Jay, I'll shepherd the two detector/contender/network module changes. On Mon, Jul 11, 2016 at 2:44 AM, Jay JN Guo <[email protected]> wrote:
> > Shuai, > > I think you are right. AFAIK, replicated_log interacts with zk in only > following two ways: > > 1) replicated_log creates znode and maintain 'membership' via > zookeeper::Group. It actually stores pid under zk_url/log_replicas. > 2) replicated_log detects other replicas using pid created in previous step > and store them in set<UPID> pids [1]. This is done via ZookeeperNetwork. > > Other than these, replicas inter-communicate with others through protobuf > processes. Since there's only one active master at a time, that master will > be the proposer (coordinator) and others being acceptor. So there is no > need for leader election in replicated_log. > > Please correct me if I'm wrong. > > Thanks, > /J > > [1] https://github.com/apache/mesos/blob/master/src/log/network.hpp#L316 > > Shuai Lin <[email protected]> wrote on 07/11/2016 00:13:12: > > > From: Shuai Lin <[email protected]> > > To: dev <[email protected]> > > Cc: Jie Yu <[email protected]>, Kapil Arya <[email protected]> > > Date: 07/11/2016 00:13 > > Subject: Re: [Replicated Log] Enable Mesos to use etcd for replicated_log > > > > > > > > i.e. The MasterContender is the piece that decides the "coordinator" of > the > > > replicated log. > > > > > > IINM master contender/detector is not related to replicated logs. The > only > > thing they have in common (when using zookeeper) is they both get the > > zookeeper servers list from the `--zk` flag. > > > > > > On Sat, Jul 9, 2016 at 1:54 AM, Joseph Wu <[email protected]> wrote: > > > > > Jay, > > > > > > (1) Looks like we missed this when we modularized the > > > MasterDetector/Contender [1]. We need to expand on src/master/main.cpp > a > > > bit. > > > Can you file a bug? (cc: Kapil) I can shepherd if Kapil doesn't have > the > > > cycles. > > > > > > (2) The bit of the replicated log which relies on ZK is a small portion > > > called the ZookeeperNetwork [2]. The job of this component is to watch > the > > > ZK group for membership changes. Log replication messages are > broadcasted > > > to all members in this "network abstraction". > > > This is also a piece that needs to be modularized. (Can you file > another > > > bug? :) > > > > > > (3) The replicated log is something stored locally on the master (i.e. > > > LevelDB). The network abstraction has some similarity with the > > > MasterDetector, but those pieces are otherwise unrelated. > > > i.e. The MasterContender is the piece that decides the "coordinator" of > the > > > replicated log. But the replicated log uses it's own implementation of > > > Paxos after the coordinator is chosen. > > > > > > [1] https://issues.apache.org/jira/browse/MESOS-4610 > > > [2] > https://github.com/apache/mesos/blob/master/src/log/network.hpp#L107 > > > > > > On Fri, Jul 8, 2016 at 9:25 AM, Avinash Sridharan > <[email protected]> > > > wrote: > > > > > > > +Jie > > > > > > > > I think replicated log uses ZK only for leader election. Hence, > without > > > ZK > > > > the quorum is hard-coded to 1. > > > > > > > > For (#2), trying to understand what you mean by replicated log being > > > > pluggable? You mean turning of replicated log on the Master for > storing > > > > Registrar information? > > > > > > > > On Fri, Jul 8, 2016 at 2:26 AM, Jay JN Guo <[email protected]> > > > wrote: > > > > > > > > > > > > > > > > > > > Hi, > > > > > > > > > > We are working on a Mesos module to substitute Zookeeper with Etcd. > > > > > Contender and detector are done through modulerized interfaces, > > > however, > > > > > replicated_log is still coupled with ZK. Here are my questions: > > > > > > > > > > #1 What's the difference between replicated_log with/without ZK? > > > Without > > > > > flag --zk, Log is constructed with hardcoded quorum of 1. Does it > > > assume > > > > > master to be running in non-HA mode? Otherwise, we observed that > znodes > > > > are > > > > > created in ZK to store log_replica information, does it help Paxos > > > > > coordination in some way? > > > > > #2 We hope to make replicated_log pluggable. Some code change need > to > > > > > happen in Mesos upstream (interface modulerization, extra flags, > etc). > > > So > > > > > we wonder if someone could shepherd them? Also, it would be great > if we > > > > > could get some help on better understanding replicated_log > internals. > > > > > #3 Is there a plan to use replicated_log to do master > contend/detect > > > > > instead of ZK? If yes, what's the status? > > > > > > > > > > Your help and suggestions are highly appreciated!! > > > > > > > > > > Thanks, > > > > > /Jay > > > > > > > > > > > > > > > > > > > > > -- > > > > Avinash Sridharan, Mesosphere > > > > +1 (323) 702 5245 > > > > > > > >
