Re: [Engine-devel] SSH Soft Fencing

From: "Livnat Peer" <lpeer(a)redhat.com&gt; To: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt; Cc: engine-devel(a)ovirt.org Sent: Sunday, June 30, 2013 8:06:28 AM Subject: Re: [Engine-devel] SSH Soft Fencing On 06/30/2013 05:46 AM, Yair Zaslavsky wrote: > > > ----- Original Message ----- >> From: "Barak Azulay" <bazulay(a)redhat.com&gt; >> To: "Martin Perina" <mperina(a)redhat.com&gt; >> Cc: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt;, engine-devel(a)ovirt.org, "Eli >> Mesika" <emesika(a)redhat.com&gt; >> Sent: Thursday, June 27, 2013 8:31:35 PM >> Subject: Re: SSH Soft Fencing >> >> >> >> ----- Original Message ----- >>> From: "Eli Mesika" <emesika(a)redhat.com&gt; >>> To: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt; >>> Cc: "Martin Perina" <mperina(a)redhat.com&gt;, engine-devel(a)ovirt.org, "Barak >>> Azulay" <bazulay(a)redhat.com&gt; >>> Sent: Thursday, June 27, 2013 5:55:29 PM >>> Subject: Re: SSH Soft Fencing >>> >>> >>> >>> ----- Original Message ----- >>>> From: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt; >>>> To: "Eli Mesika" <emesika(a)redhat.com&gt; >>>> Cc: "Martin Perina" <mperina(a)redhat.com&gt;, engine-devel(a)ovirt.org, "Barak >>>> Azulay" <bazulay(a)redhat.com&gt; >>>> Sent: Thursday, June 27, 2013 5:43:17 PM >>>> Subject: Re: SSH Soft Fencing >>>> >>>> >>>> >>>> ----- Original Message ----- >>>>> From: "Eli Mesika" <emesika(a)redhat.com&gt; >>>>> To: "Martin Perina" <mperina(a)redhat.com&gt; >>>>> Cc: engine-devel(a)ovirt.org, "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt;, >>>>> "Barak >>>>> Azulay" <bazulay(a)redhat.com&gt; >>>>> Sent: Thursday, June 27, 2013 3:48:39 PM >>>>> Subject: Re: SSH Soft Fencing >>>>> >>>>> >>>>> >>>>> ----- Original Message ----- >>>>>> From: "Martin Perina" <mperina(a)redhat.com&gt; >>>>>> To: engine-devel(a)ovirt.org >>>>>> Cc: "Yair Zaslavsky" <yzaslavs(a)redhat.com&gt;, "Barak Azulay" >>>>>> <bazulay(a)redhat.com&gt;, "Eli Mesika" <emesika(a)redhat.com&gt; >>>>>> Sent: Thursday, June 27, 2013 1:51:06 PM >>>>>> Subject: SSH Soft Fencing >>>>>> >>>>>> Hi, >>>>>> >>>>>> SSH Soft Fencing is a new feature for 3.3 and it tries to restart >>>>>> VDSM >>>>>> using SSH connection on non responsive hosts prior to real fencing. >>>>>> More info can be found at >>>>>> >>>>>> http://www.ovirt.org/Automatic_Fencing#Automatic_Fencing_in_oVirt_3.3 >>>>>> >>>>>> In current SSH Soft Fencing implementation the restart VDSM using SSH >>>>>> command is part of standard fencing implementation in >>>>>> VdsNotRespondingTreatmentCommand. But this command is executed only >>>>>> if a host has a valid PM configuration. If host doesn't have a valid >>>>>> PM configuration, the execution of the command is disabled and host >>>>>> state is change to Non Responsive. >>>>>> >>>>>> So my question are: >>>>>> >>>>>> 1) Should SSH Soft Fencing be executed on hosts without valid PM >>>>>> configuration? >>>>> >>>>> I think that the answer should be yes. The vdsm restart will solve most >>>>> of >>>>> problems , so why not using it whether a PM agent is defined or not. >>>> I agree. >>>> I would like to say that I also don't like the fact that >>>> VdsNotRespondingTreatment extends RestartVdsCommand. >>>> One should ask if "non responding treatment is a restart vds operation" >>>> or >>>> maybe RestartVdsCommand is just a step in the non responding treatment >>>> (inheritance vs containment/delegation). >>>> I think that VdsNotRespodingTreatment should delegate the call to >>>> RestartVdsCommand as the 2nd step after issuing the Soft Fencing >>>> command. >>>> Thoughts anyone? >>> >>> That would be a nice and needed re-factoring >> >> I would say yes - but would add it only with appropriate configuration >> (enableAutoSoftVdsmRestartWhenNoPMAvailable .... I hate the name) > > +1 on configuration. > Configuration must reside at host-related entities (i.e - VdsStatic). > > Yair > Why would a user like to avoid fencing VDSM when host becomes non-responsive? I think that adding another configuration option is cumbersome with no real value.

Livnat >> >> >> >>> >>>> >>>>> >>>>>> >>>>>> 2) Should VDSM restart using SSH command be reimplemented >>>>>> as standalone command to be usable also in other parts of engine? >>>>>> If 1) is true, I think it will have to be done anyway. >>>> >>>> I agree here. >>>>> >>>>> +1 >> >> On one hand it makes sense, but I have several questions on the above: >> - Who do we think may want to use such a command ? >> - Should (or even can) we limit the use of such command to >> noneResponsiveTreatment ? >> >> Having general commands available to all code when there is only one >> specific >> case we are using it might be a bit riskey, >> Especially when we talk about restarting something. >> >> Thoughts ? >> >> >> >>>>> >>>>>> >>>>>> >>>>>> Martin Perina >>>>>> >>>>> >>>> >>> >> > _______________________________________________ > Engine-devel mailing list > Engine-devel(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/engine-devel > _______________________________________________ Engine-devel mailing list Engine-devel(a)ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel