From 5393109ee7bda9c8a820990028692a9f2ab8c418 Mon Sep 17 00:00:00 2001
From: John Zhao <yunjzhao@ebay.com>
Date: Tue, 15 Mar 2016 15:03:54 -0700
Subject: [PATCH] KYLIN-1497 make three <class>.getInstance thread safe

---
 .../main/java/org/apache/kylin/dict/DictionaryManager.java    | 10 ++++++----
 .../java/org/apache/kylin/dict/lookup/SnapshotManager.java    | 10 ++++++----
 .../src/main/java/org/apache/kylin/job/dao/ExecutableDao.java | 11 ++++++-----
 3 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/core-dictionary/src/main/java/org/apache/kylin/dict/DictionaryManager.java b/core-dictionary/src/main/java/org/apache/kylin/dict/DictionaryManager.java
index ce04b55..b7c95da 100644
--- a/core-dictionary/src/main/java/org/apache/kylin/dict/DictionaryManager.java
+++ b/core-dictionary/src/main/java/org/apache/kylin/dict/DictionaryManager.java
@@ -62,10 +62,12 @@ public class DictionaryManager {
     public static DictionaryManager getInstance(KylinConfig config) {
         DictionaryManager r = CACHE.get(config);
         if (r == null) {
-            r = new DictionaryManager(config);
-            CACHE.put(config, r);
-            if (CACHE.size() > 1) {
-                logger.warn("More than one singleton exist");
+            synchronized (DictionaryManager.class) {
+                r = CACHE.get(config);
+                if (r == null) {
+                    r = new DictionaryManager(config);
+                    CACHE.put(config, r);
+                }
             }
         }
         return r;
diff --git a/core-dictionary/src/main/java/org/apache/kylin/dict/lookup/SnapshotManager.java b/core-dictionary/src/main/java/org/apache/kylin/dict/lookup/SnapshotManager.java
index 53bf60d..9562b8d 100644
--- a/core-dictionary/src/main/java/org/apache/kylin/dict/lookup/SnapshotManager.java
+++ b/core-dictionary/src/main/java/org/apache/kylin/dict/lookup/SnapshotManager.java
@@ -44,10 +44,12 @@ public class SnapshotManager {
     public static SnapshotManager getInstance(KylinConfig config) {
         SnapshotManager r = SERVICE_CACHE.get(config);
         if (r == null) {
-            r = new SnapshotManager(config);
-            SERVICE_CACHE.put(config, r);
-            if (SERVICE_CACHE.size() > 1) {
-                logger.warn("More than one singleton exist");
+            synchronized (SnapshotManager.class) {
+                r = SERVICE_CACHE.get(config);
+                if (r == null) {
+                    r = new SnapshotManager(config);
+                    SERVICE_CACHE.put(config, r);
+                }
             }
         }
         return r;
diff --git a/core-job/src/main/java/org/apache/kylin/job/dao/ExecutableDao.java b/core-job/src/main/java/org/apache/kylin/job/dao/ExecutableDao.java
index 1869ca7..d063ee7 100644
--- a/core-job/src/main/java/org/apache/kylin/job/dao/ExecutableDao.java
+++ b/core-job/src/main/java/org/apache/kylin/job/dao/ExecutableDao.java
@@ -49,12 +49,13 @@ public class ExecutableDao {
     public static ExecutableDao getInstance(KylinConfig config) {
         ExecutableDao r = CACHE.get(config);
         if (r == null) {
-            r = new ExecutableDao(config);
-            CACHE.put(config, r);
-            if (CACHE.size() > 1) {
-                logger.warn("More than one singleton exist");
+            synchronized (ExecutableDao.class) {
+                r = CACHE.get(config);
+                if (r == null) {
+                    r = new ExecutableDao(config);
+                    CACHE.put(config, r);
+                }
             }
-
         }
         return r;
     }
-- 
2.5.4 (Apple Git-61)