Need a mechanism to block consecutive invocations of SL7 init reload command
systemctl reload is non-blocking, namely, when we issue systemctl reload command,
it returns immediately while the reload is still in progress.
This opens a possibility we can issue a second reload command while the first is still in progress.
We need a mechanism to prevent this sort of situation.
#2 Updated by HyunWoo Kim over 2 years ago
- Status changed from Assigned to Work in progress
Modified two files, creation/reconfig_frontend and frontend/glideinFrontend.py
and added a new file lib/lockSupport.py
in order to implement a block in a non-blocking reload call in Sl7 init.
All code changes are in v3/17570.
Current tests seem to work.
I will have to make lib/lockSupport.py more sophisticated.
How can I sophisticate lockSupport? For this, I first need to refine or polish what will be requirements for this component? 1. this thing is independent of the main pid in /var/lib/gwms-frontend/vofrontend/lock/frontend.lock 2. this thing is solely and merely needed during the duration of a reload process.. this means - I can just pick a unique name e.g. /tmp/frontend_reload_lock - I just need to make sure this file does not exist when the system(frontend or factory) starts - and this file is created only when the following set of codes are executed + signal.signal(signal.SIGHUP, hupsignal) + def hupsignal(signr, frame): raise HUPException, "Received signal %s" % signr + except HUPException: signal.signal( signal.SIGHUP, signal.SIG_IGN ) os.execv( "creation/reconfig_frontend", ['reconfig_frontend', '-sighupreload', '-xml', '/etc/gwms-frontend/frontend.xml'] ) - and this file is destroyed right before the execution return from reconfig_frontend to glideinFrontend.py if sighupreload: mylock = lockSupport.LockSupport() mylock.delete() os.execv( os.path.join(FRONTEND_DIR, "glideinFrontend.py"), ['glideinFrontend', '/var/lib/gwms-frontend/vofrontend'] )
I just realized that I might NOT need this lockSupport altogether, i.e. this only thing that I need would be except HUPException: signal.signal( signal.SIGHUP, signal.SIG_IGN ) The purpose of this lines is in order to invoke raise HUPException, "Received signal %s" % signr only the first time, i.e. when the mylock does not exist. def hupsignal(signr, frame): mylock = lockSupport.LockSupport() if mylock.check(): print "doing nothing" else: mylock.create() raise HUPException, "Received signal %s" % signr But my initial tests claim that this structure alone does not completely block the redundant invocations of kill -SIGHUP. I might need both mylock and signal.signal( signal.SIGHUP, signal.SIG_IGN )