Create a Logging span exporter (#592)

* a simple logging span exporter

exporters/logging/build.gradle

@@ -0,0 +1,21 @@
+description = 'OpenTelemetry - Logging Exporter'
+
+buildscript {
+    repositories {
+        maven { url "https://plugins.gradle.org/m2/" }
+    }
+}
+
+dependencies {
+    api project(':opentelemetry-sdk')
+
+    signature "org.codehaus.mojo.signature:java17:1.0@signature"
+    signature "net.sf.androidscents.signature:android-api-level-14:4.0_r4@signature"
+}
+
+animalsniffer {
+    // Don't check sourceSets.jmh and sourceSets.test
+    sourceSets = [
+            sourceSets.main
+    ]
+}

exporters/logging/src/main/java/io/opentelemetry/exporters/logging/LoggingExporter.java

@@ -0,0 +1,38 @@
+/*
+ * 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
+ *
+ *     http://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.
+ */
+
+package io.opentelemetry.exporters.logging;
+
+import io.opentelemetry.sdk.trace.SpanData;
+import io.opentelemetry.sdk.trace.export.SpanExporter;
+import java.util.List;
+import java.util.logging.Logger;
+
+/** A Span Exporter that logs every span at INFO level using java.util.logging. */
+public class LoggingExporter implements SpanExporter {
+  private static final Logger logger = Logger.getLogger(LoggingExporter.class.getName());
+
+  @Override
+  public ResultCode export(List<SpanData> spans) {
+    for (SpanData span : spans) {
+      logger.info("span: " + span);
+    }
+    return ResultCode.SUCCESS;
+  }
+
+  @Override
+  public void shutdown() {}
+}

exporters/logging/src/test/java/io/opentelemetry/exporters/logging/LoggingExporterTest.java

@@ -0,0 +1,60 @@
+/*
+ * 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
+ *
+ *     http://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.
+ */
+
+package io.opentelemetry.exporters.logging;
+
+import static java.util.Collections.singletonList;
+import static java.util.Collections.singletonMap;
+import static org.junit.Assert.assertEquals;
+
+import io.opentelemetry.common.Timestamp;
+import io.opentelemetry.sdk.trace.SpanData;
+import io.opentelemetry.sdk.trace.export.SpanExporter.ResultCode;
+import io.opentelemetry.trace.AttributeValue;
+import io.opentelemetry.trace.Span.Kind;
+import io.opentelemetry.trace.SpanId;
+import io.opentelemetry.trace.Status;
+import io.opentelemetry.trace.TraceId;
+import io.opentelemetry.trace.util.Events;
+import org.junit.Test;
+
+public class LoggingExporterTest {
+  @Test
+  public void returnCode() throws Exception {
+    LoggingExporter exporter = new LoggingExporter();
+    long startTimeSecondsSinceEpoch = System.currentTimeMillis() / 1000;
+    SpanData spanData =
+        SpanData.newBuilder()
+            .setTraceId(new TraceId(1234L, 6789L))
+            .setSpanId(new SpanId(9876L))
+            .setStartTimestamp(Timestamp.create(startTimeSecondsSinceEpoch, 0))
+            .setEndTimestamp(Timestamp.create(startTimeSecondsSinceEpoch, 100))
+            .setStatus(Status.OK)
+            .setName("testSpan")
+            .setKind(Kind.INTERNAL)
+            .setTimedEvents(
+                singletonList(
+                    SpanData.TimedEvent.create(
+                        Timestamp.create(startTimeSecondsSinceEpoch, 50),
+                        Events.create(
+                            "somethingHappenedHere",
+                            singletonMap(
+                                "important", AttributeValue.booleanAttributeValue(true))))))
+            .build();
+    ResultCode resultCode = exporter.export(singletonList(spanData));
+    assertEquals(ResultCode.SUCCESS, resultCode);
+  }
+}

settings.gradle

@@ -5,6 +5,7 @@ include ":opentelemetry-api"
 include ":opentelemetry-contrib-runtime-metrics"
 include ":opentelemetry-contrib-trace-utils"
 include ":opentelemetry-exporters-jaeger"
+include ":opentelemetry-exporters-logging"
 include ":opentelemetry-opentracing-shim"
 include ":opentelemetry-proto"
 include ":opentelemetry-sdk"
@@ -19,6 +20,7 @@ project(':opentelemetry-contrib-runtime-metrics').projectDir =
         "$rootDir/contrib/runtime_metrics" as File
 project(':opentelemetry-contrib-trace-utils').projectDir = "$rootDir/contrib/trace_utils" as File
 project(':opentelemetry-exporters-jaeger').projectDir = "$rootDir/exporters/jaeger" as File
+project(':opentelemetry-exporters-logging').projectDir = "$rootDir/exporters/logging" as File
 project(':opentelemetry-opentracing-shim').projectDir = "$rootDir/opentracing_shim" as File
 project(':opentelemetry-sdk').projectDir = "$rootDir/sdk" as File
 project(':opentelemetry-sdk-contrib-async-processor').projectDir =