Developing for HDFS in C++, Python on Linux

Environment Setup

Developing locally requires some environment setup.

First, you must install a Hadoop release for Linux, which contains the libhdfs RPC client library

wget -q -O hadoop-$HADOOP_VERSION.tar.gz "$HADOOP_VERSION/hadoop-$HADOOP_VERSION.tar.gz" && 
    tar -zxf hadoop-$HADOOP_VERSION.tar.gz

# You can put this wherever you wish
sudo mv hadoop-$HADOOP_VERSION /opt/hadoop-$HADOOP_VERSION

After installing Hadoop, you must do some environment setup:

# This is where you installed Hadoop
export HADOOP_HOME=/opt/hadoop-$HADOOP_VERSION

# Add Hadoop Java libraries to your CLASSPATH, and 
# add native libraries to LD_LIBRARY_PATH
export CLASSPATH=`$HADOOP_HOME/bin/hadoop classpath --glob`
export HADOOP_OPTS="$HADOOP_OPTS -Djava.library.path=$HADOOP_HOME/lib/native"

# Set ARROW_HOME to the location of your Arrow repository checkout
export CLASSPATH=$ARROW_HOME/integration/hdfs:$CLASSPATH

Running local HDFS cluster, running unit tests

With the above environment setup out of the way, we can spin up a local HDFS cluster with docker-compose:

$ docker-compose up hdfs-data-node-1

This will start the HDFS namenode on localhost with RPC port 9000. The C++ and Python unit tests rely on these environment variables:

export ARROW_HDFS_TEST_HOST=localhost

Now, you should be able to run the unit tests:

# From a C++ source build
$ debug/arrow-io-hdfs-test

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