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Subject [GitHub] [drill] arina-ielchiieva commented on a change in pull request #2000: DRILL-7607: Support dynamic credit based flow control
Date Tue, 03 Mar 2020 09:13:35 GMT
arina-ielchiieva commented on a change in pull request #2000: DRILL-7607: Support dynamic credit
based flow control
URL: https://github.com/apache/drill/pull/2000#discussion_r386879614
 
 

 ##########
 File path: exec/java-exec/src/main/java/org/apache/drill/exec/rpc/DynamicSemaphore.java
 ##########
 @@ -0,0 +1,84 @@
+/*
+ * 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.drill.exec.rpc;
+
+import java.util.concurrent.Semaphore;
+import java.util.concurrent.atomic.AtomicBoolean;
+import java.util.concurrent.locks.ReentrantLock;
+
+/**
+ * Dynamic credit based flow control:
+ * The sender initially sends batch to the sender by the initial static credit (3).
+ * The receiver will calculate a runtime credit value while sampling some received batches.
The runtime
+ * generated credit value will be sent to the receiver as an ack value. The sender will change
to the
+ * runtime generated credit value while received the ack credit value.
+ *
+ * The ack credit value has three type numeric value with different meaning:
+ *  0 : meaning no explicit credit value to the sender, just keep the initial static credit
based fc.
+ *  -1: meaning the receiver has gone to wrong to solve the query.
+ *  value greater than 0:  meaning a runtime generated credit value for the sender to change
to.
+ */
+public class DynamicSemaphore {
+
+    private static int INITIAL_STATIC_CREDIT = 3;
+    private Semaphore semaphore = new Semaphore(INITIAL_STATIC_CREDIT);
+    private AtomicBoolean changed = new AtomicBoolean(false);
+    private ReentrantLock lock = new ReentrantLock();
 
 Review comment:
   final?

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