Limit the number of tests run concurrently (#12572)

Change-Id: I015e92ccc9be963543032c14dd9d051bcba58e53

uitest/src/com/vaadin/tests/tb3/ParallelScheduler.java

@@ -20,7 +20,6 @@ import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Executors;
 import java.util.concurrent.Future;
 
 import org.junit.runners.model.RunnerScheduler;
@@ -33,8 +32,18 @@ import org.junit.runners.model.RunnerScheduler;
  */
 public class ParallelScheduler implements RunnerScheduler {
     private final List<Future<Object>> fResults = new ArrayList<Future<Object>>();
+    private ExecutorService fService;
 
-    private final ExecutorService fService = Executors.newCachedThreadPool();
+    /**
+     * Creates a parallel scheduler which will use the given executor service
+     * when submitting test jobs.
+     * 
+     * @param service
+     *            The service to use for tests
+     */
+    public ParallelScheduler(ExecutorService service) {
+        fService = service;
+    }
 
     @Override
     public void schedule(final Runnable childStatement) {

uitest/src/com/vaadin/tests/tb3/TB3Runner.java

@@ -19,6 +19,8 @@ package com.vaadin.tests.tb3;
 import java.lang.reflect.Method;
 import java.util.LinkedList;
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 
 import org.junit.Test;
 import org.junit.runners.BlockJUnit4ClassRunner;
@@ -40,9 +42,21 @@ import com.vaadin.tests.tb3.AbstractTB3Test.BrowserUtil;
  */
 public class TB3Runner extends BlockJUnit4ClassRunner {
 
+    /**
+     * This is the total limit of actual JUnit test instances run in parallel
+     */
+    private static final int MAX_CONCURRENT_TESTS = 50;
+
+    /**
+     * This is static so it is shared by all tests running concurrently on the
+     * same machine and thus can limit the number of threads in use.
+     */
+    private static final ExecutorService service = Executors
+            .newFixedThreadPool(MAX_CONCURRENT_TESTS);
+
     public TB3Runner(Class<?> klass) throws InitializationError {
         super(klass);
-        setScheduler(new ParallelScheduler());
+        setScheduler(new ParallelScheduler(service));
     }
 
     @Override

uitest/src/com/vaadin/tests/tb3/TB3TestSuite.java

@@ -28,6 +28,8 @@ import java.util.Collections;
 import java.util.Comparator;
 import java.util.Enumeration;
 import java.util.List;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.jar.JarEntry;
 
 import org.junit.runners.Suite;
@@ -41,11 +43,24 @@ import org.junit.runners.model.InitializationError;
  */
 public class TB3TestSuite extends Suite {
 
+    /**
+     * This only restricts the number of test suites running concurrently. The
+     * number of tests to run concurrently are configured in {@link TB3Runner}.
+     */
+    private static final int MAX_CONCURRENT_TEST_SUITES = 20;
+
+    /**
+     * This is static so it is shared by all test suites running concurrently on
+     * the same machine and thus can limit the number of threads in use.
+     */
+    private final ExecutorService service = Executors
+            .newFixedThreadPool(MAX_CONCURRENT_TEST_SUITES);
+
     public TB3TestSuite(Class<?> klass,
             Class<? extends AbstractTB3Test> baseClass, String basePackage,
             String[] ignorePackages) throws InitializationError {
         super(klass, findTests(baseClass, basePackage, ignorePackages));
-        setScheduler(new ParallelScheduler());
+        setScheduler(new ParallelScheduler(service));
     }
 
     /**