200994 - DNS: multiple connection attempts to non-existent host (using SRC=)

Status: RESOLVED WORKSFORME

(Core :: Networking, defect)

Description

[Daniel Wang]

spin off from bug 200935

If you have <script src> in your body, Mozilla will wait until the script
is fully loaded before proceeding. However, if you have multiple <script>
referencing files in non-existent host, Mozilla will try to load each one
of them, resulting in delayed layout. It should just skip all these files
after the first timeout.

Comment 1

[Daniel Wang]

Attachment: testcase

Comment 2

[Darin Fisher]

there is no state held to remember the fact that a DNS lookup failed.  we could
perhaps add something like this to the DNS service.  we'd of course want to
forget about failures rather quickly in case the problem is only intermittent. 
caching a failure for a second or two might be reasonable.

-> gordon

Comment 3

[gordon]

I think we'd want to tie it to a "page-load" somehow, which probably means
adding yet *another* cache at a higher level (load group?).

Darin, your suggestion of caching failures for just a second or two may be a
"good enough" solution.  It shouldn't be too difficult to implement, so we could
try it and see how well it works.

Comment 4

[Darin Fisher]

gordon: exactly.  the complexity of doing it per-page is probably prohibitive in
the short term (1.4).

Comment 5

[benc]

This problem should not significantly slow down load times, unless the user's
local DNS server is very slow (or possibly not doing caching, which would be bad).

Since this is a DNS problem, probably bug 208312 is one solution.

There are errors like connection establishment timeout or connection refused
that do take longer, and the wrong series of events might create a significant
delay. You could have caching of all connection-type errors in necko, but it
doesn't seem like a high priority.

Comment 6

[Patrick McManus [:mcmanus]]

we havea  short negative dns cache nwo