diff --git a/service-t/src/com/android/server/net/NetworkStatsObservers.java b/service-t/src/com/android/server/net/NetworkStatsObservers.java
index c51a886dcc..df4e7f5e65 100644
--- a/service-t/src/com/android/server/net/NetworkStatsObservers.java
+++ b/service-t/src/com/android/server/net/NetworkStatsObservers.java
@@ -44,6 +44,7 @@ import android.util.Log;
 import android.util.SparseArray;
 
 import com.android.internal.annotations.VisibleForTesting;
+import com.android.net.module.util.PerUidCounter;
 
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -63,10 +64,17 @@ class NetworkStatsObservers {
 
     private static final int DUMP_USAGE_REQUESTS_COUNT = 200;
 
+    // The maximum number of request allowed per uid before an exception is thrown.
+    @VisibleForTesting
+    static final int MAX_REQUESTS_PER_UID = 100;
+
     // All access to this map must be done from the handler thread.
     // indexed by DataUsageRequest#requestId
     private final SparseArray<RequestInfo> mDataUsageRequests = new SparseArray<>();
 
+    // Request counters per uid, this is thread safe.
+    private final PerUidCounter mDataUsageRequestsPerUid = new PerUidCounter(MAX_REQUESTS_PER_UID);
+
     // Sequence number of DataUsageRequests
     private final AtomicInteger mNextDataUsageRequestId = new AtomicInteger();
 
@@ -89,8 +97,9 @@ class NetworkStatsObservers {
         DataUsageRequest request = buildRequest(context, inputRequest, callingUid);
         RequestInfo requestInfo = buildRequestInfo(request, callback, callingPid, callingUid,
                 callingPackage, accessLevel);
-
         if (LOG) Log.d(TAG, "Registering observer for " + requestInfo);
+        mDataUsageRequestsPerUid.incrementCountOrThrow(callingUid);
+
         getHandler().sendMessage(mHandler.obtainMessage(MSG_REGISTER, requestInfo));
         return request;
     }
@@ -189,6 +198,7 @@ class NetworkStatsObservers {
 
         if (LOG) Log.d(TAG, "Unregistering " + requestInfo);
         mDataUsageRequests.remove(request.requestId);
+        mDataUsageRequestsPerUid.decrementCountOrThrow(callingUid);
         requestInfo.unlinkDeathRecipient();
         requestInfo.callCallback(NetworkStatsManager.CALLBACK_RELEASED);
     }
diff --git a/service/src/com/android/server/ConnectivityService.java b/service/src/com/android/server/ConnectivityService.java
index 67a64d564b..d3a267af45 100644
--- a/service/src/com/android/server/ConnectivityService.java
+++ b/service/src/com/android/server/ConnectivityService.java
@@ -1187,6 +1187,7 @@ public class ConnectivityService extends IConnectivityManager.Stub
     /**
      * Keeps track of the number of requests made under different uids.
      */
+    // TODO: Remove the hack and use com.android.net.module.util.PerUidCounter instead.
     public static class PerUidCounter {
         private final int mMaxCountPerUid;
 
diff --git a/tests/unit/java/com/android/server/net/NetworkStatsObserversTest.java b/tests/unit/java/com/android/server/net/NetworkStatsObserversTest.java
index 13a85e875d..e8c9637fa6 100644
--- a/tests/unit/java/com/android/server/net/NetworkStatsObserversTest.java
+++ b/tests/unit/java/com/android/server/net/NetworkStatsObserversTest.java
@@ -32,6 +32,7 @@ import static android.text.format.DateUtils.MINUTE_IN_MILLIS;
 import static com.android.testutils.DevSdkIgnoreRuleKt.SC_V2;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThrows;
 import static org.junit.Assert.assertTrue;
 import static org.mockito.Matchers.any;
 import static org.mockito.Matchers.anyInt;
@@ -64,6 +65,7 @@ import org.mockito.Mock;
 import org.mockito.Mockito;
 import org.mockito.MockitoAnnotations;
 
+import java.util.ArrayList;
 import java.util.Objects;
 
 /**
@@ -184,6 +186,51 @@ public class NetworkStatsObserversTest {
         assertEquals(THRESHOLD_BYTES, request2.thresholdInBytes);
     }
 
+    @Test
+    public void testRegister_limit() throws Exception {
+        final DataUsageRequest inputRequest = new DataUsageRequest(
+                DataUsageRequest.REQUEST_ID_UNSET, sTemplateWifi, THRESHOLD_BYTES);
+
+        // Register maximum requests for red.
+        final ArrayList<DataUsageRequest> redRequests = new ArrayList<>();
+        for (int i = 0; i < NetworkStatsObservers.MAX_REQUESTS_PER_UID; i++) {
+            final DataUsageRequest returnedRequest =
+                    mStatsObservers.register(mContext, inputRequest, mUsageCallback,
+                            PID_RED, UID_RED, PACKAGE_RED, NetworkStatsAccess.Level.DEVICE);
+            redRequests.add(returnedRequest);
+            assertTrue(returnedRequest.requestId > 0);
+        }
+
+        // Verify request exceeds the limit throws.
+        assertThrows(IllegalStateException.class, () ->
+                mStatsObservers.register(mContext, inputRequest, mUsageCallback,
+                    PID_RED, UID_RED, PACKAGE_RED, NetworkStatsAccess.Level.DEVICE));
+
+        // Verify another uid is not affected.
+        final ArrayList<DataUsageRequest> blueRequests = new ArrayList<>();
+        for (int i = 0; i < NetworkStatsObservers.MAX_REQUESTS_PER_UID; i++) {
+            final DataUsageRequest returnedRequest =
+                    mStatsObservers.register(mContext, inputRequest, mUsageCallback,
+                            PID_BLUE, UID_BLUE, PACKAGE_BLUE, NetworkStatsAccess.Level.DEVICE);
+            blueRequests.add(returnedRequest);
+            assertTrue(returnedRequest.requestId > 0);
+        }
+
+        // Again, verify request exceeds the limit throws for the 2nd uid.
+        assertThrows(IllegalStateException.class, () ->
+                mStatsObservers.register(mContext, inputRequest, mUsageCallback,
+                        PID_RED, UID_RED, PACKAGE_RED, NetworkStatsAccess.Level.DEVICE));
+
+        // Unregister all registered requests. Note that exceptions cannot be tested since
+        // unregister is handled in the handler thread.
+        for (final DataUsageRequest request : redRequests) {
+            mStatsObservers.unregister(request, UID_RED);
+        }
+        for (final DataUsageRequest request : blueRequests) {
+            mStatsObservers.unregister(request, UID_BLUE);
+        }
+    }
+
     @Test
     public void testUnregister_unknownRequest_noop() throws Exception {
         DataUsageRequest unknownRequest = new DataUsageRequest(