DataDog · jbachorik · Mar 5, 2021 · Feb 18, 2021 · Feb 18, 2021 · Feb 18, 2021
@@ -14,6 +14,7 @@ dependencies {
   compile project(':dd-java-agent:agent-logging')
   compile project(':dd-trace-api')
   compile project(':internal-api')
+  implementation project(':internal-api:internal-api-8')
   compile deps.slf4j
   // ^ Generally a bad idea for libraries, but we're shadowing.
 
@@ -31,7 +32,7 @@ compileMain_java11Java.options.forkOptions.javaHome = file(System.env.JAVA_11_HO
 compileMain_java11Java.sourceCompatibility = JavaVersion.VERSION_1_8
 compileMain_java11Java.targetCompatibility = JavaVersion.VERSION_1_8
 dependencies {
-  main_java11CompileOnly project(':internal-api')
+  main_java11CompileOnly project(':internal-api:internal-api-8')
   main_java11CompileOnly "org.projectlombok:lombok:${project.lombok.version}" transitive false
   main_java11AnnotationProcessor "org.projectlombok:lombok:${project.lombok.version}" transitive false
 }

@@ -1,27 +1,28 @@
 package datadog.trace.bootstrap.instrumentation.exceptions;
 
 import datadog.trace.api.Config;
+import datadog.trace.api.sampling.AdaptiveSampler;
 import java.time.Duration;
 import java.time.temporal.ChronoUnit;
 import jdk.jfr.EventType;
 
 final class ExceptionSampler {
   /*
    * Fixed 0.5 second sampling window.
-   * Logic in StreamingSampler relies on sampling window being small compared to (in our case) recording duration:
+   * Logic in AdaptiveSampler relies on sampling window being small compared to (in our case) recording duration:
    * sampler may overshoot on one given window but should average to samplesPerWindow in the long run.
    */
   private static final Duration SAMPLING_WINDOW = Duration.of(500, ChronoUnit.MILLIS);
 
-  private final StreamingSampler sampler;
+  private final AdaptiveSampler sampler;
   private final EventType exceptionSampleType;
 
   ExceptionSampler(final Config config) {
     this(SAMPLING_WINDOW, getSamplesPerWindow(config), samplingWindowsPerRecording(config));
   }
 
   ExceptionSampler(final Duration windowDuration, final int samplesPerWindow, final int lookback) {
-    sampler = new StreamingSampler(windowDuration, samplesPerWindow, lookback);
+    sampler = new AdaptiveSampler(windowDuration, samplesPerWindow, lookback);
     exceptionSampleType = EventType.getEventType(ExceptionSampleEvent.class);
   }
 

@@ -92,6 +92,7 @@ shadowJar {
     exclude(project(':dd-java-agent:agent-logging'))
     exclude(project(':dd-trace-api'))
     exclude(project(':internal-api'))
+    exclude(project(':internal-api:internal-api-8'))
     exclude(dependency('org.slf4j::'))
   }
 }

@@ -47,11 +47,23 @@ class AgentTestRunnerTest extends AgentTestRunner {
           if (!jfrSupported && info.getName().startsWith("datadog.trace.bootstrap.instrumentation.exceptions.")) {
             continue; // skip exception-profiling classes - they won't load if JFR is not available
           }
-          Class<?> bootstrapClass = Class.forName(info.getName())
-          if (bootstrapClass.getClassLoader() != BOOTSTRAP_CLASSLOADER) {
-            bootstrapClassesIncorrectlyLoaded.add(bootstrapClass)
+          try {
+            Class<?> bootstrapClass = Class.forName(info.getName())
+            if (bootstrapClass.getClassLoader() != BOOTSTRAP_CLASSLOADER) {
+              bootstrapClassesIncorrectlyLoaded.add(bootstrapClass)
+            }
+            break
+          } catch (UnsupportedClassVersionError e) {
+            // A dirty hack to allow passing this test on Java 7
+            if (info.getName().startsWith("datadog.trace.api.sampling.")) {
+              // The rate limiting sampler support is consciously compiled to Java 8 bytecode
+              // The sampler will not be used unless JFR is available -> running on Java 8+
+              // Simply ignore the error as the class will not be even attempted to get loaded on Java 7
+              break
+            }
+            // rethrow the exception otherwise
+            throw e
           }
-          break
         }
       }
     }

@@ -0,0 +1,22 @@
+ext {
+  enableJunitPlatform = true
+  minJavaVersionForTests = JavaVersion.VERSION_1_8
+}
+
+apply from: "$rootDir/gradle/java.gradle"
+
+sourceCompatibility = JavaVersion.VERSION_1_8
+targetCompatibility = JavaVersion.VERSION_1_8
+
+minimumBranchCoverage = 0.8
+
+dependencies {
+  compile project(':internal-api')
+
+  testCompile deps.junit5
+  testCompile deps.jmc
+  testCompile deps.commonsMath
+  testCompile deps.mockito
+  testCompile deps.slf4j
+  testCompile project(":utils:test-utils")
+}
@@ -1,4 +1,4 @@
-package datadog.trace.bootstrap.instrumentation.exceptions;
+package datadog.trace.api.sampling;
 
 import datadog.trace.util.AgentTaskScheduler;
 import datadog.trace.util.AgentTaskScheduler.Task;
@@ -10,7 +10,7 @@
 import java.util.concurrent.atomic.LongAdder;
 
 /**
- * A streaming (non-remembering) sampler.
+ * An adaptive streaming (non-remembering) sampler.
  *
  * <p>The sampler attempts to generate at most N samples per fixed time window in randomized
  * fashion. For this it divides the timeline into 'sampling windows' of constant duration. Each
@@ -31,7 +31,7 @@
  * compensate for too rapid changes in the incoming events rate and maintain the target average
  * number of samples per window.
  */
-class StreamingSampler {
+public final class AdaptiveSampler {
 
   /*
    * Number of windows to look back when computing carried over budget.
@@ -86,7 +86,7 @@ boolean addSample(final long limit) {
    * @param lookback the number of windows to consider in averaging the sampling rate
    * @param taskScheduler agent task scheduler to use for periodic rolls
    */
-  StreamingSampler(
+  public AdaptiveSampler(
       final Duration windowDuration,
       final int samplesPerWindow,
       final int lookback,
@@ -113,7 +113,8 @@ boolean addSample(final long limit) {
    * @param samplesPerWindow the maximum number of samples in the sampling window
    * @param lookback the number of windows to consider in averaging the sampling rate
    */
-  StreamingSampler(final Duration windowDuration, final int samplesPerWindow, final int lookback) {
+  public AdaptiveSampler(
+      final Duration windowDuration, final int samplesPerWindow, final int lookback) {
     this(windowDuration, samplesPerWindow, lookback, AgentTaskScheduler.INSTANCE);
   }
 
@@ -122,7 +123,7 @@ boolean addSample(final long limit) {
    *
    * @return {@literal true} if the event should be sampled
    */
-  final boolean sample() {
+  public final boolean sample() {
     final Counts counts = countsRef.get();
     counts.addTest();
     if (ThreadLocalRandom.current().nextDouble() < probability) {
@@ -173,12 +174,12 @@ private static double computeIntervalAlpha(final int lookback) {
   /*
    * Important to use explicit class to avoid implicit hard references to StreamingSampler from within scheduler
    */
-  private static class RollWindowTask implements Task<StreamingSampler> {
+  private static class RollWindowTask implements Task<AdaptiveSampler> {
 
     static final RollWindowTask INSTANCE = new RollWindowTask();
 
     @Override
-    public void run(final StreamingSampler target) {
+    public void run(final AdaptiveSampler target) {
       target.rollWindow();
     }
   }

@@ -1,4 +1,4 @@
-package datadog.trace.bootstrap.instrumentation.exceptions;
+package datadog.trace.api.sampling;
 
 import static java.lang.Math.abs;
 import static java.lang.Math.round;
@@ -37,10 +37,9 @@
  * can be run multiple times - the number of iteration is passed in in {@literal
  * com.datadog.profiling.exceptions.test-iterations} system property.
  */
-@ExtendWith(MockitoExtension.class)
 @Slf4j
-class StreamingSamplerTest {
-
+@ExtendWith(MockitoExtension.class)
+class AdaptiveSamplerTest {
   private static final Duration WINDOW_DURATION = Duration.ofSeconds(1);
 
   /** Generates windows with numbers of events according to Poisson distribution */
@@ -177,8 +176,8 @@ private static class WindowSamplingResult {
   private static final int LOOKBACK = 30;
 
   @Mock AgentTaskScheduler taskScheduler;
-  @Captor ArgumentCaptor<Task<StreamingSampler>> rollWindowTaskCaptor;
-  @Captor ArgumentCaptor<StreamingSampler> rollWindowTargetCaptor;
+  @Captor ArgumentCaptor<Task<AdaptiveSampler>> rollWindowTaskCaptor;
+  @Captor ArgumentCaptor<AdaptiveSampler> rollWindowTargetCaptor;
 
   @BeforeEach
   public void setup() {
@@ -272,8 +271,8 @@ private void testSamplerInline(
     log.info(
         "> mode: {}, windows: {}, SAMPLES_PER_WINDOW: {}, LOOKBACK: {}, max error: {}%",
         windowEventsSupplier, WINDOWS, SAMPLES_PER_WINDOW, LOOKBACK, maxErrorPercent);
-    final StreamingSampler sampler =
-        new StreamingSampler(WINDOW_DURATION, SAMPLES_PER_WINDOW, LOOKBACK, taskScheduler);
+    final AdaptiveSampler sampler =
+        new AdaptiveSampler(WINDOW_DURATION, SAMPLES_PER_WINDOW, LOOKBACK, taskScheduler);
 
     // simulate event generation and sampling for the given number of sampling windows
     final long expectedSamples = WINDOWS * SAMPLES_PER_WINDOW;
@@ -356,7 +355,7 @@ private void reportSampleIndexSkew(double[] sampleIndexSkewPerWindow) {
    *     samples and the sample index skew
    */
   private WindowSamplingResult generateWindowEventsAndSample(
-      IntSupplier windowEventsSupplier, StreamingSampler sampler, Mean mean) {
+      IntSupplier windowEventsSupplier, AdaptiveSampler sampler, Mean mean) {
     int samples = 0;
     int events = windowEventsSupplier.getAsInt();
     mean.clear();
@@ -427,8 +426,8 @@ private void testSamplerConcurrently(
     final AtomicLong allSamples = new AtomicLong(0);
     final AtomicLong receivedEvents = new AtomicLong(0);
 
-    final StreamingSampler sampler =
-        new StreamingSampler(WINDOW_DURATION, SAMPLES_PER_WINDOW, LOOKBACK, taskScheduler);
+    final AdaptiveSampler sampler =
+        new AdaptiveSampler(WINDOW_DURATION, SAMPLES_PER_WINDOW, LOOKBACK, taskScheduler);
     final CyclicBarrier startBarrier = new CyclicBarrier(threadCount);
     final CyclicBarrier endBarrier = new CyclicBarrier(threadCount, this::rollWindow);
     final Mean[] means = new Mean[threadCount];

@@ -0,0 +1 @@
+mock-maker-inline
@@ -33,6 +33,7 @@ include ':dd-trace-ot'
 
 // agent projects
 include ':internal-api'
+include ':internal-api:internal-api-8'
 include ':dd-trace-core'
 include ':dd-trace-core:jfr-openjdk'
 include ':dd-java-agent'