Hi, Miles,
Thanks for your information. I applied this but the problem still exists. By the way, when this happens, the CPUs are idle and doing nothing.
Yunhong On Fri, 18 Jan 2008, Miles Osborne wrote:
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>
