Compatibility

Given Avatica’s client-server model, it is no surprise that compatibility is important to the users and developers of Apache Calcite Avatica. This document defines what guarantees are made by Avatica with respect to compatibility between Avatica client and server across versions. This document is still a work in progress with many areas still requiring definition. Contributions are always welcome.

Avatica Technology Compatibility Kit (TCK)

The Avatica TCK project is a framework designed to automatically test an Avatica client against an Avatica server. A collection of JUnit tests, a YAML configuration file, and a Ruby script defines the TCK. The JUnit tests invoke specific portions of both the client and server components of Avatica to verify that they work as expected. The Ruby script uses the YAML configuration file to define the set of client and server version pairs to run the JUnit tests against.

In the YAML configuration file, a name (e.g. 1.6.0) and the following three items define an Avatica version:

  1. A filesystem path to an Avatica client jar (e.g. groupId=org.apache.calcite.avatica, artifactId=avatica)
  2. A URL to a running instance of an Avatica server
  3. A JDBC URL template to the Avatica server for the Avatica client JDBC driver.

Users of the TCK define the collection of versions (defined by the above information) and the location of the avatica-tck jar by a YAML configuration file. An example YAML configuration file is bundled with the project.

Traditionally, Avatica does not provide any implementation of the Avatica server as the value in Avatica is recognized in the integrating project (e.g. Apache Drill or Apache Phoenix). However, for the purposes of compatibility testing, it makes sense that Avatica provides a standalone server instance. A new artifact is introduced to Avatica with the original TCK codebase called avatica-standalone-server. This artifact is a runnable jar (e.g. java -jar) which starts an instance of the Avatica server on a random port using the in-memory HSQLDB database. This artifacts makes it extremely simple to start a version of the Avatica server for the specific version of Avatica to be tested.

As mentioned, the Ruby script is the entry point for the TCK. Invoking the Ruby script which prints a summary of testing each specified version against itself and all other versions in the YAML configuration. An example summary is presented below which is the result of testing versions 1.6.0, 1.7.1 and 1.8.0-SNAPSHOT:

``` Summary:

Identity test scenarios (ran 3)

Testing identity for version v1.6.0: Passed Testing identity for version v1.7.1: Passed Testing identity for version v1.8.0-SNAPSHOT: Failed

All test scenarios (ran 6)

Testing client v1.6.0 against server v1.7.1: Passed Testing client v1.6.0 against server v1.8.0-SNAPSHOT: Failed Testing client v1.7.1 against server v1.6.0: Passed Testing client v1.7.1 against server v1.8.0-SNAPSHOT: Failed Testing client v1.8.0-SNAPSHOT against server v1.6.0: Failed Testing client v1.8.0-SNAPSHOT against server v1.7.1: Failed ```

It is not always expected that all tested version-pairs will pass unless the test is written with specific knowledge about past bugs in Avatica itself. While Avatica tries to handle all of these edge cases implicitly, it is not always feasible or desirable to do so. Adding new test cases is as easy as writing a JUnit test case in the TCK module, but there is presently no automation around verifying the test cases as a part of the Maven build.

For more information on running this TCK, including specific instructions for running the TCK, reference the provided README file.