Anyway, if no objections on merging this into master, let's do it? So that we can start working on the follow-on features, such as table based replication storage, and synchronous replication, etc.
Thanks. 2018-01-09 7:19 GMT+08:00 Stack <st...@duboce.net>: > On Mon, Jan 8, 2018 at 2:50 PM, 张铎(Duo Zhang) <palomino...@gmail.com> > wrote: > > > This 'new' feature only changes DDL part, not the core part of > replication, > > i.e, how to read wal entries and how to replicate it to the remote > cluster, > > etc. And also there is no pb message/storage layout change, you can think > > of this as a big refactoring. Theoretically we even do not need to add > new > > UTs for this feature, i.e, no extra stability works. The only visible > > change to users is that it may require more time on modifying peers in > > shell. So in general I think it is less hurt to include it in the coming > > release? > > > > And why I think it SHOULD be included in our 2.0 release is that, the > > synchronous guarantee is really a good thing for our replication related > > UTs. The correctness of the current Test***Replication usually depends > on a > > flakey condition - we will not do a log rolling between the modification > on > > zk and the actual loading of the modification on RS. And we have also > done > > a hard work to cleanup the lockings in ReplicationSourceManager and add a > > fat comment to say why it should be synchronized in this way. In general, > > the new code is much easier to read, test and debug, and also reduce the > > possibility of flakeyness, which could help us a lot when we start to > > stabilize our build. > > > > Thanks. > > > > > You see it as a big bug fix Duo? > Kind of. Just like the AM v1, we can do lots of fix to make it more stable, but we know that we can not fix all the problems since we store state in several places and it is a 'mission impossible' to make all the states stay in sync under every situation... So we introduce AM v2. For the replication peer tracking, it is the same problem. It is hard to do fencing with zk watcher since it is asynchronous, so the UTs are always kind of flakey in theoretical. And we depend on replication heavily at Xiaomi, it is always a pain for us. > > I'm late to review. Will have a look after beta-1 goes out. This stuff > looks great from outside, especially distributed procedure framework which > we need all over the place. > > In general I have no problem w/ this in master and an hbase 2.1 (2.1 could > be soon after 2.0). Its late for big stuff in 2.0.... but let me take a > looksee sir. > Thanks sir. All the concerns here about whether we should merge this into 2.0 are reasonable, I know. Although I really want this in 2.0 because I believe it will help a lot for stabilizing, I'm OK with merge it to 2.1 only if you guys all think so. > > St.Ack > > > > > > > 2018-01-09 4:53 GMT+08:00 Apekshit Sharma <a...@cloudera.com>: > > > > > Same questions as Josh's. > > > 1) We have RCs for beta1 now, which means only commits that can go in > are > > > bug fixes only. This change - although important, needed from long time > > and > > > well done (testing, summary, etc) - seems rather very large to get into > > 2.0 > > > now. Needs good justification why it has to be 2.1 instead of 2.0. > > > > > > -- Appy > > > > > > > > > On Mon, Jan 8, 2018 at 8:34 AM, Josh Elser <els...@apache.org> wrote: > > > > > > > -0 From a general project planning point-of-view (not based on the > > > > technical merit of the code) I am uncomfortable about pulling in a > > brand > > > > new feature after we've already made one beta RC. > > > > > > > > Duo -- can you expand on why this feature is so important that we > > should > > > > break our release plan? Are there problems that would make including > > this > > > > in a 2.1/3.0 unnecessarily difficult? Any kind of color you can > provide > > > on > > > > "why does this need to go into 2.0?" would be helpful. > > > > > > > > > > > > On 1/6/18 1:54 AM, Duo Zhang wrote: > > > > > > > >> https://issues.apache.org/jira/browse/HBASE-19397 > > > >> > > > >> We aim to move the peer modification framework from zk watcher to > > > >> procedure > > > >> v2 in this issue and the work is done now. > > > >> > > > >> Copy the release note here: > > > >> > > > >> Introduce 5 procedures to do peer modifications: > > > >> > > > >>> AddPeerProcedure > > > >>> RemovePeerProcedure > > > >>> UpdatePeerConfigProcedure > > > >>> EnablePeerProcedure > > > >>> DisablePeerProcedure > > > >>> > > > >>> The procedures are all executed with the following stage: > > > >>> 1. Call pre CP hook, if an exception is thrown then give up > > > >>> 2. Check whether the operation is valid, if not then give up > > > >>> 3. Update peer storage. Notice that if we have entered this stage, > > then > > > >>> we > > > >>> can not rollback any more. > > > >>> 4. Schedule sub procedures to refresh the peer config on every RS. > > > >>> 5. Do post cleanup if any. > > > >>> 6. Call post CP hook. The exception thrown will be ignored since we > > > have > > > >>> already done the work. > > > >>> > > > >>> The procedure will hold an exclusive lock on the peer id, so now > > there > > > is > > > >>> no concurrent modifications on a single peer. > > > >>> > > > >>> And now it is guaranteed that once the procedure is done, the peer > > > >>> modification has already taken effect on all RSes. > > > >>> > > > >>> Abstracte a storage layer for replication peer/queue manangement, > and > > > >>> refactored the upper layer to remove zk related > naming/code/comment. > > > >>> > > > >>> Add pre/postExecuteProcedures CP hooks to RegionServerObserver, and > > add > > > >>> permission check for executeProcedures method which requires the > > caller > > > >>> to > > > >>> be system user or super user. > > > >>> > > > >>> On rolling upgrade: just do not do any replication peer > modifications > > > >>> during the rolling upgrading. There is no pb/layout changes on the > > > >>> peer/queue storage on zk. > > > >>> > > > >>> > > > >> And there are other benefits. > > > >> First, we have introduced a general procedure framework to send > tasks > > to > > > >> RS > > > >> and report the report back to Master. It can be used to implement > > other > > > >> operations such as ACL change. > > > >> Second, zk is used as a external storage now since we do not depend > on > > > zk > > > >> watcher any more, it will be much easier to implement a 'table > based' > > > >> replication peer/queue storage. > > > >> > > > >> Please vote: > > > >> [+1] Agree > > > >> [-1] Disagree > > > >> [0] Neutral > > > >> > > > >> Thanks. > > > >> > > > >> > > > > > > > > > -- > > > > > > -- Appy > > > > > >
