Add Logger interface (open-telemetry#94)

packages/opentelemetry-core/src/common/NoopLogger.ts

@@ -0,0 +1,32 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { Logger } from '@opentelemetry/types';
+
+/** No-op implementation of Logger */
+export class NoopLogger implements Logger {
+  // By default does nothing
+  debug(message: string, ...args: unknown[]) {}
+
+  // By default does nothing
+  error(message: string, ...args: unknown[]) {}
+
+  // By default does nothing
+  warn(message: string, ...args: unknown[]) {}
+
+  // By default does nothing
+  info(message: string, ...args: unknown[]) {}
+}

packages/opentelemetry-types/src/common/Logger.ts

@@ -0,0 +1,25 @@
+/**
+ * Copyright 2019, OpenTelemetry Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+export type LogFunction = (message: string, ...args: unknown[]) => void;
+
+/** Defines a logger interface. */
+export interface Logger {
+  error: LogFunction;
+  warn: LogFunction;
+  info: LogFunction;
+  debug: LogFunction;
+}

packages/opentelemetry-types/src/index.ts

@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+export * from './common/Logger';
 export * from './context/propagation/Propagator';
 export * from './distributed_context/DistributedContext';
 export * from './distributed_context/EntryValue';