From 7a7d43c2371507b22bf2a6be8fce11023e5cc7b7 Mon Sep 17 00:00:00 2001
From: Gunnar Morling <gunnar.morling@googlemail.com>
Date: Thu, 18 Jan 2018 14:03:07 +0100
Subject: [PATCH] DBZ-516 Returning control also from BlockingReader

---
 .../connector/mysql/BlockingReader.java       | 27 ++++++++++---------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/BlockingReader.java b/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/BlockingReader.java
index 9b32764fd..11b7dd53b 100644
--- a/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/BlockingReader.java
+++ b/debezium-connector-mysql/src/main/java/io/debezium/connector/mysql/BlockingReader.java
@@ -6,13 +6,16 @@
 package io.debezium.connector.mysql;
 
 import java.util.List;
-import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.atomic.AtomicReference;
 
 import org.apache.kafka.connect.source.SourceRecord;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import io.debezium.config.ConfigurationDefaults;
+import io.debezium.util.Clock;
+import io.debezium.util.Metronome;
+
 /**
  * A component that blocks doing nothing until the connector task is stopped
  *
@@ -23,22 +26,27 @@ public class BlockingReader implements Reader {
     protected final Logger logger = LoggerFactory.getLogger(getClass());
     private final AtomicReference<Runnable> uponCompletion = new AtomicReference<>();
     private final AtomicReference<State> state = new AtomicReference<>();
-
-    private final CountDownLatch latch = new CountDownLatch(1);
+    private final Metronome metronome;
 
     private final String name;
 
     public BlockingReader(String name) {
         this.name = name;
+        this.metronome = Metronome.parker(ConfigurationDefaults.RETURN_CONTROL_INTERVAL, Clock.SYSTEM);
+
     }
 
     /**
-     * Waits indefinitely until the connector task is shut down
+     * Does nothing until the connector task is shut down, but regularly returns control back to Connect in order for being paused if requested.
      */
     @Override
     public List<SourceRecord> poll() throws InterruptedException {
-        latch.await();
-        state.set(State.STOPPING);
+        if (state.get() == State.STOPPED) {
+            return null;
+        }
+
+        metronome.pause();
+        state.compareAndSet(State.RUNNING, State.STOPPING);
 
         return null;
     }
@@ -63,12 +71,7 @@ public void start() {
     @Override
     public void stop() {
         try {
-            try {
-                state.set(State.STOPPED);
-            }
-            finally {
-                latch.countDown();
-            }
+            state.set(State.STOPPED);
 
             // Cleanup Resources
             Runnable completionHandler = uponCompletion.getAndSet(null); // set to null so that we call it only once