On Fri, Mar 6, 2015 at 1:50 PM, <m.roth at 5-cent.us> wrote:>> >> I don't think I need to 'prove' that computer programs do repeatable >> things. I just want to know the version numbers that need to be >> installed - something relatively easy to check. > <snip> > Two other thoughts: first, that it worked perfectly fine the last leap > second, and second, that ntpd, according to the manpage, can and will > adjust for seconds of difference with no problem at all, since that's it's > job.Errr, no. It did _not_ work fine in the last leap second. If you run threaded applications (including, but not exclusively, java) or applications that called usleep the kernel would spin with 100% CPU use until you reset the date with some means other than ntp. How could you have missed that: http://www.wired.com/2012/07/leap-second-bug-wreaks-havoc-with-java-linux/. Every other sysadmin in the world got calls in the middle of the night to fix their servers. -- Les Mikesell lesmikesell at gmail.com
Les Mikesell wrote:> On Fri, Mar 6, 2015 at 1:50 PM, <m.roth at 5-cent.us> wrote: >>> >>> I don't think I need to 'prove' that computer programs do repeatable >>> things. I just want to know the version numbers that need to be >>> installed - something relatively easy to check. >> <snip> >> Two other thoughts: first, that it worked perfectly fine the last leap >> second, and second, that ntpd, according to the manpage, can and will >> adjust for seconds of difference with no problem at all, since that's >> it's job. > > Errr, no. It did _not_ work fine in the last leap second. If you run > threaded applications (including, but not exclusively, java) or > applications that called usleep the kernel would spin with 100% CPU > use until you reset the date with some means other than ntp. How > could you have missed that: > http://www.wired.com/2012/07/leap-second-bug-wreaks-havoc-with-java-linux/. > > Every other sysadmin in the world got calls in the middle of the night > to fix their servers.Ah, the system was fine, it was java that failed. And we've got a few tomcat apps... but IIRC, we fixed them the next day - we're "tier 3", and so "not critical", and could do that. mark
On Fri, Mar 6, 2015 at 2:26 PM, <m.roth at 5-cent.us> wrote:> >> >> Every other sysadmin in the world got calls in the middle of the night >> to fix their servers. > > Ah, the system was fine, it was java that failed. And we've got a few > tomcat apps... but IIRC, we fixed them the next day - we're "tier 3", and > so "not critical", and could do that.No, it was _not_ java that failed. The kernel was spinning instead of scheduling threads. Any threaded application would have triggered the kernel bug - or a usleep() call from a non-threaded application. By the time I got the call I was able to google the fix about resetting the date, but the guys who manage some SuSE systems started earlier and ended up rebooting some of them - and they don't run java applications. -- Les Mikesell lesmikesell at gmail.com