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From "Du, Fan" <fan...@intel.com>
Subject How does Mesos parse hadoop command??
Date Wed, 04 Nov 2015 08:34:02 GMT
Hi Mesos experts

I setup a small mesos cluster with 1 master and 6 slaves,
and deploy hdfs on the same cluster topology, both with root user role.

#cat spark-1.5.1-bin-hadoop2.6/conf/spark-env.sh
export MESOS_NATIVE_JAVA_LIBRARY=/usr/local/lib/libmesos.so
export 
JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.91-2.6.2.1.el7_1.x86_64/jre/
export SPARK_EXECUTOR_URI=hdfs://test/spark-1.5.1-bin-hadoop2.6.tgz

When I run a simple SparkPi test
#export MASTER=mesos://Mesos_Master_IP:5050
#spark-1.5.1-bin-hadoop2.6/bin/run-example SparkPi 10000

I got this on slaves:

I1104 22:24:02.238471 14518 fetcher.cpp:414] Fetcher Info: 
{"cache_directory":"\/tmp\/mesos\/fetch\/slaves\/556b49c1-7e6a-4f99-b320-c3f0c849e836-S6\/root","items":[{"action":"BYPASS_CACHE","uri":{"extract":true,"value":"hdfs:\/\/test\/spark-1.5.1-bin-hadoop2.6.tgz"}}],"sandbox_directory":"\/ws\/mesos\/slaves\/556b49c1-7e6a-4f99-b320-c3f0c849e836-S6\/frameworks\/556b49c1-7e6a-4f99-b320-c3f0c849e836-0003\/executors\/556b49c1-7e6a-4f99-b320-c3f0c849e836-S6\/runs\/9ec70f41-67d5-4a95-999f-933f3aa9e261","user":"root"}
I1104 22:24:02.240910 14518 fetcher.cpp:369] Fetching URI 
'hdfs://test/spark-1.5.1-bin-hadoop2.6.tgz'
I1104 22:24:02.240931 14518 fetcher.cpp:243] Fetching directly into the 
sandbox directory
I1104 22:24:02.240952 14518 fetcher.cpp:180] Fetching URI 
'hdfs://test/spark-1.5.1-bin-hadoop2.6.tgz'
E1104 22:24:02.245264 14518 shell.hpp:90] Command 'hadoop version 2>&1' 
failed; this is the output:
sh: hadoop: command not found
Failed to fetch 'hdfs://test/spark-1.5.1-bin-hadoop2.6.tgz': Skipping 
fetch with Hadoop client: Failed to execute 'hadoop version 2>&1'; the 
command was either not found or exited with a non-zero exit status: 127
Failed to synchronize with slave (it's probably exited)


As for "sh: hadoop: command not found", it indicates when mesos executes 
"hadoop version" command,
it cannot find any valid hadoop command, but actually when I log into 
the slave, "hadoop vesion"
runs well, because I update hadoop path into PATH env.

cat ~/.bashrc
export 
JAVA_HOME=/usr/lib/jvm/java-1.7.0-openjdk-1.7.0.91-2.6.2.1.el7_1.x86_64/jre/
export HADOOP_PREFIX=/opt/hadoop-2.6.0
export HADOOP_HOME=$HADOOP_PREFIX
export HADOOP_COMMON_HOME=$HADOOP_PREFIX
export HADOOP_CONF_DIR=$HADOOP_PREFIX/etc/hadoop
export HADOOP_HDFS_HOME=$HADOOP_PREFIX
export HADOOP_MAPRED_HOME=$HADOOP_PREFIX
export HADOOP_YARN_HOME=$HADOOP_PREFIX
export PATH=$PATH:$HADOOP_PREFIX/sbin:$HADOOP_PREFIX/bin

I also try to set hadoop_home when launching mesos-slave, hmm, no luck, 
the slave
complains it can find JAVA_HOME env when executing "hadoop version"

Finally I check the Mesos code where this error happens, it looks quite 
straight forward.

  ./src/hdfs/hdfs.hpp
  44 // HTTP GET on hostname:port and grab the information in the
  45 // <title>...</title> (this is the best hack I can think of to get
  46 // 'fs.default.name' given the tools available).
  47 struct HDFS
  48 {
  49   // Look for `hadoop' first where proposed, otherwise, look for
  50   // HADOOP_HOME, otherwise, assume it's on the PATH.
  51   explicit HDFS(const std::string& _hadoop)
  52     : hadoop(os::exists(_hadoop)
  53              ? _hadoop
  54              : (os::getenv("HADOOP_HOME").isSome()
  55                 ? path::join(os::getenv("HADOOP_HOME").get(), 
"bin/hadoop")
  56                 : "hadoop")) {}
  57
  58   // Look for `hadoop' in HADOOP_HOME or assume it's on the PATH.
  59   HDFS()
  60     : hadoop(os::getenv("HADOOP_HOME").isSome()
  61              ? path::join(os::getenv("HADOOP_HOME").get(), 
"bin/hadoop")
  62              : "hadoop") {}
  63
  64   // Check if hadoop client is available at the path that was set.
  65   // This can be done by executing `hadoop version` command and
  66   // checking for status code == 0.
  67   Try<bool> available()
  68   {
  69     Try<std::string> command = strings::format("%s version", hadoop);
  70
  71     CHECK_SOME(command);
  72
  73     // We are piping stderr to stdout so that we can see the error (if
  74     // any) in the logs emitted by `os::shell()` in case of failure.
  75     Try<std::string> out = os::shell(command.get() + " 2>&1");
  76
  77     if (out.isError()) {
  78       return Error(out.error());
  79     }
  80
  81     return true;
  82   }

It puzzled me for a while, am I missing something obviously?
Thanks in advance.


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