Denis Witt wrote: > Bob Proulx wrote: > > I assume from this that services are being monitored. If they are > > restarted and during the restart the monitoring detects that the > > service is offline then it triggers an alert. And whatever the > > First it will try to restart the service, if this fails the service > will be migrated to another node.
Ah... And so the plot thickens! Quick monitoring, sense a failure, trigger a restart on a different node. And of course I think that would all work fine but it would generate a lot of noise to wade through when there are upgrades that restart daemons. > > setting of "Maintenance-Mode" does basically tells the monitoring to > > ignore any problem for that time period. Is that about right? > > Yes. But it will disable the monitor for all services on all nodes, > which isn't always needed. Hmm... (Thinking... No ideas.) > > > At the moment I try out update-rc.d to avoid any service to be > > > restarted during upgrade, but I wonder if there might be a better > > > solution. > > > > It's policy-rc.d, of course, not update-rc. > > > That is an idea. Every use of a postinst script to restart a daemon > > should be gated by policy-rc.d. And you could always approve the > > restart but that script could at that time put the node into your > > maintenance-mode right then. Don't know what you would use to return > > it to regular service afterward. Perhaps after a timeout. > > That is a nice idea, thanks. Another idea. There is probably an apt post hook (untried) such as APT::Update::Post-Invoke-Success that could be used at the very end to return the node back to normal service. I know that apt-show-versions uses it to run an update script after apt has finished. > At the moment policy-rc.d just exit with 101. The problem I see with that is that you won't actually ever restart the daemon when it needs to be restarted. In some cases it simply means that you won't have the security upgrade. That would be typical of a production host running Debian Stable. So that may be acceptable for you. (But in other cases such as Unstable/Testing a restart is often required in order to complete the upgrade. In some other cases the running daemon really needs to be restarted in order to work with the new environment around it.) If you are doing this then you really want to run 'checkrestart' (from the debian-goodies package) on a regular basis and deal with what it reports. Because otherwise the daemons may be vulnerable to security vulnerabilities that were fixed by the upgrade and installed but never restarted to take effect. Good luck! Bob
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