Merge pull request #436 from DataDog/mar-kolya/use-WeakConcurrentMap-suggestions

WeakMap improvements

dd-java-agent/agent-bootstrap/src/main/java/datadog/trace/bootstrap/WeakMap.java

@@ -73,5 +73,10 @@ public interface WeakMap<K, V> {
     public void put(final K key, final V value) {
       map.put(key, value);
     }
+
+    @Override
+    public String toString() {
+      return map.toString();
+    }
   }
 }

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/WeakMapSuppliers.java

@@ -1,6 +1,7 @@
 package datadog.trace.agent.tooling;
 
 import com.blogspot.mydailyjava.weaklockfree.WeakConcurrentMap;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.collect.MapMaker;
 import datadog.trace.bootstrap.WeakMap;
 import java.lang.ref.WeakReference;
@@ -35,9 +36,11 @@ class WeakMapSuppliers {
    * second.
    */
   static class WeakConcurrent implements WeakMap.Supplier {
-    private static final long CLEAN_FREQUENCY_SECONDS = 1;
+
     private static final long SHUTDOWN_WAIT_SECONDS = 5;
 
+    @VisibleForTesting static final long CLEAN_FREQUENCY_SECONDS = 1;
+
     private static final ThreadFactory THREAD_FACTORY =
         new ThreadFactory() {
           @Override
@@ -49,28 +52,7 @@ class WeakMapSuppliers {
           }
         };
 
-    private static final ScheduledExecutorService CLEANER =
-        Executors.newScheduledThreadPool(1, THREAD_FACTORY);
-
-    static {
-      try {
-        Runtime.getRuntime()
-            .addShutdownHook(
-                new Thread() {
-                  @Override
-                  public void run() {
-                    try {
-                      CLEANER.shutdownNow();
-                      CLEANER.awaitTermination(SHUTDOWN_WAIT_SECONDS, TimeUnit.SECONDS);
-                    } catch (final InterruptedException e) {
-                      // Don't bother waiting then...
-                    }
-                  }
-                });
-      } catch (final IllegalStateException ex) {
-        // The JVM is already shutting down.
-      }
-    }
+    private final ScheduledExecutorService cleanerExecutorService;
 
     private final Queue<WeakReference<WeakConcurrentMap>> suppliedMaps =
         new ConcurrentLinkedQueue<>();
@@ -79,24 +61,41 @@ class WeakMapSuppliers {
         new Runnable() {
           @Override
           public void run() {
-            cleanMaps();
+            for (final Iterator<WeakReference<WeakConcurrentMap>> iterator =
+                    suppliedMaps.iterator();
+                iterator.hasNext(); ) {
+              final WeakConcurrentMap map = iterator.next().get();
+              if (map == null) {
+                iterator.remove();
+              } else {
+                map.expungeStaleEntries();
+              }
+            }
           }
         };
 
     WeakConcurrent() {
-      CLEANER.scheduleAtFixedRate(
+      cleanerExecutorService = Executors.newScheduledThreadPool(1, THREAD_FACTORY);
+      cleanerExecutorService.scheduleAtFixedRate(
           runnable, CLEAN_FREQUENCY_SECONDS, CLEAN_FREQUENCY_SECONDS, TimeUnit.SECONDS);
-    }
 
-    public void cleanMaps() {
-      for (final Iterator<WeakReference<WeakConcurrentMap>> iterator = suppliedMaps.iterator();
-          iterator.hasNext(); ) {
-        final WeakConcurrentMap map = iterator.next().get();
-        if (map == null) {
-          iterator.remove();
-        } else {
-          map.expungeStaleEntries();
-        }
+      try {
+        Runtime.getRuntime()
+            .addShutdownHook(
+                new Thread() {
+                  @Override
+                  public void run() {
+                    try {
+                      cleanerExecutorService.shutdownNow();
+                      cleanerExecutorService.awaitTermination(
+                          SHUTDOWN_WAIT_SECONDS, TimeUnit.SECONDS);
+                    } catch (final InterruptedException e) {
+                      // Don't bother waiting then...
+                    }
+                  }
+                });
+      } catch (final IllegalStateException ex) {
+        // The JVM is already shutting down.
       }
     }
 
@@ -150,5 +149,10 @@ class WeakMapSuppliers {
     public <K, V> WeakMap<K, V> get() {
       return new WeakMap.MapAdapter<>(new MapMaker().weakKeys().<K, V>makeMap());
     }
+
+    public <K, V> WeakMap<K, V> get(int concurrencyLevel) {
+      return new WeakMap.MapAdapter<>(
+          new MapMaker().concurrencyLevel(concurrencyLevel).weakKeys().<K, V>makeMap());
+    }
   }
 }

dd-java-agent/agent-tooling/src/test/groovy/datadog/trace/agent/tooling/WeakConcurrentSupplierTest.groovy

@@ -2,44 +2,105 @@ package datadog.trace.agent.tooling
 
 import datadog.trace.agent.test.TestUtils
 import datadog.trace.bootstrap.WeakMap
+import spock.lang.Shared
 import spock.lang.Specification
 
+import java.lang.ref.WeakReference
+import java.util.concurrent.TimeUnit
+
 class WeakConcurrentSupplierTest extends Specification {
-  def supplier = new WeakMapSuppliers.WeakConcurrent()
+  @Shared
+  def weakConcurrentSupplier = new WeakMapSuppliers.WeakConcurrent()
+  @Shared
+  def weakInlineSupplier = new WeakMapSuppliers.WeakConcurrent.Inline()
+  @Shared
+  def guavaSupplier = new WeakMapSuppliers.Guava()
 
-  def setup() {
-    WeakMap.Provider.provider.set(supplier)
-  }
-
-  def "calling new adds to the list"() {
-    when:
-    def map1 = WeakMap.Provider.newWeakMap().map
-
-    then:
-    supplier.suppliedMaps.iterator().next().get() == map1
-
-    when:
-    def map2 = WeakMap.Provider.newWeakMap().map
-    def iterator = supplier.suppliedMaps.iterator()
-
-    then:
-    iterator.next().get() == map1
-    iterator.next().get() == map2
-  }
-
-  def "calling cleanMaps does cleanup"() {
+  def "Calling newWeakMap on #name creates independent maps"() {
     setup:
+    WeakMap.Provider.provider.set(supplier)
+    def key = new Object()
+    def map1 = WeakMap.Provider.newWeakMap()
+    def map2 = WeakMap.Provider.newWeakMap()
+
+    when:
+    map1.put(key, "value1")
+    map2.put(key, "value2")
+
+    then:
+    map1.get(key) == "value1"
+    map2.get(key) == "value2"
+
+    where:
+    name             | supplier
+    "WeakConcurrent" | weakConcurrentSupplier
+    "WeakInline"     | weakInlineSupplier
+    "Guava"          | guavaSupplier
+  }
+
+  def "Unreferenced map get cleaned up on #name"() {
+    setup:
+    WeakMap.Provider.provider.set(supplier)
     def map = WeakMap.Provider.newWeakMap()
-    map.put(new Object(), "value")
+    def ref = new WeakReference(map)
+
+    when:
+    map = null
+    TestUtils.awaitGC()
+
+    then:
+    ref.get() == null
+
+    where:
+    name             | supplier
+    "WeakConcurrent" | weakConcurrentSupplier
+    "WeakInline"     | weakInlineSupplier
+    "Guava"          | guavaSupplier
+  }
+
+  def "Unreferenced keys get cleaned up on #name"() {
+    setup:
+    def key = new Object()
+    map.put(key, "value")
     TestUtils.awaitGC()
 
     expect:
-    map.size() == 1 // This might result in an error if supplier's cleaner thread is activated.
+    map.size() == 1
 
     when:
-    supplier.cleanMaps()
+    key = null
+    TestUtils.awaitGC()
+
+    if (name == "WeakConcurrent") {
+      // Sleep enough time for cleanup thread to get scheduled.
+      // But on a very slow box (or high load) scheduling may not be exactly predictable
+      // so we try a few times.
+      int count = 0
+      while (map.size() != 0 && count < 10) {
+        Thread.sleep(TimeUnit.SECONDS.toMillis(WeakMapSuppliers.WeakConcurrent.CLEAN_FREQUENCY_SECONDS))
+        count++
+      }
+    }
+
+    // Hit map a few times to trigger unreferenced entries cleanup.
+    // Exact number of times that we need to hit map is implementation dependent.
+    // For Guava it i specified in
+    // com.google.common.collect.MapMakerInternalMap.DRAIN_THRESHOLD = 0x3F
+    if (name == "Guava" || name == "WeakInline") {
+      for (int i = 0; i <= 0x3F; i++) {
+        map.get("test")
+      }
+    }
 
     then:
     map.size() == 0
+
+    where:
+    name             | map
+    "WeakConcurrent" | weakConcurrentSupplier.get()
+    "WeakInline"     | weakInlineSupplier.get()
+    // Guava's cleanup process depends on concurrency level,
+    // and in order to be able to test it we need to set concurrency to 1
+    "Guava"          | guavaSupplier.get(1)
   }
 }