org.apache.hadoop.hbase.client

Interface AsyncTable.CoprocessorCallback<R>

Enclosing interface:

AsyncTable<C extends ScanResultConsumerBase>

@InterfaceAudience.Public
public static interface AsyncTable.CoprocessorCallback<R>

The callback when we want to execute a coprocessor call on a range of regions.

As the locating itself also takes some time, the implementation may want to send rpc calls on the fly, which means we do not know how many regions we have when we get the return value of the rpc calls, so we need an onComplete() which is used to tell you that we have passed all the return values to you(through the onRegionComplete(RegionInfo, Object) or onRegionError(RegionInfo, Throwable) calls), i.e, there will be no onRegionComplete(RegionInfo, Object) or onRegionError(RegionInfo, Throwable) calls in the future.

Here is a pseudo code to describe a typical implementation of a range coprocessor service method to help you better understand how the AsyncTable.CoprocessorCallback will be called. The callback in the pseudo code is our AsyncTable.CoprocessorCallback. And notice that the whenComplete is CompletableFuture.whenComplete.

 locateThenCall(byte[] row) {
   locate(row).whenComplete((location, locateError) -> {
     if (locateError != null) {
       callback.onError(locateError);
       return;
     }
     incPendingCall();
     region = location.getRegion();
     if (region.getEndKey() > endKey) {
       locateEnd = true;
     } else {
       locateThenCall(region.getEndKey());
     }
     sendCall().whenComplete((resp, error) -> {
       if (error != null) {
         callback.onRegionError(region, error);
       } else {
         callback.onRegionComplete(region, resp);
       }
       if (locateEnd && decPendingCallAndGet() == 0) {
         callback.onComplete();
       }
     });
   });
 }
 

Method Summary

Modifier and Type	Method and Description
void	onComplete() Indicate that all responses of the regions have been notified by calling onRegionComplete(RegionInfo, Object) or onRegionError(RegionInfo, Throwable).
void	onError(Throwable error) Indicate that we got an error which does not belong to any regions.
void	onRegionComplete(RegionInfo region, R resp) Indicate that the respose of a region is available
void	onRegionError(RegionInfo region, Throwable error) Indicate that the error for a region is available

Method Detail

onRegionComplete

void onRegionComplete(RegionInfo region,
                      R resp)

Indicate that the respose of a region is available

Parameters:

region - the region that the response belongs to

resp - the response of the coprocessor call

onRegionError

void onRegionError(RegionInfo region,
                   Throwable error)

Indicate that the error for a region is available

Parameters:

region - the region that the error belongs to

error - the response error of the coprocessor call

onComplete

void onComplete()

Indicate that all responses of the regions have been notified by calling onRegionComplete(RegionInfo, Object) or onRegionError(RegionInfo, Throwable).

onError

void onError(Throwable error)

Indicate that we got an error which does not belong to any regions. Usually a locating error.