(11: Resource temporarily unavailable)

[Anto]

Hello everybody,

I have been doing some debugging and I saw messages like below from each 
request.
================================================================================================
.
2011/01/09 16:01:25 [debug] 26532#0: *29 http keepalive handler
2011/01/09 16:01:25 [debug] 26532#0: *29 malloc: 08B42288:1024
2011/01/09 16:01:25 [debug] 26532#0: *29 recv: fd:3 -1 of 1024
2011/01/09 16:01:25 [debug] 26532#0: *29 recv() not ready (11: Resource 
temporarily unavailable)
2011/01/09 16:01:55 [debug] 26532#0: *29 event timer del: 3: 1800158943
2011/01/09 16:01:55 [debug] 26532#0: *29 http keepalive handler
.
2011/01/09 16:28:46 [debug] 26532#0: *30 http keepalive handler
2011/01/09 16:28:46 [debug] 26532#0: *30 malloc: 08B42288:1024
2011/01/09 16:28:46 [debug] 26532#0: *30 recv: fd:3 -1 of 1024
2011/01/09 16:28:46 [debug] 26532#0: *30 recv() not ready (11: Resource 
temporarily unavailable)
2011/01/09 16:29:16 [debug] 26532#0: *30 event timer del: 3: 1801799968
2011/01/09 16:28:46 [debug] 26532#0: *30 http keepalive handler
.
================================================================================================

Sometime there are also some messages as below.
================================================================================================
.
2011/01/09 07:06:35 [debug] 5111#0: *125 http run request: 
"/index.php?arg=news&page=1"
2011/01/09 07:06:35 [debug] 5111#0: *125 http upstream check client, 
write event:1, "/index.php"
2011/01/09 07:06:35 [debug] 5111#0: *125 http upstream recv(): -1 (11: 
Resource temporarily unavailable)
2011/01/09 07:06:35 [debug] 5111#0: *125 post event 09BB2804
2011/01/09 07:06:35 [debug] 5111#0: *125 post event 09BB502C
2011/01/09 07:06:35 [debug] 5111#0: *125 delete posted event 09BB502C
.
================================================================================================

At the moment, the traffic on my test server only comes from my PC which 
only does the request once in a while, instead of doing stress test. So 
I believe the default settings (on my nginx and Debian) are much more 
than enough to provide the resource for that kind of requests.

I am wondering if the "Resource temporarily unavailable" message would 
be an indication that nginx is waiting for something and would do retry 
if it doesn't get anything. If my nginx would get thousands of requests, 
I believe that would be a waste time doing wait and retry, which would 
significantly make my nginx slow.

At the moment, I don't notice any issue. Should I worry about this? If 
so, what could the probable causes of that message be?

Kind regards,

Anto