From 8032206236b3045526217933cdb76a904888fac0 Mon Sep 17 00:00:00 2001
From: Michael Stack <stack@apache.org>
Date: Tue, 28 Sep 2010 05:29:29 +0000
Subject: [PATCH] HBASE-2646 Compaction requests should be prioritized to
 prevent blocking; remove of hbase-3038 added by mistake

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1002020 13f79535-47bb-0310-9956-ffa450edef68
---
 .../wal/SequenceFileLogReader.java            | 43 ++++---------------
 1 file changed, 9 insertions(+), 34 deletions(-)

diff --git a/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogReader.java b/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogReader.java
index 114a8ef2ddd..4332f9382b8 100644
--- a/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogReader.java
+++ b/src/main/java/org/apache/hadoop/hbase/regionserver/wal/SequenceFileLogReader.java
@@ -20,7 +20,7 @@
 
 package org.apache.hadoop.hbase.regionserver.wal;
 
-import java.io.FilterInputStream;
+import java.io.EOFException;
 import java.io.IOException;
 import java.lang.Class;
 import java.lang.reflect.Constructor;
@@ -78,43 +78,18 @@ public class SequenceFileLogReader implements HLog.Reader {
         this.length = l;
       }
 
-      // This section can be confusing.  It is specific to how HDFS works.
-      // Let me try to break it down.  This is the problem:
-      //
-      //  1. HDFS DataNodes update the NameNode about a filename's length 
-      //     on block boundaries or when a file is closed. Therefore, 
-      //     if an RS dies, then the NN's fs.getLength() can be out of date
-      //  2. this.in.available() would work, but it returns int &
-      //     therefore breaks for files > 2GB (happens on big clusters)
-      //  3. DFSInputStream.getFileLength() gets the actual length from the DNs
-      //  4. DFSInputStream is wrapped 2 levels deep : this.in.in
-      //
-      // So, here we adjust getPos() using getFileLength() so the
-      // SequenceFile.Reader constructor (aka: first invocation) comes out 
-      // with the correct end of the file:
-      //         this.end = in.getPos() + length;
       @Override
       public long getPos() throws IOException {
         if (this.firstGetPosInvocation) {
           this.firstGetPosInvocation = false;
-          long adjust = 0;
-
-          try {
-            Field fIn = FilterInputStream.class.getDeclaredField("in");
-            fIn.setAccessible(true);
-            Object realIn = fIn.get(this.in);
-            long realLength = ((Long)realIn.getClass().
-                getMethod("getFileLength", new Class<?> []{}).
-                invoke(realIn, new Object []{})).longValue();
-            assert(realLength >= this.length);
-            adjust = realLength - this.length;
-          } catch(Exception e) {
-            SequenceFileLogReader.LOG.warn(
-              "Error while trying to get accurate file length.  " +
-              "Truncation / data loss may occur if RegionServers die.", e);
-          }
-
-          return adjust + super.getPos();
+          // Tell a lie.  We're doing this just so that this line up in
+          // SequenceFile.Reader constructor comes out with the correct length
+          // on the file:
+          //         this.end = in.getPos() + length;
+          long available = this.in.available();
+          // Length gets added up in the SF.Reader constructor so subtract the
+          // difference.  If available < this.length, then return this.length.
+          return available >= this.length? available - this.length: this.length;
         }
         return super.getPos();
       }