Thanks for confirming Andrey. In this case, I think the appropriate approach would be for the new client to first attempt the new RPC, look for a NoSuchMethod kind of exception, and fall back to the old RPC. This transparent fallback would be required as long as online compatibility is required.
-n On Thursday, March 5, 2015, Andrey Stepachev <oct...@gmail.com> wrote: > Hi Nick, > > > I suppose it's possible the client in the master is never used outside of > localhost, I haven't checked that bit. > > Client is definitely used to access meta, which can be hosted anywhere, > so basically we can face with situation when master is upgraded and > hits old region server. > > On Thu, Mar 5, 2015 at 5:21 AM, Nick Dimiduk <ndimi...@gmail.com > <javascript:;>> wrote: > > > My point was that we cannot make this guarantee as there's a client > > embedded in the master (and perhaps other places). We can't enforce the > > order in which components are upgraded, which makes it possible for the > new > > client in the new master to reach out to an old RS during the rolling > > upgrade. > > > > I suppose it's possible the client in the master is never used outside of > > localhost, I haven't checked that bit. > > > > On Wednesday, March 4, 2015, lars hofhansl <la...@apache.org > <javascript:;>> wrote: > > > > > The idea actually was that a new client can never be 100% supported, > > since > > > a user could use it accessing new features that the server does not > > > understand.The reverse is always possible, since the old client can > > expose > > > anything new unduly we can always upgrade the server as old as it > doesn't > > > break the old client. > > > Supporting both ways is too limiting I think, at least for minor > version. > > > For example we might want to add a *new* RPC.As long as we only support > > old > > > client with new servers we can do that. In any other combination that > > would > > > not (as easily) possible. > > > That's why I phrased it only that way in my version proposal. > > > > > > For patch releases it's reasonable to support it both ways.The book is > > > currently unavailable from the HBase site, so I can't check the exact > > > wording we ended up with. > > > > > > -- Lars > > > From: Nick Dimiduk <ndimi...@gmail.com <javascript:;> > <javascript:;>> > > > To: hbase-dev <dev@hbase.apache.org <javascript:;> <javascript:;>> > > > Sent: Wednesday, March 4, 2015 4:49 PM > > > Subject: Re: Client-Server wire compatibility? > > > > > > I believe your posted example is intended to be supported. There's no > > > enforcement, for instance, that the master is upgraded before all RS's. > > > > > > > > > > > > On Wed, Mar 4, 2015 at 4:06 PM, Matteo Bertozzi < > theo.berto...@gmail.com <javascript:;> > > > <javascript:;>> > > > wrote: > > > > > > > the book (http://hbase.apache.org/book.html#hbase.versioning) > > > > talks about "only allow upgrading the server first" to use new APIs. > > > > > > > > what about a new client talking to an old server for "old" > operations? > > > > For example: If I have a 1.1 client, can I ask a 1.0 server to > create a > > > > table? > > > > > > > > > > > > > > > > > > > -- > Andrey. >
