[dynamic control] wire up first policy

[jackshirazi]

Description:

Wire up TraceSamplingRatePolicy so it can be used in config.

Existing Issue(s):

#2546

Testing:

Added

Documentation:

Included

Outstanding items:

Wiring up the policy pipeline:

• Generic: message -> provider -> policy -> policy handler -> implementer
• eg "change sampling rate" message -> OpampPolicyProvider -> TraceSamplingRatePolicy -> PolicyStore -> TraceSamplingRatePolicyImplementer

Steps needed for the wiring:

• configuring the pipeline
  • DONE: PolicyInitConfig
• providers reading policies, eg OpampPolicyProvider, FilePolicyProvider, etc
  • DONE: OpampPolicyProvider
• implementers applying policies, eg TraceSamplingRatePolicyImplementer
  • DONE: TraceSamplingRatePolicyImplementer
• policy structures (eg TraceSamplingRatePolicy) that the provider converts messages into
  • DONE: TraceSamplingRatePolicy
• registering config to policy structures (eg "trace_sampling_rate_policy" registered to TraceSamplingRatePolicy)
  • This PR
• initializing policy classes (eg TraceSamplingRatePolicy needs to install a custom sampler)
  • DONE: TraceSamplingRatePolicy initialization
• activate configured providers (eg start OpampPolicyprovider reading from it's source)
  • TBD
• register implementers for policies (eg a new TraceSamplingRatePolicy is applied by a TraceSamplingRatePolicyImplementer)
  • TBD
• link the provider to processing policies and applying implementers
  • DONE PolicyInit

[Copilot]

Pull request overview

This PR aims to make the first dynamic-control policy (TraceSamplingRatePolicy) selectable via policy-init configuration by registering the policy type string to its policy class/initializer, and ensuring the policy initializer produces the corresponding implementer.

Changes:

• Added registration hook so TraceSamplingRatePolicy can be registered with PolicyInit.registerPolicyType(...).
• Updated TraceSamplingRatePolicy.initialize(...) to return a PolicyImplementer (created with the installed DelegatingSampler).
• Added a PolicyInitTest covering the “no init-config properties present” (non-initialization) path.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
dynamic-control/src/test/java/io/opentelemetry/contrib/dynamic/policy/registry/PolicyInitTest.java	Adds tests around PolicyInit.init(...) behavior when init-config properties are absent.
dynamic-control/src/main/java/io/opentelemetry/contrib/dynamic/policy/tracesampling/TraceSamplingRatePolicy.java	Returns an implementer from initialization and adds a policy-type registration method.
dynamic-control/src/main/java/io/opentelemetry/contrib/dynamic/policy/registry/PolicyInit.java	Registers TraceSamplingRatePolicy in the static bootstrap.

Comments suppressed due to low confidence (2)

dynamic-control/src/test/java/io/opentelemetry/contrib/dynamic/policy/registry/PolicyInitTest.java:57

• These two tests are currently identical (both only verify that YAML/JSON init config properties are missing) but the second test name refers to missing top-level declarative telemetry policy config. Consider removing the duplicate or rewriting one test to exercise PolicyInit.initFromDeclarativeConfig(...) so the test intent matches what’s actually being validated.

  @Test
  void doesNotInitializePolicyWhenTopLevelTelemetryPolicyDeclarativeConfigMissing() {
    AutoConfigurationCustomizer customizer = mock(AutoConfigurationCustomizer.class);
    PolicyInit.init(customizer);
    Function<ConfigProperties, Map<String, String>> propertiesCustomizer =
        capturePropertiesCustomizer(customizer);

    ConfigProperties config = mock(ConfigProperties.class);
    when(config.getString(PolicyInitConfig.POLICY_INIT_CONFIG_PROPERTY_YAML)).thenReturn(null);
    when(config.getString(PolicyInitConfig.POLICY_INIT_CONFIG_PROPERTY_JSON)).thenReturn(null);
    Map<String, String> ignored = propertiesCustomizer.apply(config);

dynamic-control/src/test/java/io/opentelemetry/contrib/dynamic/policy/registry/PolicyInitTest.java:76

• invokeStaticNoArg() uses reflective access (setAccessible(true)) to call TraceSamplingRatePolicy.resetForTest. This is brittle (can be restricted by JVM access rules) and makes the test harder to maintain. Prefer placing the test in the same package as the method, or exposing a test-only reset hook without reflection (e.g., package-private in the test package or an explicit @VisibleForTesting-style method).

  private static void invokeStaticNoArg(Class<?> targetClass, String methodName) throws Exception {
    Method method = targetClass.getDeclaredMethod(methodName);
    method.setAccessible(true);
    method.invoke(null);
  }