Add Snapshot Profiling Feature Flag and Scaffolding (#2170)

* Add feature flag to enable/disable the snapshot profiler.

* Include snapshot profiling feature flag configuration in the profiling config logging output.

* Add OpenTelemetry SDK customizer scaffolding for the snapshot profiler.

* Add test for to confirm that the snapshot profiler is disabled by default.

* Add explanation comments in OpenTelemetrySdkExtension.

* Applying spotless code formatting.

* Remove unnecessary ActivationNotifier interface in favor of built in Runnable.

* Rename logger in SnapshotProfilingSdkCustomizer to lowercase.

* Remove snapshot profiler configuration logging.

* Remove unnecessary implementation of the OpenTelemetry interface in OpenTelemetrySdkExtension as that functionality is not needed by the current tests.

* Apply spotless formatting changes.

* Remove configuration logging snapshot profiling tests.

* Update license file.

* Apply spotless code formatting.

licenses/licenses.md

@@ -1,7 +1,7 @@
 
 # splunk-otel-javaagent
 ## Dependency License Report
-_2025-01-31 10:12:43 EET_
+_2025-02-03 11:01:31 PST_
 ## Apache License, Version 2.0
 
 **1** **Group:** `com.squareup.okhttp3` **Name:** `okhttp` **Version:** `4.12.0` 

profiler/src/main/java/com/splunk/opentelemetry/profiler/Configuration.java

@@ -69,6 +69,9 @@ public class Configuration implements AutoConfigurationCustomizerProvider {
   public static final String CONFIG_KEY_TRACING_STACKS_ONLY = "splunk.profiler.tracing.stacks.only";
   private static final String CONFIG_KEY_STACK_DEPTH = "splunk.profiler.max.stack.depth";
 
+  public static final String CONFIG_KEY_ENABLE_SNAPSHOT_PROFILER =
+      "splunk.snapshot.profiler.enabled";
+
   @Override
   public void customize(AutoConfigurationCustomizer autoConfiguration) {
     autoConfiguration.addPropertiesSupplier(this::defaultProperties);
@@ -83,6 +86,8 @@ Map<String, String> defaultProperties() {
     config.put(CONFIG_KEY_MEMORY_ENABLED, String.valueOf(DEFAULT_MEMORY_ENABLED));
     config.put(CONFIG_KEY_MEMORY_EVENT_RATE, DEFAULT_MEMORY_EVENT_RATE);
     config.put(CONFIG_KEY_CALL_STACK_INTERVAL, DEFAULT_CALL_STACK_INTERVAL.toMillis() + "ms");
+
+    config.put(CONFIG_KEY_ENABLE_SNAPSHOT_PROFILER, "false");
     return config;
   }
 

profiler/src/main/java/com/splunk/opentelemetry/profiler/snapshot/SnapshotProfilingSdkCustomizer.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.splunk.opentelemetry.profiler.snapshot;
+
+import static com.splunk.opentelemetry.profiler.Configuration.CONFIG_KEY_ENABLE_SNAPSHOT_PROFILER;
+import static java.util.Collections.emptyMap;
+
+import com.google.auto.service.AutoService;
+import com.google.common.annotations.VisibleForTesting;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizer;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizerProvider;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import java.util.logging.Logger;
+
+@AutoService(AutoConfigurationCustomizerProvider.class)
+public class SnapshotProfilingSdkCustomizer implements AutoConfigurationCustomizerProvider {
+  private static final Logger logger =
+      Logger.getLogger(SnapshotProfilingSdkCustomizer.class.getName());
+
+  private final Runnable activationNotifier;
+
+  public SnapshotProfilingSdkCustomizer() {
+    this(() -> logger.info("Snapshot profiling activated"));
+  }
+
+  @VisibleForTesting
+  SnapshotProfilingSdkCustomizer(Runnable activationNotifier) {
+    this.activationNotifier = activationNotifier;
+  }
+
+  @Override
+  public void customize(AutoConfigurationCustomizer autoConfigurationCustomizer) {
+    autoConfigurationCustomizer.addPropertiesCustomizer(
+        config -> {
+          if (snapshotProfilingEnabled(config)) {
+            activationNotifier.run();
+          }
+          return emptyMap();
+        });
+  }
+
+  private boolean snapshotProfilingEnabled(ConfigProperties config) {
+    return config.getBoolean(CONFIG_KEY_ENABLE_SNAPSHOT_PROFILER, false);
+  }
+}

profiler/src/test/java/com/splunk/opentelemetry/profiler/ConfigurationTest.java

@@ -96,4 +96,11 @@ void getOtlpProtocol() {
     String result = Configuration.getOtlpProtocol(DefaultConfigProperties.create(map));
     assertEquals("test2", result);
   }
+
+  @Test
+  void snapshotProfilingDisabledByDefault() {
+    Configuration configuration = new Configuration();
+    var properties = configuration.defaultProperties();
+    assertEquals("false", properties.get("splunk.snapshot.profiler.enabled"));
+  }
 }

profiler/src/test/java/com/splunk/opentelemetry/profiler/snapshot/OpenTelemetrySdkExtension.java

@@ -0,0 +1,146 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.splunk.opentelemetry.profiler.snapshot;
+
+import io.opentelemetry.context.propagation.TextMapPropagator;
+import io.opentelemetry.sdk.OpenTelemetrySdk;
+import io.opentelemetry.sdk.OpenTelemetrySdkBuilder;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizer;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizerProvider;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
+import io.opentelemetry.sdk.resources.Resource;
+import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
+import io.opentelemetry.sdk.trace.samplers.Sampler;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.BiFunction;
+import java.util.function.Function;
+import java.util.function.Supplier;
+import org.junit.jupiter.api.extension.AfterEachCallback;
+import org.junit.jupiter.api.extension.ExtensionContext;
+
+public class OpenTelemetrySdkExtension implements AfterEachCallback {
+  public static Builder builder() {
+    return new Builder();
+  }
+
+  private final OpenTelemetrySdk sdk;
+
+  private OpenTelemetrySdkExtension(OpenTelemetrySdk sdk) {
+    this.sdk = sdk;
+  }
+
+  @Override
+  public void afterEach(ExtensionContext extensionContext) {
+    sdk.close();
+  }
+
+  /**
+   * An extremely simplified adaptation of the OpenTelemetry class
+   * AutoConfiguredOpenTelemetrySdkBuilder, designed explicitly to facilitate easier component-like
+   * testing of custom OpenTelemetry Java Agent extensions.
+   */
+  public static class Builder {
+    private final SdkCustomizer customizer = new SdkCustomizer();
+    private final Map<String, String> properties = new HashMap<>();
+
+    public Builder withProperty(String name, String value) {
+      properties.put(name, value);
+      return this;
+    }
+
+    public Builder with(AutoConfigurationCustomizerProvider provider) {
+      provider.customize(customizer);
+      return this;
+    }
+
+    /**
+     * Simplified re-implementation of AutoConfiguredOpenTelemetrySdkBuilder's build method. The
+     * OpenTelemetry SDK is only configured with features necessary to pass existing test use cases.
+     */
+    public OpenTelemetrySdkExtension build() {
+      overrideProperties();
+
+      OpenTelemetrySdkBuilder sdkBuilder = OpenTelemetrySdk.builder();
+      OpenTelemetrySdk sdk = sdkBuilder.build();
+
+      return new OpenTelemetrySdkExtension(sdk);
+    }
+
+    private void overrideProperties() {
+      var properties = DefaultConfigProperties.createFromMap(this.properties);
+      for (var customizer : customizer.propertyCustomizers) {
+        var overrides = customizer.apply(properties);
+        properties = properties.withOverrides(overrides);
+      }
+    }
+  }
+
+  private static class SdkCustomizer implements AutoConfigurationCustomizer {
+    private final List<Function<ConfigProperties, Map<String, String>>> propertyCustomizers =
+        new ArrayList<>();
+
+    @Override
+    public AutoConfigurationCustomizer addTracerProviderCustomizer(
+        BiFunction<SdkTracerProviderBuilder, ConfigProperties, SdkTracerProviderBuilder>
+            tracerProviderCustomizer) {
+      return this;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addPropagatorCustomizer(
+        BiFunction<? super TextMapPropagator, ConfigProperties, ? extends TextMapPropagator>
+            textMapPropagator) {
+      return this;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addPropertiesCustomizer(
+        Function<ConfigProperties, Map<String, String>> propertiesCustomizer) {
+      this.propertyCustomizers.add(propertiesCustomizer);
+      return this;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addResourceCustomizer(
+        BiFunction<? super Resource, ConfigProperties, ? extends Resource> biFunction) {
+      return this;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addSamplerCustomizer(
+        BiFunction<? super Sampler, ConfigProperties, ? extends Sampler> biFunction) {
+      return null;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addSpanExporterCustomizer(
+        BiFunction<? super SpanExporter, ConfigProperties, ? extends SpanExporter> biFunction) {
+      return this;
+    }
+
+    @Override
+    public AutoConfigurationCustomizer addPropertiesSupplier(
+        Supplier<Map<String, String>> supplier) {
+      return this;
+    }
+  }
+}

profiler/src/test/java/com/splunk/opentelemetry/profiler/snapshot/SnapshotProfilingSdkCustomizerTest.java

@@ -0,0 +1,82 @@
+/*
+ * Copyright Splunk Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.splunk.opentelemetry.profiler.snapshot;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.api.Nested;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.RegisterExtension;
+
+class SnapshotProfilingSdkCustomizerTest {
+  private final ObservableActivationNotifier activationNotifier =
+      new ObservableActivationNotifier();
+  private final SnapshotProfilingSdkCustomizer customizer =
+      new SnapshotProfilingSdkCustomizer(activationNotifier);
+
+  @Nested
+  class TestSnapshotProfilingDisabledByDefault {
+    @RegisterExtension
+    public final OpenTelemetrySdkExtension s =
+        OpenTelemetrySdkExtension.builder().with(customizer).build();
+
+    @Test
+    void customizeOpenTelemetrySdk() {
+      assertFalse(activationNotifier.activated);
+    }
+  }
+
+  @Nested
+  class TestEnableSnapshotProfiling {
+    @RegisterExtension
+    public final OpenTelemetrySdkExtension s =
+        OpenTelemetrySdkExtension.builder()
+            .with(customizer)
+            .withProperty("splunk.snapshot.profiler.enabled", "true")
+            .build();
+
+    @Test
+    void customizeOpenTelemetrySdk() {
+      assertTrue(activationNotifier.activated);
+    }
+  }
+
+  @Nested
+  class TestDisableSnapshotProfiling {
+    @RegisterExtension
+    public final OpenTelemetrySdkExtension s =
+        OpenTelemetrySdkExtension.builder()
+            .with(customizer)
+            .withProperty("splunk.snapshot.profiler.enabled", "false")
+            .build();
+
+    @Test
+    void customizeOpenTelemetrySdk() {
+      assertFalse(activationNotifier.activated);
+    }
+  }
+
+  private static class ObservableActivationNotifier implements Runnable {
+    private boolean activated = false;
+
+    @Override
+    public void run() {
+      this.activated = true;
+    }
+  }
+}