Observability Dev Services with Grafana OTel LGTM

@Path("/api")
public class SimpleEndpoint {
    private static final Logger log = Logger.getLogger(SimpleEndpoint.class);

    @Inject
    MeterRegistry registry;

    @PostConstruct
    public void start() {
        Gauge.builder("xvalue", arr, a -> arr[0])
                .baseUnit("X")
                .description("Some random x")
                .tag("my_key", "x")
                .register(registry);
    }

    // ...
}

public class LgtmTestBase {

    @ConfigProperty(name = "grafana.endpoint")
    String endpoint; // NOTE -- injected Grafana endpoint!

    @Test
    public void testTracing() {
        String response = RestAssured.get("/api/poke?f=100").body().asString();
        System.out.println(response);
        GrafanaClient client = new GrafanaClient(endpoint, "admin", "admin");
        Awaitility.await().atMost(61, TimeUnit.SECONDS).until(
                client::user,
                u -> "admin".equals(u.login));
        Awaitility.await().atMost(61, TimeUnit.SECONDS).until(
                () -> client.query("xvalue_X"),
                result -> !result.data.result.isEmpty());
    }

}

// simple Grafana HTTP client

public class GrafanaClient {
    private static final ObjectMapper MAPPER = new ObjectMapper();

    private final String url;
    private final String username;
    private final String password;

    public GrafanaClient(String url, String username, String password) {
        this.url = url;
        this.username = username;
        this.password = password;
    }

    private <T> void handle(
            String path,
            Function<HttpRequest.Builder, HttpRequest.Builder> method,
            HttpResponse.BodyHandler<T> bodyHandler,
            BiConsumer<HttpResponse<T>, T> consumer) {
        try {
            String credentials = username + ":" + password;
            String encodedCredentials = Base64.getEncoder().encodeToString(credentials.getBytes());

            HttpClient httpClient = HttpClient.newHttpClient();
            HttpRequest.Builder builder = HttpRequest.newBuilder()
                    .uri(URI.create(url + path))
                    .header("Authorization", "Basic " + encodedCredentials);
            HttpRequest request = method.apply(builder).build();

            HttpResponse<T> response = httpClient.send(request, bodyHandler);
            int code = response.statusCode();
            if (code < 200 || code > 299) {
                throw new IllegalStateException("Bad response: " + code + " >> " + response.body());
            }
            consumer.accept(response, response.body());
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new RuntimeException(e);
        }
    }

    public User user() {
        AtomicReference<User> ref = new AtomicReference<>();
        handle(
                "/api/user",
                HttpRequest.Builder::GET,
                HttpResponse.BodyHandlers.ofString(),
                (r, b) -> {
                    try {
                        User user = MAPPER.readValue(b, User.class);
                        ref.set(user);
                    } catch (JsonProcessingException e) {
                        throw new UncheckedIOException(e);
                    }
                });
        return ref.get();
    }

    public QueryResult query(String query) {
        AtomicReference<QueryResult> ref = new AtomicReference<>();
        handle(
                "/api/datasources/proxy/1/api/v1/query?query=" + query,
                HttpRequest.Builder::GET,
                HttpResponse.BodyHandlers.ofString(),
                (r, b) -> {
                    try {
                        QueryResult result = MAPPER.readValue(b, QueryResult.class);
                        ref.set(result);
                    } catch (JsonProcessingException e) {
                        throw new UncheckedIOException(e);
                    }
                });
        return ref.get();
    }
}