This page covers how to build Flink {{ site.version }} from sources.
In order to build Flink you need the source code. Either [download the source of a release]({{ site.download_url }}) or [clone the git repository]({{ site.github_url }}).
In addition you need Maven 3 and a JDK (Java Development Kit). Flink requires at least Java 8 to build.
NOTE: Maven 3.3.x can build Flink, but will not properly shade away certain dependencies. Maven 3.2.5 creates the libraries properly. To build unit tests use Java 8u51 or above to prevent failures in unit tests that use the PowerMock runner.
To clone from git, enter:
{% highlight bash %} git clone {{ site.github_url }} {% endhighlight %}
The simplest way of building Flink is by running:
{% highlight bash %} mvn clean install -DskipTests {% endhighlight %}
This instructs Maven (mvn) to first remove all existing builds (clean) and then create a new Flink binary (install).
To speed up the build you can skip tests, QA plugins, and JavaDocs:
{% highlight bash %} mvn clean install -DskipTests -Dfast {% endhighlight %}
The default build adds a Flink-specific JAR for Hadoop 2, to allow using Flink with HDFS and YARN.
Flink shades away some of the libraries it uses, in order to avoid version clashes with user programs that use different versions of these libraries. Among the shaded libraries are Google Guava, Asm, Apache Curator, Apache HTTP Components, Netty, and others.
The dependency shading mechanism was recently changed in Maven and requires users to build Flink slightly differently, depending on their Maven version:
Maven 3.0.x, 3.1.x, and 3.2.x It is sufficient to call mvn clean install -DskipTests in the root directory of Flink code base.
Maven 3.3.x The build has to be done in two steps: First in the base directory, then in the distribution project:
{% highlight bash %} mvn clean install -DskipTests cd flink-dist mvn clean install {% endhighlight %}
Note: To check your Maven version, run mvn --version.
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{% info %} Most users do not need to do this manually. The [download page]({{ site.download_url }}) contains binary packages for common Hadoop versions.
Flink has dependencies to HDFS and YARN which are both dependencies from Apache Hadoop. There exist many different versions of Hadoop (from both the upstream project and the different Hadoop distributions). If you are using a wrong combination of versions, exceptions can occur.
Hadoop is only supported from version 2.4.0 upwards. You can also specify a specific Hadoop version to build against:
{% highlight bash %} mvn clean install -DskipTests -Dhadoop.version=2.6.1 {% endhighlight %}
To build Flink against a vendor specific Hadoop version, issue the following command:
{% highlight bash %} mvn clean install -DskipTests -Pvendor-repos -Dhadoop.version=2.6.1-cdh5.0.0 {% endhighlight %}
The -Pvendor-repos activates a Maven build profile that includes the repositories of popular Hadoop vendors such as Cloudera, Hortonworks, or MapR.
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{% info %} Users that purely use the Java APIs and libraries can ignore this section.
Flink has APIs, libraries, and runtime modules written in Scala. Users of the Scala API and libraries may have to match the Scala version of Flink with the Scala version of their projects (because Scala is not strictly backwards compatible).
Since version 1.7 Flink builds with Scala version 2.11 and 2.12.
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If your home directory is encrypted you might encounter a java.io.IOException: File name too long exception. Some encrypted file systems, like encfs used by Ubuntu, do not allow long filenames, which is the cause of this error.
The workaround is to add:
{% highlight xml %} -Xmax-classfile-name 128 {% endhighlight %}
in the compiler configuration of the pom.xml file of the module causing the error. For example, if the error appears in the flink-yarn module, the above code should be added under the <configuration> tag of scala-maven-plugin. See this issue for more information.
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