Do you have long GC delays? On Tue, Sep 1, 2009 at 4:51 PM, Satish Bhatti <cthd2...@gmail.com> wrote:
> Session timeout is 30 seconds. > > On Tue, Sep 1, 2009 at 4:26 PM, Patrick Hunt <ph...@apache.org> wrote: > > > What is your client timeout? It may be too low. > > > > also see this section on handling recoverable errors: > > http://wiki.apache.org/hadoop/ZooKeeper/ErrorHandling > > > > connection loss in particular needs special care since: > > "When a ZooKeeper client loses a connection to the ZooKeeper server there > > may be some requests in flight; we don't know where they were in their > > flight at the time of the connection loss. " > > > > Patrick > > > > > > Satish Bhatti wrote: > > > >> I have recently started running on EC2 and am seeing quite a few > >> ConnectionLoss exceptions. Should I just catch these and retry? Since > I > >> assume that eventually, if the shit truly hits the fan, I will get a > >> SessionExpired? > >> Satish > >> > >> On Mon, Jul 6, 2009 at 11:35 AM, Ted Dunning <ted.dunn...@gmail.com> > >> wrote: > >> > >> We have used EC2 quite a bit for ZK. > >>> > >>> The basic lessons that I have learned include: > >>> > >>> a) EC2's biggest advantage after scaling and elasticity was conformity > of > >>> configuration. Since you are bringing machines up and down all the > time, > >>> they begin to act more like programs and you wind up with boot scripts > >>> that > >>> give you a very predictable environment. Nice. > >>> > >>> b) EC2 interconnect has a lot more going on than in a dedicated VLAN. > >>> That > >>> can make the ZK servers appear a bit less connected. You have to plan > >>> for > >>> ConnectionLoss events. > >>> > >>> c) for highest reliability, I switched to large instances. On > >>> reflection, > >>> I > >>> think that was helpful, but less important than I thought at the time. > >>> > >>> d) increasing and decreasing cluster size is nearly painless and is > >>> easily > >>> scriptable. To decrease, do a rolling update on the survivors to > update > >>> their configuration. Then take down the instance you want to lose. To > >>> increase, do a rolling update starting with the new instances to update > >>> the > >>> configuration to include all of the machines. The rolling update > should > >>> bounce each ZK with several seconds between each bounce. Rescaling the > >>> cluster takes less than a minute which makes it comparable to EC2 > >>> instance > >>> boot time (about 30 seconds for the Alestic ubuntu instance that we > used > >>> plus about 20 seconds for additional configuration). > >>> > >>> On Mon, Jul 6, 2009 at 4:45 AM, David Graf <david.g...@28msec.com> > >>> wrote: > >>> > >>> Hello > >>>> > >>>> I wanna set up a zookeeper ensemble on amazon's ec2 service. In my > >>>> > >>> system, > >>> > >>>> zookeeper is used to run a locking service and to generate unique > id's. > >>>> Currently, for testing purposes, I am only running one instance. Now, > I > >>>> > >>> need > >>> > >>>> to set up an ensemble to protect my system against crashes. > >>>> The ec2 services has some differences to a normal server farm. E.g. > the > >>>> data saved on the file system of an ec2 instance is lost if the > instance > >>>> crashes. In the documentation of zookeeper, I have read that zookeeper > >>>> > >>> saves > >>> > >>>> snapshots of the in-memory data in the file system. Is that needed for > >>>> recovery? Logically, it would be much easier for me if this is not the > >>>> > >>> case. > >>> > >>>> Additionally, ec2 brings the advantage that serves can be switch on > and > >>>> > >>> off > >>> > >>>> dynamically dependent on the load, traffic, etc. Can this advantage be > >>>> utilized for a zookeeper ensemble? Is it possible to add a zookeeper > >>>> > >>> server > >>> > >>>> dynamically to an ensemble? E.g. dependent on the in-memory load? > >>>> > >>>> David > >>>> > >>>> > >> > -- Ted Dunning, CTO DeepDyve
