DO NOT MERGE IpConnectivityMetrics reads buffer size in settings

Test: IpConnectivityMetricsTest passes. Also manually changed the new
setting and verified the buffer size is as expected after flushing the
buffer.
Bug: 32198637

(cherry pick from commit 05686dbb6b)

Change-Id: Ie7ca1638533479601c5983bb6e54705003561b6c

core/java/android/provider/Settings.java

@@ -7162,6 +7162,13 @@ public final class Settings {
         */
        public static final String MOBILE_DATA_ALWAYS_ON = "mobile_data_always_on";
 
+        /**
+         * Size of the event buffer for IP connectivity metrics.
+         * @hide
+         */
+        public static final String CONNECTIVITY_METRICS_BUFFER_SIZE =
+              "connectivity_metrics_buffer_size";
+
        /** {@hide} */
        public static final String NETSTATS_ENABLED = "netstats_enabled";
        /** {@hide} */

services/core/java/com/android/server/connectivity/IpConnectivityMetrics.java

@@ -22,6 +22,7 @@ import android.net.IIpConnectivityMetrics;
 import android.net.metrics.IpConnectivityLog;
 import android.os.IBinder;
 import android.os.Parcelable;
+import android.provider.Settings;
 import android.text.TextUtils;
 import android.util.Base64;
 import android.util.Log;
@@ -32,6 +33,7 @@ import java.io.FileDescriptor;
 import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.ArrayList;
+import java.util.function.ToIntFunction;
 
 import static com.android.server.connectivity.metrics.IpConnectivityLogClass.IpConnectivityEvent;
 
@@ -44,6 +46,8 @@ final public class IpConnectivityMetrics extends SystemService {
 
     // Default size of the event buffer. Once the buffer is full, incoming events are dropped.
     private static final int DEFAULT_BUFFER_SIZE = 2000;
+    // Maximum size of the event buffer.
+    private static final int MAXIMUM_BUFFER_SIZE = DEFAULT_BUFFER_SIZE * 10;
 
     // Lock ensuring that concurrent manipulations of the event buffer are correct.
     // There are three concurrent operations to synchronize:
@@ -63,11 +67,18 @@ final public class IpConnectivityMetrics extends SystemService {
     @GuardedBy("mLock")
     private int mCapacity;
 
-    public IpConnectivityMetrics(Context ctx) {
+    private final ToIntFunction<Context> mCapacityGetter;
+
+    public IpConnectivityMetrics(Context ctx, ToIntFunction<Context> capacityGetter) {
         super(ctx);
+        mCapacityGetter = capacityGetter;
         initBuffer();
     }
 
+    public IpConnectivityMetrics(Context ctx) {
+        this(ctx, READ_BUFFER_SIZE);
+    }
+
     @Override
     public void onStart() {
         if (DBG) Log.d(TAG, "onStart");
@@ -86,7 +97,7 @@ final public class IpConnectivityMetrics extends SystemService {
 
     @VisibleForTesting
     public int bufferCapacity() {
-        return DEFAULT_BUFFER_SIZE; // TODO: read from config
+        return mCapacityGetter.applyAsInt(getContext());
     }
 
     private void initBuffer() {
@@ -226,4 +237,13 @@ final public class IpConnectivityMetrics extends SystemService {
             getContext().enforceCallingOrSelfPermission(what, "IpConnectivityMetrics");
         }
     };
+
+    private static final ToIntFunction<Context> READ_BUFFER_SIZE = (ctx) -> {
+        int size = Settings.Global.getInt(ctx.getContentResolver(),
+                Settings.Global.CONNECTIVITY_METRICS_BUFFER_SIZE, DEFAULT_BUFFER_SIZE);
+        if (size <= 0) {
+            return DEFAULT_BUFFER_SIZE;
+        }
+        return Math.min(size, MAXIMUM_BUFFER_SIZE);
+    };
 }

services/tests/servicestests/src/com/android/server/connectivity/IpConnectivityMetricsTest.java

@@ -57,7 +57,7 @@ public class IpConnectivityMetricsTest extends TestCase {
 
     public void setUp() {
         MockitoAnnotations.initMocks(this);
-        mService = new IpConnectivityMetrics(mCtx);
+        mService = new IpConnectivityMetrics(mCtx, (ctx) -> 2000);
     }
 
     public void testLoggingEvents() throws Exception {