A question about cross-version client/server compatibility

[Shawn Heisey <ap...@elyograg.org>]

Somebody on the solr-user mailing list has posed a question about
whether they can use ZK 3.4.12 on the server side and a specific version
of Solr on the client side.  The specific version of Solr they're asking
about includes ZK 3.4.10 for its client code.

I would not anticipate any issues running with 3.4.10 on the client side
and 3.4.12 on the server side, so I think I can safely answer their
question, but I have a more general question to ask.

Are there ANY mixed version matchups that present problems, assuming the
server is running a newer version than the client?  I would never advise
running a server version that's older than the client.

The very first release of Solr to feature ZK integration was 4.0-ALPHA,
and eventually the stable 4.0.0 release, which included ZK 3.3.6.  The
subsequent version of Solr, which was 4.1.0, included ZK 3.4.5.  We
expect to include ZK 3.4.12 with the next release of Solr - 7.4.0.

I did a simple test with Solr 4.0.0 against a single ZK 3.4.12 server. 
It started just fine.  The testing was not exhaustive, but I saw zero
problems.

What I intend to say on the solr-user thread is that ZK 3.4.12 can be
used with ALL SolrCloud versions, but I thought I should sanity-check
that statement here before I make it.

Thanks,
Shawn

Re: A question about cross-version client/server compatibility

[Michael Han <ha...@apache.org>]

Please check out Backward Compatibility section in
https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement.

A few other comments inline.

On Tue, May 22, 2018 at 2:47 PM, Shawn Heisey <ap...@elyograg.org> wrote:

> Somebody on the solr-user mailing list has posed a question about
> whether they can use ZK 3.4.12 on the server side and a specific version
> of Solr on the client side.  The specific version of Solr they're asking
> about includes ZK 3.4.10 for its client code.
>
> I would not anticipate any issues running with 3.4.10 on the client side
> and 3.4.12 on the server side, so I think I can safely answer their
> question, but I have a more general question to ask.
>
> Are there ANY mixed version matchups that present problems, assuming the
> server is running a newer version than the client?  I would never advise
> running a server version that's older than the client.
>

If the mixed versions are not compatible (see the reference in the link),
there might be problems.


>
> The very first release of Solr to feature ZK integration was 4.0-ALPHA,
> and eventually the stable 4.0.0 release, which included ZK 3.3.6.  The
> subsequent version of Solr, which was 4.1.0, included ZK 3.4.5.  We
> expect to include ZK 3.4.12 with the next release of Solr - 7.4.0.
>
> I did a simple test with Solr 4.0.0 against a single ZK 3.4.12 server.
> It started just fine.  The testing was not exhaustive, but I saw zero
> problems.
>
> What I intend to say on the solr-user thread is that ZK 3.4.12 can be
> used with ALL SolrCloud versions, but I thought I should sanity-check
> that statement here before I make it.
>

ZK 3.4.x is compatible with ZK 3.3.y releases (major.minor is compatible
with major.(minor-1)), so in your case this statement should be true.


> Thanks,
> Shawn
>
>