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https://issues.apache.org/jira/browse/SOLR-3383?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Per Steffensen updated SOLR-3383:
---------------------------------
Attachment: SOLR-3383.patch
Early patch attached to show details about suggested implementation and to get
feedback.
The patch should fit on top of your revision 1327417. The branch for doing the
code for this issue, was created from the branch where we did the SOLR-3173,
SOLR-3178 and SOLR-3382 changes, so it contains parts of an old fix for those.
Some of those parts have been reverted or changed in the latest patch attached
to SOLR-3178, so they are basically outdated. Hope you are able to distill what
is related to SOLR-3383 and what is not.
Basically the idea is that all public methods for doing requests using SolrJ
SolrServer's or SolrRequest-subclasses, has been changed from returning
responses (in the general form of NamedList<Object> or in the specialized form
of SolrResponse-subclasses) into returning Futures of responses.
Exceptions originating from the server, that you used to get when you called
one of those public methods, you will now not get before you call get on the
returned Future.
The benefits are that you (if your chain of SolrServers contains a real async
implementation) as a client, can go do other stuff from the time you send the
request (by calling one of those public methods) and until the time you inspect
the response (fetched by calling get on the returned Future). Besides that we
will be able to get responses back from ConcurrentSolrServer.
As is right now you need to have ConcurrentSolrServer in your chain of
SolrServers in order to get real async behaviour, because the rest of the
SolrServers does not really support it. If you dont use ConcurrentSolrServer
your client thread will basically not get its Future back from a call to one of
those public methods mentioned at the top, before the response has been
received from the server and calling get on the Future will immediately give
the client the reponse anyway. So not much acheived. But that can all easily be
changed by modifying the HttpSolrServer to be able to run in a async mode where
it has its own threadpool in which it does requests. That can easily be coded,
and will to a big extend eliminate the need for a ConcurrentSolrServer to begin
with. We will make this feature of the HttpSolrServer, and attach it if you
like the idea represented by this issue SOLR-3383.
The patch is a little bit dependent on the patch attached to SOLR-3178, in the
way that it deals with e.g. PartialErrors in places where it needs to, but we
can deal with that later.
This is just to present the idea in code and give you something to look at and
comment on.
Regards, Per Steffensen
> Async responses in SolrJ
> ------------------------
>
> Key: SOLR-3383
> URL: https://issues.apache.org/jira/browse/SOLR-3383
> Project: Solr
> Issue Type: Improvement
> Components: clients - java
> Affects Versions: 3.5
> Reporter: Per Steffensen
> Assignee: Per Steffensen
> Labels: async, asynchronous, concurrency, query, solrj, update
> Fix For: 4.0
>
> Attachments: SOLR-3383.patch
>
>
> Today it is like this
> - SolrServer.request returns NamedList<Object>
> - SolrRequest.process returns SolrResponse
> - Public methods on SolrServer like addX, optimize, commit, queryX etc.
> returns subclasses of SolrResponse (e.g. "add" returns UpdateResponse)
> - etc
> This is all synchronous - that is, the calling thread of those methods will
> wait for the response before being able to continue. I believe the industry
> today agrees that "operations" like client-server network-requireing
> operations should be done asynchronously seens from the client API. Therefore
> basically we should change those methods
> - SolrServer.request returns Future<NamedList<Object>>
> - SolrRequest.process returns Future<SolrResponse>
> - SolrServer.xxx returns Future<subclass of SolrResponse>
> and make the appropriate changes in the implementations below.
> My main argument for this right now, is that ConcurrentUpdateSolrServer
> really is not able to hand over responses to the calling client. Guess that
> it is also the reason why it is only a "Update"-SolrServer and not a complete
> SolrServer (being able to do queries etc.) - updates does not require sending
> responses (except primitive errors) back to the client, queries etc does. Now
> that we do "finegrained error propagation" (SOLR-3382) in order to send
> "unique key constraint"- and "versioning"-errors (SOLR-3173 and SOLR-3178)
> back to the client in responses to update-request, suddenly it is not true
> anymore that updates does not require sending responses back to the client.
> Making the changes suggested above (returning Futures) would
> - Allow ConcurrentUpdateSolrServer to be used for updates potentially
> resulting in "unique key constraint"- and "versioning"-errors
> - Allow ConcurrentUpdateSolrServer to become ConcurrentSolrServer - also
> being able to do queries etc
> - Do cool stuff like SOLR-3384
> - Make SolrJ more modern with respect to asynchronous principles
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