280808 - XMLHttpRequest leaks

Status: RESOLVED FIXED

(Core :: XML, defect)

Description

[Alex Fritze]

XMLHttpRequests leak about 5KB/request in current Mozilla/Firefox trunk builds.
This is a regression from earlier builds. Firefox 1.0 e.g. only leaks requests
if the network is down (a bug in itself).

A testcase is at http://www.croczilla.com/~alex/req/req.html.
The testcase generates aynchronous XMLHttpRequests and lets you adjust the
interval between requests & the page requested.
For current trunk builds on Windows the leak rate at the default interval (50ms)
is about 100KB/s.

FF1.0 will not leak if the network is up and running (even if the requested page
doesn't exist). If you unplug your network connection, however, it also starts
leaking.

Comment 1

[Alex Fritze]

A little further investigation shows that it is the nsXMLHttpRequest objects
themselves that are leaking. The leak doesn't seem to have anything to do with
onload, etc. listeners, and it only occurs if send() is called on the request
object.

Comment 2

[Alex Fritze]

Attachment: patch for nsHttpChannel.cpp

Turns out this is a regression caused by bug#261083.
If nsHttpChannel::SetNotificationCallbacks() is called with nsnull, we must
make sure to null-out mHttpEventSink & mProgressSink as well, or otherwise we
end up with a reference cycle nsHttpChannel <--> nsXMLHttpRequest.

Comment 3

[Darin Fisher]

Hmm... this works, but I think it might be better to release those objects in
nsHttpChannel::OnStopRequest once we know that we will no longer need them.  Can
you give that a try?

Comment 4

[Alex Fritze]

Attachment: 2nd try

How about this?

Comment 5

[Darin Fisher]

Comment on attachment 173220 [details] [diff] [review]
2nd try

r=darin

Comment 6

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 173220 [details] [diff] [review]
2nd try

sr=bzbarsky

Comment 7

[Alex Fritze]

Checked in.