fix: FootprintForkedTest was also measuring Spock mock

Removing the 'features' mock makes the test more predicatable.

Author: bric3

dd-trace-core/build.gradle

@@ -91,7 +91,7 @@ dependencies {
   testImplementation project(':remote-config:remote-config-core')
   testImplementation group: 'org.msgpack', name: 'msgpack-core', version: '0.8.20'
   testImplementation group: 'org.msgpack', name: 'jackson-dataformat-msgpack', version: '0.8.20'
-  testImplementation group: 'org.openjdk.jol', name: 'jol-core', version: '0.16'
+  testImplementation group: 'org.openjdk.jol', name: 'jol-core', version: '0.17'
   testImplementation group: 'commons-codec', name: 'commons-codec', version: '1.3'
   testImplementation group: 'com.amazonaws', name: 'aws-lambda-java-events', version:'3.11.0'
   testImplementation group: 'com.google.protobuf', name: 'protobuf-java', version: '3.14.0'

dd-trace-core/src/test/groovy/datadog/trace/common/metrics/FootprintForkedTest.groovy

@@ -25,10 +25,11 @@ class FootprintForkedTest extends DDSpecification {
     setup:
     CountDownLatch latch = new CountDownLatch(1)
     ValidatingSink sink = new ValidatingSink(latch)
-    DDAgentFeaturesDiscovery features = Mock(DDAgentFeaturesDiscovery)
-    features.supportsMetrics() >> true
-    features.spanKindsToComputedStats() >> []
-    features.peerTags() >> []
+    DDAgentFeaturesDiscovery features = Stub(DDAgentFeaturesDiscovery) {
+      it.supportsMetrics() >> true
+      it.spanKindsToComputedStats() >> []
+      it.peerTags() >> []
+    }
     ConflatingMetricsAggregator aggregator = new ConflatingMetricsAggregator(
       new WellKnownTags("runtimeid","hostname", "env", "service", "version","language"),
       [].toSet() as Set<String>,
@@ -37,8 +38,10 @@ class FootprintForkedTest extends DDSpecification {
       1000,
       1000,
       100,
-      SECONDS)
-    long baseline = footprint(aggregator)
+      SECONDS
+    )
+    // Removing the 'features' as it's a mock, and mocks are heavyweight, e.g. around 22MiB
+    def baseline = footprint(aggregator, features)
     aggregator.start()
 
     when: "lots of traces are published"
@@ -72,7 +75,8 @@ class FootprintForkedTest extends DDSpecification {
     assert latch.await(30, SECONDS)
 
     then:
-    footprint(aggregator) - baseline <= 10 * 1024 * 1024
+    def layout = footprint(aggregator, features)
+    layout.totalSize() - baseline.totalSize() <= 10 * 1024 * 1024
 
     cleanup:
     aggregator.close()
@@ -136,9 +140,14 @@ class FootprintForkedTest extends DDSpecification {
   }
 
 
-  static long footprint(Object o) {
-    GraphLayout layout = GraphLayout.parseInstance(o)
-    System.err.println(layout.toFootprint())
-    return layout.totalSize()
+  static GraphLayout footprint(Object root, Object... excludedRootFieldInstance) {
+    GraphLayout layout = GraphLayout.parseInstance(root)
+
+    excludedRootFieldInstance.each {
+      layout = layout.subtract(GraphLayout.parseInstance(it))
+    }
+
+    println layout.toFootprint()
+    return layout
   }
 }