Bugs item #1727418, was opened at 2007-05-29 08:57
Message generated for change (Comment added) made by gagenellina
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Category: Python Library
Group: Python 2.5
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Arno Stienen (arnostienen)
Assigned to: Nobody/Anonymous (nobody)
Summary: xmlrpclib waits indefinately
Initial Comment:
I'm not sure if it is a Python bug, but I'm having problems using xmlrpclib to
connect to a remote server.
When using this code to connect
to a remote XML-RPC server (C++, xmlrpc++0.7 library):
import xmlrpclib
server = xmlrpclib.Server("http://10.10.101.62:29500";)
print server.Connection_Request("roberto")
the Python command line 'hangs' until I kill the server. Then, the
correct output is suddenly displayed:
{'state': 0, 'id_session': '2Z3EUSLJFA13', 'port': 29501,
'str': 'Connection accepted. Session attached.'}
Yet a slightly simpler call works flawlessly:
import xmlrpclib
server = xmlrpclib.Server("http://10.10.101.62:29500";)
print server.Info_RT('Master')
{'state': 0, 'str': 'Info_RT'}
Looking at the TCP packages (using Wireshark), the first
Connection_Request flow as follows (c=python client,s= xml-rpcserver):
1 c>s SYN
2 s>c SYN,ACK
3 c>s ACK
4 c>s PSH,ACK (setting content-type: text/xml)
5 s>c ACK
6 c>s PSH,ACK (xml-rpc request)
7 s>c ACK
8 s>c PSH,ACK (xml-rpc results, correct)
9 c>s ACK
At this point, Python 'hangs' until I kill (-9) the server (28 seconds
later), and then these last packages are send:
10 s>c FIN,ACK
11 c>s FIN,ACk
12 s>c ACK
After which Python continues and prints the xml-rpc results on the
screen. Strangely, before Python hangs, it has already received the
package with the results, but doesn't do anything with it.
For comparison, this is the package flow for the Info_RT method, which
returns within a second with the correct result on the Python command line:
1 c>s SYN
2 s>c SYN,ACK
3 c>s ACK
4 c>s PSH,ACK (setting content-type: text/xml)
5 s>c ACK
6 c>s PSH,ACK (xml-rpc request)
7 s>c ACK
8 s>c PSH,ACK (xml-rpc results, correct)
9 s>c FIN,ACK
10 c>s ACK
11 c>s FIN,ACk
12 s>c ACK
Notice the reverse order of packages 9 and 10. Could this be it? Is
Python waiting until the server sends a FIN package? But if so, why?
Looking at the Python trace, this might be it. A diff between the trace
of the killed Connection_Request and the Info_RT resulted only in
expected differences (due to different length of parameters). But when
diffing the traces of the killed and non-killed Connection_Request,
something else is visible. The killed Connection_Request ends with:
[...]
string:318: return sep.join(words)
xmlrpclib:866: self._type = "params"
xmlrpclib:769: try:
xmlrpclib:770: f = self.dispatch[tag]
xmlrpclib:771: except KeyError:
xmlrpclib:772: pass # unknown tag ?
xmlrpclib:1273: if sock:
xmlrpclib:1274: response = sock.recv(1024)
xmlrpclib:1277: if not response:
xmlrpclib:1278: break
xmlrpclib:1283: file.close()
socket:218: try:
socket:219: if self._sock:
socket:220: self.flush()
socket:232: if self._wbuf:
socket:222: self._sock = None
xmlrpclib:1284: p.close()
xmlrpclib:530: self._parser.Parse("", 1) # end of data
xmlrpclib:531: del self._target, self._parser # get rid of
circular references
xmlrpclib:1286: return u.close()
xmlrpclib:741: if self._type is None or self._marks:
xmlrpclib:743: if self._type == "fault":
xmlrpclib:745: return tuple(self._stack)
socket:225: try:
socket:226: self.close()
socket:218: try:
socket:219: if self._sock:
socket:222: self._sock = None
xmlrpclib:1386: if len(response) == 1:
xmlrpclib:1387: response = response[0]
xmlrpclib:1389: return response
__main__:26: print result
{'state': 0, 'id_session': 'QDLY3GP9FBM5', 'port': 29501, 'str':
'Connection accepted. Session attached.'}
But the non-killed Connection_Request looks like:
[...]
return sep.join(words)
xmlrpclib:866: self._type = "params"
xmlrpclib:769: try:
xmlrpclib:770: f = self.dispatch[tag]
xmlrpclib:771: except KeyError:
xmlrpclib:772: pass # unknown tag ?
xmlrpclib:1273: if sock:
xmlrpclib:1274: response = sock.recv(1024)
socket:225: try:
socket:226: self.close()
socket:218: try:
socket:219: if self._sock:
socket:220: self.flush()
socket:232: if self._wbuf:
socket:222: self._sock = None
(In the diff there is a gap between the xmlrpclib:1274 and socket:225
lines, as compared to the killed Connection_Request; perhaps Ctrl+C
still executes the "socket try close" lines?)
If you want to do your own 'diff' on the Python traces, or look at the
TCP packages in more details with Wireshark, here are the files for the
correctly working Info_RT and faulty Connection_Request methods:
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-infort-python.ws
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-infort-python-ws.txt
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-infort-trace.txt
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-conreq-python.ws
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-conreq-python-ws.txt
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-conreq-trace.txt
http://ctw-bw008.ctw.utwente.nl/~arno/rtaixml/roberto-conreq-trace-hardbreak.txt
(The first three ConReq files all include killing the server after ~28
seconds, thus resulting in the correct output. In the fourth files,
tracing is stopped before the server is killed. It is therefor the trace
up to the 'hanging point'. Note that the first two Wireshark packages
are not TCP, but ARP, thus the file has a total of 14 packages, not 12
as above.)
Really, any help here is appreciated!
----------------------------------------------------------------------
Comment By: Gabriel Genellina (gagenellina)
Date: 2007-06-01 22:19
Message:
Logged In: YES
user_id=479790
Originator: NO
Copying a reply from Tijs <[EMAIL PROTECTED]> posted at c.l.p.
<http://permalink.gmane.org/gmane.comp.python.general/524601>:
---
After having a quick look at your files, I conclude that the problem is in
a
combination of two problems:
1. Your server is crap. It answers an HTTP/1.0 request by an HTTP/1.1
response without specifying any Connection header and without closing the
connection. Normally, a simple client that is not HTTP/1.1-aware expects
the connection to close. HTTP/1.1 leaves the connection open by default.
2. The Python implementation of xmlrpc is not very robust. It just waits
for
the connection to close. A well-written client (like your Java client)
would detect the presence of a Content-Length header and use that.
The other request is OK because the server closes the connection after
having sent the response. Why the difference? Don't know, but it is
something server-side.
Try to force the server to send HTTP/1.0 responses, or turn off
keep-alive,
or something like that. Otherwise, adapt xmlrpclib.py to robustly handle
1.1 responses.
---
----------------------------------------------------------------------
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