Add matrix build of JDK versions

[SuperQ]

Test build on various OpenJDK versions.

Signed-off-by: SuperQ [email protected]

[SuperQ]

Something was broken with the CircleCI webhook. I removed the integration and re-added. Looks like it's building again.

[fstab]

FYI: I added TestContainers as part of my OpenTelemetry exemplars branch to test compatibility with different Java versions (including Java 6, which causes the most problems):

client_java/integration_tests/java_versions/src/test/java/io/prometheus/smoketest/JavaVersionsIT.java

Lines 35 to 43 in 103eb59

	@Parameterized.Parameters(name="{0}")
	public static String[] images() {
	return new String[] {
	"openjdk:11-jre",
	"openjdk:8-jre",
	"ticketfly/java:6",
	"ibmjava:8-jre",
	};
	}

It's not merged yet.

These are two different things: The TestContainers tests make sure that the binary client_java library is compatible with different Java versions, while your change makes sure that you can build the library from source with different versions.

It would be perfectly fine if we require Java 11 to build client_java but release a binary that is compatible with Java 6.

[fstab]

TestContainers use Docker to run tests against Docker containers. In order to make them work with CircleCI, we need to switch to machine images:

client_java/.circleci/config.yml

Lines 1 to 18 in 103eb59

	version: 2
	machine: true
	jobs:
	build:
	machine:
	image: ubuntu-2004:202010-01
	working_directory: ~/circleci-java
	steps:
	- checkout
	- restore_cache:
	key: maven-dependencies-{{ checksum "pom.xml" }}
	- run: mvn clean verify
	- save_cache:
	paths:
	- ~/.m2
	key: maven-dependencies-{{ checksum "pom.xml" }}
	orbs:
	prometheus: prometheus/[email protected]

Not sure if we can convert your PR to use machine images.

[fstab]

I like the idea to have a clear definition which Java versions can be used to build client_java, and I think it's a great idea to have automated tests for that. It would be perfect if we could find a way to do this and still support Docker-based TestContainers.

[SuperQ]

We can run the TestContainers with setup_remote_docker. We can start with any base image like cimg/base.

So basically something like this:

jobs:
  test_containers:
    steps:
    - checkout
    - setup_remote_docker
    - run: docker docker docker

[fstab]

I am hoping to get the OpenTelemetry exemplars branch done this week. I'll try the setup_remote_docker then.

[fstab]

Note: client_java now has a Jetty Jakarta Servlet example (https://github.com/prometheus/client_java/blob/master/simpleclient_servlet_jakarta/src/test/java/io/prometheus/client/exporter/ExampleBenchmark.java) which requires Java 11 to build.