Re: [libvirt] [PATCH v2] Make LXC container startup/shutdown/I/O more robust

On Thu, Feb 24, 2011 at 13:42:18 +0000, Daniel P. Berrange wrote: > The current LXC I/O controller looks for HUP to detect > when a guest has quit. This isn't reliable as during > initial bootup it is possible that 'init' will close > the console and let mingetty re-open it. The shutdown > of containers was also flakey because it only killed > the libvirt I/O controller and expected container > processes to gracefully follow. > > Change the I/O controller such that when it see HUP > or an I/O error, it uses kill($PID, 0) to see if the > process has really quit. > > Change the container shutdown sequence to use the > virCgroupKillPainfully function to ensure every > really goes away > > This change makes the use of the 'cpu', 'cpuacct' > and 'memory' cgroups controllers compulsory with > LXC The documentation in drvlxc.html says cpuacct, memory, and devices are the mandatory controllers and the code lxcVmStart() agrees with that so this commit message needs to be corrected.

> @@ -341,7 +352,8 @@ ignorable_epoll_accept_errno(int errnum) > static int lxcControllerMain(int monitor, > int client, > int appPty, > - int contPty) > + int contPty, > + pid_t container) > { > int rc = -1; > int epollFd; > @@ -447,7 +459,13 @@ static int lxcControllerMain(int monitor, > ++numActive; > } > } else if (epollEvent.events & EPOLLHUP) { > - VIR_DEBUG("EPOLLHUP from fd %d", epollEvent.data.fd); > + if (lxcPidGone(container)) > + goto cleanup; > + curFdOff = epollEvent.data.fd == appPty ? 0 : 1; > + if (fdArray[curFdOff].active) { > + fdArray[curFdOff].active = 0; > + --numActive; > + } > continue; Heh, thanks for the opportunity to learn about epoll. This might be a trivial question but... what if we get EPOLLIN event immediately followed by EPOLLHUP on the same fd? Do we end up leaving the data unread until another EPOLLIN arrives? Although it shouldn't be a big deal since we will just read the data from init after the console gets reopened by mingetty.

... > @@ -2844,7 +2811,7 @@ static virDriver lxcDriver = { > lxcDomainLookupByName, /* domainLookupByName */ > lxcDomainSuspend, /* domainSuspend */ > lxcDomainResume, /* domainResume */ > - lxcDomainShutdown, /* domainShutdown */ > + NULL, /* domainShutdown */ > NULL, /* domainReboot */ > lxcDomainDestroy, /* domainDestroy */ > lxcGetOSType, /* domainGetOSType */ So we lost virDomainShutdown for LXC. I guess that's because it didn't really work anyway, right? I wonder if there is a way to do graceful shutdown for a container without having a special deamon in it.