From 9f7ecc2b02817eda8642fd0c8a5dc3e25be8d520 Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Sat, 29 May 2010 17:21:18 +0000
Subject: [PATCH] HBASE-2625 Make testDynamicBloom()'s randomness deterministic

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@949423 13f79535-47bb-0310-9956-ffa450edef68
---
 CHANGES.txt                                   |  2 ++
 .../hbase/util/TestByteBloomFilter.java       | 22 +++++++++++++++----
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/CHANGES.txt b/CHANGES.txt
index f36384f7de6..52b6dc2c359 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -1260,6 +1260,8 @@ Release 0.20.0 - Tue Sep  8 12:53:05 PDT 2009
    HBASE-1743  [debug tool] Add regionsInTransition list to ClusterStatus
                detailed output
    HBASE-1772  Up the default ZK session timeout from 30seconds to 60seconds
+   HBASE-2625  Make testDynamicBloom()'s "randomness" deterministic
+               (Nicolas Spiegelberg via Stack)
 
   OPTIMIZATIONS
    HBASE-1412  Change values for delete column and column family in KeyValue
diff --git a/src/test/java/org/apache/hadoop/hbase/util/TestByteBloomFilter.java b/src/test/java/org/apache/hadoop/hbase/util/TestByteBloomFilter.java
index 77e9e3ecc5d..a082af68779 100644
--- a/src/test/java/org/apache/hadoop/hbase/util/TestByteBloomFilter.java
+++ b/src/test/java/org/apache/hadoop/hbase/util/TestByteBloomFilter.java
@@ -26,6 +26,7 @@ import java.io.DataInputStream;
 import java.io.DataOutputStream;
 import java.nio.ByteBuffer;
 import java.util.BitSet;
+import java.util.Random;
 
 import junit.framework.TestCase;
 
@@ -150,13 +151,23 @@ public class TestByteBloomFilter extends TestCase {
         Hash.MURMUR_HASH);
     bf1.allocBloom();
     
+    long seed = System.currentTimeMillis();
+    Random r = new Random(seed);
+    System.out.println("seed = " + seed);
+    
     for (int i = 0; i < keyInterval*4; ++i) { // add
-      if (Math.random() > 0.5) {
+      if (r.nextBoolean()) {
         bf1.add(Bytes.toBytes(i));
         valid.set(i);
+        
+        // we assume only 2 blooms in this test, so exit before a 3rd is made
+        if (bf1.getKeyCount() == 2000) {
+          break;
+        }
       }
     }
-    assertTrue(2 <= bf1.bloomCount() && bf1.bloomCount() <= 3);
+    assertTrue(2 <= bf1.bloomCount());
+    System.out.println("keys added = " + bf1.getKeyCount());
 
     // test serialization/deserialization
     ByteArrayOutputStream metaOut = new ByteArrayOutputStream();
@@ -178,8 +189,11 @@ public class TestByteBloomFilter extends TestCase {
       }
     }
     
-    // note that actualErr = err * bloomCount
-    // error rate should be roughly: (keyInterval*2)*(err*2), allow some tolerance
+    // Dynamic Blooms are a little sneaky.  The error rate currently isn't 
+    // 'err', it's err * bloomCount.  bloomCount == 2000/1000 == 2 in this case
+    // So, the actual error rate should be roughly: 
+    //    (keyInterval*2) * err * bloomCount
+    // allow some tolerance
     System.out.println("False positives: " + falsePositives);
     assertTrue(falsePositives <= (keyInterval*5)*err); 
   }