Github user kl0u commented on a diff in the pull request:
https://github.com/apache/flink/pull/5342#discussion_r163506043
--- Diff:
flink-streaming-java/src/main/java/org/apache/flink/streaming/api/functions/TimeBoundedStreamJoinOperator.java
---
@@ -0,0 +1,328 @@
+/*
+ * 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.flink.streaming.api.functions;
+
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.api.common.state.MapState;
+import org.apache.flink.api.common.state.MapStateDescriptor;
+import org.apache.flink.api.common.state.ValueState;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeinfo.TypeHint;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+import org.apache.flink.api.java.tuple.Tuple2;
+import org.apache.flink.api.java.tuple.Tuple3;
+import org.apache.flink.streaming.api.operators.AbstractStreamOperator;
+import org.apache.flink.streaming.api.operators.TimestampedCollector;
+import org.apache.flink.streaming.api.operators.TwoInputStreamOperator;
+import org.apache.flink.streaming.api.watermark.Watermark;
+import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
+
+import java.util.ArrayList;
+import java.util.LinkedList;
+import java.util.List;
+
+import static
org.apache.flink.api.common.typeinfo.BasicTypeInfo.LONG_TYPE_INFO;
+
+// TODO: Make bucket granularity adaptable
+
+/**
+ * A TwoInputStreamOperator to execute time-bounded stream inner joins.
+ * <p>
+ * By using a configurable lower and upper bound this operator will emit
exactly those pairs
+ * (T1, T2) where t2.ts â [T1.ts + lowerBound, T1.ts + upperBound]. Both
the lower and the
+ * upper bound can be configured to be either inclusive or exclusive.
+ *
+ * @param <T1> The type of the elements in the left stream
+ * @param <T2> The type of the elements in the right stream
+ */
+public class TimeBoundedStreamJoinOperator<T1, T2>
+ extends AbstractStreamOperator<Tuple2<T1, T2>>
--- End diff --
To be able to accommodate a special user-defined function (like in the case
of the `ProcessFunction`), the operator should extend the
`AbstractUdfStreamOperator`. This function can be passed as an argument to the
constructor of the operator, and it should be applied whenever we have an
element successfully joined with another one (`processElement1()` and
`processElement2()`).
The function should be an `AbstractRichFunction` and it should have a
single (abstract) method `processElement(...)` which takes as argument a
`Context` object which should give access at least to the 2 elements being
joined and their respective timestamps. We may consider in the future giving
also access to the timer service, as done in the case of the `ProcessFunction`
for keyed streams.
---
