Support TrafficStatsRateLimitCache
This is used in follow-up changes to rate-limit TrafficStats
get* API calls.
Test: atest ConnectivityCoverageTests:android.net.connectivity.com.android.server.net.TrafficStatsRateLimitCacheTest
Bug: N/A
Change-Id: I91bc71dda3a1b7c0b5525278b3c04d12492972fa
diff --git a/service-t/src/com/android/server/net/TrafficStatsRateLimitCache.java b/service-t/src/com/android/server/net/TrafficStatsRateLimitCache.java
new file mode 100644
index 0000000..8598ac4
--- /dev/null
+++ b/service-t/src/com/android/server/net/TrafficStatsRateLimitCache.java
@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.net;
+
+import android.annotation.NonNull;
+import android.annotation.Nullable;
+import android.net.NetworkStats;
+
+import com.android.internal.annotations.GuardedBy;
+
+import java.time.Clock;
+import java.util.HashMap;
+import java.util.Objects;
+
+/**
+ * A thread-safe cache for storing and retrieving {@link NetworkStats.Entry} objects,
+ * with an adjustable expiry duration to manage data freshness.
+ */
+class TrafficStatsRateLimitCache {
+ private final Clock mClock;
+ private final long mExpiryDurationMs;
+
+ /**
+ * Constructs a new {@link TrafficStatsRateLimitCache} with the specified expiry duration.
+ *
+ * @param clock The {@link Clock} to use for determining timestamps.
+ * @param expiryDurationMs The expiry duration in milliseconds.
+ */
+ TrafficStatsRateLimitCache(@NonNull Clock clock, long expiryDurationMs) {
+ mClock = clock;
+ mExpiryDurationMs = expiryDurationMs;
+ }
+
+ private static class TrafficStatsCacheKey {
+ @Nullable
+ public final String iface;
+ public final int uid;
+
+ TrafficStatsCacheKey(@Nullable String iface, int uid) {
+ this.iface = iface;
+ this.uid = uid;
+ }
+
+ @Override
+ public boolean equals(Object o) {
+ if (this == o) return true;
+ if (!(o instanceof TrafficStatsCacheKey)) return false;
+ TrafficStatsCacheKey that = (TrafficStatsCacheKey) o;
+ return uid == that.uid && Objects.equals(iface, that.iface);
+ }
+
+ @Override
+ public int hashCode() {
+ return Objects.hash(iface, uid);
+ }
+ }
+
+ private static class TrafficStatsCacheValue {
+ public final long timestamp;
+ @NonNull
+ public final NetworkStats.Entry entry;
+
+ TrafficStatsCacheValue(long timestamp, NetworkStats.Entry entry) {
+ this.timestamp = timestamp;
+ this.entry = entry;
+ }
+ }
+
+ @GuardedBy("mMap")
+ private final HashMap<TrafficStatsCacheKey, TrafficStatsCacheValue> mMap = new HashMap<>();
+
+ /**
+ * Retrieves a {@link NetworkStats.Entry} from the cache, associated with the given key.
+ *
+ * @param iface The interface name to include in the cache key. Null if not applicable.
+ * @param uid The UID to include in the cache key. {@code UID_ALL} if not applicable.
+ * @return The cached {@link NetworkStats.Entry}, or null if not found or expired.
+ */
+ @Nullable
+ NetworkStats.Entry get(String iface, int uid) {
+ final TrafficStatsCacheKey key = new TrafficStatsCacheKey(iface, uid);
+ synchronized (mMap) { // Synchronize for thread-safety
+ final TrafficStatsCacheValue value = mMap.get(key);
+ if (value != null && !isExpired(value.timestamp)) {
+ return value.entry;
+ } else {
+ mMap.remove(key); // Remove expired entries
+ return null;
+ }
+ }
+ }
+
+ /**
+ * Stores a {@link NetworkStats.Entry} in the cache, associated with the given key.
+ *
+ * @param iface The interface name to include in the cache key. Null if not applicable.
+ * @param uid The UID to include in the cache key. {@code UID_ALL} if not applicable.
+ * @param entry The {@link NetworkStats.Entry} to store in the cache.
+ */
+ void put(String iface, int uid, @NonNull final NetworkStats.Entry entry) {
+ Objects.requireNonNull(entry);
+ final TrafficStatsCacheKey key = new TrafficStatsCacheKey(iface, uid);
+ synchronized (mMap) { // Synchronize for thread-safety
+ mMap.put(key, new TrafficStatsCacheValue(mClock.millis(), entry));
+ }
+ }
+
+ /**
+ * Clear the cache.
+ */
+ void clear() {
+ synchronized (mMap) {
+ mMap.clear();
+ }
+ }
+
+ private boolean isExpired(long timestamp) {
+ return mClock.millis() > timestamp + mExpiryDurationMs;
+ }
+}
diff --git a/tests/unit/java/com/android/server/net/TrafficStatsRateLimitCacheTest.kt b/tests/unit/java/com/android/server/net/TrafficStatsRateLimitCacheTest.kt
new file mode 100644
index 0000000..27e6f96
--- /dev/null
+++ b/tests/unit/java/com/android/server/net/TrafficStatsRateLimitCacheTest.kt
@@ -0,0 +1,89 @@
+/*
+ * Copyright (C) 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.net
+
+import android.net.NetworkStats
+import com.android.testutils.DevSdkIgnoreRunner
+import java.time.Clock
+import kotlin.test.assertEquals
+import kotlin.test.assertNull
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.mockito.Mockito.mock
+import org.mockito.Mockito.`when`
+
+@RunWith(DevSdkIgnoreRunner::class)
+class TrafficStatsRateLimitCacheTest {
+ companion object {
+ private const val expiryDurationMs = 1000L
+ }
+
+ private val clock = mock(Clock::class.java)
+ private val entry = mock(NetworkStats.Entry::class.java)
+ private val cache = TrafficStatsRateLimitCache(clock, expiryDurationMs)
+
+ @Test
+ fun testGet_returnsEntryIfNotExpired() {
+ cache.put("iface", 2, entry)
+ `when`(clock.millis()).thenReturn(500L) // Set clock to before expiry
+ val result = cache.get("iface", 2)
+ assertEquals(entry, result)
+ }
+
+ @Test
+ fun testGet_returnsNullIfExpired() {
+ cache.put("iface", 2, entry)
+ `when`(clock.millis()).thenReturn(2000L) // Set clock to after expiry
+ assertNull(cache.get("iface", 2))
+ }
+
+ @Test
+ fun testGet_returnsNullForNonExistentKey() {
+ val result = cache.get("otherIface", 99)
+ assertNull(result)
+ }
+
+ @Test
+ fun testPutAndGet_retrievesCorrectEntryForDifferentKeys() {
+ val entry1 = mock(NetworkStats.Entry::class.java)
+ val entry2 = mock(NetworkStats.Entry::class.java)
+
+ cache.put("iface1", 2, entry1)
+ cache.put("iface2", 4, entry2)
+
+ assertEquals(entry1, cache.get("iface1", 2))
+ assertEquals(entry2, cache.get("iface2", 4))
+ }
+
+ @Test
+ fun testPut_overridesExistingEntry() {
+ val entry1 = mock(NetworkStats.Entry::class.java)
+ val entry2 = mock(NetworkStats.Entry::class.java)
+
+ cache.put("iface", 2, entry1)
+ cache.put("iface", 2, entry2) // Put with the same key
+
+ assertEquals(entry2, cache.get("iface", 2))
+ }
+
+ @Test
+ fun testClear() {
+ cache.put("iface", 2, entry)
+ cache.clear()
+ assertNull(cache.get("iface", 2))
+ }
+}