Add autoconfiguration wrapper artifact

api/all/src/main/java/io/opentelemetry/api/GlobalOpenTelemetry.java

@@ -10,6 +10,10 @@
 import io.opentelemetry.context.propagation.ContextPropagators;
 import io.opentelemetry.spi.OpenTelemetryFactory;
 import io.opentelemetry.spi.trace.TracerProviderFactory;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.logging.Level;
+import java.util.logging.Logger;
 import javax.annotation.Nullable;
 
 /**
@@ -30,7 +34,11 @@
  * @see ContextPropagators
  */
 public final class GlobalOpenTelemetry {
+  // Visible for testing
+  static final Logger logger = Logger.getLogger(GlobalOpenTelemetry.class.getName());
+
   private static final Object mutex = new Object();
+
   @Nullable private static volatile OpenTelemetry globalOpenTelemetry;
 
   private GlobalOpenTelemetry() {}
@@ -48,6 +56,13 @@ public static OpenTelemetry get() {
     if (globalOpenTelemetry == null) {
       synchronized (mutex) {
         if (globalOpenTelemetry == null) {
+
+          OpenTelemetry autoConfigured = maybeAutoConfigure();
+          if (autoConfigured != null) {
+            set(autoConfigured);
+            return autoConfigured;
+          }
+
           OpenTelemetryFactory openTelemetryFactory = Utils.loadSpi(OpenTelemetryFactory.class);
           if (openTelemetryFactory != null) {
             set(openTelemetryFactory.create());
@@ -115,4 +130,31 @@ public static Tracer getTracer(String instrumentationName, String instrumentatio
   public static ContextPropagators getPropagators() {
     return get().getPropagators();
   }
+
+  @Nullable
+  private static OpenTelemetry maybeAutoConfigure() {
+    final Class<?> openTelemetrySdkAutoConfiguration;
+    try {
+      openTelemetrySdkAutoConfiguration =
+          Class.forName("io.opentelemetry.sdk.autoconfigure.OpenTelemetrySdkAutoConfiguration");
+    } catch (ClassNotFoundException e) {
+      return null;
+    }
+
+    try {
+      Method initialize = openTelemetrySdkAutoConfiguration.getMethod("initialize");
+      return (OpenTelemetry) initialize.invoke(null);
+    } catch (NoSuchMethodException | IllegalAccessException e) {
+      throw new IllegalStateException(
+          "OpenTelemetrySdkAutoConfiguration detected on classpath "
+              + "but could not invoke initialize method. This is a bug in OpenTelemetry.",
+          e);
+    } catch (InvocationTargetException t) {
+      logger.log(
+          Level.SEVERE,
+          "Error automatically configuring OpenTelemetry SDK. OpenTelemetry will not be enabled.",
+          t.getTargetException());
+      return null;
+    }
+  }
 }

build.gradle

@@ -199,6 +199,7 @@ subprojects {
                     jsr305                      : "com.google.code.findbugs:jsr305:${findBugsJsr305Version}",
                     prometheus_client           : "io.prometheus:simpleclient:${prometheusVersion}",
                     prometheus_client_common    : "io.prometheus:simpleclient_common:${prometheusVersion}",
+                    prometheus_client_httpserver: "io.prometheus:simpleclient_httpserver:${prometheusVersion}",
                     protobuf                    : "com.google.protobuf:protobuf-java",
                     protobuf_util               : "com.google.protobuf:protobuf-java-util",
                     zipkin_reporter             : "io.zipkin.reporter2:zipkin-reporter",

sdk-extensions/autoconfigure/build.gradle

@@ -0,0 +1,74 @@
+plugins {
+    id "java-library"
+    id "maven-publish"
+
+    id "org.unbroken-dome.test-sets"
+    id "ru.vyarus.animalsniffer"
+}
+
+description = 'OpenTelemetry SDK Auto-configuration'
+ext.moduleName = "io.opentelemetry.sdk.autoconfigure"
+
+testSets {
+    testConfigError
+    testFullConfig
+    testPrometheus
+}
+
+dependencies {
+    api project(':sdk:all'),
+            project(':sdk:metrics')
+
+    compileOnly project(':extensions:trace-propagators')
+    compileOnly project(':exporters:jaeger')
+    compileOnly project(':exporters:logging')
+    compileOnly project(':exporters:otlp:all')
+    compileOnly project(':exporters:otlp:metrics')
+    compileOnly project(':exporters:prometheus')
+    compileOnly libraries.prometheus_client_httpserver
+    compileOnly project(':exporters:zipkin')
+
+    testImplementation project(':proto'),
+            project(':sdk:testing'),
+            'com.linecorp.armeria:armeria-junit5',
+            'com.linecorp.armeria:armeria-grpc'
+    testRuntimeOnly 'io.grpc:grpc-netty-shaded'
+
+    testFullConfigImplementation project(':extensions:trace-propagators')
+    testFullConfigImplementation project(':exporters:jaeger')
+    testFullConfigImplementation project(':exporters:logging')
+    testFullConfigImplementation project(':exporters:otlp:all')
+    testFullConfigImplementation project(':exporters:otlp:metrics')
+    testFullConfigImplementation project(':exporters:prometheus')
+    testFullConfigImplementation libraries.prometheus_client_httpserver
+    testFullConfigImplementation project(':exporters:zipkin')
+
+    testConfigErrorImplementation project(':extensions:trace-propagators')
+    testConfigErrorImplementation project(':exporters:jaeger')
+    testConfigErrorImplementation project(':exporters:logging')
+    testConfigErrorImplementation project(':exporters:otlp:all')
+    testConfigErrorImplementation project(':exporters:otlp:metrics')
+    testConfigErrorImplementation project(':exporters:prometheus')
+    testConfigErrorImplementation libraries.prometheus_client_httpserver
+    testConfigErrorImplementation project(':exporters:zipkin')
+    testConfigErrorImplementation libraries.junit_pioneer
+
+    testPrometheusImplementation project(':exporters:prometheus')
+    testPrometheusImplementation libraries.prometheus_client_httpserver
+}
+
+testFullConfig {
+    environment("OTEL_RESOURCE_ATTRIBUTES", "service.name=test,cat=meow")
+    environment("OTEL_EXPORTER", "otlp,jaeger,zipkin")
+    environment("OTEL_PROPAGATORS", "tracecontext,baggage,b3,b3multi,jaeger,ottracer,xray")
+    environment("OTEL_BSP_SCHEDULE_DELAY_MILLIS", "10")
+    environment("OTEL_IMR_EXPORT_INTERVAL", "10")
+    environment("OTEL_EXPORTER_OTLP_HEADERS", "cat=meow,dog=bark")
+    environment("OTEL_EXPORTER_OTLP_TIMEOUT", "5000")
+    environment("OTEL_SPAN_ATTRIBUTE_COUNT_LIMIT", "2")
+}
+
+testPrometheus {
+    environment("OTEL_EXPORTER", "prometheus")
+    environment("OTEL_IMR_EXPORT_INTERVAL", "10")
+}

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

@@ -0,0 +1,25 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.autoconfigure;
+
+final class ClasspathUtil {
+
+  @SuppressWarnings("UnusedException")
+  static void checkClassExists(String className, String featureName, String requiredLibrary) {
+    try {
+      Class.forName(className);
+    } catch (ClassNotFoundException unused) {
+      throw new ConfigurationException(
+          featureName
+              + " enabled but "
+              + requiredLibrary
+              + " not found on classpath. "
+              + "Make sure to add it as a dependency to enable this feature.");
+    }
+  }
+
+  private ClasspathUtil() {}
+}

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

@@ -0,0 +1,135 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.autoconfigure;
+
+import java.util.AbstractMap;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Locale;
+import java.util.Map;
+import java.util.stream.Collectors;
+import javax.annotation.Nullable;
+
+class ConfigProperties {
+
+  static ConfigProperties get() {
+    return new ConfigProperties(System.getProperties(), System.getenv());
+  }
+
+  // Visible for testing
+  @SuppressWarnings({"unchecked", "rawtypes"})
+  static ConfigProperties createForTest(Map<String, String> properties) {
+    return new ConfigProperties((Map) properties, Collections.emptyMap());
+  }
+
+  private final Map<String, String> config;
+
+  private ConfigProperties(
+      Map<Object, Object> systemProperties, Map<String, String> environmentVariables) {
+    Map<String, String> config = new HashMap<>();
+    environmentVariables.forEach(
+        (name, value) -> config.put(name.toLowerCase(Locale.ROOT).replace('_', '.'), value));
+    systemProperties.forEach(
+        (key, value) -> config.put(((String) key).toLowerCase(Locale.ROOT), (String) value));
+
+    this.config = config;
+  }
+
+  @Nullable
+  String getString(String name) {
+    return config.get(name);
+  }
+
+  @Nullable
+  @SuppressWarnings("UnusedException")
+  Integer getInt(String name) {
+    String value = config.get(name);
+    if (value == null || value.isEmpty()) {
+      return null;
+    }
+    try {
+      return Integer.parseInt(value);
+    } catch (NumberFormatException ex) {
+      throw newInvalidPropertyException(name, value, "integer");
+    }
+  }
+
+  @Nullable
+  @SuppressWarnings("UnusedException")
+  Long getLong(String name) {
+    String value = config.get(name);
+    if (value == null || value.isEmpty()) {
+      return null;
+    }
+    try {
+      return Long.parseLong(value);
+    } catch (NumberFormatException ex) {
+      throw newInvalidPropertyException(name, value, "long");
+    }
+  }
+
+  @Nullable
+  @SuppressWarnings("UnusedException")
+  Double getDouble(String name) {
+    String value = config.get(name);
+    if (value == null || value.isEmpty()) {
+      return null;
+    }
+    try {
+      return Double.parseDouble(value);
+    } catch (NumberFormatException ex) {
+      throw newInvalidPropertyException(name, value, "double");
+    }
+  }
+
+  List<String> getCommaSeparatedValues(String name) {
+    String value = config.get(name);
+    if (value == null) {
+      return Collections.emptyList();
+    }
+    return Arrays.stream(value.split(","))
+        .map(String::trim)
+        .filter(s -> !s.isEmpty())
+        .collect(Collectors.toList());
+  }
+
+  Map<String, String> getCommaSeparatedMap(String name) {
+    return getCommaSeparatedValues(name).stream()
+        .map(
+            keyValuePair ->
+                Arrays.stream(keyValuePair.split("=", 2))
+                    .map(String::trim)
+                    .filter(s -> !s.isEmpty())
+                    .collect(Collectors.toList()))
+        .map(
+            splitKeyValuePairs -> {
+              if (splitKeyValuePairs.size() != 2) {
+                throw new ConfigurationException(
+                    "Map property key missing value: " + name + "=" + config.get(name));
+              }
+              return new AbstractMap.SimpleImmutableEntry<>(
+                  splitKeyValuePairs.get(0), splitKeyValuePairs.get(1));
+            })
+        // If duplicate keys, prioritize later ones similar to duplicate system properties on a
+        // Java command line.
+        .collect(
+            Collectors.toMap(
+                Map.Entry::getKey, Map.Entry::getValue, (first, next) -> next, LinkedHashMap::new));
+  }
+
+  boolean getBoolean(String name) {
+    return Boolean.parseBoolean(config.get(name));
+  }
+
+  private static ConfigurationException newInvalidPropertyException(
+      String name, String value, String type) {
+    throw new ConfigurationException(
+        "Invalid value for property " + name + "=" + value + ". Must be a " + type + ".");
+  }
+}

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

@@ -0,0 +1,16 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.autoconfigure;
+
+/** An exception that is thrown if the user-provided configuration is invalid. */
+public final class ConfigurationException extends RuntimeException {
+
+  private static final long serialVersionUID = 4717640118051490483L;
+
+  ConfigurationException(String message) {
+    super(message);
+  }
+}