Provides a daemon and a client library that provides a (TCP) socket forwarding mechanism. This should be used in scenarios where one wants to provide "safe" restarting of another daemon. This means there is an uninterrupted listening for client connections, and the new process seemlessly picks up handling of connections from the exiting process. However, the exiting process is free to service in-progress connections until done.
It is intended that this program controls the launching of your real daemon. It does eliminate the need for your daemon to do the typical fork-and-detach setup, as this wrapper daemon will have already done so, at least by default. See the Execution section below for more details.
An example benefit: I have a daemon which is serving up home directory data to users. Normally, upgrading this daemon would require everyone stop, logout, upgrade the daemon and restart. With SocketProtector, one can just upgrade the binary, and assuming no command line options need to be changed, trigger a SIGHUP to the SocketProtector pid.
A note for users of Upstart (i.e. Ubuntu): Upstart does not currently seem to provide a proper "reload" function to it's init scripts. Instead of being able to send a SIGHUP, it seems to merely do a service stop and start, which does mean an interruption, as the SocketProtector process would have to go away. It is recommended to use the normal old SysV init.d mechanism such you can provide a reload command that sends a SIGHUP.
No configure system has been defined yet. But using the provided ninja build file, one can edit the build variables and cause the code to compile. If you just run "ninja", it should place the daemon executable, a static library to link against and a sample client program in a Build folder in the local folder.
Normally, this program will be put as the launching program in an /etc/init style script. The method of calling it is as such, assuming it's installed to /usr/bin:
/usr/bin/SocketProtector --pid-file /var/run/name-of-pid -- /usr/bin/MyRealDaemon --arg1 --arg2
where everything following the empty double dash are provided as arguments to the process. If you just want to see it in action first:
Build/SocketProtector -f 4321 -- Build/SampleClient 4321
This will keep it in the foreground and launch SampleClient and start listening on port 4321. At this point, in another shell, you can do something like:
echo "Hello, World" | nc localhost 4321
sending a SIGHUP signal to the daemon process will trigger it to close the first socket forwarding connection to indicate that the first child should exit, and then relaunch the child process.