Re: [amfphp] Sleep & NextFrame Results

[Patrick M. <li...@5e...>]

Ok,

I did some tests myself and here is what I discovered:

The Flash player seems to accumulate the calls for a frame.
The correct way to see this is adding a call to
NetDebug::trace("In method now"); in the invoked remote
method. This will add a single trace header per request. So
if you call 20 remote methods, and you see only one trace in
the NetConnection debugger, there was only one call. If you
call 20 remote methods, and see 20 trace actions in the
NetConnection debugger, that means it was sent as separate
calls. Any number between 1 and 20 traces means the call was
split into several batches.

Now I tried with deferred (next frame) calls and while I saw
several traces in the NetConnection debugger, it still
showed the odd behaviour with sleep. So it seemed either that:

1. The web server or PHP is single threaded (unlikely)
2. The Flash player was waiting for a remote response before
sending the next request (just as unlikely)

But in fact it's none of the above. I verified this by doing 
packet sniffing using TCP Spy and multiple calls with 
sleeep(1) in some methods and not in others. As it turns out 
Flash opens a limited number of connections; on my system, 
using the standalone version or the ActiveX in IE or the 
plugin in Firefox, it creates 2 connections.

That means that Flash has a limited number of channels to 
send data through. So if one is blocked, (for example by a 
sleep) and the other one is clear, data will continue to be 
passed in the clear channel. As soon as both channels are 
blocked it will seem as though Flash or Apache or PHP are 
single-threaded, when in fact it's a question of number of 
open connections.

I wanted to test this theory by doing the following:

Create a service with two methods, one called method1 and 
another called method2. Method1 contains sleep(10) and 
method2 is empty. They return either 1 or 2 so we can easily 
see which returns before or after.

So I created a Flash file that would call method1 and then 
call method2 in a setInterval(200). In theory, every return 
from method2 should come before method1. On the other hand, 
if I would call method1 two times (seperated by an interval 
to disable batch calls) before the method2 setInterval, it 
would, in theory, block borh channels.

Now here is the caveat: the player in the IDE and the 
standalone/plugin/ActiveX players behave differently. In the 
IDE, it waits for both calls to come back before starting to 
send new ones, while in the standalone, as soon as one 
channel is free it starts a new request.

If you test the above in the standalone, it will work as 
expected, but not in the IDE.

While I was working with this, I noticed that when a 
connection is interrupted, the number of headers int is 
replaced by garbage, and it can severally crash AMFPHP and 
Apache if error_log is on, so I solved that issue (ie: it 
used to make the error log grow by 20 megs per AMFPHP call). 
So please download the new bleeding edge version for that 
issue now solved.

http://www.5etdemi.com/uploads/amfphpbeta.zip

Patrick

JesterXL wrote:
> Ok, I tried what your blog entry said, Patrick, but the next frame ignores 
> sleep... like, check this out:
> 
> - call ping, it returns true
> - call 100 pings, and the 101st is another function, all done in a while 
> loop returns the calls in the exact order I sent them.
> 
> ...however, if I call the function that makes PHP sleep for 10 seconds, and 
> then call ping over 1 frame later, it still waits for the sleep to end.  So, 
> waiting a frame does not solve the sleep issue.
> 
> :: tests on PHP 5 server ::
> 
> Yep, same there too.  PHP4 is running Apache & Linux something, PHP5 is 
> being run on IIS on Windows 2k I think.
> 
> My Java co-worker at work said that it's up to the webserver or servlet or 
> whatever to determine how the webserver performs... but this appears to me 
> that PHP is single-threaded and just eats things in the order it receives 
> them.  This seems kind of lame (again); is this a PHP thing or what?
> 
> --JesterXL 
> 
> 
> 
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