[bind10-dev] What to do when msgq can't write to a reader?

[Shane Kerr]

All,

I have a ticket concerning a bug that makes BIND 10 stop working
properly on my server, ticket #420:

https://bind10.isc.org/ticket/420

Basically if something is not reading it's msgq properly then the msgq
blocks writing to it.

It's annoying me enough that I want to fix it. The question is, what is
the correct behavior if a reader is not reading?

I think there are two basic options:

     1. Close the connection.
     2. Buffer the data.

Neither are perfect or simple.

Option #1 means that a process that is busy for a period of time may get
disconnected.

Option #2 still needs some sort of way to handle a full buffer (after
all, Unix sockets have something like 4096 bytes of buffer, so there is
some already), uses more resources, and delays quick handling of a
broken connections.

So, I think I would like to implement option #1 (also naming & shaming
the process involved for debugging purposes!), unless there are any
objections.

(Note that a more extreme version of #1 might be to terminate the stuck
process, rather than simply closing the connection.)

BTW, when looking at this I found a cool page about Unix domain sockets:

http://www.wsinnovations.com/softeng/articles/uds.html

This even points out some Linux-specific features that I wish were
portable. :-P

--
Shane