Limit camara connection retries to 50Hz (#759)

Author: SamCarlberg

core/src/main/java/edu/wpi/grip/core/sources/CameraSource.java

@@ -9,6 +9,7 @@
 import edu.wpi.grip.core.sockets.SocketHints;
 import edu.wpi.grip.core.util.ExceptionWitness;
 import edu.wpi.grip.core.util.service.AutoRestartingService;
+import edu.wpi.grip.core.util.service.CooldownRestartPolicy;
 import edu.wpi.grip.core.util.service.LoggingListener;
 import edu.wpi.grip.core.util.service.RestartableService;
 
@@ -185,7 +186,8 @@ public void copyNewMat(Mat matToCopy) {
                   public void updatesComplete() {
                     eventBus.post(new SourceHasPendingUpdateEvent(CameraSource.this));
                   }
-                }, getExceptionWitness()::clearException));
+                }, getExceptionWitness()::clearException),
+            new CooldownRestartPolicy(20, TimeUnit.MILLISECONDS)); // 50Hz retry rate
 
     this.cameraService.addListener(new Listener() {
       @Override

core/src/main/java/edu/wpi/grip/core/util/service/AutoRestartingService.java

@@ -15,6 +15,8 @@
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 
@@ -67,7 +69,7 @@ public AutoRestartingService(final Supplier<S> factory,
    * @param factory This should always supply a new instance of the service that can be restarted.
    */
   public AutoRestartingService(final Supplier<S> factory) {
-    this(factory, () -> true);
+    this(factory, ServiceRestartPolicy.IMMEDIATE);
   }
 
   /**
@@ -203,8 +205,18 @@ private final class RestartListener extends Listener {
 
     @Override
     public void failed(final State from, final Throwable failure) {
-      if (policy.shouldRestart()) {
+      final long delay = policy.restartDelay();
+      if (delay <= 0) {
         startAsync(false);
+      } else {
+        try {
+          Thread.sleep(TimeUnit.NANOSECONDS.toMillis(delay));
+          startAsync(false);
+        } catch (InterruptedException e) {
+          Logger.getLogger(AutoRestartingService.class.getName())
+              .log(Level.SEVERE, "Could not sleep for " + delay + "ns", e);
+          Thread.currentThread().interrupt();
+        }
       }
     }
   }

core/src/main/java/edu/wpi/grip/core/util/service/CooldownRestartPolicy.java

@@ -46,8 +46,8 @@ public void notifyRestart() {
   }
 
   @Override
-  public boolean shouldRestart() {
-    return stopwatch.elapsed(timeUnit) > interval;
+  public long restartDelay() {
+    return timeUnit.toNanos(interval) - stopwatch.elapsed(TimeUnit.NANOSECONDS);
   }
 
 }

core/src/main/java/edu/wpi/grip/core/util/service/ServiceRestartPolicy.java

@@ -6,13 +6,22 @@
 @FunctionalInterface
 public interface ServiceRestartPolicy {
 
+  /**
+   * A restart policy that has a service restart immediately.
+   */
+  ServiceRestartPolicy IMMEDIATE = () -> 0L;
+
   /**
    * Policy might want to keep track of when the latest restarts have happened.
    */
   default void notifyRestart() {
-        /* no-op */
+    /* no-op */
   }
 
-  boolean shouldRestart();
+  /**
+   * When the service should restart, in nanoseconds from the point when the service failed. A value
+   * less than or equal to zero means an immediate restart.
+   */
+  long restartDelay();
 
 }

core/src/test/java/edu/wpi/grip/core/util/service/AutoRestartingServiceTest.java

@@ -77,9 +77,10 @@ public void tearDown() {
 
   @Test
   public void testStartStopMultipleTimes() throws InterruptedException {
-    final RecordingSupplier recordingSupplier = new RecordingSupplier(WaitOnRunService::new);
+    final RecordingSupplier<WaitOnRunService> recordingSupplier =
+        new RecordingSupplier<>(WaitOnRunService::new);
     final AutoRestartingService<WaitOnRunService> restartingService =
-        new AutoRestartingService<>(recordingSupplier, () -> false);
+        new AutoRestartingService<>(recordingSupplier, ServiceRestartPolicy.IMMEDIATE);
 
     assertFalse("Start should not have been called", restartingService.getDelegate().startUpCalled);
 
@@ -117,9 +118,10 @@ public void testStartStopMultipleTimes() throws InterruptedException {
 
   @Test
   public void testCallStartTwiceFails() throws InterruptedException {
-    final RecordingSupplier recordingSupplier = new RecordingSupplier<>(WaitOnRunService::new);
+    final RecordingSupplier<WaitOnRunService> recordingSupplier =
+        new RecordingSupplier<>(WaitOnRunService::new);
     final AutoRestartingService<WaitOnRunService> restartingService =
-        new AutoRestartingService<>(recordingSupplier, () -> false);
+        new AutoRestartingService<>(recordingSupplier, ServiceRestartPolicy.IMMEDIATE);
 
     restartingService.startAsync();
     try {
@@ -141,10 +143,10 @@ public void testCallStartTwiceFails() throws InterruptedException {
 
   @Test
   public void testServiceStaysRunningIfThrowOnRunning() throws InterruptedException {
-    final RecordingSupplier recordingSupplier =
+    final RecordingSupplier<WaitThenThrowOnRunService> recordingSupplier =
         new RecordingSupplier<>(WaitThenThrowOnRunService::new);
     final AutoRestartingService<WaitThenThrowOnRunService> restartingService =
-        new AutoRestartingService<>(recordingSupplier, () -> true);
+        new AutoRestartingService<>(recordingSupplier, ServiceRestartPolicy.IMMEDIATE);
 
     @SuppressWarnings("PMD.PrematureDeclaration")
     final Service initialDelegate = restartingService.getDelegate();
@@ -182,9 +184,10 @@ public void testServiceStaysRunningIfThrowOnRunning() throws InterruptedExceptio
 
   @Test
   public void testListenerGetsAddedToRunningService() throws InterruptedException {
-    final RecordingSupplier recordingSupplier = new RecordingSupplier(() -> new WaitOnRunService());
+    final RecordingSupplier<WaitOnRunService> recordingSupplier =
+        new RecordingSupplier<>(WaitOnRunService::new);
     final AutoRestartingService<WaitOnRunService> restartingService =
-        new AutoRestartingService(recordingSupplier, () -> false);
+        new AutoRestartingService<>(recordingSupplier, ServiceRestartPolicy.IMMEDIATE);
     final boolean[] startingListener = {false};
     final boolean[] stoppingListener = {false};
 

ui/src/test/java/edu/wpi/grip/ui/components/StartStoppableButtonTest.java

@@ -2,6 +2,7 @@
 
 import edu.wpi.grip.core.util.service.AutoRestartingService;
 import edu.wpi.grip.core.util.service.RestartableService;
+import edu.wpi.grip.core.util.service.ServiceRestartPolicy;
 
 import com.google.common.util.concurrent.AbstractIdleService;
 
@@ -37,7 +38,7 @@ protected void startUp() {
       protected void shutDown() {
         /* no-op */
       }
-    }, () -> false);
+    }, ServiceRestartPolicy.IMMEDIATE);
     startStoppableButton = new StartStoppableButton(restartableService);
     Scene scene = new Scene(startStoppableButton, 800, 600);
     stage.setScene(scene);