Hi Everyone, Any thoughts? Do we need consider changing abrupt shutdown to
Implementations in some other hadoop eco system projects for your reference. Hadoop - kill [SIGTERM] HBase - kill [SIGTERM] and then "kill -9" [SIGKILL] if process hung ZooKeeper - "kill -9" [SIGKILL] -----Original Message----- From: Laxman [mailto:lakshman...@huawei.com] Sent: Wednesday, July 13, 2011 12:36 PM To: 'dev@zookeeper.apache.org' Subject: RE: Does abrupt kill corrupts the datadir? Hi Mahadev, Shutdown hook is just a quick thought. Another approach can be just give a kill [SIGTERM] call which can be interpreted by process. First look at the "kill -9" triggered the following scenario. >In worst case, if latest snaps in all zookeeper nodes gets corrupted there >is a chance of dataloss. How does zookeeper can deal with this scenario gracefully? Also, I feel we should give a chance to application to shutdown gracefully before abrupt shutdown. http://en.wikipedia.org/wiki/SIGKILL Because SIGKILL gives the process no opportunity to do cleanup operations on terminating, in most system shutdown procedures an attempt is first made to terminate processes using SIGTERM, before resorting to SIGKILL. http://rackerhacker.com/2010/03/18/sigterm-vs-sigkill/ The application can determine what it wants to do once a SIGTERM is received. While most applications will clean up their resources and stop, some may not. An application may be configured to do something completely different when a SIGTERM is received. Also, if the application is in a bad state, such as waiting for disk I/O, it may not be able to act on the signal that was sent. Most system administrators will usually resort to the more abrupt signal when an application doesn't respond to a SIGTERM. -----Original Message----- From: Mahadev Konar [mailto:maha...@hortonworks.com] Sent: Wednesday, July 13, 2011 12:02 PM To: dev@zookeeper.apache.org Subject: Re: Does abrupt kill corrupts the datadir? Hi Laxman, The servers takes care of all the issues with data integrity, so a kill -9 is OK. Shutdown hooks are tricky. Also, the best way to make sure everything works reliably is use kill -9 :). Thanks mahadev On 7/12/11 11:16 PM, "Laxman" <lakshman...@huawei.com> wrote: >When we stop zookeeper through zkServer.sh stop, we are aborting the >zookeeper process using "kill -9". > > > >129 stop) > >130 echo -n "Stopping zookeeper ... " > >131 if [ ! -f "$ZOOPIDFILE" ] > >132 then > >133 echo "error: could not find file $ZOOPIDFILE" > >134 exit 1 > >135 else > >136 $KILL -9 $(cat "$ZOOPIDFILE") > >137 rm "$ZOOPIDFILE" > >138 echo STOPPED > >139 exit 0 > >140 fi > >141 ;; > > > > > >This may corrupt the snapshot and transaction logs. Also, its not >recommended to use "kill -9". > >In worst case, if latest snaps in all zookeeper nodes gets corrupted there >is a chance of dataloss. > > > >How about introducing a shutdown hook which will ensure zookeeper is >shutdown gracefully when we call stop? > > > >Note: This is just an observation and its not found in a test. > > > >-- > >Thanks, > >Laxman >
