Add support for log emitter provider

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/DefaultLogEmitter.java

@@ -0,0 +1,81 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.logs;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.logs.data.Severity;
+import java.time.Instant;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * No-op implementations of {@link LogEmitter}.
+ *
+ * <p>This implementation should induce as close to zero overhead as possible.
+ */
+@ThreadSafe
+class DefaultLogEmitter implements LogEmitter {
+
+  private static final DefaultLogEmitter INSTANCE = new DefaultLogEmitter();
+  private static final LogBuilder BUILDER_INSTANCE = new NoopLogBuilder();
+
+  static LogEmitter getInstance() {
+    return INSTANCE;
+  }
+
+  @Override
+  public LogBuilder logBuilder() {
+    return BUILDER_INSTANCE;
+  }
+
+  // Noop implementation of LogBuilder.
+  private static final class NoopLogBuilder implements LogBuilder {
+
+    @Override
+    public LogBuilder setEpoch(long timestamp, TimeUnit unit) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setEpoch(Instant instant) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setContext(Context context) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setSeverity(Severity severity) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setSeverityText(String severityText) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setName(String name) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setBody(String body) {
+      return this;
+    }
+
+    @Override
+    public LogBuilder setAttributes(Attributes attributes) {
+      return this;
+    }
+
+    @Override
+    public void emit() {}
+  }
+}

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/DefaultLogEmitterProvider.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.logs;
+
+/** A {@link LogEmitterProvider} that does nothing. */
+class DefaultLogEmitterProvider implements LogEmitterProvider {
+
+  private static final DefaultLogEmitterProvider INSTANCE = new DefaultLogEmitterProvider();
+  private static final LogEmitterBuilder BUILDER_INSTANCE = new NoopLogBuilder();
+
+  public static LogEmitterProvider getInstance() {
+    return INSTANCE;
+  }
+
+  @Override
+  public LogEmitterBuilder logEmitterBuilder(String instrumentationName) {
+    return BUILDER_INSTANCE;
+  }
+
+  private DefaultLogEmitterProvider() {}
+
+  private static class NoopLogBuilder implements LogEmitterBuilder {
+    @Override
+    public LogEmitterBuilder setSchemaUrl(String schemaUrl) {
+      return this;
+    }
+
+    @Override
+    public LogEmitterBuilder setInstrumentationVersion(String instrumentationVersion) {
+      return this;
+    }
+
+    @Override
+    public LogEmitter build() {
+      return DefaultLogEmitter.getInstance();
+    }
+  }
+}

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/LogEmitterProvider.java

@@ -0,0 +1,48 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.logs;
+
+import javax.annotation.concurrent.ThreadSafe;
+
+/**
+ * A registry for creating named {@link LogEmitter}s.
+ *
+ * <p>A LogEmitterProvider represents a configured (or noop) Log collection system that can be used
+ * to instrument code.
+ *
+ * <p>The name <i>Provider</i> is for consistency with other languages and it is <b>NOT</b> loaded
+ * using reflection.
+ */
+@ThreadSafe
+public interface LogEmitterProvider {
+
+  /**
+   * Gets or creates a named and versioned log instance.
+   *
+   * @param instrumentationName The name of the instrumentation library, not the name of the
+   *     instrument*ed* library.
+   * @return a log emitter instance.
+   */
+  default LogEmitter get(String instrumentationName) {
+    return logEmitterBuilder(instrumentationName).build();
+  }
+
+  /**
+   * Creates a LogEmitterBuilder for a named log instance.
+   *
+   * @param instrumentationName The name of the instrumentation library, not the name of the
+   *     instrument*ed* library.
+   * @return a LogEmitterBuilder instance.
+   */
+  LogEmitterBuilder logEmitterBuilder(String instrumentationName);
+
+  /**
+   * Returns a no-op {@link LogEmitterProvider} which provides meters which do not record or emit.
+   */
+  static LogEmitterProvider noop() {
+    return DefaultLogEmitterProvider.getInstance();
+  }
+}

sdk/logs/src/main/java/io/opentelemetry/sdk/logs/SdkLogEmitterProvider.java

@@ -16,7 +16,7 @@
 import java.util.logging.Logger;
 
 /** SDK registry for creating {@link LogEmitter}s. */
-public final class SdkLogEmitterProvider implements Closeable {
+public final class SdkLogEmitterProvider implements LogEmitterProvider, Closeable {
 
   static final String DEFAULT_EMITTER_NAME = "unknown";
   private static final Logger LOGGER = Logger.getLogger(SdkLogEmitterProvider.class.getName());
@@ -47,6 +47,7 @@ public static SdkLogEmitterProviderBuilder builder() {
    * @param instrumentationName the name of the instrumentation library
    * @return a log emitter instance
    */
+  @Override
   public LogEmitter get(String instrumentationName) {
     return logEmitterBuilder(instrumentationName).build();
   }
@@ -57,6 +58,7 @@ public LogEmitter get(String instrumentationName) {
    * @param instrumentationName the name of the instrumentation library
    * @return a log emitter builder instance
    */
+  @Override
   public LogEmitterBuilder logEmitterBuilder(String instrumentationName) {
     if (instrumentationName == null || instrumentationName.isEmpty()) {
       LOGGER.fine("LogEmitter requested without instrumentation name.");

sdk/logs/src/test/java/io/opentelemetry/sdk/logs/DefaultLogEmitterProviderTest.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.logs;
+
+import static org.junit.jupiter.api.Assertions.assertSame;
+
+import org.junit.jupiter.api.Test;
+
+class DefaultLogEmitterProviderTest {
+
+  private final LogEmitterProvider logEmitterProvider = DefaultLogEmitterProvider.getInstance();
+
+  @Test
+  void builder_doesNotThrow() {
+    LogEmitterProvider.noop()
+        .logEmitterBuilder("test")
+        .setSchemaUrl("http://url")
+        .setInstrumentationVersion("version")
+        .build();
+  }
+
+  @Test
+  void builder_default() {
+    assertSame(logEmitterProvider.get("test"), DefaultLogEmitter.getInstance());
+  }
+}

sdk/logs/src/test/java/io/opentelemetry/sdk/logs/DefaultLogEmitterTest.java

@@ -0,0 +1,33 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.sdk.logs;
+
+import io.opentelemetry.api.common.Attributes;
+import io.opentelemetry.context.Context;
+import io.opentelemetry.sdk.logs.data.Severity;
+import java.time.Instant;
+import java.util.concurrent.TimeUnit;
+import org.junit.jupiter.api.Test;
+
+class DefaultLogEmitterTest {
+
+  private static final LogEmitter logEmitter = DefaultLogEmitter.getInstance();
+
+  @Test
+  void noopLogEmitter_doesNotThrow() {
+    logEmitter
+        .logBuilder()
+        .setName("test")
+        .setBody("1")
+        .setSeverity(Severity.INFO)
+        .setEpoch(1L, TimeUnit.NANOSECONDS)
+        .setAttributes(Attributes.empty())
+        .setContext(Context.current())
+        .setEpoch(Instant.now())
+        .setSeverityText("INFO")
+        .emit();
+  }
+}