[FLINK-37601] Remove Unirest dependency in PrometheusReporterTest

[r-sidd]

What is the purpose of the change

Remove Unirest dependency in PrometheusReporterTest

Brief change log

This change removes the dependency on the Unirest HTTP client library. Unirest was only used in PrometheusReporterTest for polling metrics. This commit replaces the single usage of Unirest.get() with the standard Java HttpClient, reducing external dependencies.

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): yes
• The public API, i.e., is any changed class annotated with @Public(Evolving): no
• The serializers: no
• The runtime per-record code paths (performance sensitive): no
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: no
• The S3 file system connector: no

Documentation

• Does this pull request introduce a new feature? no
• If yes, how is the feature documented? not applicable

[flinkbot]

CI report:

• 1ea02b5 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build

[hlteoh37]

Thanks for this contribution @r-sidd ! Library upgrade LGTM.

However, since we only use Unirest in one specific place for testing,
https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-prometheus/src/test/java/org/apache/flink/metrics/prometheus/PrometheusReporterTest.java#L248

Maybe we can consider instead removing the dependency on Unirest altogether by replacing the call Unirest.get() with calls to Java's default HttpClient instead?

    private static final HttpClient HTTP_CLIENT = HttpClient.newHttpClient();

    static HttpResponse<String> pollMetrics(int port) throws IOException, InterruptedException {
        return HTTP_CLIENT.send(
                HttpRequest.newBuilder()
                .uri(URI.create("http://localhost:" + port + "/metrics"))
                .GET()
                .build(), HttpResponse.BodyHandlers.ofString());
    }

A bit more verbose, but reduces dependencies when needed!

[r-sidd]

Thanks for this contribution @r-sidd ! Library upgrade LGTM.

However, since we only use Unirest in one specific place for testing, https://github.com/apache/flink/blob/master/flink-metrics/flink-metrics-prometheus/src/test/java/org/apache/flink/metrics/prometheus/PrometheusReporterTest.java#L248

Maybe we can consider instead removing the dependency on Unirest altogether by replacing the call Unirest.get() with calls to Java's default HttpClient instead?

    private static final HttpClient HTTP_CLIENT = HttpClient.newHttpClient();

    static HttpResponse<String> pollMetrics(int port) throws IOException, InterruptedException {
        return HTTP_CLIENT.send(
                HttpRequest.newBuilder()
                .uri(URI.create("http://localhost:" + port + "/metrics"))
                .GET()
                .build(), HttpResponse.BodyHandlers.ofString());
    }

A bit more verbose, but reduces dependencies when needed!

Yea sure, does makes sense. Do you want me to make these changes in this PR itself? If so do let me know, will make the changes :)

[r-sidd]

Hi @hlteoh37, thanks for the suggestion and the code, I've made the changes and pushed :)

[davidradl]

@r-sidd this last change looks good. Please could you amend the Jira and PR title and text to describe the problem you are now fixing.

[r-sidd]

@r-sidd this last change looks good. Please could you amend the Jira and PR title and text to describe the problem you are now fixing.

Yes sure, let me do that

[r-sidd]

@r-sidd this last change looks good. Please could you amend the Jira and PR title and text to describe the problem you are now fixing.

@davidradl I've updated the Jira and the PR details :)