[systemd-devel] lighttp unit - graceful reload of configfiles by sending signal to $MAINPID

[Alexander E. Patrakov]

18.01.2011 16:51, Lennart Poettering пишет:
> On Tue, 18.01.11 16:41, Alexander E. Patrakov (patrakov at gmail.com) wrote:
>
>>> How is this implemented in detail? Sending SIGINT is async, so at the
>>> time you start the new instance you cannot be sure that the old instance
>>> has stopped listening?
>> Indeed, there is a race here. That's why "/bin/sleep 1" in my
>> initial service file.
> Hmm, what's the lighthttp people's take on this? They came up with the
> scheme, so how do they think this problem should be handled?

They usleep(5 * 1000) and, if the new copy of lighttpd still fails to 
start due to a race, sleep again and attempt to start it again, ad 
infinitum.

> (One possible solution could be if the old and the new instance would
> communicate and pass the listening sockets via some AF_UNIX
> socket/SCM_RIGHTS or so. But that is not trivial.)

I came with a different (albeit systemd-specific) solution. The solution 
(implemented as an attached patch) is to fork() after we closed all the 
listening sockets and exit immediately in the parent. This way, the 
chlid continues to serve already-requested files, and systemd has a 
race-free indication that it can restart lighttpd via Restart=always. 
Please review the patch and the service file. One known problem: the 
patch is completely untested with server.max-worker > 0.

-- 
Alexander E. Patrakov
-------------- next part --------------
A non-text attachment was scrubbed...
Name: lighttpd-1.4.28-fork.patch
Type: text/x-patch
Size: 699 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/systemd-devel/attachments/20110118/29c84925/attachment.bin>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: lighttpd.service
URL: <http://lists.freedesktop.org/archives/systemd-devel/attachments/20110118/29c84925/attachment.asc>