ARROW-4625: [Flight][Java] Add method to await Flight server terminat…

…ion in Java

Apologies for all the tiny PRs...trying to clean up some small API things we've run into.

Author: David Li <David.M.Li@twosigma.com>

Closes #4110 from lihalite/arrow-4625 and squashes the following commits:

1e0d67f <David Li> Add method to await Flight server termination in Java

java/flight/src/main/java/org/apache/arrow/flight/FlightServer.java

@@ -62,6 +62,11 @@ public int getPort() {
     return server.getPort();
   }
 
+  /** Block until the server shuts down. */
+  public void awaitTermination() throws InterruptedException {
+    server.awaitTermination();
+  }
+
   public void close() throws InterruptedException {
     server.shutdown();
     final boolean terminated = server.awaitTermination(3000, TimeUnit.MILLISECONDS);

java/flight/src/main/java/org/apache/arrow/flight/example/ExampleFlightServer.java

@@ -53,6 +53,10 @@ public void start() throws IOException {
     flightServer.start();
   }
 
+  public void awaitTermination() throws InterruptedException {
+    flightServer.awaitTermination();
+  }
+
   public InMemoryStore getStore() {
     return mem;
   }
@@ -74,8 +78,6 @@ public static void main(String[] args) throws Exception {
         e.printStackTrace();
       }
     }));
-    while (true) {
-      Thread.sleep(30000);
-    }
+    efs.awaitTermination();
   }
 }

java/flight/src/main/java/org/apache/arrow/flight/example/integration/IntegrationTestServer.java

@@ -57,9 +57,7 @@ private void run(String[] args) throws Exception {
       }
     }));
 
-    while (true) {
-      Thread.sleep(30000);
-    }
+    efs.awaitTermination();
   }
 
   public static void main(String[] args) {

java/flight/src/test/java/org/apache/arrow/flight/perf/TestPerf.java

@@ -85,9 +85,6 @@ public void throughput() throws Exception {
                   new Location(FlightTestUtil.LOCALHOST, port)));
           final FlightClient client = new FlightClient(a, server.getLocation());
       ) {
-
-        server.start();
-
         final FlightInfo info = client.getInfo(getPerfFlightDescriptor(50_000_000L, 4095, 2));
         ListeningExecutorService pool = MoreExecutors.listeningDecorator(Executors.newFixedThreadPool(4));
         List<ListenableFuture<Result>> results = info.getEndpoints()
@@ -104,7 +101,7 @@ public void throughput() throws Exception {
 
         double seconds = r.nanos * 1.0d / 1000 / 1000 / 1000;
         System.out.println(String.format(
-            "Transferred %d records totaling %s bytes at %f mb/s. %f record/s. %f batch/s.",
+            "Transferred %d records totaling %s bytes at %f MiB/s. %f record/s. %f batch/s.",
             r.rows,
             r.bytes,
             (r.bytes * 1.0d / 1024 / 1024) / seconds,