I had the same problem. If I recall, the fix is to add the following to your hadoop-site.xml file:
<property> <name>mapred.reduce.copy.backoff</name> <value>5</value> </property> See hadoop-1984 Miles On 18/01/2008, Yunhong Gu1 <[EMAIL PROTECTED]> wrote: > > > Hi, > > If someone knows how to fix the problem described below, please help me > out. Thanks! > > I am testing Hadoop on 2-node cluster and the "reduce" always hangs at > some stage, even if I use different clusters. My OS is Debian Linux kernel > 2.6 (AMD Opteron w/ 4GB Mem). Hadoop verision is 0.15.2. Java version is > 1.5.0_01-b08. > > I simply tried "./bin/hadoop jar hadoop-0.15.2-test.jar mrbench" and when > the map stage finishes, the reduce stage will hang somewhere in the > middle, sometimes at 0%. I also tried any other mapreduce program I can > find in the example jar package but they all hang. > > The log file simply print > 2008-01-18 15:15:50,831 INFO org.apache.hadoop.mapred.TaskTracker: > task_200801181424_0004_r_000000_0 0.0% reduce > copy > > 2008-01-18 15:15:56,841 INFO org.apache.hadoop.mapred.TaskTracker: > task_200801181424_0004_r_000000_0 0.0% reduce > copy > > 2008-01-18 15:16:02,850 INFO org.apache.hadoop.mapred.TaskTracker: > task_200801181424_0004_r_000000_0 0.0% reduce > copy > > > forever. > > The program does work if I start Hadoop only on single node. > > Below is my hadoop-site.xml configuration: > > <configuration> > > <property> > <name>fs.default.name</name> > <value>10.0.0.1:60000</value> > </property> > > <property> > <name>mapred.job.tracker</name> > <value>10.0.0.1:60001</value> > </property> > > <property> > <name>dfs.data.dir</name> > <value>/raid/hadoop/data</value> > </property> > > <property> > <name>mapred.local.dir</name> > <value>/raid/hadoop/mapred</value> > </property> > > <property> > <name>hadoop.tmp.dir</name> > <value>/raid/hadoop/tmp</value> > </property> > > <property> > <name>mapred.child.java.opts</name> > <value>-Xmx1024m</value> > </property> > > <property> > <name>mapred.tasktracker.tasks.maximum</name> > <value>4</value> > </property> > > <!-- > <property> > <name>mapred.map.tasks</name> > <value>7</value> > </property> > > <property> > <name>mapred.reduce.tasks</name> > <value>3</value> > </property> > --> > > <property> > <name>fs.inmemory.size.mb</name> > <value>200</value> > </property> > > <property> > <name>dfs.block.size</name> > <value>134217728</value> > </property> > > <property> > <name>io.sort.factor</name> > <value>100</value> > </property> > > <property> > <name>io.sort.mb</name> > <value>200</value> > </property> > > <property> > <name>io.file.buffer.size</name> > <value>131072</value> > </property> > > </configuration> > >
