com.basho.riak.client.api.commands.kv

Class MultiFetch

java.lang.Object

com.basho.riak.client.api.RiakCommand<ResponseType,List<Location>>

com.basho.riak.client.api.commands.kv.MultiFetch

public final class MultiFetch
extends RiakCommand<ResponseType,List<Location>>

Command used to fetch multiple values from Riak.

Riak itself does not support pipelining of requests. MutliFetch addresses this issue by using a thread to parallelize and manage a set of async fetch operations for a given set of keys.

The result of executing this command is a List of RiakFuture objects, each one representing a single fetch operation. The returned RiakFuture that contains that list completes when all the FetchValue operations contained have finished.

 MultiFetch multifetch = ...;
 MultiFetch.Response response = client.execute(multifetch);
 List<MyPojo> myResults = new ArrayList<MyPojo>();
 for (RiakFuture<FetchValue.Response, Location> f : response)
 {
     try
     {
          FetchValue.Response response = f.get();
          myResults.add(response.getValue(MyPojo.class));
     }
     catch (ExecutionException e)
     {
         // log error, etc.
     }
 }

The maximum number of concurrent requests defaults to 10. This can be changed when constructing the operation.

Be aware that because requests are being parallelized performance is also dependent on the client's underlying connection pool. If there are no connections available performance will suffer initially as connections will need to be established or worse they could time out.

Be aware that for responsiveness to the caller thread, the requests are run on a Daemon worker thread. Shutting down the client JVM before the future is complete will result in unexpected behavior, and an incomplete result.

Since:

2.0

Author:

Dave Rusek

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MultiFetch.Builder Used to construct a MutiFetch command.
static class	MultiFetch.Response The response from Riak for a MultiFetch command.

Field Summary

Fields

Modifier and Type	Field and Description
protected Map<RiakOption<?>,Object>	options

Method Summary

Modifier and Type	Method and Description
protected FetchValue.Builder	createBaseBuilderType(Location location)
protected MultiFetch.Response	createResponseType(List<RiakFuture<FetchValue.Response,Location>> riakFutures)
boolean	equals(Object o)
protected RiakFuture<ResponseType,List<Location>>	executeAsync(RiakCluster cluster)
protected RiakFuture<FetchValue.Response,Location>	executeBaseCommandAsync(FetchValue command, RiakCluster cluster)
int	hashCode()
String	toString()

Methods inherited from class com.basho.riak.client.api.RiakCommand

execute, execute

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

options

protected final Map<RiakOption<?>,Object> options

Method Detail

createResponseType

protected MultiFetch.Response createResponseType(List<RiakFuture<FetchValue.Response,Location>> riakFutures)

createBaseBuilderType

protected FetchValue.Builder createBaseBuilderType(Location location)

executeBaseCommandAsync

protected RiakFuture<FetchValue.Response,Location> executeBaseCommandAsync(FetchValue command,
                                                                           RiakCluster cluster)

executeAsync

protected RiakFuture<ResponseType,List<Location>> executeAsync(RiakCluster cluster)

Specified by:

executeAsync in class RiakCommand<ResponseType extends Iterable<RiakFuture<BaseResponseType,Location>>,List<Location>>

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object