Add BSP configuration option (#2165)

* Add BSP configuration option

* Rename env var to match otel

Author: trask

agent/agent-tooling/src/main/java/com/microsoft/applicationinsights/agent/internal/init/OpenTelemetryConfigurer.java

@@ -43,8 +43,10 @@
 import io.opentelemetry.sdk.trace.SdkTracerProviderBuilder;
 import io.opentelemetry.sdk.trace.data.SpanData;
 import io.opentelemetry.sdk.trace.export.BatchSpanProcessor;
+import io.opentelemetry.sdk.trace.export.BatchSpanProcessorBuilder;
 import io.opentelemetry.sdk.trace.export.SpanExporter;
 import io.opentelemetry.semconv.trace.attributes.SemanticAttributes;
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
@@ -161,9 +163,20 @@ private static BatchSpanProcessor createExporter(Configuration configuration) {
     }
 
     // using BatchSpanProcessor in order to get off of the application thread as soon as possible
-    // using batch size 1 because need to convert to SpanData as soon as possible to grab data for
-    // live metrics. the real batching is done at a lower level
-    return BatchSpanProcessor.builder(currExporter).setMaxExportBatchSize(1).build();
+    BatchSpanProcessorBuilder builder = BatchSpanProcessor.builder(currExporter);
+
+    String delayMillisStr = System.getenv("APPLICATIONINSIGHTS_PREVIEW_BSP_SCHEDULE_DELAY");
+    if (delayMillisStr != null) {
+      // experimenting with flushing at small interval instead of using batch size 1
+      // (suspect this may be better performance on small containers)
+      builder.setScheduleDelay(Duration.ofMillis(Integer.parseInt(delayMillisStr)));
+    } else {
+      // using batch size 1 because need to convert to SpanData as soon as possible to grab data for
+      // live metrics. the real batching is done at a lower level
+      builder.setMaxExportBatchSize(1);
+    }
+
+    return builder.setScheduleDelay(Duration.ofMillis(100)).build();
   }
 
   private static class BackCompatHttpUrlProcessor implements SpanExporter {