.app_obj = TestAppClass
swap.SWAP.__init__(self, *args, **kwargs)
where 'TestAppClass' is the application object from WSGI and '/canal'
is the prefix for what is served by the SCGI Web-server-side process.
Then execute the SCGI handler "as usual" by doing something like this::
scgi_server.SCGIServer(TestAppHandler, port=4000).serve()
and point mod_scgi (or whatever your SCGI front end is) at port 4000.
Kudos to the WSGI folk for writing a nice PEP & the Quixote folk for
writing a nice extensible SCGI server for Python!
"""
import six
import sys
import time
from scgi import scgi_server
def debug(msg):
timestamp = time.strftime("%Y-%m-%d %H:%M:%S",
time.localtime(time.time()))
sys.stderr.write("[%s] %s\n" % (timestamp, msg))
class SWAP(scgi_server.SCGIHandler):
"""
SCGI->WSGI application proxy: let an SCGI server execute WSGI
application objects.
"""
app_obj = None
prefix = None
def __init__(self, *args, **kwargs):
assert self.app_obj, "must set app_obj"
assert self.prefix is not None, "must set prefix"
args = (self,) + args
scgi_server.SCGIHandler.__init__(*args, **kwargs)
def handle_connection(self, conn):
"""
Handle an individual connection.
"""
input = conn.makefile("r")
output = conn.makefile("w")
environ = self.read_env(input)
environ['wsgi.input'] = input
environ['wsgi.errors'] = sys.stderr
environ['wsgi.version'] = (1, 0)
environ['wsgi.multithread'] = False
environ['wsgi.multiprocess'] = True
environ['wsgi.run_once'] = False
# dunno how SCGI does HTTPS signalling; can't test it myself... @CTB
if environ.get('HTTPS','off') in ('on','1'):
environ['wsgi.url_scheme'] = 'https'
else:
environ['wsgi.url_scheme'] = 'http'
## SCGI does some weird environ manglement. We need to set
## SCRIPT_NAME from 'prefix' and then set PATH_INFO from
## REQUEST_URI.
prefix = self.prefix
path = environ['REQUEST_URI'][len(prefix):].split('?', 1)[0]
environ['SCRIPT_NAME'] = prefix
environ['PATH_INFO'] = path
headers_set = []
headers_sent = []
chunks = []
def write(data):
chunks.append(data)
def start_response(status, response_headers, exc_info=None):
if exc_info:
try:
if headers_sent:
# Re-raise original exception if headers sent
six.reraise(exc_info[0], exc_info[1], exc_info[2])
finally:
exc_info = None # avoid dangling circular ref
elif headers_set:
raise AssertionError("Headers already set!")
headers_set[:] = [status, response_headers]
return write
###
result = self.app_obj(environ, start_response)
try:
for data in result:
chunks.append(data)
# Before the first output, send the stored headers
if not headers_set:
# Error -- the app never called start_response
status = '500 Server Error'
response_headers = [('Content-type', 'text/html')]
chunks = ["XXX start_response never called"]
else:
status, response_headers = headers_sent[:] = headers_set
output.write('Status: %s\r\n' % status)
for header in response_headers:
output.write('%s: %s\r\n' % header)
output.write('\r\n')
for data in chunks:
output.write(data)
finally:
if hasattr(result,'close'):
result.close()
# SCGI backends use connection closing to signal 'fini'.
try:
input.close()
output.close()
conn.close()
except IOError as err:
debug("IOError while closing connection ignored: %s" % err)
def serve_application(application, prefix, port=None, host=None, max_children=None):
"""
Serve the specified WSGI application via SCGI proxy.
``application``
The WSGI application to serve.
``prefix``
The prefix for what is served by the SCGI Web-server-side process.
``port``
Optional port to bind the SCGI proxy to. Defaults to SCGIServer's
default port value.
``host``
Optional host to bind the SCGI proxy to. Defaults to SCGIServer's
default host value.
``host``
Optional maximum number of child processes the SCGIServer will
spawn. Defaults to SCGIServer's default max_children value.
"""
class SCGIAppHandler(SWAP):
def __init__ (self, *args, **kwargs):
self.prefix = prefix
self.app_obj = application
SWAP.__init__(self, *args, **kwargs)
kwargs = dict(handler_class=SCGIAppHandler)
for kwarg in ('host', 'port', 'max_children'):
if locals()[kwarg] is not None:
kwargs[kwarg] = locals()[kwarg]
scgi_server.SCGIServer(**kwargs).serve()
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