move otel autoconfigure out of the braintrust sdk

Author: realark

braintrust-java-agent/internal/src/main/java/dev/braintrust/agent/OtelAutoConfig.java

@@ -0,0 +1,48 @@
+package dev.braintrust.agent;
+
+import com.google.auto.service.AutoService;
+import dev.braintrust.Braintrust;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizer;
+import io.opentelemetry.sdk.autoconfigure.spi.AutoConfigurationCustomizerProvider;
+import io.opentelemetry.sdk.logs.SdkLoggerProvider;
+import io.opentelemetry.sdk.metrics.SdkMeterProvider;
+import java.util.concurrent.atomic.AtomicInteger;
+import lombok.extern.slf4j.Slf4j;
+
+@Slf4j
+@AutoService(AutoConfigurationCustomizerProvider.class)
+public class OtelAutoConfig implements AutoConfigurationCustomizerProvider {
+    @Override
+    public void customize(AutoConfigurationCustomizer autoConfiguration) {
+        autoConfiguration.addTracerProviderCustomizer(
+                ((sdkTracerProviderBuilder, configProperties) -> {
+                    try {
+                        var bridgeClass =
+                                OtelAutoConfig.class
+                                        .getClassLoader()
+                                        .loadClass("dev.braintrust.bootstrap.BraintrustBridge");
+                        AtomicInteger otelInstallCount =
+                                (AtomicInteger)
+                                        bridgeClass.getDeclaredField("otelInstallCount").get(null);
+                        if (!otelInstallCount.compareAndSet(0, 1)) {
+                            log.warn(
+                                    "otel install invoked more than once. This should not happen."
+                                            + " Bailing.");
+                            return sdkTracerProviderBuilder;
+                        }
+                    } catch (ClassNotFoundException e) {
+                        // running without autoinstrumentation
+                    } catch (Exception e) {
+                        log.info(
+                                "failed to invoke autoinstrumention bridge. Non-fatal. Continuing",
+                                e);
+                    }
+                    Braintrust.get()
+                            .openTelemetryEnable(
+                                    sdkTracerProviderBuilder,
+                                    SdkLoggerProvider.builder(),
+                                    SdkMeterProvider.builder());
+                    return sdkTracerProviderBuilder;
+                }));
+    }
+}

braintrust-otel-extension/build.gradle

@@ -25,6 +25,14 @@ evaluationDependsOn(':braintrust-sdk')
 
 dependencies {
   implementation project(':braintrust-sdk')
+
+  // OTel SDK + autoconfigure SPI — needed to compile OtelAutoConfig.
+  // At runtime these are provided by the OTel Java agent, so they are compileOnly.
+  compileOnly "io.opentelemetry:opentelemetry-sdk:${otelVersion}"
+  compileOnly "io.opentelemetry:opentelemetry-sdk-extension-autoconfigure-spi:${otelVersion}"
+
+  // SLF4J API — needed at compile time for Lombok's @Slf4j annotation.
+  compileOnly "org.slf4j:slf4j-api:${slf4jVersion}"
 }
 
 jar {