Oliver Henriot writes:
Well, first, I'd assumed that the reason "Resource temporarily unavailable" meant something wasn't as smooth as it could be and,
The server had some data it wanted to send, and eagerly tried to send it - but it's sending faster than the network can accept it, or the client isn't reading the responses it requested, or the network is flaky, or...
I don't know exactly what leads to which errno, but the point remains is that this is normal and not an error. Though as you can see from the above list, some of the reasons can be errors on someone's part, so if you are having server problems this can indicate the trouble. Otherwise forget it.
secondly, I thought "errno" was a contraction of "error number" but maybe I'm wrong?
errno is the name of a system variable in the C language, with that meaning, yes. You've asked for detailed logging about what the server is doing, instead of just using the default and recommended loglevel (256), so that's what you are receiving.
But the doc should make a clearer distinction between "debugging" log levels and "informational" loglevels. I just had a "duh, users might not know C and errno is C" moment when I saw your guess about errno:-)