Avro: IDL & RPC

Avro IDL & RPC

Other serialization formats such as Thrift, Protocol Buffers, and others provide an Interface Definition Language(IDL). IDL allows the user to express a schema similar to you can write code in a programming language, rather than using JSON to specify the schema. Avro offers an equivalent: Avro IDL.

The Avro IDL comes with its own rules and syntax. It appear similar to popular languages like Java, C++, and Python. We’ll present a simple example demonstrating the use of IDL. More details can be found here. Each Avro IDL file defines a single Avro Protocol. When compiled, the output is a JSON format Avro Protocol file with extension .avpr. We can represent a car record in IDL format as follows:

/**
 * Car schema expressed in Avro IDL as a protocol
 */
@namespace("io.datajek")
protocol CarProtocol {

  record Car {
    string make;
    string model;
    int year;
    int horsepower;
  }

string carToString(Car car);
}

Once we define the .avdl file, we can convert it into an .avpr file like this:

java -jar avro-tools-1.9.1.jar idl carProtocol.avdl

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