feat: adds support to group logs of the same http request

src/main/java/com/google/cloud/logging/logback/TraceLoggingEventEnhancer.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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 com.google.cloud.logging.logback;
+
+import ch.qos.logback.classic.spi.ILoggingEvent;
+import com.google.cloud.logging.LogEntry;
+import org.slf4j.MDC;
+
+/** Adds support for grouping logs by incoming http request */
+public class TraceLoggingEventEnhancer implements LoggingEventEnhancer {
+
+  // A key used by Cloud Logging for trace Id
+  private static final String TRACE_ID = "logging.googleapis.trace";
+
+  /**
+   * Set the Trace ID associated with any logging done by the current thread.
+   *
+   * @param id The traceID, in the form projects/[PROJECT_ID]/traces/[TRACE_ID]
+   */
+  public static void setCurrentTraceId(String id) {
+    MDC.put(TRACE_ID, id);
+  }
+
+  /**
+   * Get the Trace ID associated with any logging done by the current thread.
+   *
+   * @return id The traceID
+   */
+  public static String getCurrentTraceId() {
+    return MDC.get(TRACE_ID);
+  }
+
+  @Override
+  public void enhanceLogEntry(LogEntry.Builder builder, ILoggingEvent e) {
+    Object value = e.getMDCPropertyMap().get(TRACE_ID);
+    String traceId = value != null ? value.toString() : null;
+    if (traceId != null) {
+      builder.setTrace(traceId);
+    }
+  }
+}

src/test/java/com/google/cloud/logging/logback/TraceLoggingEventEnhancerTest.java

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+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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 com.google.cloud.logging.logback;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import ch.qos.logback.classic.spi.LoggingEvent;
+import com.google.cloud.logging.LogEntry;
+import com.google.cloud.logging.Payload.StringPayload;
+import org.junit.Before;
+import org.junit.Test;
+
+public class TraceLoggingEventEnhancerTest {
+  private TraceLoggingEventEnhancer classUnderTest;
+
+  @Before
+  public void setUp() {
+    classUnderTest = new TraceLoggingEventEnhancer();
+  }
+
+  @Test
+  public void testEnhanceLogEntry() {
+    // setup
+    String traceId = "abc";
+    TraceLoggingEventEnhancer.setCurrentTraceId(traceId);
+    LoggingEvent loggingEvent = new LoggingEvent();
+    loggingEvent.setMessage("this is a test");
+    LogEntry.Builder builder = LogEntry.newBuilder(StringPayload.of("this is a test"));
+
+    // act
+    classUnderTest.enhanceLogEntry(builder, loggingEvent);
+    LogEntry logEntry = builder.build();
+
+    // assert - Trace Id should be recorded as explicit Trace field, not as a label
+    assertThat(traceId.equalsIgnoreCase(logEntry.getTrace()));
+  }
+
+  @Test
+  public void testGetCurrentTraceId() {
+    // setup
+    String traceId = "abc";
+    TraceLoggingEventEnhancer.setCurrentTraceId(traceId);
+
+    // act
+    String currentTraceId = TraceLoggingEventEnhancer.getCurrentTraceId();
+
+    // assert
+    assertThat(traceId.equalsIgnoreCase(currentTraceId));
+  }
+}