From 79732e171600186c50a2dc2a43249116aef8125e Mon Sep 17 00:00:00 2001
From: Mohammad Arshad <arshad@apache.org>
Date: Sun, 30 Aug 2020 20:59:39 +0530
Subject: [PATCH] HBASE-24940: runCatalogJanitor() API should return -1 to
 indicate already running status

---
 .../org/apache/hadoop/hbase/client/Admin.java |  2 +-
 .../hadoop/hbase/master/CatalogJanitor.java   |  4 ++-
 .../hbase/master/TestCatalogJanitor.java      | 25 +++++++++++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java b/hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java
index 40db1c1ac044..f4fd14a12429 100644
--- a/hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java
+++ b/hbase-client/src/main/java/org/apache/hadoop/hbase/client/Admin.java
@@ -903,7 +903,7 @@ default boolean normalize() throws IOException {
   /**
    * Ask for a scan of the catalog table.
    *
-   * @return the number of entries cleaned
+   * @return the number of entries cleaned. Returns -1 if previous run is in progress.
    * @throws IOException if a remote or network exception occurs
    */
   int runCatalogJanitor() throws IOException;
diff --git a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/CatalogJanitor.java b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/CatalogJanitor.java
index e991f3f8ef37..b01b7d937700 100644
--- a/hbase-server/src/main/java/org/apache/hadoop/hbase/master/CatalogJanitor.java
+++ b/hbase-server/src/main/java/org/apache/hadoop/hbase/master/CatalogJanitor.java
@@ -162,13 +162,15 @@ private static boolean isRIT(AssignmentManager am) {
    * Run janitorial scan of catalog <code>hbase:meta</code> table looking for
    * garbage to collect.
    * @return How many items gc'd whether for merge or split.
+   *   Returns -1 if previous scan is in progress.
    */
   int scan() throws IOException {
     int gcs = 0;
     try {
       if (!alreadyRunning.compareAndSet(false, true)) {
         LOG.debug("CatalogJanitor already running");
-        return gcs;
+        // -1 indicates previous scan is in progress
+        return -1;
       }
       this.lastReport = scanForReport();
       if (!this.lastReport.isEmpty()) {
diff --git a/hbase-server/src/test/java/org/apache/hadoop/hbase/master/TestCatalogJanitor.java b/hbase-server/src/test/java/org/apache/hadoop/hbase/master/TestCatalogJanitor.java
index fe08abfec13b..a9f6968c2fcf 100644
--- a/hbase-server/src/test/java/org/apache/hadoop/hbase/master/TestCatalogJanitor.java
+++ b/hbase-server/src/test/java/org/apache/hadoop/hbase/master/TestCatalogJanitor.java
@@ -25,6 +25,8 @@
 import static org.mockito.Mockito.spy;
 
 import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import java.util.NavigableMap;
 import java.util.Objects;
@@ -550,6 +552,29 @@ public void testDuplicateHFileResolution() throws Exception {
     assertArchiveEqualToOriginal(storeFiles, archivedStoreFiles, fs, true);
   }
 
+  @Test
+  public void testAlreadyRunningStatus() throws Exception {
+    int numberOfThreads = 2;
+    List<Integer> gcValues = new ArrayList<>();
+    Thread[] threads = new Thread[numberOfThreads];
+    for (int i = 0; i < numberOfThreads; i++) {
+      threads[i] = new Thread(() -> {
+        try {
+          gcValues.add(janitor.scan());
+        } catch (IOException e) {
+          throw new RuntimeException(e);
+        }
+      });
+    }
+    for (int i = 0; i < numberOfThreads; i++) {
+      threads[i].start();
+    }
+    for (int i = 0; i < numberOfThreads; i++) {
+      threads[i].join();
+    }
+    assertTrue("One janitor.scan() call should have returned -1", gcValues.contains(-1));
+  }
+
   private FileStatus[] addMockStoreFiles(int count, MasterServices services, Path storedir)
     throws IOException {
     // get the existing store files