Add first two gitblit specific metrics

Added metrics for:

1. git_garbage_collects_total
2. ldap_sync_latency_seconds.

src/main/java/com/gitblit/service/GarbageCollectorService.java

@@ -23,6 +23,7 @@
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import io.prometheus.client.Counter;
 import org.eclipse.jgit.api.GarbageCollectCommand;
 import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.lib.Repository;
@@ -35,6 +36,8 @@
 import com.gitblit.models.RepositoryModel;
 import com.gitblit.utils.FileUtils;
 
+import static com.gitblit.service.PrometheusMetrics.GIT_GARBAGE_COLLECTS_TOTAL;
+
 /**
  * The Garbage Collector Service handles periodic garbage collection in repositories.
  *
@@ -129,6 +132,9 @@ public void close() {
 		forceClose.set(true);
 	}
 
+	private final Counter garbageCollectsTotal = Counter.build()
+			.name(GIT_GARBAGE_COLLECTS_TOTAL).help(GIT_GARBAGE_COLLECTS_TOTAL).register();
+
 	@Override
 	public void run() {
 		if (!isReady()) {
@@ -200,7 +206,7 @@ public void run() {
 
 					// do the deed
 					gc.call();
-
+					garbageCollectsTotal.inc();
 					garbageCollected = true;
 				}
 			} catch (Exception e) {

src/main/java/com/gitblit/service/LdapSyncService.java

@@ -17,20 +17,25 @@
 
 import java.util.concurrent.atomic.AtomicBoolean;
 
+import io.prometheus.client.Histogram;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import com.gitblit.IStoredSettings;
 import com.gitblit.Keys;
 import com.gitblit.auth.LdapAuthProvider;
 
+import static com.gitblit.service.PrometheusMetrics.LDAP_SYNC_LATENCY_SECONDS;
+
 /**
  * @author Alfred Schmid
  *
  */
 public final class LdapSyncService implements Runnable {
 
 	private final Logger logger = LoggerFactory.getLogger(LdapSyncService.class);
+	private final Histogram ldapSyncLatency = Histogram.build().name(LDAP_SYNC_LATENCY_SECONDS).
+            help(LDAP_SYNC_LATENCY_SECONDS).register();
 
 	private final IStoredSettings settings;
 
@@ -51,12 +56,14 @@ public LdapSyncService(IStoredSettings settings, LdapAuthProvider ldapAuthProvid
 	public void run() {
 		logger.info("Starting user and group sync with ldap service");
 		if (!running.getAndSet(true)) {
+			Histogram.Timer requestTimer = ldapSyncLatency.startTimer();
 			try {
 				ldapAuthProvider.sync();
 			} catch (Exception e) {
 				logger.error("Failed to synchronize with ldap", e);
 			} finally {
 				running.getAndSet(false);
+				requestTimer.observeDuration();
 			}
 		}
 		logger.info("Finished user and group sync with ldap service");

src/main/java/com/gitblit/service/PrometheusMetrics.java

@@ -0,0 +1,10 @@
+package com.gitblit.service;
+
+class PrometheusMetrics {
+
+    /** Number of garbage collects  */
+    static final String GIT_GARBAGE_COLLECTS_TOTAL = "git_garbage_collects_total";
+
+    /** Ldap Sync Latency in second */
+    static final String LDAP_SYNC_LATENCY_SECONDS = "ldap_sync_latency_seconds";
+}