Added (undocumented) /v3/_gc endpoint.

Triggering full GCs should not be required. Only for testing.

cdstar-rest/src/main/java/de/gwdg/cdstar/rest/v3/ApiV3Module.java

@@ -14,6 +14,7 @@ public class ApiV3Module implements RestBlueprint {
 		cfg.install(new ServiceEndpoint());
 		cfg.install(new ServiceHealthEndpoint());
 		cfg.install(new ServiceMetricsEndpoint());
+		cfg.install(new ServiceGCEndpoint());
 		cfg.install(new TransactionEndpoint());
 		cfg.install(new VaultEndpoint());
 		cfg.install(new ArchiveEndpoint());

cdstar-rest/src/main/java/de/gwdg/cdstar/rest/v3/ServiceGCEndpoint.java

+package de.gwdg.cdstar.rest.v3;
+
+import java.io.IOException;
+import java.lang.management.ManagementFactory;
+import java.lang.management.MemoryMXBean;
+import java.lang.management.MemoryUsage;
+
+import de.gwdg.cdstar.rest.api.RestBlueprint;
+import de.gwdg.cdstar.rest.api.RestConfig;
+import de.gwdg.cdstar.rest.api.RestContext;
+import de.gwdg.cdstar.rest.utils.SessionHelper;
+import de.gwdg.cdstar.runtime.client.auth.ServicePermission;
+
+/**
+ * Undocumented API to trigger a full GC run.
+ */
+public class ServiceGCEndpoint implements RestBlueprint {
+	@Override
+	public void configure(RestConfig cfg) {
+		cfg.route("/_gc").POST(this::handlePostGC);
+	}
+
+	public GCResult handlePostGC(RestContext ctx) throws IOException {
+		SessionHelper.ensurePermitted(ctx, ServicePermission.HEALTH.asStringPermission());
+		return new GCResult(ManagementFactory.getMemoryMXBean());
+	}
+
+	public class GCResult {
+		public final MemoryUsage before;
+		public final MemoryUsage after;
+		public final double time;
+
+		public GCResult(MemoryMXBean mem) {
+			before = mem.getHeapMemoryUsage();
+			final long t1 = System.nanoTime();
+			System.gc();
+			time = ((double) (System.nanoTime() - t1)) / 1000000000;
+			after = mem.getHeapMemoryUsage();
+		}
+	}
+}