Add basic integration test for OtlpMeterRegistry and the OTel collector

dependencies.gradle

@@ -38,6 +38,7 @@ def VERSIONS = [
         'info.ganglia.gmetric4j:gmetric4j:latest.release',
         'io.prometheus:simpleclient_common:0.15.+',
         'io.prometheus:simpleclient_pushgateway:0.15.+',
+        'io.rest-assured:rest-assured:latest.release',
         'javax.cache:cache-api:latest.release',
         'javax.inject:javax.inject:1',
         'javax.xml.bind:jaxb-api:2.3.+',

implementations/micrometer-registry-otlp/build.gradle

@@ -8,6 +8,9 @@ dependencies {
 
     testImplementation project(':micrometer-test')
     testImplementation 'uk.org.webcompere:system-stubs-jupiter:latest.release'
+    testImplementation 'io.rest-assured:rest-assured'
+    testImplementation 'org.testcontainers:junit-jupiter'
+    testImplementation 'org.awaitility:awaitility'
 }
 
 // new module in 1.9. This should be removed in later branches.

implementations/micrometer-registry-otlp/src/test/java/io/micrometer/registry/otlp/OTelCollectorIntegrationTest.java

@@ -0,0 +1,121 @@
+/*
+ * Copyright 2023 VMware, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package io.micrometer.registry.otlp;
+
+import io.micrometer.core.instrument.*;
+import io.restassured.response.Response;
+import org.junit.jupiter.api.Tag;
+import org.junit.jupiter.api.Test;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.junit.jupiter.Container;
+import org.testcontainers.junit.jupiter.Testcontainers;
+
+import java.time.Duration;
+
+import static io.restassured.RestAssured.given;
+import static org.awaitility.Awaitility.await;
+import static org.hamcrest.Matchers.*;
+import static org.testcontainers.containers.BindMode.READ_ONLY;
+import static uk.org.webcompere.systemstubs.SystemStubs.withEnvironmentVariables;
+
+/**
+ * Integration tests for {@link OtlpMeterRegistry} and the OTel collector
+ *
+ * @author Jonatan Ivanov
+ */
+@Testcontainers
+@Tag("docker")
+class OTelCollectorIntegrationTest {
+
+    private static final String OPENMETRICS_100 = "application/openmetrics-text; version=1.0.0; charset=utf-8";
+
+    private static final String CONFIG_FILE_NAME = "collector-config.yml";
+
+    @Container
+    private final GenericContainer<?> container = new GenericContainer("otel/opentelemetry-collector-contrib")
+        .withCommand("--config=/etc/" + CONFIG_FILE_NAME)
+        .withClasspathResourceMapping(CONFIG_FILE_NAME, "/etc/" + CONFIG_FILE_NAME, READ_ONLY)
+        .withExposedPorts(4318, 9090); // HTTP receiver, Prometheus exporter
+
+    @Test
+    void collectorShouldExportMetrics() throws Exception {
+        MeterRegistry registry = createOtlpMeterRegistryForContainer(container);
+        Counter.builder("test.counter").register(registry).increment(42);
+        Gauge.builder("test.gauge", () -> 12).register(registry);
+        Timer.builder("test.timer").register(registry).record(Duration.ofMillis(123));
+        DistributionSummary.builder("test.distributionsummary").register(registry).record(24);
+
+        await().atMost(Duration.ofSeconds(5))
+            .pollDelay(Duration.ofMillis(100))
+            .pollInterval(Duration.ofMillis(100))
+            .untilAsserted(() -> whenPrometheusScraped().then().body(not(empty())));
+
+        // @formatter:off
+        // tags can vary depending on where you run your tests:
+        //  - IDE: no telemetry_sdk_version tag
+        //  - Gradle: telemetry_sdk_version has the version number
+        whenPrometheusScraped().then().body(
+            containsString("{job=\"test\",service_name=\"test\",telemetry_sdk_language=\"java\",telemetry_sdk_name=\"io.micrometer\""),
+
+            matchesPattern("(?s)^.*test_counter\\{.+} 42\\n.*$"),
+            matchesPattern("(?s)^.*test_gauge\\{.+} 12\\n.*$"),
+
+            matchesPattern("(?s)^.*test_timer_count\\{.+} 1\\n.*$"),
+            matchesPattern("(?s)^.*test_timer_sum\\{.+} 123\\n.*$"),
+            matchesPattern("(?s)^.*test_timer_bucket\\{.+,le=\"\\+Inf\"} 1\\n.*$"),
+
+            matchesPattern("(?s)^.*test_distributionsummary_count\\{.+} 1\\n.*$"),
+            matchesPattern("(?s)^.*test_distributionsummary_sum\\{.+} 24\\n.*$"),
+            matchesPattern("(?s)^.*test_distributionsummary_bucket\\{.+,le=\"\\+Inf\"} 1\\n.*$")
+        );
+        // @formatter:on
+    }
+
+    private OtlpMeterRegistry createOtlpMeterRegistryForContainer(GenericContainer<?> container) throws Exception {
+        return withEnvironmentVariables("OTEL_SERVICE_NAME", "test")
+            .execute(() -> new OtlpMeterRegistry(createOtlpConfigForContainer(container), Clock.SYSTEM));
+    }
+
+    private OtlpConfig createOtlpConfigForContainer(GenericContainer<?> container) {
+        return new OtlpConfig() {
+            @Override
+            public String url() {
+                return String.format("http://%s:%d/v1/metrics", container.getHost(), container.getMappedPort(4318));
+            }
+
+            @Override
+            public Duration step() {
+                return Duration.ofSeconds(1);
+            }
+
+            @Override
+            public String get(String key) {
+                return null;
+            }
+        };
+    }
+
+    private Response whenPrometheusScraped() {
+        // @formatter:off
+        return given()
+            .port(container.getMappedPort(9090))
+            .accept(OPENMETRICS_100)
+            .when()
+            .get("/metrics");
+        // @formatter:on
+    }
+
+}

implementations/micrometer-registry-otlp/src/test/resources/collector-config.yml

@@ -0,0 +1,35 @@
+#
+# Copyright 2023 VMware, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+receivers:
+  otlp:
+    protocols:
+      grpc:
+      http:
+
+exporters:
+  # https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/exporter/prometheusexporter
+  prometheus:
+    endpoint: '0.0.0.0:9090'
+    metric_expiration: 1m
+    enable_open_metrics: true
+    resource_to_telemetry_conversion:
+      enabled: true
+
+service:
+  pipelines:
+    metrics:
+      receivers: [otlp]
+      exporters: [prometheus]