Package org.apache.flink.streaming.api.functions.async

Interface AsyncFunction<IN,​OUT>

  • Type Parameters:
    IN - The type of the input elements.
    OUT - The type of the returned elements.
    All Superinterfaces:
    Function, Serializable
    All Known Implementing Classes:
    AsyncFunctionRunner, AsyncLookupJoinRunner, AsyncLookupJoinWithCalcRunner, RichAsyncFunction
    @PublicEvolving
public interface AsyncFunction<IN,​OUT>
extends Function, Serializable
    A function to trigger Async I/O operation.

    For each #asyncInvoke, an async io operation can be triggered, and once it has been done, the result can be collected by calling ResultFuture.complete(java.util.Collection<OUT>). For each async operation, its context is stored in the operator immediately after invoking #asyncInvoke, avoiding blocking for each stream input as long as the internal buffer is not full.

    ResultFuture can be passed into callbacks or futures to collect the result data. An error can also be propagate to the async IO operator by ResultFuture.completeExceptionally(Throwable).

    Callback example usage: 

    
 public class HBaseAsyncFunc implements AsyncFunction<String, String> {

   public void asyncInvoke(String row, ResultFuture<String> result) throws Exception {
     HBaseCallback cb = new HBaseCallback(result);
     Get get = new Get(Bytes.toBytes(row));
     hbase.asyncGet(get, cb);
   }
 }

    Future example usage: 

    
 public class HBaseAsyncFunc implements AsyncFunction<String, String> {

   public void asyncInvoke(String row, final ResultFuture<String> result) throws Exception {
     Get get = new Get(Bytes.toBytes(row));
     ListenableFuture<Result> future = hbase.asyncGet(get);
     Futures.addCallback(future, new FutureCallback<Result>() {
       public void onSuccess(Result result) {
         List<String> ret = process(result);
         result.complete(ret);
       }
       public void onFailure(Throwable thrown) {
         result.completeExceptionally(thrown);
       }
     });
   }
 }

    • Method Detail

      • asyncInvoke

        void asyncInvoke​(IN input,
                 ResultFuture<OUT> resultFuture)
          throws Exception
        Trigger async operation for each stream input.
        Parameters:
        input - element coming from an upstream task
        resultFuture - to be completed with the result data
        Throws:
        Exception - in case of a user code error. An exception will make the task fail and trigger fail-over process.