Allow adding span processors when building a tracer provider. (#2223)

* Allow adding span processors when building a tracer provider.

* Drift

* Mutate provided providers too for now.

* Spot

sdk/all/src/test/java/io/opentelemetry/sdk/OpenTelemetrySdkTest.java

@@ -24,6 +24,7 @@
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.trace.IdGenerator;
 import io.opentelemetry.sdk.trace.SdkTracerProvider;
+import io.opentelemetry.sdk.trace.SpanProcessor;
 import io.opentelemetry.sdk.trace.config.TraceConfig;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
 import org.junit.jupiter.api.Test;
@@ -38,6 +39,7 @@ class OpenTelemetrySdkTest {
   @Mock private SdkMeterProvider meterProvider;
   @Mock private ContextPropagators propagators;
   @Mock private Clock clock;
+  @Mock private SpanProcessor spanProcessor;
 
   @Test
   void testGetGlobal() {

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkTracerProvider.java

@@ -13,6 +13,7 @@
 import io.opentelemetry.sdk.internal.ComponentRegistry;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.trace.config.TraceConfig;
+import java.util.List;
 import java.util.logging.Level;
 import java.util.logging.Logger;
 import javax.annotation.Nullable;
@@ -40,8 +41,13 @@ public static SdkTracerProviderBuilder builder() {
   }
 
   SdkTracerProvider(
-      Clock clock, IdGenerator idsGenerator, Resource resource, TraceConfig traceConfig) {
-    this.sharedState = new TracerSharedState(clock, idsGenerator, resource, traceConfig);
+      Clock clock,
+      IdGenerator idsGenerator,
+      Resource resource,
+      TraceConfig traceConfig,
+      List<SpanProcessor> spanProcessors) {
+    this.sharedState =
+        new TracerSharedState(clock, idsGenerator, resource, traceConfig, spanProcessors);
     this.tracerSdkComponentRegistry =
         new ComponentRegistry<>(
             instrumentationLibraryInfo -> new SdkTracer(sharedState, instrumentationLibraryInfo));

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/SdkTracerProviderBuilder.java

@@ -9,10 +9,13 @@
 import io.opentelemetry.sdk.internal.SystemClock;
 import io.opentelemetry.sdk.resources.Resource;
 import io.opentelemetry.sdk.trace.config.TraceConfig;
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Objects;
 
 /** Builder of {@link SdkTracerProvider}. */
 public final class SdkTracerProviderBuilder {
+  private final List<SpanProcessor> spanProcessors = new ArrayList<>();
 
   private Clock clock = SystemClock.getInstance();
   private IdGenerator idsGenerator = IdGenerator.random();
@@ -67,13 +70,23 @@ public SdkTracerProviderBuilder setTraceConfig(TraceConfig traceConfig) {
     return this;
   }
 
+  /**
+   * Add a SpanProcessor to the span pipeline that will be built.
+   *
+   * @return this
+   */
+  public SdkTracerProviderBuilder addSpanProcessor(SpanProcessor spanProcessor) {
+    spanProcessors.add(spanProcessor);
+    return this;
+  }
+
   /**
    * Create a new TraceSdkProvider instance.
    *
    * @return An initialized TraceSdkProvider.
    */
   public SdkTracerProvider build() {
-    return new SdkTracerProvider(clock, idsGenerator, resource, traceConfig);
+    return new SdkTracerProvider(clock, idsGenerator, resource, traceConfig, spanProcessors);
   }
 
   SdkTracerProviderBuilder() {}

sdk/trace/src/main/java/io/opentelemetry/sdk/trace/TracerSharedState.java

@@ -30,11 +30,16 @@ final class TracerSharedState {
   private final List<SpanProcessor> registeredSpanProcessors = new ArrayList<>();
 
   TracerSharedState(
-      Clock clock, IdGenerator idGenerator, Resource resource, TraceConfig traceConfig) {
+      Clock clock,
+      IdGenerator idGenerator,
+      Resource resource,
+      TraceConfig traceConfig,
+      List<SpanProcessor> spanProcessors) {
     this.clock = clock;
     this.idGenerator = idGenerator;
     this.resource = resource;
     this.activeTraceConfig = traceConfig;
+    spanProcessors.forEach(this::addSpanProcessor);
   }
 
   Clock getClock() {