ref(core): Measure the hostname cache TTL on a monotonic ticker (JAVA-579)

CHANGELOG.md

@@ -37,6 +37,7 @@
 ### Internal
 
 - Deprecate `AndroidCurrentDateProvider.getInstance()` in favor of `MonotonicTicker`, which counts time spent in deep sleep and cannot be confused with the epoch-based `CurrentDateProvider` ([#6103](https://github.com/getsentry/sentry-java/pull/6103))
+- Measure the hostname cache TTL on a monotonic ticker, so that a device time change no longer shortens or extends it ([#6100](https://github.com/getsentry/sentry-java/pull/6100))
 
 ## 8.56.0
 

sentry/src/main/java/io/sentry/HostnameCache.java

@@ -1,5 +1,8 @@
 package io.sentry;
 
+import io.sentry.time.Deadline;
+import io.sentry.time.JavaMonotonicTicker;
+import io.sentry.time.MonotonicTicker;
 import io.sentry.util.AutoClosableReentrantLock;
 import io.sentry.util.Objects;
 import java.net.InetAddress;
@@ -21,9 +24,9 @@
  * Time sensitive cache in charge of keeping track of the hostname. The {@code
  * InetAddress.getLocalHost().getCanonicalHostName()} call can be quite expensive and could be
  * called for the creation of each {@link SentryEvent}. This system will prevent unnecessary costs
- * by keeping track of the hostname for a period defined during the construction. For performance
- * purposes, the operation of retrieving the hostname will automatically fail after a period of time
- * defined by {@link #GET_HOSTNAME_TIMEOUT} without result.
+ * by keeping track of the hostname for a period defined by {@link #HOSTNAME_CACHE_DURATION}. For
+ * performance purposes, the operation of retrieving the hostname will automatically fail after a
+ * period of time defined by {@link #GET_HOSTNAME_TIMEOUT} without result.
  *
  * <p>HostnameCache is a singleton and its instance should be obtained through {@link
  * HostnameCache#getInstance()}.
@@ -42,14 +45,13 @@ public final class HostnameCache {
   private static final @NotNull AutoClosableReentrantLock staticLock =
       new AutoClosableReentrantLock();
 
-  /** Time for which the cache is kept. */
-  private final long cacheDuration;
+  private final @NotNull MonotonicTicker ticker;
 
   /** Current value for hostname (might change over time). */
   @Nullable private volatile String hostname;
 
-  /** Time at which the cache should expire. */
-  private volatile long expirationTimestamp;
+  /** When the cached hostname goes stale. */
+  private volatile @NotNull Deadline cacheFreshUntil;
 
   /** Whether a cache update thread is currently running or not. */
   private final @NotNull AtomicBoolean updateRunning = new AtomicBoolean(false);
@@ -71,25 +73,25 @@ public final class HostnameCache {
   }
 
   private HostnameCache() {
-    this(HOSTNAME_CACHE_DURATION);
-  }
-
-  HostnameCache(long cacheDuration) {
     // avoid method refs on Android due to some issues with older AGP setups
     // noinspection Convert2MethodRef
-    this(cacheDuration, () -> InetAddress.getLocalHost());
+    this(() -> InetAddress.getLocalHost(), JavaMonotonicTicker.getInstance());
   }
 
   /**
    * Sets up a cache for the hostname.
    *
-   * @param cacheDuration cache duration in milliseconds.
    * @param getLocalhost a callback to obtain the localhost address - this is mostly here because of
    *     testability
+   * @param ticker the ticker the cache lifetime is measured on
    */
-  HostnameCache(long cacheDuration, final @NotNull Callable<InetAddress> getLocalhost) {
-    this.cacheDuration = cacheDuration;
+  HostnameCache(
+      final @NotNull Callable<InetAddress> getLocalhost, final @NotNull MonotonicTicker ticker) {
     this.getLocalhost = Objects.requireNonNull(getLocalhost, "getLocalhost is required");
+    this.ticker = Objects.requireNonNull(ticker, "ticker is required");
+    // Nothing resolved yet, so the cache is stale rather than fresh until updateCache says
+    // otherwise.
+    this.cacheFreshUntil = Deadline.passed(ticker);
     // A single thread executor whose worker thread times out while idle, so no thread is kept
     // alive between the infrequent cache refreshes.
     final @NotNull ThreadPoolExecutor executor =
@@ -122,8 +124,7 @@ boolean isClosed() {
    */
   @Nullable
   public String getHostname() {
-    if (expirationTimestamp < System.currentTimeMillis()
-        && updateRunning.compareAndSet(false, true)) {
+    if (cacheFreshUntil.hasPassed() && updateRunning.compareAndSet(false, true)) {
       updateCache();
     }
 
@@ -136,7 +137,8 @@ private void updateCache() {
         () -> {
           try {
             hostname = getLocalhost.call().getCanonicalHostName();
-            expirationTimestamp = System.currentTimeMillis() + cacheDuration;
+            cacheFreshUntil =
+                Deadline.after(ticker, HOSTNAME_CACHE_DURATION, TimeUnit.MILLISECONDS);
           } finally {
             updateRunning.set(false);
           }
@@ -156,7 +158,7 @@ private void updateCache() {
   }
 
   private void handleCacheUpdateFailure() {
-    expirationTimestamp = System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(1);
+    cacheFreshUntil = Deadline.after(ticker, 1, TimeUnit.SECONDS);
   }
 
   private static final class HostnameCacheThreadFactory implements ThreadFactory {

sentry/src/test/java/io/sentry/HostnameCacheTest.kt

@@ -2,6 +2,7 @@ package io.sentry
 
 import com.google.common.truth.Truth.assertThat
 import io.sentry.test.getProperty
+import io.sentry.time.TestMonotonicTicker
 import java.net.InetAddress
 import java.util.concurrent.ThreadPoolExecutor
 import java.util.concurrent.TimeUnit
@@ -14,7 +15,7 @@ class HostnameCacheTest {
   private fun getSut(): HostnameCache {
     val address = mock<InetAddress>()
     whenever(address.canonicalHostName).thenReturn("myhost")
-    return HostnameCache(TimeUnit.HOURS.toMillis(1)) { address }
+    return HostnameCache({ address }, TestMonotonicTicker())
   }
 
   @Test
@@ -23,6 +24,22 @@ class HostnameCacheTest {
     assertThat(cache.hostname).isEqualTo("myhost")
   }
 
+  @Test
+  fun `hostname is re-resolved only once the cache duration has elapsed`() {
+    val ticker = TestMonotonicTicker()
+    val address = mock<InetAddress>()
+    whenever(address.canonicalHostName).thenReturn("first", "second")
+    val cache = HostnameCache({ address }, ticker)
+
+    assertThat(cache.hostname).isEqualTo("first")
+
+    ticker.advance(4, TimeUnit.HOURS)
+    assertThat(cache.hostname).isEqualTo("first")
+
+    ticker.advance(1, TimeUnit.HOURS)
+    assertThat(cache.hostname).isEqualTo("second")
+  }
+
   @Test
   fun `worker thread times out while idle instead of staying alive`() {
     val cache = getSut()

sentry/src/test/java/io/sentry/MainEventProcessorTest.kt

@@ -6,9 +6,11 @@ import io.sentry.protocol.DebugMeta
 import io.sentry.protocol.SdkVersion
 import io.sentry.protocol.SentryTransaction
 import io.sentry.protocol.User
+import io.sentry.time.TestMonotonicTicker
 import io.sentry.util.HintUtils
 import java.lang.RuntimeException
 import java.net.InetAddress
+import java.util.concurrent.TimeUnit
 import kotlin.test.AfterTest
 import kotlin.test.Test
 import kotlin.test.assertEquals
@@ -17,7 +19,6 @@ import kotlin.test.assertNotNull
 import kotlin.test.assertNull
 import kotlin.test.assertSame
 import kotlin.test.assertTrue
-import org.awaitility.kotlin.await
 import org.mockito.Mockito
 import org.mockito.kotlin.mock
 import org.mockito.kotlin.reset
@@ -36,6 +37,7 @@ class MainEventProcessorTest {
       }
     val scopes = mock<IScopes>()
     val getLocalhost = mock<InetAddress>()
+    val hostnameCacheTicker = TestMonotonicTicker()
     lateinit var sentryTracer: SentryTracer
     private val hostnameCacheMock = Mockito.mockStatic(HostnameCache::class.java)
 
@@ -48,7 +50,6 @@ class MainEventProcessorTest {
       serverName: String? = "server",
       host: String? = null,
       resolveHostDelay: Long? = null,
-      hostnameCacheDuration: Long = 10,
       proguardUuid: String? = null,
       bundleIds: List<String>? = null,
       modules: Map<String, String>? = null,
@@ -76,7 +77,7 @@ class MainEventProcessorTest {
       whenever(scopes.options).thenReturn(sentryOptions)
       sentryTracer = SentryTracer(TransactionContext("", ""), scopes)
 
-      val hostnameCache = HostnameCache(hostnameCacheDuration) { getLocalhost }
+      val hostnameCache = HostnameCache({ getLocalhost }, hostnameCacheTicker)
       hostnameCacheMock.`when`<Any> { HostnameCache.getInstance() }.thenReturn(hostnameCache)
 
       return MainEventProcessor(sentryOptions)
@@ -401,7 +402,7 @@ class MainEventProcessorTest {
 
   @Test
   fun `uses cache to retrieve servername for subsequent events`() {
-    val processor = fixture.getSut(serverName = null, host = "aHost", hostnameCacheDuration = 1000)
+    val processor = fixture.getSut(serverName = null, host = "aHost")
     val firstEvent = SentryEvent()
     processor.process(firstEvent, Hint())
     assertEquals("aHost", firstEvent.serverName)
@@ -420,12 +421,11 @@ class MainEventProcessorTest {
 
     reset(fixture.getLocalhost)
     whenever(fixture.getLocalhost.canonicalHostName).thenReturn("newHost")
+    fixture.hostnameCacheTicker.advance(6, TimeUnit.HOURS)
 
-    await.untilAsserted {
-      val secondEvent = SentryEvent()
-      processor.process(secondEvent, Hint())
-      assertEquals("newHost", secondEvent.serverName)
-    }
+    val secondEvent = SentryEvent()
+    processor.process(secondEvent, Hint())
+    assertEquals("newHost", secondEvent.serverName)
   }
 
   @Test