Socket based activation for systemd is a really cool feature for my dev
system.
Prior to using socket based activation, on my dev system I would have 2
choices:
1) Automatically start mysql, apache, php fastcgi, memcached, mongodb
and a dozen other services just in case I happen to be working with them
on this particular bootup.
2) Manually start them when needed....usually /after/ trying to test
something and discovering the service isn't running.
With socket based activation, I can start up dozens of servers on
different sockets and they won't bog my system down - they only truely
activate if they are actually used.
However, there is still a missing item to this feature[or it's not
missing and I am simply unaware of it] - there is no way to do the
reverse. IE if apache is running on my server there is no way to
configure things so if there are no active socket connections for 30
minutes, have it automatically shutdown and pass the socket control back.
Not only would this be great for my dev system, it would also be almost
everything needed for servers. A lot of server admins don't like the
idea of socket activation because it means that when they boot a server,
they won't know if there is some blocker for a server to run[corrupted
database files for example] until it is actually used. With the
ability to hibernate/sleep/whatever - a server can be configured to:
1) On bootup, use socket activation for all those expensive servers like
mysql, apache, etc. This means that unless there is active traffic to
the system, the server can skip starting all those daemons and boot faster.
2) Using systemd scheduled tasks, very simple probes to the various
sockets can be activated 5 minutes after bootup is complete. That way
if there is a corruption issue, system admins will be notified shortly
after bootup when apache/mysql/mongo is activated by the socket probe
and fails to start.
3) Using the hibernation feature, 35 minutes[or whatever the schedule
is] after bootup, those services will be suspended, freeing resources
that aren't being used.
So I'm curious if this feature is somewhere in socket activation I'm not
aware of[it might simply be needing to write the proper systemd
configuration files] or if it is something that would need to be added?
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