raminqaf commented on code in PR #15601:
URL: https://github.com/apache/kafka/pull/15601#discussion_r1545727392


##########
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KStreamKStreamJoin.java:
##########
@@ -16,276 +16,98 @@
  */
 package org.apache.kafka.streams.kstream.internals;
 
+import static 
org.apache.kafka.streams.StreamsConfig.InternalConfig.EMIT_INTERVAL_MS_KSTREAMS_OUTER_JOIN_SPURIOUS_RESULTS_FIX;
+import static 
org.apache.kafka.streams.processor.internals.metrics.TaskMetrics.droppedRecordsSensor;
+
+import java.util.Optional;
 import org.apache.kafka.common.metrics.Sensor;
-import org.apache.kafka.streams.KeyValue;
 import org.apache.kafka.streams.StreamsConfig;
 import org.apache.kafka.streams.kstream.ValueJoinerWithKey;
 import org.apache.kafka.streams.kstream.internals.KStreamImplJoin.TimeTracker;
 import 
org.apache.kafka.streams.kstream.internals.KStreamImplJoin.TimeTrackerSupplier;
 import org.apache.kafka.streams.processor.api.ContextualProcessor;
-import org.apache.kafka.streams.processor.api.Processor;
 import org.apache.kafka.streams.processor.api.ProcessorContext;
 import org.apache.kafka.streams.processor.api.ProcessorSupplier;
-import org.apache.kafka.streams.processor.api.Record;
 import org.apache.kafka.streams.processor.internals.InternalProcessorContext;
 import org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl;
-import org.apache.kafka.streams.state.KeyValueIterator;
 import org.apache.kafka.streams.state.KeyValueStore;
 import org.apache.kafka.streams.state.WindowStore;
-import org.apache.kafka.streams.state.WindowStoreIterator;
 import org.apache.kafka.streams.state.internals.LeftOrRightValue;
 import org.apache.kafka.streams.state.internals.TimestampedKeyAndJoinSide;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-import java.util.Optional;
-
-import static 
org.apache.kafka.streams.StreamsConfig.InternalConfig.EMIT_INTERVAL_MS_KSTREAMS_OUTER_JOIN_SPURIOUS_RESULTS_FIX;
-import static 
org.apache.kafka.streams.processor.internals.metrics.TaskMetrics.droppedRecordsSensor;
-
-class KStreamKStreamJoin<K, V1, V2, VOut> implements ProcessorSupplier<K, V1, 
K, VOut> {
-    private static final Logger LOG = 
LoggerFactory.getLogger(KStreamKStreamJoin.class);
 
+abstract class KStreamKStreamJoin<K, V1, V2, VOut> implements 
ProcessorSupplier<K, V1, K, VOut> {
+    protected final ValueJoinerWithKey<? super K, ? super V1, ? super V2, ? 
extends VOut> joiner;
+    protected final long joinGraceMs;
+    protected final boolean outer;
+    protected final long joinBeforeMs;
+    protected final long joinAfterMs;
     private final String otherWindowName;
-    private final long joinBeforeMs;
-    private final long joinAfterMs;
-    private final long joinGraceMs;
     private final boolean enableSpuriousResultFix;
     private final long windowsBeforeMs;
     private final long windowsAfterMs;
-
-    private final boolean outer;
-    private final boolean isLeftSide;
     private final Optional<String> outerJoinWindowName;
-    private final ValueJoinerWithKey<? super K, ? super V1, ? super V2, ? 
extends VOut> joiner;
 
     private final TimeTrackerSupplier sharedTimeTrackerSupplier;
 
-    KStreamKStreamJoin(final boolean isLeftSide,
-                       final String otherWindowName,
-                       final JoinWindowsInternal windows,
-                       final ValueJoinerWithKey<? super K, ? super V1, ? super 
V2, ? extends VOut> joiner,
-                       final boolean outer,
-                       final Optional<String> outerJoinWindowName,
-                       final TimeTrackerSupplier sharedTimeTrackerSupplier) {
-        this.isLeftSide = isLeftSide;
+    KStreamKStreamJoin(final String otherWindowName,
+            final JoinWindowsInternal windows,
+            final long joinBeforeMs,
+            final long joinAfterMs,
+            final ValueJoinerWithKey<? super K, ? super V1, ? super V2, ? 
extends VOut> joiner,
+            final Optional<String> outerJoinWindowName,
+            final TimeTrackerSupplier sharedTimeTrackerSupplier,
+            final boolean outer) {
         this.otherWindowName = otherWindowName;
-        if (isLeftSide) {
-            this.joinBeforeMs = windows.beforeMs;
-            this.joinAfterMs = windows.afterMs;
-        } else {
-            this.joinBeforeMs = windows.afterMs;
-            this.joinAfterMs = windows.beforeMs;
-        }
         this.windowsAfterMs = windows.afterMs;
         this.windowsBeforeMs = windows.beforeMs;
-        this.joinGraceMs = windows.gracePeriodMs();
+        this.joinBeforeMs = joinBeforeMs;
+        this.joinAfterMs = joinAfterMs;
         this.enableSpuriousResultFix = windows.spuriousResultFixEnabled();
         this.joiner = joiner;
-        this.outer = outer;
+        this.joinGraceMs = windows.gracePeriodMs();
         this.outerJoinWindowName = outerJoinWindowName;
         this.sharedTimeTrackerSupplier = sharedTimeTrackerSupplier;
+        this.outer = outer;
     }
 
-    @Override
-    public Processor<K, V1, K, VOut> get() {
-        return new KStreamKStreamJoinProcessor();
-    }
-
-    private class KStreamKStreamJoinProcessor extends ContextualProcessor<K, 
V1, K, VOut> {
-        private WindowStore<K, V2> otherWindowStore;
-        private Sensor droppedRecordsSensor;
-        private Optional<KeyValueStore<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V1, V2>>> outerJoinStore = Optional.empty();
-        private InternalProcessorContext<K, VOut> internalProcessorContext;
-        private TimeTracker sharedTimeTracker;
+    protected abstract class KStreamKStreamJoinProcessor extends 
ContextualProcessor<K, V1, K, VOut> {
+        protected WindowStore<K, V2> otherWindowStore;
+        protected Sensor droppedRecordsSensor;
+        protected Optional<KeyValueStore<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V1, V2>>> leftOuterJoinStore =
+                Optional.empty();
+        protected Optional<KeyValueStore<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V2, V1>>> rightOuterJoinStore =
+                Optional.empty();
+        protected InternalProcessorContext<K, VOut> internalProcessorContext;
+        protected TimeTracker sharedTimeTracker;
 
         @Override
         public void init(final ProcessorContext<K, VOut> context) {
             super.init(context);
             internalProcessorContext = (InternalProcessorContext<K, VOut>) 
context;
 
             final StreamsMetricsImpl metrics = (StreamsMetricsImpl) 
context.metrics();
-            droppedRecordsSensor = 
droppedRecordsSensor(Thread.currentThread().getName(), 
context.taskId().toString(), metrics);
+            droppedRecordsSensor =
+                    droppedRecordsSensor(Thread.currentThread().getName(), 
context.taskId().toString(), metrics);
             otherWindowStore = context.getStateStore(otherWindowName);
             sharedTimeTracker = 
sharedTimeTrackerSupplier.get(context.taskId());
 
             if (enableSpuriousResultFix) {
-                outerJoinStore = 
outerJoinWindowName.map(context::getStateStore);
+                leftOuterJoinStore = 
outerJoinWindowName.map(context::getStateStore);
+                rightOuterJoinStore = 
outerJoinWindowName.map(context::getStateStore);
 
                 sharedTimeTracker.setEmitInterval(
-                    StreamsConfig.InternalConfig.getLong(
-                        context.appConfigs(),
-                        
EMIT_INTERVAL_MS_KSTREAMS_OUTER_JOIN_SPURIOUS_RESULTS_FIX,
-                        1000L
-                    )
+                        StreamsConfig.InternalConfig.getLong(
+                                context.appConfigs(),
+                                
EMIT_INTERVAL_MS_KSTREAMS_OUTER_JOIN_SPURIOUS_RESULTS_FIX,
+                                1000L
+                        )
                 );
             }
         }
 
-        @SuppressWarnings("unchecked")
-        @Override
-        public void process(final Record<K, V1> record) {
-            final long inputRecordTimestamp = record.timestamp();
-            final long timeFrom = Math.max(0L, inputRecordTimestamp - 
joinBeforeMs);
-            final long timeTo = Math.max(0L, inputRecordTimestamp + 
joinAfterMs);
-            sharedTimeTracker.advanceStreamTime(inputRecordTimestamp);
-
-            if (outer && record.key() == null && record.value() != null) {
-                context().forward(record.withValue(joiner.apply(record.key(), 
record.value(), null)));
-                return;
-            } else if (StreamStreamJoinUtil.skipRecord(record, LOG, 
droppedRecordsSensor, context())) {
-                return;
-            }
-
-            // Emit all non-joined records which window has closed
-            if (inputRecordTimestamp == sharedTimeTracker.streamTime) {
-                outerJoinStore.ifPresent(store -> 
emitNonJoinedOuterRecords(store, record));
-            }
-
-            boolean needOuterJoin = outer;
-            try (final WindowStoreIterator<V2> iter = 
otherWindowStore.fetch(record.key(), timeFrom, timeTo)) {
-                while (iter.hasNext()) {
-                    needOuterJoin = false;
-                    final KeyValue<Long, V2> otherRecord = iter.next();
-                    final long otherRecordTimestamp = otherRecord.key;
-
-                    outerJoinStore.ifPresent(store -> {
-                        // use putIfAbsent to first read and see if there's 
any values for the key,
-                        // if yes delete the key, otherwise do not issue a put;
-                        // we may delete some values with the same key early 
but since we are going
-                        // range over all values of the same key even after 
failure, since the other window-store
-                        // is only cleaned up by stream time, so this is okay 
for at-least-once.
-                        
store.putIfAbsent(TimestampedKeyAndJoinSide.make(!isLeftSide, record.key(), 
otherRecordTimestamp), null);
-                    });
-
-                    context().forward(
-                        record.withValue(joiner.apply(record.key(), 
record.value(), otherRecord.value))
-                               .withTimestamp(Math.max(inputRecordTimestamp, 
otherRecordTimestamp)));
-                }
-
-                if (needOuterJoin) {
-                    // The maxStreamTime contains the max time observed in 
both sides of the join.
-                    // Having access to the time observed in the other join 
side fixes the following
-                    // problem:
-                    //
-                    // Say we have a window size of 5 seconds
-                    //  1. A non-joined record with time T10 is seen in the 
left-topic (maxLeftStreamTime: 10)
-                    //     The record is not processed yet, and is added to 
the outer-join store
-                    //  2. A non-joined record with time T2 is seen in the 
right-topic (maxRightStreamTime: 2)
-                    //     The record is not processed yet, and is added to 
the outer-join store
-                    //  3. A joined record with time T11 is seen in the 
left-topic (maxLeftStreamTime: 11)
-                    //     It is time to look at the expired records. T10 and 
T2 should be emitted, but
-                    //     because T2 was late, then it is not fetched by the 
window store, so it is not processed
-                    //
-                    // See KStreamKStreamLeftJoinTest.testLowerWindowBound() 
tests
-                    //
-                    // This condition below allows us to process the 
out-of-order records without the need
-                    // to hold it in the temporary outer store
-                    if (!outerJoinStore.isPresent() || timeTo < 
sharedTimeTracker.streamTime) {
-                        
context().forward(record.withValue(joiner.apply(record.key(), record.value(), 
null)));
-                    } else {
-                        sharedTimeTracker.updatedMinTime(inputRecordTimestamp);
-                        outerJoinStore.ifPresent(store -> store.put(
-                            TimestampedKeyAndJoinSide.make(isLeftSide, 
record.key(), inputRecordTimestamp),
-                            LeftOrRightValue.make(isLeftSide, 
record.value())));
-                    }
-                }
-            }
-        }
-
-        @SuppressWarnings("unchecked")
-        private void emitNonJoinedOuterRecords(
-            final KeyValueStore<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V1, V2>> store,
-            final Record<K, V1> record) {
-
-            // calling `store.all()` creates an iterator what is an expensive 
operation on RocksDB;
-            // to reduce runtime cost, we try to avoid paying those cost
-
-            // only try to emit left/outer join results if there _might_ be 
any result records
-            if (sharedTimeTracker.minTime + joinAfterMs + joinGraceMs >= 
sharedTimeTracker.streamTime) {
-                return;
-            }
-            // throttle the emit frequency to a (configurable) interval;
-            // we use processing time to decouple from data properties,
-            // as throttling is a non-functional performance optimization
-            if (internalProcessorContext.currentSystemTimeMs() < 
sharedTimeTracker.nextTimeToEmit) {
-                return;
-            }
-
-            // Ensure `nextTimeToEmit` is synced with `currentSystemTimeMs`, 
if we dont set it everytime,
-            // they can get out of sync during a clock drift
-            sharedTimeTracker.nextTimeToEmit = 
internalProcessorContext.currentSystemTimeMs();
-            sharedTimeTracker.advanceNextTimeToEmit();
-
-            // reset to MAX_VALUE in case the store is empty
-            sharedTimeTracker.minTime = Long.MAX_VALUE;
-
-            try (final KeyValueIterator<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V1, V2>> it = store.all()) {
-                TimestampedKeyAndJoinSide<K> prevKey = null;
-
-                while (it.hasNext()) {
-                    boolean outerJoinLeftBreak = false;
-                    boolean outerJoinRightBreak = false;
-                    final KeyValue<TimestampedKeyAndJoinSide<K>, 
LeftOrRightValue<V1, V2>> next = it.next();
-                    final TimestampedKeyAndJoinSide<K> 
timestampedKeyAndJoinSide = next.key;
-                    final LeftOrRightValue<V1, V2> value = next.value;
-                    final K key = timestampedKeyAndJoinSide.getKey();
-                    final long timestamp = 
timestampedKeyAndJoinSide.getTimestamp();
-                    sharedTimeTracker.minTime = timestamp;
-
-                    // Skip next records if window has not closed
-                    final long outerJoinLookBackTimeMs = 
getOuterJoinLookBackTimeMs(timestampedKeyAndJoinSide);
-                    if (sharedTimeTracker.minTime + outerJoinLookBackTimeMs + 
joinGraceMs >= sharedTimeTracker.streamTime) {
-                        if (timestampedKeyAndJoinSide.isLeftSide()) {
-                            outerJoinLeftBreak = true; // there are no more 
candidates to emit on left-outerJoin-side
-                        } else {
-                            outerJoinRightBreak = true; // there are no more 
candidates to emit on right-outerJoin-side
-                        }
-                        if (outerJoinLeftBreak && outerJoinRightBreak) {
-                            break; // there are no more candidates to emit on 
left-outerJoin-side and
-                                    // right-outerJoin-side
-                        } else {
-                            continue; // there are possibly candidates left on 
the other outerJoin-side
-                        }
-                    }
-
-                    final VOut nullJoinedValue;
-                    if (isLeftSide) {
-                        nullJoinedValue = joiner.apply(key,
-                                value.getLeftValue(),
-                                value.getRightValue());
-                    } else {
-                        nullJoinedValue = joiner.apply(key,
-                                (V1) value.getRightValue(),
-                                (V2) value.getLeftValue());
-                    }
-
-                    context().forward(
-                        
record.withKey(key).withValue(nullJoinedValue).withTimestamp(timestamp)
-                    );
-
-                    if (prevKey != null && 
!prevKey.equals(timestampedKeyAndJoinSide)) {
-                        // blind-delete the previous key from the outer window 
store now it is emitted;
-                        // we do this because this delete would remove the 
whole list of values of the same key,
-                        // and hence if we delete eagerly and then fail, we 
would miss emitting join results of the later
-                        // values in the list.
-                        // we do not use delete() calls since it would incur 
extra get()
-                        store.put(prevKey, null);
-                    }
-
-                    prevKey = timestampedKeyAndJoinSide;
-                }
-
-                // at the end of the iteration, we need to delete the last key
-                if (prevKey != null) {
-                    store.put(prevKey, null);
-                }
-            }
-        }
-
-        private long getOuterJoinLookBackTimeMs(final 
TimestampedKeyAndJoinSide<K> timestampedKeyAndJoinSide) {
+        protected long getOuterJoinLookBackTimeMs(final 
TimestampedKeyAndJoinSide<K> timestampedKeyAndJoinSide) {
             // depending on the JoinSide we fill in the outerJoinLookBackTimeMs
-            if (timestampedKeyAndJoinSide.isLeftSide()) {
+            if (timestampedKeyAndJoinSide.getJoinSide() == JoinSide.LEFT) {

Review Comment:
   A side note: This decision could not be removed. In the 
KStreamKStreamRightJoin, there are some tests that fetch the value from the 
rightOuterStore, and the value contains the left-side value.
   
   In the KStreamKStreamLeftJoin this call was not needed.



##########
streams/src/main/java/org/apache/kafka/streams/kstream/internals/KStreamKStreamLeftJoin.java:
##########
@@ -0,0 +1,201 @@
+/*
+ * 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.kafka.streams.kstream.internals;
+
+import java.util.Optional;
+import org.apache.kafka.streams.KeyValue;
+import org.apache.kafka.streams.kstream.ValueJoinerWithKey;
+import 
org.apache.kafka.streams.kstream.internals.KStreamImplJoin.TimeTrackerSupplier;
+import org.apache.kafka.streams.processor.api.Processor;
+import org.apache.kafka.streams.processor.api.Record;
+import org.apache.kafka.streams.state.KeyValueIterator;
+import org.apache.kafka.streams.state.KeyValueStore;
+import org.apache.kafka.streams.state.WindowStoreIterator;
+import org.apache.kafka.streams.state.internals.LeftOrRightValue;
+import org.apache.kafka.streams.state.internals.TimestampedKeyAndJoinSide;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class KStreamKStreamLeftJoin<K, V1, V2, VOut> extends KStreamKStreamJoin<K, 
V1, V2, VOut> {
+    private static final Logger LOG = 
LoggerFactory.getLogger(KStreamKStreamJoin.class);
+
+    KStreamKStreamLeftJoin(final String otherWindowName,
+            final JoinWindowsInternal windows,
+            final ValueJoinerWithKey<? super K, ? super V1, ? super V2, ? 
extends VOut> joiner,
+            final boolean outer,
+            final Optional<String> outerJoinWindowName,
+            final TimeTrackerSupplier sharedTimeTrackerSupplier) {
+        super(otherWindowName, windows, windows.beforeMs, windows.afterMs, 
joiner, outerJoinWindowName,
+                sharedTimeTrackerSupplier, outer);
+    }
+
+    @Override
+    public Processor<K, V1, K, VOut> get() {
+        return new KStreamKStreamLeftJoinProcessor();
+    }
+
+    private class KStreamKStreamLeftJoinProcessor extends 
KStreamKStreamJoinProcessor {
+        @Override
+        public void process(final Record<K, V1> leftRecord) {
+            final long inputRecordTimestamp = leftRecord.timestamp();
+            final long timeFrom = Math.max(0L, inputRecordTimestamp - 
joinBeforeMs);
+            final long timeTo = Math.max(0L, inputRecordTimestamp + 
joinAfterMs);
+            sharedTimeTracker.advanceStreamTime(inputRecordTimestamp);
+
+            if (outer && leftRecord.key() == null && leftRecord.value() != 
null) {
+                final VOut leftJoinValue = joiner.apply(leftRecord.key(), 
leftRecord.value(), null);
+                context().forward(leftRecord.withValue(leftJoinValue));
+                return;
+            } else if (StreamStreamJoinUtil.skipRecord(leftRecord, LOG, 
droppedRecordsSensor, context())) {
+                return;
+            }
+
+            // Emit all non-joined records which window has closed
+            if (inputRecordTimestamp == sharedTimeTracker.streamTime) {
+                leftOuterJoinStore.ifPresent(store -> 
emitNonJoinedOuterRecords(store, leftRecord));
+            }
+
+            boolean needOuterJoin = outer;
+            try (final WindowStoreIterator<V2> iter = 
otherWindowStore.fetch(leftRecord.key(), timeFrom, timeTo)) {

Review Comment:
   I also have a couple of questions. When is this store getting filled? I 
couldn't find anywhere where we call `.put()` for this window store. 



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