[GitHub] [samza] mynameborat commented on a change in pull request #905: SAMZA-2055: Async high level api

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mynameborat commented on a change in pull request #905: SAMZA-2055: Async high level api
URL: https://github.com/apache/samza/pull/905#discussion_r270075454
 
 

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 File path: samza-api/src/main/java/org/apache/samza/operators/functions/AsyncFlatMapFunction.java
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 @@ -0,0 +1,43 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.samza.operators.functions;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.concurrent.CompletionStage;
+import org.apache.samza.annotation.InterfaceStability;
+
+
+/**
+ * Transforms an input message into a collection of 0 or more messages, possibly of a different type.
+ *
+ * @param <M>  type of the input message
+ * @param <OM>  type of the transformed messages
+ */
+@InterfaceStability.Unstable
+public interface AsyncFlatMapFunction<M, OM> extends InitableFunction, ClosableFunction, Serializable {
+
+  /**
+   * Transforms the provided message into a collection of 0 or more messages.
+   *
+   * @param message  the input message to be transformed
+   * @return  a collection of 0 or more transformed messages
+   */
+  CompletionStage<Collection<OM>> apply(M message);
 
 Review comment:
   I too initially had CompletableFuture and then moved to CompletionStage. CompletionStage offers much stricter async programming semantics and CompletableFuture is concrete implementation of the CompletionStage interface. I chose to go with the interface.

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