Hello,
I have a problem that I actually don't think is specific to webware, but which
occurrs with it (and Spyce). In any case, I suspect I am not the only one to
have run into it.
I was about to write a short version followed by a long version, but the short
version ended up being long, so nevermind:
I have a servlet that pushes large amounts of data to the client (file
download). This is done inside of a loop. The problem is that sometimes (or
always, depending on browser I think - not fully investigated, see below for
details) when the client closes the tcp connection prematurely, the python
process/thread runniung the servlet starts looping with 100% cpu usage.
I did a strace on the process and it seemed to be doing this repeatedly:
send(9,
"3\3457_~\250N\210hw\377.-)\1M\233C$7{\235B\5\3074[\34&"...,
8192, 0) = -1 EPIPE (Broken pipe)
send(9,
"3\3457_~\250N\210hw\377.-)\1M\233C$7{\235B\5\3074[\34&"...,
8192, 0) = -1 EPIPE (Broken pipe)
And the loop in my code gets run several time per second (though not more than
perhaps 25/second, so each write() seems to take some time).
Now the question is:
(1) Why isn't an exception raised?
(2) write() returns None, so a theory someone had on #python @ freenode that I
should be checking the return code, and not assuming full write even though
it's blocking I/O, was not applicable.
(3) How am I supposed to handle this?
Note that this only happens under some circumstances. When I do it with links
locally on the box (aborting a transfer mid-way) it always happens. With
Opera over a 1 mbit link, it seems to happen sometimes, but not always (which
would explain why I didn't catch it in testing).
With MSIE it seems to happen at least sometimes, because this whole thing
started when the system was deployed and I had 50 people downloading at the
same time, most of them using MSIE.
It may also be dependent on some state on the server. During initial
observations it seemed that everything worked fine for quite a while (with 50
people downloading and several requests/second for other pages being handled
at the same time), and then after some random point in time the load quickly
spiked from around 1 to 40+ (over 100 after a while). This however was with
spyce; the little testing I have done so far after porting the thing to
WebWare indicates it's more immediate/common with WebWare (not meaning
WebWare is doing something wrong; just a co-relation).
I am running the app through apache->wkcgi->webware.
The try/finally block with the while loop in my code looks like this (ignore
the downloadManager stuff, it's just book keeping using poorly named
methods...):
try:
file = open(filePath, 'r')
stat = os.stat(filePath)
response.setHeader('Content-Type', 'application/octet-stream')
response.setHeader('Content-Length', str(stat.st_size))
response.setHeader('Content-Disposition', 'attachment; filename=' +
filename)
while 1:
downloadManager.registerDownloader(verifier)
data = file.read(50000)
if len(data) == 0:
break
bytesWritten = response.write(data)
response.flush()
downloadManager.registerBytesDownloaded(len(data))
finally:
downloadManager.unregisterDownloader(verifier)
if file:
file.close()
--
/ Peter Schuller, InfiDyne Technologies HB
PGP userID: 0xE9758B7D or 'Peter Schuller <[EMAIL PROTECTED]>'
Key retrival: Send an E-Mail to [EMAIL PROTECTED]
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