Prototype file config extensions

sdk-extensions/autoconfigure/README.md

@@ -40,10 +40,11 @@ environment variables, e.g., `OTEL_TRACES_EXPORTER=zipkin`.
   * [Periodic Metric Reader](#periodic-metric-reader)
   * [Metric exporters](#metric-exporters)
     + [Prometheus exporter](#prometheus-exporter)
-  * [Cardinality limits](#cardinality-limits)
+  * [Cardinality Limits](#cardinality-limits)
 - [Logger provider](#logger-provider)
-- [Batch log record processor](#batch-log-record-processor)
+  * [Batch log record processor](#batch-log-record-processor)
 - [Customizing the OpenTelemetry SDK](#customizing-the-opentelemetry-sdk)
+- [File Configuration](#file-configuration)
 
 <!-- tocstop -->
 
@@ -347,7 +348,7 @@ a Prometheus server scrapes from.
 
 The following configuration options are specific to `SdkLoggerProvider`. See [general configuration](#general-configuration) for general configuration.
 
-## Batch log record processor
+### Batch log record processor
 
 | System property                 | Environment variable            | Description                                                                        |
 |---------------------------------|---------------------------------|------------------------------------------------------------------------------------|
@@ -361,3 +362,22 @@ The following configuration options are specific to `SdkLoggerProvider`. See [ge
 Autoconfiguration exposes SPI [hooks](../autoconfigure-spi/src/main/java/io/opentelemetry/sdk/autoconfigure/spi) for customizing behavior programmatically as needed.
 It's recommended to use the above configuration properties where possible, only implementing the SPI to add functionality not found in the
 SDK by default.
+
+## File Configuration
+
+**Experimental**: File based configuration is experimental and subject to breaking changes.
+
+File configuration allows for configuration via a YAML as described
+in [opentelemetry-configuration](https://github.com/open-telemetry/opentelemetry-configuration)
+and [file configuration](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/configuration/file-configuration.md).
+
+To use, include `io.opentelemetry:opentelemetry-sdk-extension:incubator:<version>` and specify the
+path to the config file as described in the table below.
+
+| System property  | Environment variable | Purpose                                                    |
+|------------------|----------------------|------------------------------------------------------------|
+| otel.config.file | OTEL_CONFIG_FILE     | The path to the SDK configuration file. Defaults to unset. |
+
+NOTE: When a config file is specified, other environment variables described in this document along
+with SPI [customizations](#customizing-the-opentelemetry-sdk) are ignored. The contents of the file
+alone dictate SDK configuration.

sdk-extensions/autoconfigure/build.gradle.kts

@@ -58,6 +58,7 @@ testing {
         implementation(project(":sdk:testing"))
         implementation(project(":sdk:trace-shaded-deps"))
         implementation(project(":sdk-extensions:jaeger-remote-sampler"))
+        implementation(project(":sdk-extensions:incubator"))
 
         implementation("com.google.guava:guava")
         implementation("io.opentelemetry.proto:opentelemetry-proto")

sdk-extensions/autoconfigure/src/main/java/io/opentelemetry/sdk/autoconfigure/AutoConfiguredOpenTelemetrySdkBuilder.java

@@ -32,7 +32,12 @@
 import io.opentelemetry.sdk.trace.export.SpanExporter;
 import io.opentelemetry.sdk.trace.samplers.Sampler;
 import java.io.Closeable;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.io.InputStream;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashMap;
@@ -331,6 +336,13 @@
 
     ConfigProperties config = getConfig();
 
+    AutoConfiguredOpenTelemetrySdk fromFileConfiguration = maybeConfigureFromFile(config);
+    if (fromFileConfiguration != null) {
+      maybeRegisterShutdownHook(fromFileConfiguration.getOpenTelemetrySdk());
+      maybeSetAsGlobal(fromFileConfiguration.getOpenTelemetrySdk());
+      return fromFileConfiguration;
+    }
+
     Resource resource =
         ResourceConfiguration.configureResource(config, spiHelper, resourceCustomizer);
 
@@ -391,18 +403,8 @@
         openTelemetrySdk = sdkBuilder.build();
       }
 
-      // NOTE: Shutdown hook registration is untested. Modify with caution.
-      if (registerShutdownHook) {
-        Runtime.getRuntime().addShutdownHook(shutdownHook(openTelemetrySdk));
-      }
-
-      if (setResultAsGlobal) {
-        GlobalOpenTelemetry.set(openTelemetrySdk);
-        GlobalEventEmitterProvider.set(
-            SdkEventEmitterProvider.create(openTelemetrySdk.getSdkLoggerProvider()));
-        logger.log(
-            Level.FINE, "Global OpenTelemetry set to {0} by autoconfiguration", openTelemetrySdk);
-      }
+      maybeRegisterShutdownHook(openTelemetrySdk);
+      maybeSetAsGlobal(openTelemetrySdk);
 
       return AutoConfiguredOpenTelemetrySdk.create(openTelemetrySdk, resource, config);
     } catch (RuntimeException e) {
@@ -424,6 +426,65 @@
     }
   }
 
+  @Nullable
+  private static AutoConfiguredOpenTelemetrySdk maybeConfigureFromFile(ConfigProperties config) {
+    String configurationFile = config.getString("OTEL_CONFIG_FILE");
+    if (configurationFile == null || configurationFile.isEmpty()) {
+      return null;
+    }
+    FileInputStream fis;
+    try {
+      fis = new FileInputStream(configurationFile);
+    } catch (FileNotFoundException e) {
+      throw new ConfigurationException("Configuration file not found", e);
+    }
+    try {
+      Class<?> configurationFactory =
+          Class.forName("io.opentelemetry.sdk.extension.incubator.fileconfig.ConfigurationFactory");
+      Method parse = configurationFactory.getMethod("parse", InputStream.class);
+      Object model = parse.invoke(null, fis);
+      Class<?> openTelemetryConfiguration =
+          Class.forName(
+              "io.opentelemetry.sdk.extension.incubator.fileconfig.internal.model.OpenTelemetryConfiguration");
+      Method interpret = configurationFactory.getMethod("interpret", openTelemetryConfiguration);
+      OpenTelemetrySdk sdk = (OpenTelemetrySdk) interpret.invoke(null, model);
+      Method toConfigProperties =
+          configurationFactory.getMethod("toConfigProperties", openTelemetryConfiguration);
+      ConfigProperties configProperties = (ConfigProperties) toConfigProperties.invoke(null, model);
+      // Note: can't access file configuration resource without reflection so setting a dummy
+      // resource
+      return AutoConfiguredOpenTelemetrySdk.create(sdk, Resource.getDefault(), configProperties);
+    } catch (ClassNotFoundException | NoSuchMethodException | IllegalAccessException e) {
+      throw new ConfigurationException(
+          "Error configuring from file. Is opentelemetry-sdk-extension-incubator on the classpath?",
+          e);
+    } catch (InvocationTargetException e) {
+      Throwable cause = e.getCause();
+      if (cause instanceof ConfigurationException) {
+        throw (ConfigurationException) cause;
+      }
+      throw new ConfigurationException("Unexpected error configuring from file", e);
+    }
+  }
+
+  private void maybeRegisterShutdownHook(OpenTelemetrySdk openTelemetrySdk) {
+    if (!registerShutdownHook) {
+      return;
+    }
+    Runtime.getRuntime().addShutdownHook(shutdownHook(openTelemetrySdk));
+  }
+
+  private void maybeSetAsGlobal(OpenTelemetrySdk openTelemetrySdk) {
+    if (!setResultAsGlobal) {
+      return;
+    }
+    GlobalOpenTelemetry.set(openTelemetrySdk);
+    GlobalEventEmitterProvider.set(
+        SdkEventEmitterProvider.create(openTelemetrySdk.getSdkLoggerProvider()));
+    logger.log(
+        Level.FINE, "Global OpenTelemetry set to {0} by autoconfiguration", openTelemetrySdk);
+  }
+
   @SuppressWarnings("deprecation") // Support deprecated SdkTracerProviderConfigurer
   private void mergeSdkTracerProviderConfigurer() {
     for (io.opentelemetry.sdk.autoconfigure.spi.traces.SdkTracerProviderConfigurer configurer :

sdk-extensions/autoconfigure/src/test/java/io/opentelemetry/sdk/autoconfigure/FileConfigurationTest.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.autoconfigure;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigProperties;
+import io.opentelemetry.sdk.autoconfigure.spi.ConfigurationException;
+import io.opentelemetry.sdk.autoconfigure.spi.internal.DefaultConfigProperties;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+class FileConfigurationTest {
+
+  @Test
+  void configFile(@TempDir Path tempDir) throws IOException {
+    String yaml =
+        "file_format: \"0.1\"\n"
+            + "resource:\n"
+            + "  attributes:\n"
+            + "    service.name: test\n"
+            + "tracer_provider:\n"
+            + "  processors:\n"
+            + "    - simple:\n"
+            + "        exporter:\n"
+            + "          console: {}\n";
+    Path path = tempDir.resolve("otel-config.yaml");
+    Files.write(path, yaml.getBytes(StandardCharsets.UTF_8));
+    ConfigProperties config =
+        DefaultConfigProperties.createFromMap(
+            Collections.singletonMap("OTEL_CONFIG_FILE", path.toString()));
+
+    assertThatThrownBy(() -> AutoConfiguredOpenTelemetrySdk.builder().setConfig(config).build())
+        .isInstanceOf(ConfigurationException.class)
+        .hasMessage(
+            "Error configuring from file. Is opentelemetry-sdk-extension-incubator on the classpath?");
+  }
+}