If classloader isolation is in place, then dependency versions can freely be upgraded as won't pollute apps space (things get trickier if there is an ON/OFF switch).
On Thu, Mar 5, 2015 at 9:21 PM, Allen Wittenauer <a...@altiscale.com> wrote: > > Is there going to be a general upgrade of dependencies? I'm thinking of > jetty & jackson in particular. > > On Mar 5, 2015, at 5:24 PM, Andrew Wang <andrew.w...@cloudera.com> wrote: > > > I've taken the liberty of adding a Hadoop 3 section to the Roadmap wiki > > page. In addition to the two things I've been pushing, I also looked > > through Allen's list (thanks Allen for making this) and picked out the > > shell script rewrite and the removal of HFTP as big changes. This would > be > > the place to propose features for inclusion in 3.x, I'd particularly > > appreciate help on the YARN/MR side. > > > > Based on what I'm hearing, let me modulate my proposal to the following: > > > > - We avoid cutting branch-3, and release off of trunk. The trunk-only > > changes don't look that scary, so I think this is fine. This does mean we > > need to be more rigorous before merging branches to trunk. I think > > Vinod/Giri's work on getting test-patch.sh runs on non-trunk branches > would > > be very helpful in this regard. > > - We do not include anything to break wire compatibility unless (as Jason > > says) it's an unbelievably awesome feature. > > - No harm in rolling alphas from trunk, as it doesn't lock us to anything > > compatibility wise. Downstreams like releases. > > > > I'll take Steve's advice about not locking GA to a given date, but I also > > share his belief that we can alpha/beta/GA faster than it took for Hadoop > > 2. Let's roll some intermediate releases, work on the roadmap items, and > > see how we're feeling in a few months. > > > > Best, > > Andrew > > > > On Thu, Mar 5, 2015 at 3:21 PM, Siddharth Seth <ss...@apache.org> wrote: > > > >> I think it'll be useful to have a discussion about what else people > would > >> like to see in Hadoop 3.x - especially if the change is potentially > >> incompatible. Also, what we expect the release schedule to be for major > >> releases and what triggers them - JVM version, major features, the need > for > >> incompatible changes ? Assuming major versions will not be released > every 6 > >> months/1 year (adoption time, fairly disruptive for downstream projects, > >> and users) - considering additional features/incompatible changes for > 3.x > >> would be useful. > >> > >> Some features that come to mind immediately would be > >> 1) enhancements to the RPC mechanics - specifically support for AsynRPC > / > >> two way communication. There's a lot of places where we re-use > heartbeats > >> to send more information than what would be done if the PRC layer > supported > >> these features. Some of this can be done in a compatible manner to the > >> existing RPC sub-system. Others like 2 way communication probably > cannot. > >> After this, having HDFS/YARN actually make use of these changes. The > other > >> consideration is adoption of an alternate system ike gRpc which would be > >> incompatible. > >> 2) Simplification of configs - potentially separating client side > configs > >> and those used by daemons. This is another source of perpetual confusion > >> for users. > >> > >> Thanks > >> - Sid > >> > >> > >> On Thu, Mar 5, 2015 at 2:46 PM, Steve Loughran <ste...@hortonworks.com> > >> wrote: > >> > >>> Sorry, outlook dequoted Alejandros's comments. > >>> > >>> Let me try again with his comments in italic and proofreading of mine > >>> > >>> On 05/03/2015 13:59, "Steve Loughran" <ste...@hortonworks.com<mailto: > >>> ste...@hortonworks.com>> wrote: > >>> > >>> > >>> > >>> On 05/03/2015 13:05, "Alejandro Abdelnur" <tuc...@gmail.com<mailto: > >>> tuc...@gmail.com><mailto:tuc...@gmail.com>> wrote: > >>> > >>> IMO, if part of the community wants to take on the responsibility and > >> work > >>> that takes to do a new major release, we should not discourage them > from > >>> doing that. > >>> > >>> Having multiple major branches active is a standard practice. > >>> > >>> Looking @ 2.x, the major work (HDFS HA, YARN) meant that it did take a > >>> long time to get out, and during that time 0.21, 0.22, got released and > >>> ignored; 0.23 picked up and used in production. > >>> > >>> The 2.04-alpha release was more of a troublespot as it got picked up > >>> widely enough to be used in products, and changes were made between > that > >>> alpha & 2.2 itself which raised compatibility issues. > >>> > >>> For 3.x I'd propose > >>> > >>> > >>> 1. Have less longevity of 3.x alpha/beta artifacts > >>> 2. Make clear there are no guarantees of compatibility from > alpha/beta > >>> releases to shipping. Best effort, but not to the extent that it gets > in > >>> the way. More succinctly: we will care more about seamless migration > from > >>> 2.2+ to 3.x than from a 3.0-alpha to 3.3 production. > >>> 3. Anybody who ships code based on 3.x alpha/beta to recognise and > >>> accept policy (2). Hadoop's "instability guarantee" for the 3.x > >> alpha/beta > >>> phase > >>> > >>> As well as backwards compatibility, we need to think about Forwards > >>> compatibility, with the goal being: > >>> > >>> Any app written/shipped with the 3.x release binaries (JAR and native) > >>> will work in and against a 3.y Hadoop cluster, for all x, y in Natural > >>> where y>=x and is-release(x) and is-release(y) > >>> > >>> That's important, as it means all server-side changes in 3.x which are > >>> expected to to mandate client-side updates: protocols, HDFS erasure > >>> decoding, security features, must be considered complete and stable > >> before > >>> we can say is-release(x). In an ideal world, we'll even get the > semantics > >>> right with tests to show this. > >>> > >>> Fixing classpath hell downstream is certainly one feature I am +1 on. > >> But: > >>> it's only one of the features, and given there's not any design doc on > >> that > >>> JIRA, way too immature to set a release schedule on. An alpha schedule > >> with > >>> no-guarantees and a regular alpha roll, could be viable, as new > features > >> go > >>> in and can then be used to experimentally try this stuff in branches of > >>> Hbase (well volunteered, Stack!), etc. Of course instability guarantees > >>> will be transitive downstream. > >>> > >>> > >>> This time around we are not replacing the guts as we did from Hadoop 1 > to > >>> Hadoop 2, but superficial surgery to address issues were not considered > >> (or > >>> was too much to take on top of the guts transplant). > >>> > >>> For the split brain concern, we did a great of job maintaining Hadoop 1 > >> and > >>> Hadoop 2 until Hadoop 1 faded away. > >>> > >>> And a significant argument about 2.0.4-alpha to 2.2 protobuf/HDFS > >>> compatibility. > >>> > >>> > >>> Based on that experience I would say that the coexistence of Hadoop 2 > and > >>> Hadoop 3 will be much less demanding/traumatic. > >>> > >>> The re-layout of all the source trees was a major change there, > assuming > >>> there's no refactoring or switch of build tools then picking things > back > >>> will be tractable > >>> > >>> > >>> Also, to facilitate the coexistence we should limit Java language > >> features > >>> to Java 7 (even if the runtime is Java 8), once Java 7 is not used > >> anymore > >>> we can remove this limitation. > >>> > >>> +1; setting javac.version will fix this > >>> > >>> What is nice about having java 8 as the base JVM is that it means you > can > >>> be confident that all Hadoop 3 servers will be JDK8+, so downstream > apps > >>> and libs can use all Java 8 features they want to. > >>> > >>> There's one policy change to consider there which is possibly, just > >>> possibly, we could allow new modules in hadoop-tools to adopt Java 8 > >>> languages early, provided everyone recognised that "backport to > branch-2" > >>> isn't going to happen. > >>> > >>> -Steve > >>> > >>> > >> > >
