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From st...@duboce.net
Subject Re: Review Request: [HBASE-2321] [HBASE-2002] Add support for per-region dynamically registered RPC endpoints for coprocessors and allow configurable RPC client/server implementations
Date Tue, 05 Oct 2010 06:09:48 GMT

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I got as far as ipc and then stopped for now.

Really impressive Gary.  Pity its so ugly (Not your fault that ipc -- Call, Invoke, etc. --
and Proxy interface is so).  But it looks like the needed flexibility is there -- and it'll


    Action is a new class so we are not breaking any pre-exisiting API here (Even so, erasure
would reduce this API change to the old I believe anyways?).


    I think the fact that this class if of coprocessors needs to be highlighted better.  Batch
is a super generic name yet this Batch is only for CPs.  A subpackage for these CP classes
would be a pain would it?  Any other way of grouping these CP classes?  A prefix?  Just throwing
it out there (I'm sure you thought about it and had a reason for not going these routes).


    But, this method's name is 'returning'?
    So, it executes the 'method' of 'protocol' and returns the hosting  'Call' whose invocation
has already run?
    Should it be 'execute' or 'executeCall' or 'invokeCall', etc.




    Do you need the 'Batch.' prefix here?


    (but of interest, how does this differ from setCause?  Or, could you pass the ite to the
IOE constructor?


    Good javadoc.


    Should this method be 'public' since its only called in here -- whats returned out of
a 'returning' is an exhausted call.. the receiving caller will not be doing a call invocation?


    I don't see Callback passed to call in the above.  I suppose how Callback works will become
clear later.


    ... against a Coprocessor?
    Maybe add above?


    This is fair I suppose if only one coprocessor per region (Is that true)?


    This class is for CPs only?


    Want to call this out as a CP method?


    So this would be for a single cooprocessor implementation. 
    You say above that we do an rpc per row but are the rpcs run serially or in parallell?
 If parallel, thats sweet.


    So, here is a case where row designates a region, right?  Not a 'row'.  If all these CP
classes were in a sub-package, you could do a package-info on CP w/ examples, etc. -- copy/paste
of the stuff you have above?


    I thought the client pollution would be worse than it is.


    Whats going on here?  You are rigging the createCallable so it can be used by CPs?
    (no objection, just asking)


    Should this be public?  Its not in HConnection, is it?  Or, rather, why is it not in HConnection?


    Again, this is rigging MultiAction to support the CP parameterized types?


    OK.  This is a nice explaination.  Good doc.


    What if I pass more than one key for a region?  Will CP run twice?


    oh, you don't have to repeat this doc up in HTable.  I'd remove it and replace it '@Override'.


    This all looks like an improvement.


    You have to say something about 'inclusive'?

- stack

On 2010-10-04 16:28:39, Gary Helmling wrote:
> -----------------------------------------------------------
> This is an automatically generated e-mail. To reply, visit:
> http://review.cloudera.org/r/816/
> -----------------------------------------------------------
> (Updated 2010-10-04 16:28:39)
> Review request for hbase, Andrew Purtell and Jonathan Gray.
> Summary
> -------
> This is really two separate patches in one, though with some overlapping changes.  If
necessary I can split them apart for separate review.  Please let me know if that would make
review easier.
> Part 1:
> ==============
> Port over of HADOOP-6422 to the HBase RPC code.  The goal of this change is to allow
alternate RPC client/server implementations to be enabled through a simple configuration change.
 Ultimately I would like to use this to allow secure RPC to be enabled through configuration,
while not blocking normal (current) RPC operation on non-secure Hadoop versions.
> This portion of the patch abstracts out two interfaces from the RPC code:
> RpcEngine: HBaseRPC uses this to obtain proxy instances for client calls and server instances
for HMaster and HRegionServer
> RpcServer: this allows differing RPC server implementations, breaking the dependency
on HBaseServer
> The bulk of the current code from HBaseRPC is moved into WritableRpcEngine and is unchanged
other than the interface requirements.  So the current call path remains the same, other than
the HBaseRPC.getProtocolEngine() abstraction.
> Part 2:
> ===============
> The remaining changes provide server-side hooks for registering new RPC protocols/handlers
(per-region to support coprocessors), and client side hooks to support dynamic execution of
the registered protocols.
> The new RPC protocol actions are constrained to org.apache.hadoop.hbase.ipc.CoprocessorProtocol
implementations (which extends VersionedProtocol) to prevent arbitrary execution of methods
against HMasterInterface, HRegionInterface, etc.
> For protocol handler registration, HRegionServer provides a new method:
>   public <T extends CoprocessorProtocol> boolean registerProtocol(
>       byte[] region, Class<T> protocol, T handler)
> which builds a Map of region name to protocol instances for dispatching client calls.
> Client invocations are performed through HTable, which adds the following methods:
>   public <T extends CoprocessorProtocol> T proxy(Class<T> protocol, Row row)
> This directly returns a proxy instance to the CoprocessorProtocol implementation registered
for the region serving row "row".  Any method calls will be proxied to the region's server
and invoked using the map of registered region name -> handler instances.
> Calls directed against multiple rows are a bit more complicated.  They are supported
with the methods:
>   public <T extends CoprocessorProtocol, R> void exec(
>       Class<T> protocol, List<? extends Row> rows,
>       BatchCall<T,R> callable, BatchCallback<R> callback)
>   public <T extends CoprocessorProtocol, R> void exec(
>       Class<T> protocol, RowRange range,
>       BatchCall<T,R> callable, BatchCallback<R> callback)
> where BatchCall and BatchCallback are simple interfaces defining the methods to be called
and a callback instance to be invoked for each result.
> For the sample CoprocessorProtocol interface:
>   interface PingProtocol extends CoprocessorProtocol {
>     public String ping();
>     public String hello(String name);
>   }
> a client invocation might look like:
>     final Map<byte[],R> results = new TreeMap<byte[],R>(...)
>     List<Row> rows = ...
>     table.exec(PingProtocol.class, rows,
>         new HTable.BatchCall<PingProtocol,String>() {
>           public String call(PingProtocol instance) {
>             return instance.ping();
>           }
>         },
>         new BatchCallback<R>(){
>           public void update(byte[] region, byte[] row, R value) {
>             results.put(region, value);
>           }
>         });
> The BatchCall.call() method will be invoked for each row in the passed in list, and the
BatchCallback.update() method will be invoked for each return value.  However, currently the
PingProtocol.ping() invocation will result in a separate RPC call per row, which is less that
> Support is in place to make use of the HRegionServer.multi() invocations for batched
RPC (see the org.apache.hadoop.hbase.client.Exec class), but this does not mesh well with
the current client-side interface.
> In addition to standard code review, I'd appreciate any thoughts on the client interactions
in particular, and whether they would meet some of the anticipated uses of coprocessors.
> This addresses bug HBASE-2002.
>     http://issues.apache.org/jira/browse/HBASE-2002
> Diffs
> -----
>   src/main/java/org/apache/hadoop/hbase/client/Action.java 556ea81 
>   src/main/java/org/apache/hadoop/hbase/client/Batch.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/client/Exec.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/client/ExecResult.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/client/HConnection.java 65f7618 
>   src/main/java/org/apache/hadoop/hbase/client/HConnectionManager.java 866ba92 
>   src/main/java/org/apache/hadoop/hbase/client/HTable.java 0dbf263 
>   src/main/java/org/apache/hadoop/hbase/client/HTableInterface.java 74593bf 
>   src/main/java/org/apache/hadoop/hbase/client/MultiAction.java c6ea838 
>   src/main/java/org/apache/hadoop/hbase/client/MultiResponse.java 91bd04b 
>   src/main/java/org/apache/hadoop/hbase/client/RowRange.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/client/Scan.java 29b3cb0 
>   src/main/java/org/apache/hadoop/hbase/io/HbaseObjectWritable.java 83f623d 
>   src/main/java/org/apache/hadoop/hbase/ipc/ConnectionHeader.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/CoprocessorProtocol.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/ExecRPCInvoker.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/HBaseClient.java 2b5eeb6 
>   src/main/java/org/apache/hadoop/hbase/ipc/HBaseRPC.java e23a629 
>   src/main/java/org/apache/hadoop/hbase/ipc/HBaseServer.java e4c356d 
>   src/main/java/org/apache/hadoop/hbase/ipc/HRegionInterface.java ee5dd8f 
>   src/main/java/org/apache/hadoop/hbase/ipc/Invocation.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/RpcEngine.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/RpcServer.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/ipc/WritableRpcEngine.java PRE-CREATION 
>   src/main/java/org/apache/hadoop/hbase/master/HMaster.java fb1e834 
>   src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java 0a4fbce 
>   src/main/java/org/apache/hadoop/hbase/regionserver/HRegionServer.java 89f499a 
>   src/main/java/org/apache/hadoop/hbase/rest/client/RemoteHTable.java d4166cf 
>   src/main/resources/hbase-default.xml 5fafe65 
>   src/test/java/org/apache/hadoop/hbase/regionserver/TestServerCustomProtocol.java PRE-CREATION

> Diff: http://review.cloudera.org/r/816/diff
> Testing
> -------
> Thanks,
> Gary

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