Transport is a framework for writing performant user-defined functions (UDFs) that are portable across a variety of engines including Apache Spark, Apache Hive, and Presto. UDFs written with Transport are also capable of directly processing data stored in formats such as Avro. With Transport, developers only need to implement their UDF logic once using the Transport API. Transport then takes care of translating the UDF to a native version targeted at a specific engine or format. Currently, the Transport framework is capable of generating engine-artifacts for Spark, Hive, and Presto, and format-artifacts for Avro. Further details on Transport can be found in this LinkedIn Engineering blog post.
This is an example of what it takes to define a Transportable UDF. It is simple and quite self-explanatory.
public class MapFromTwoArraysFunction extends StdUDF2<StdArray, StdArray, StdMap> implements TopLevelStdUDF {
private StdType _mapType;
@Override
public List<String> getInputParameterSignatures() {
return ImmutableList.of(
"array(K)",
"array(V)"
);
}
@Override
public String getOutputParameterSignature() {
return "map(K,V)";
}
@Override
public void init(StdFactory stdFactory) {
super.init(stdFactory);
_mapType = getStdFactory().createStdType(getOutputParameterSignature());
}
@Override
public StdMap eval(StdArray a1, StdArray a2) {
if (a1.size() != a2.size()) {
return null;
}
StdMap map = getStdFactory().createMap(_mapType);
for (int i = 0; i < a1.size(); i++) {
map.put(a1.get(i), a2.get(i));
}
return map;
}
@Override
public String getFunctionName() {
return "map_from_two_arrays";
}
@Override
public String getFunctionDescription() {
return "A function to create a map out of two arrays";
}
}
In the example above, StdMap
and StdArray
are interfaces that
provide high-level map and array operations to their
objects. Depending on the engine where this UDF is executed, those
interfaces are implemented differently to deal with native data types
used by that engine. getStdFactory()
is a method used to create
objects that conform to a given data type (such as a map whose keys
are of the type of elements in the first array and values are of the
type of elements in the second array). StdUDF2
is an abstract class
to express a UDF that takes two parameters. It is parametrized by the
UDF input types and the UDF output type. A more detailed documentation
of the API usage can be found in the Transportable UDF API user
guide.
Clone the repository:
git clone https://github.com/linkedin/transport.git
Change directory to transport
:
cd transport
Build:
gradle build
This project requires Java 1.8.0_151
or higher.
Either set JAVA_HOME
to the home of an appropriate version and use gradle build
as described above, or use the gradlew
and set org.gradle.java.home
to the Java home
of an appropriate version:
./gradlew -Dorg.gradle.java.home=/path/to/java/home build
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