When this was happening to us, there was a block replication error and
one node was in an endless loop trying to replicate a block to another
node which would not accept it. In our case most of the cluster was idle
but a cpu on the machine trying send the block was heavily used.
We never were able to isolate the cause, and it stopped happening for us
when we upgraded to 0.15.1
---
Attributor is hiring Hadoop Wranglers, contact if interested.
Yunhong Gu1 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>
