Merge branch 'stable-2.14' into stable-2.15

* stable-2.14:
  Add option to exclude metrics

Change-Id: I91aaeaf3e0d9c7bb2e58a03c13f4e2ef7d77f651

src/main/java/com/googlesource/gerrit/plugins/metricsreporters/GerritPrometheusExporter.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/metricsreporters/GerritPrometheusExporter.java b/src/main/java/com/googlesource/gerrit/plugins/metricsreporters/GerritPrometheusExporter.java
index 8cd6c56..217badb 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/metricsreporters/GerritPrometheusExporter.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/metricsreporters/GerritPrometheusExporter.java
@@ -13,13 +13,20 @@
 // limitations under the License.
 package com.googlesource.gerrit.plugins.metricsreporters;
 
+import com.codahale.metrics.Metric;
+import com.codahale.metrics.MetricFilter;
 import com.codahale.metrics.MetricRegistry;
+import com.google.gerrit.extensions.annotations.PluginName;
+import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.inject.Inject;
 import com.google.inject.Singleton;
 import io.prometheus.client.CollectorRegistry;
 import io.prometheus.client.dropwizard.DropwizardExports;
 import io.prometheus.client.exporter.MetricsServlet;
 import java.io.IOException;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
 import javax.servlet.ServletException;
 import javax.servlet.ServletRequest;
 import javax.servlet.ServletResponse;
@@ -29,14 +36,38 @@
 @Singleton
 public class GerritPrometheusExporter extends MetricsServlet {
   CapabilityChecker capabilityChecker;
+  private static final String EXCLUDE_KEY = "excludeMetrics";
 
   @Inject
-  public GerritPrometheusExporter(MetricRegistry registry, CapabilityChecker capabilityChecker) {
+  public GerritPrometheusExporter(
+      MetricRegistry registry,
+      CapabilityChecker capabilityChecker,
+      PluginConfigFactory cfgFactory,
+      @PluginName String pluginName) {
     this.capabilityChecker = capabilityChecker;
 
+    /* Copy the registry to avoid filtering the global one */
+    MetricRegistry filteredRegistry = new MetricRegistry();
+    filteredRegistry.registerAll(registry);
+
+    Set<String> excludedMetrics = new HashSet<>();
+    excludedMetrics.addAll(
+        Arrays.asList(cfgFactory.getFromGerritConfig(pluginName).getStringList(EXCLUDE_KEY)));
+
+    excludedMetrics.forEach(
+        exclude -> {
+          filteredRegistry.removeMatching(
+              new MetricFilter() {
+                @Override
+                public boolean matches(String name, Metric metric) {
+                  return name.matches(exclude);
+                }
+              });
+        });
+
     // Hook the Dropwizard registry into the Prometheus registry
     // via the DropwizardExports collector.
-    CollectorRegistry.defaultRegistry.register(new DropwizardExports(registry));
+    CollectorRegistry.defaultRegistry.register(new DropwizardExports(filteredRegistry));
   }
 
   @Override

src/main/resources/Documentation/config.md

diff --git a/src/main/resources/Documentation/config.md b/src/main/resources/Documentation/config.md
index fa180cf..265a6c7 100644
--- a/src/main/resources/Documentation/config.md
+++ b/src/main/resources/Documentation/config.md
@@ -11,6 +11,12 @@
 It is possible to allow anonymous access to the metrics by giving the capability
 to the 'Anonymous Users' group.
 
+plugin.@PLUGIN@.excludeMetrics
+:   String used to exclude metrics from the report. It can be specified multiple times.
+    Parsed as regular expression. Note, ^ and $ are automatically added around the string.
+    By default no metric is excluded.
+    For example, to exclude all cache metrics, use: `excludeMetrics = cache.*`
+
 [Back to @PLUGIN@ documentation index][index]
 
 [index]: index.html
\ No newline at end of file