Android: Synchronizing on the use of NsdManager.resolveService() (#23515)
* Android: Synchronizing on the use of NsdManager.resolveService()
* Incorporating comments from andy31415@
diff --git a/src/platform/android/java/chip/platform/NsdManagerServiceResolver.java b/src/platform/android/java/chip/platform/NsdManagerServiceResolver.java
index a3a4ecf..11b6241 100644
--- a/src/platform/android/java/chip/platform/NsdManagerServiceResolver.java
+++ b/src/platform/android/java/chip/platform/NsdManagerServiceResolver.java
@@ -25,9 +25,13 @@
import android.os.Handler;
import android.os.Looper;
import android.util.Log;
+import androidx.annotation.Nullable;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
public class NsdManagerServiceResolver implements ServiceResolver {
private static final String TAG = NsdManagerServiceResolver.class.getSimpleName();
@@ -37,8 +41,15 @@
private Handler mainThreadHandler;
private List<NsdManager.RegistrationListener> registrationListeners = new ArrayList<>();
private final CopyOnWriteArrayList<String> mMFServiceName = new CopyOnWriteArrayList<>();
+ @Nullable private final NsdManagerResolverAvailState nsdManagerResolverAvailState;
- public NsdManagerServiceResolver(Context context) {
+ /**
+ * @param context application context
+ * @param nsdManagerResolverAvailState Passing NsdManagerResolverAvailState allows
+ * NsdManagerServiceResolver to synchronize on the usage of NsdManager's resolveService() API
+ */
+ public NsdManagerServiceResolver(
+ Context context, @Nullable NsdManagerResolverAvailState nsdManagerResolverAvailState) {
this.nsdManager = (NsdManager) context.getSystemService(Context.NSD_SERVICE);
this.mainThreadHandler = new Handler(Looper.getMainLooper());
@@ -46,6 +57,11 @@
((WifiManager) context.getSystemService(Context.WIFI_SERVICE))
.createMulticastLock("chipMulticastLock");
this.multicastLock.setReferenceCounted(true);
+ this.nsdManagerResolverAvailState = nsdManagerResolverAvailState;
+ }
+
+ public NsdManagerServiceResolver(Context context) {
+ this(context, null);
}
@Override
@@ -78,10 +94,18 @@
Log.d(TAG, "resolve: Timing out");
if (multicastLock.isHeld()) {
multicastLock.release();
+
+ if (nsdManagerResolverAvailState != null) {
+ nsdManagerResolverAvailState.signalFree();
+ }
}
}
};
+ if (nsdManagerResolverAvailState != null) {
+ nsdManagerResolverAvailState.acquireResolver();
+ }
+
this.nsdManager.resolveService(
serviceInfo,
new NsdManager.ResolveListener() {
@@ -95,6 +119,10 @@
if (multicastLock.isHeld()) {
multicastLock.release();
+
+ if (nsdManagerResolverAvailState != null) {
+ nsdManagerResolverAvailState.signalFree();
+ }
}
mainThreadHandler.removeCallbacks(timeoutRunnable);
}
@@ -120,10 +148,15 @@
if (multicastLock.isHeld()) {
multicastLock.release();
+
+ if (nsdManagerResolverAvailState != null) {
+ nsdManagerResolverAvailState.signalFree();
+ }
}
mainThreadHandler.removeCallbacks(timeoutRunnable);
}
});
+
mainThreadHandler.postDelayed(timeoutRunnable, RESOLVE_SERVICE_TIMEOUT);
}
@@ -223,4 +256,51 @@
registrationListeners.clear();
mMFServiceName.clear();
}
+
+ /**
+ * The Android NsdManager calls back on the NsdManager.ResolveListener with a
+ * FAILURE_ALREADY_ACTIVE(3) if any application code calls resolveService() on it while the
+ * resolve operation is already active (from another call made previously). An object of
+ * NsdManagerResolverAvailState allows NsdManagerServiceResolver to synchronize on the usage of
+ * NsdManager's resolveService() API
+ */
+ public static class NsdManagerResolverAvailState {
+ private static final String TAG = NsdManagerResolverAvailState.class.getSimpleName();
+
+ private Lock lock = new ReentrantLock();
+ private Condition condition = lock.newCondition();
+ private boolean busy = false;
+
+ /**
+ * Waits if the NsdManager is already busy with resolving a service. Otherwise, it marks it as
+ * busy and returns
+ */
+ public void acquireResolver() {
+ lock.lock();
+ try {
+ while (busy) {
+ Log.d(TAG, "Found NsdManager Resolver busy, waiting");
+ condition.await();
+ }
+ Log.d(TAG, "Found NsdManager Resolver free, using it and marking it as busy");
+ busy = true;
+ } catch (InterruptedException e) {
+ Log.e(TAG, "Failure while waiting for condition: " + e);
+ } finally {
+ lock.unlock();
+ }
+ }
+
+ /** Signals the NsdManager resolver as free */
+ public void signalFree() {
+ lock.lock();
+ try {
+ Log.d(TAG, "Signaling NsdManager Resolver as free");
+ busy = false;
+ condition.signal();
+ } finally {
+ lock.unlock();
+ }
+ }
+ }
}
