Simplified ListWriter await logic. (#8992)

Author: AlexeyKuznetsov-DD

dd-trace-core/src/main/java/datadog/trace/common/writer/ListWriter.java

@@ -1,36 +1,29 @@
 package datadog.trace.common.writer;
 
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+import static java.util.concurrent.TimeUnit.NANOSECONDS;
+import static java.util.concurrent.TimeUnit.SECONDS;
+
 import datadog.trace.core.DDSpan;
 import datadog.trace.core.MetadataConsumer;
-import datadog.trace.core.tagprocessor.PeerServiceCalculator;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
-import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.function.BooleanSupplier;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 /** List writer used by tests mostly */
 public class ListWriter extends CopyOnWriteArrayList<List<DDSpan>> implements Writer {
-
   private static final Logger log = LoggerFactory.getLogger(ListWriter.class);
+  private static final Filter ACCEPT_ALL = trace -> true;
 
-  public static final Filter ACCEPT_ALL =
-      new Filter() {
-        @Override
-        public boolean accept(List<DDSpan> trace) {
-          return true;
-        }
-      };
-
-  private final List<CountDownLatch> latches = new ArrayList<>();
   private final AtomicInteger traceCount = new AtomicInteger();
   private final TraceStructureWriter structureWriter = new TraceStructureWriter(true);
+  private final Object monitor = new Object();
 
-  private final PeerServiceCalculator peerServiceCalculator = new PeerServiceCalculator();
   private Filter filter = ACCEPT_ALL;
 
   public List<DDSpan> firstTrace() {
@@ -47,30 +40,44 @@ public void write(List<DDSpan> trace) {
       // remotely realistic so the test actually test something
       span.processTagsAndBaggage(MetadataConsumer.NO_OP);
     }
+
+    add(trace);
+    structureWriter.write(trace);
+
     traceCount.incrementAndGet();
-    synchronized (latches) {
-      add(trace);
-      for (final CountDownLatch latch : latches) {
-        if (size() >= latch.getCount()) {
-          while (latch.getCount() > 0) {
-            latch.countDown();
-          }
-        }
-      }
+    synchronized (monitor) {
+      monitor.notifyAll();
     }
-    structureWriter.write(trace);
   }
 
-  public boolean waitForTracesMax(final int number, int seconds)
-      throws InterruptedException, TimeoutException {
-    final CountDownLatch latch = new CountDownLatch(number);
-    synchronized (latches) {
-      if (size() >= number) {
+  private boolean awaitUntilDeadline(long timeout, TimeUnit unit, BooleanSupplier predicate)
+      throws InterruptedException {
+    final long deadline = System.nanoTime() + unit.toNanos(timeout);
+
+    while (true) {
+      if (predicate.getAsBoolean()) {
         return true;
       }
-      latches.add(latch);
+
+      long now = System.nanoTime();
+      long remaining = deadline - now;
+      if (remaining <= 0) {
+        break;
+      }
+
+      long millis = NANOSECONDS.toMillis(remaining);
+      long nanos = remaining - MILLISECONDS.toNanos(millis);
+
+      synchronized (monitor) {
+        monitor.wait(millis, (int) nanos);
+      }
     }
-    return latch.await(seconds, TimeUnit.SECONDS);
+
+    return false;
+  }
+
+  public boolean waitForTracesMax(final int number, int seconds) throws InterruptedException {
+    return awaitUntilDeadline(seconds, SECONDS, () -> traceCount.get() >= number);
   }
 
   public void waitForTraces(final int number) throws InterruptedException, TimeoutException {
@@ -88,24 +95,17 @@ public void waitForTraces(final int number) throws InterruptedException, Timeout
   }
 
   public void waitUntilReported(final DDSpan span) throws InterruptedException, TimeoutException {
-    waitUntilReported(span, 20, TimeUnit.SECONDS);
+    waitUntilReported(span, 20, SECONDS);
   }
 
   public void waitUntilReported(final DDSpan span, int timeout, TimeUnit unit)
       throws InterruptedException, TimeoutException {
-    while (true) {
-      final CountDownLatch latch = new CountDownLatch(size() + 1);
-      synchronized (latches) {
-        latches.add(latch);
-      }
-      if (isReported(span)) {
-        return;
-      }
-      if (!latch.await(timeout, unit)) {
-        String msg = "Timeout waiting for span to be reported: " + span;
-        log.warn(msg);
-        throw new TimeoutException(msg);
-      }
+    boolean reported = awaitUntilDeadline(timeout, unit, () -> isReported(span));
+
+    if (!reported) {
+      String msg = "Timeout waiting for span to be reported: " + span;
+      log.warn(msg);
+      throw new TimeoutException(msg);
     }
   }
 
@@ -142,17 +142,16 @@ public boolean flush() {
     return true;
   }
 
+  @Override
+  public void clear() {
+    super.clear();
+
+    traceCount.set(0);
+  }
+
   @Override
   public void close() {
     clear();
-    synchronized (latches) {
-      for (final CountDownLatch latch : latches) {
-        while (latch.getCount() > 0) {
-          latch.countDown();
-        }
-      }
-      latches.clear();
-    }
   }
 
   @Override