Hi,
I'm having performance problems with mod_wsgi+mod_deflate. When the
gzip output encoding is in effect, responses takes a long time to
complete (625 ms) even though no data is being sent during the last
~600 ms.
Here is my test application:
#!/usr/bin/python
def application(environ, start_response):
status = "200 OK"
output = "Hello, world 2!"
response_headers = [("Content-Type", "text/plain"),
("Content-Length", str(len(output)))]
start_response(status, response_headers)
return [output]
This is being run under Apache 2.2 with mod_wsgi 2.5 in daemon mode.
Apache has mod_deflate enabled for content type text/plain, and here
are the response headers:
Date: Fri, 20 Aug 2010 01:51:31 GMT
Server: Apache/2.2.12 (Ubuntu)
Vary: Accept-Encoding
Content-Encoding: gzip
Keep-Alive: timeout=15, max=94
Connection: Keep-Alive
Transfer-Encoding: chunked
Content-Type: text/plain
This seems to cause Firefox to wait for a long time until deciding
it's the end of content (625 ms). The Firebug request timeline looks
like:
0 Started
0 0 DNS Lookup
0 0 Connecting
0 0 Blocking
0 0 Sending
0 31ms Waiting
+31ms 594ms Receiving
+631ms 'DOMContentLoaded' (event)
+644ms 'load' (event)
If I set the Content-Type so that mod_deflate doesn't match it and the
content is sent plainly (without mod_deflate), Content-Length is
passed through nicely and the requests complete in < 50 ms:
HTTP/1.1 200 OK
Date: Fri, 20 Aug 2010 02:11:22 GMT
Server: Apache/2.2.12 (Ubuntu)
Content-Length: 15
Keep-Alive: timeout=15, max=99
Connection: Keep-Alive
Content-Type: text/plain,frigoffdeflate
And response timeline:
0 Started
0 0 DNS Lookup
0 0 Connecting
0 0 Blocking
0 0 Sending
0 32ms Waiting
+32ms 0 Receiving
+91ms 'DOMContentLoaded' (event)
+109ms 'load' (event)
Ideally I would like to have mod_deflate working to reduce transfer
time, but also have it send Content-Length for the compressed content
so responses complete as soon as the data is finished. This appears to
be the case when Apache serves static files with mod_deflate:
HTTP/1.1 200 OK
Date: Fri, 20 Aug 2010 02:12:12 GMT
Server: Apache/2.2.12 (Ubuntu)
Last-Modified: Wed, 04 Aug 2010 06:49:27 GMT
Etag: "25b51d-167-48cf9d5b50bc0"
Accept-Ranges: bytes
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 201
Keep-Alive: timeout=15, max=97
Connection: Keep-Alive
Content-Type: text/css
Any idea how to the this working properly?
Thanks,
Catalin
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