feat(web): populate the MDC when the ApplicationService gathers infor…

…mation from front50 and clouddriver

so that, for example, when gate receives an http request with an X-SPINNAKER-REQUEST-ID header, that same value appears in outgoing request headers to front50 and clouddriver.  This makes troubleshooting a whole lot easier.

gate-web/src/main/groovy/com/netflix/spinnaker/gate/services/ApplicationService.groovy

@@ -351,7 +351,7 @@ class ApplicationService {
     return result
   }
 
-  static class Front50ApplicationListRetriever implements Callable<List<Map>> {
+  static class Front50ApplicationListRetriever extends MdcWrappedCallable<List<Map>> {
     private final Front50Service front50
     private final AtomicReference<List<Map>> allApplicationsCache
     private final Object principal
@@ -363,7 +363,7 @@ class ApplicationService {
     }
 
     @Override
-    List<Map> call() throws Exception {
+    List<Map> callWithMdc() throws Exception {
       try {
         AuthenticatedRequest.propagate({
           try {
@@ -383,7 +383,7 @@ class ApplicationService {
     }
   }
 
-  static class Front50ApplicationRetriever implements Callable<Map> {
+  static class Front50ApplicationRetriever extends MdcWrappedCallable<Map> {
     private final String name
     private final Front50Service front50
     private final AtomicReference<List<Map>> allApplicationsCache
@@ -399,7 +399,7 @@ class ApplicationService {
     }
 
     @Override
-    Map call() throws Exception {
+    Map callWithMdc() throws Exception {
       try {
         AuthenticatedRequest.propagate({
           try {
@@ -422,7 +422,7 @@ class ApplicationService {
     }
   }
 
-  static class ClouddriverApplicationListRetriever implements Callable<List<Map>> {
+  static class ClouddriverApplicationListRetriever extends MdcWrappedCallable<List<Map>> {
     private final ClouddriverService clouddriver
     private final Object principal
     private final AtomicReference<List<Map>> allApplicationsCache
@@ -438,7 +438,7 @@ class ApplicationService {
     }
 
     @Override
-    List<Map> call() throws Exception {
+    List<Map> callWithMdc() throws Exception {
       try {
         AuthenticatedRequest.propagate({
           try {
@@ -458,7 +458,7 @@ class ApplicationService {
     }
   }
 
-  static class ClouddriverApplicationRetriever implements Callable<Map> {
+  static class ClouddriverApplicationRetriever extends MdcWrappedCallable<Map> {
     private final String name
     private final ClouddriverService clouddriver
     private final Object principal
@@ -471,7 +471,7 @@ class ApplicationService {
     }
 
     @Override
-    Map call() throws Exception {
+    Map callWithMdc() throws Exception {
       try {
         AuthenticatedRequest.propagate({
           try {

gate-web/src/main/java/com/netflix/spinnaker/gate/services/MdcWrappedCallable.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2023 Salesforce, Inc.
+ *
+ * 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.netflix.spinnaker.gate.services;
+
+import java.util.Map;
+import java.util.concurrent.Callable;
+import org.slf4j.MDC;
+
+/** Make a copy of the MDC at construction time available to a task. */
+public abstract class MdcWrappedCallable<T> implements Callable<T> {
+  private final Map<String, String> contextMap;
+
+  public MdcWrappedCallable() {
+    this.contextMap = MDC.getCopyOfContextMap();
+  }
+
+  /** Compute a result, with the MDC as it was at construction time of this object */
+  public abstract T callWithMdc() throws Exception;
+
+  @Override
+  public T call() throws Exception {
+    if (contextMap == null) {
+      MDC.clear();
+    } else {
+      MDC.setContextMap(contextMap);
+    }
+    return callWithMdc();
+  }
+}

gate-web/src/test/java/com/netflix/spinnaker/gate/services/MdcWrappedCallableTest.java

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2023 Salesforce, Inc.
+ *
+ * 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.netflix.spinnaker.gate.services;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import ch.qos.logback.classic.Level;
+import com.netflix.spinnaker.kork.test.log.MemoryAppender;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import org.junit.jupiter.api.Test;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import org.slf4j.MDC;
+
+class MdcWrappedCallableTest {
+  private static final Logger log = LoggerFactory.getLogger(MdcWrappedCallableTest.class);
+
+  @Test
+  void verifyMdcWrappedCallableIncludesTheMdc() throws Exception {
+    // Capture the log messages that our test callable generates
+    MemoryAppender memoryAppender = new MemoryAppender(MdcWrappedCallableTest.class);
+
+    // Provide a way to execute callables in some other thread
+    ExecutorService executorService = Executors.newCachedThreadPool();
+
+    // Put something in the MDC here, to see if it makes it into the thread that
+    // executes the operation.
+    String mdcKey = "myKey";
+    String mdcValue = "myValue";
+    MDC.put(mdcKey, mdcValue);
+
+    // The contents of the MDC at construction time of the MdcWrappedCallable
+    // are what's available when it executes, so construct it after the MDC is set.
+    Callable testCallable = new TestCallable();
+
+    // Execute the callable in another thread
+    executorService.submit(testCallable).get();
+
+    // Verify that messages logged in the MdcWrappedCallable include the info from the MDC
+    List<String> logMessages = memoryAppender.search(mdcKey + "=" + mdcValue, Level.INFO);
+    assertThat(logMessages).hasSize(1);
+
+    // And now clear the MDC and make sure the resulting operation gets the empty MDC.
+    MDC.clear();
+    Callable emptyMdcCallable = new TestCallable();
+    executorService.submit(emptyMdcCallable).get();
+
+    List<String> emptyMdcMessages = memoryAppender.search("contextMap: null", Level.INFO);
+    assertThat(emptyMdcMessages).hasSize(1);
+  }
+
+  static class TestCallable extends MdcWrappedCallable<Void> {
+    @Override
+    public Void callWithMdc() {
+      Map<String, String> contextMap = MDC.getCopyOfContextMap();
+      log.info("contextMap: {}", contextMap);
+      return null;
+    }
+  }
+}