net: detect changes to /etc/resolv.conf

[josharian]

net/dnsclient_unix.go has a TODO(rsc) near the top:

//  Check periodically whether /etc/resolv.conf has changed.

This would be very useful for us. (Not for Go 1.2, I know.) I'd happily put in the
effort to implement this, but I'd like to discuss first, to ensure that I take a good
approach and to check that there's nothing else planned that makes this moot.

The obvious question is around the "check periodically" part. Options include,
e.g.:

* Use fsnotify (extracted from or after #4068)
* Stat every n seconds
* Stat every n requests
* Stat after n DNS failures
* Stat on first request after n seconds have elapsed since last stat

Input on this?

Anything else I should be asking here?

[rsc]

Comment 1:

Please do:
* Stat on first request after n seconds have elapsed since last stat.

[robpike]

Comment 2:

Labels changed: added priority-later, removed priority-triage.

Status changed to Accepted.

[josharian]

Comment 3:

Sorry, I should have mentioned that I've started on this. I have an initial
implementation that I'm unhappy with, and I want to do some other minor cleanup first in
other CLs. I'll get that rolling shortly after 1.2 is released.

[rsc]

Comment 4:

Labels changed: added go1.3maybe.

[rsc]

Comment 5:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 6:

Labels changed: added repo-main.

[josharian]

Comment 7:

Since os/fsnotify is in the works, I'd like to wait for it to land and use it here, even
if it means that this doesn't make it into Go 1.3. (I'll do my best to get it in,
though, if os/fsnotify arrives in time.)

Owner changed to @josharian.

[gopherbot]

Comment 8 by guillaume@charmes.net:

CL for change as suggested bu rsc: https://golang.org/cl/83690045

[gopherbot]

Comment 9:

CL https://golang.org/cl/83690045 references this issue.

[gopherbot]

Comment 10:

CL https://golang.org/cl/83690045 references this issue.

[ianlancetaylor]

Comment 11:

This issue was closed by revision bf1d400.

Status changed to Fixed.