MetricType prefix config for StackdriverMeterRegistry (#3175)

Instead of hard-coding the MetricType prefix, this makes it configurable, as there are multiple options for valid prefixes, and different users may want to use different ones. The default is kept the same as before for backwards compatibility reasons.

Resolves gh-3171

Co-authored-by: Tommy Ludwig <8924140+shakuzen@users.noreply.github.com>

build.gradle

@@ -339,6 +339,8 @@ subprojects {
                     txtOutputFile = file("${project.buildDir}/reports/japi.txt")
                     ignoreMissingClasses = true
                     includeSynthetic = true
+                    // TODO remove methodExcludes when gh-3181 is resolved
+                    methodExcludes = ['io.micrometer.stackdriver.StackdriverConfig#metricTypePrefix()']
                     onlyIf { compatibleVersion != 'SKIP' }
                 }
 

implementations/micrometer-registry-stackdriver/src/main/java/io/micrometer/stackdriver/StackdriverConfig.java

@@ -83,6 +83,16 @@ default boolean useSemanticMetricTypes() {
         return getBoolean(this, "useSemanticMetricTypes").orElse(false);
     }
 
+    /**
+     * Available prefixes defined in
+     * <a href= "https://cloud.google.com/monitoring/custom-metrics#identifier">Google
+     * Cloud documentation</a>
+     * @return a prefix for MetricType
+     */
+    default String metricTypePrefix() {
+        return getString(this, "metricTypePrefix").orElse("custom.googleapis.com/");
+    }
+
     /**
      * Return {@link CredentialsProvider} to use.
      * @return {@code CredentialsProvider} to use

implementations/micrometer-registry-stackdriver/src/main/java/io/micrometer/stackdriver/StackdriverMeterRegistry.java

@@ -426,7 +426,7 @@ private void prePopulateVerifiedDescriptors() {
         }
 
         private String metricType(Meter.Id id, @Nullable String statistic) {
-            StringBuilder metricType = new StringBuilder("custom.googleapis.com/").append(getConventionName(id));
+            StringBuilder metricType = new StringBuilder(config.metricTypePrefix()).append(getConventionName(id));
             if (statistic != null) {
                 metricType.append('/').append(statistic);
             }

implementations/micrometer-registry-stackdriver/src/test/java/io/micrometer/stackdriver/MetricTypePrefixTest.java

@@ -0,0 +1,58 @@
+/*
+ * Copyright 2022 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.stackdriver;
+
+import com.google.monitoring.v3.TimeSeries;
+import io.micrometer.core.instrument.Counter;
+import io.micrometer.core.instrument.MockClock;
+import org.junit.jupiter.api.Test;
+
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class MetricTypePrefixTest {
+
+    private final Map<String, String> config = new HashMap<>(
+            Collections.singletonMap("stackdriver.projectId", "projectId"));
+
+    private final StackdriverMeterRegistry meterRegistry = new StackdriverMeterRegistry(config::get, new MockClock());
+
+    @Test
+    void metricTypePrefixWhenNotConfigured() {
+        StackdriverMeterRegistry.Batch batch = meterRegistry.new Batch();
+        List<TimeSeries> timeSeries = meterRegistry
+                .createCounter(batch, Counter.builder("counter").register(meterRegistry)).collect(Collectors.toList());
+        assertThat(timeSeries).hasSize(1);
+        assertThat(timeSeries.get(0).getMetric().getType()).isEqualTo("custom.googleapis.com/counter");
+    }
+
+    @Test
+    void metricTypePrefixWhenConfigured() {
+        config.put("stackdriver.metricTypePrefix", "external.googleapis.com/user/");
+
+        StackdriverMeterRegistry.Batch batch = meterRegistry.new Batch();
+        List<TimeSeries> timeSeries = meterRegistry
+                .createCounter(batch, Counter.builder("counter").register(meterRegistry)).collect(Collectors.toList());
+        assertThat(timeSeries).hasSize(1);
+        assertThat(timeSeries.get(0).getMetric().getType()).isEqualTo("external.googleapis.com/user/counter");
+    }
+
+}