[JENKINS-36666] Defend against some fatal startup errors (#2453)

* [JENKINS-36666] Properly report the reason for a failed call to Task.getDisplayName.

* [JENKINS-36666] Even without passing fatal=false to @Initializer, recover gracefully from a LinkageError in a task.

* Comment.

core/src/main/java/hudson/PluginManager.java

@@ -465,7 +465,7 @@ public abstract class PluginManager extends AbstractModelObject implements OnMas
                                             if(p.isActive())
                                                 activePlugins.add(p);
                                         }
-                                    } catch (CycleDetectedException e) {
+                                    } catch (CycleDetectedException e) { // TODO this should be impossible, since we override reactOnCycle to not throw the exception
                                         stop(); // disable all plugins since classloading from them can lead to StackOverflow
                                         throw e;    // let Hudson fail
                                     }

core/src/main/java/jenkins/InitReactorRunner.java

@@ -25,6 +25,8 @@ import java.util.logging.Level;
 import java.util.logging.Logger;
 
 import static java.util.logging.Level.SEVERE;
+import org.kohsuke.accmod.Restricted;
+import org.kohsuke.accmod.restrictions.NoExternalUse;
 
 /**
  * Executes the {@link Reactor} for the purpose of bootup.
@@ -61,15 +63,15 @@ public class InitReactorRunner {
         r.add(new ReactorListener() {
             final Level level = Level.parse( Configuration.getStringConfigParameter("initLogLevel", "FINE") );
             public void onTaskStarted(Task t) {
-                LOGGER.log(level,"Started "+t.getDisplayName());
+                LOGGER.log(level, "Started {0}", getDisplayName(t));
             }
 
             public void onTaskCompleted(Task t) {
-                LOGGER.log(level,"Completed "+t.getDisplayName());
+                LOGGER.log(level, "Completed {0}", getDisplayName(t));
             }
 
             public void onTaskFailed(Task t, Throwable err, boolean fatal) {
-                LOGGER.log(SEVERE, "Failed "+t.getDisplayName(),err);
+                LOGGER.log(SEVERE, "Failed " + getDisplayName(t), err);
             }
 
             public void onAttained(Milestone milestone) {
@@ -86,6 +88,17 @@ public class InitReactorRunner {
         return new ReactorListener.Aggregator(r);
     }
 
+    /** Like {@link Task#getDisplayName} but more robust. */
+    @Restricted(NoExternalUse.class)
+    public static String getDisplayName(Task t) {
+        try {
+            return t.getDisplayName();
+        } catch (RuntimeException | Error x) {
+            LOGGER.log(Level.WARNING, "failed to find displayName of " + t, x);
+            return t.toString();
+        }
+    }
+
     /**
      * Called when the init milestone is attained.
      */

core/src/main/java/jenkins/model/Jenkins.java

@@ -987,7 +987,7 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
                 if (is!=null && is.skipInitTask(task))  return;
 
                 ACL.impersonate(ACL.SYSTEM); // full access in the initialization thread
-                String taskName = task.getDisplayName();
+                String taskName = InitReactorRunner.getDisplayName(task);
 
                 Thread t = Thread.currentThread();
                 String name = t.getName();
@@ -999,11 +999,24 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
                     if(LOG_STARTUP_PERFORMANCE)
                         LOGGER.info(String.format("Took %dms for %s by %s",
                                 System.currentTimeMillis()-start, taskName, name));
+                } catch (Exception | Error x) {
+                    if (containsLinkageError(x)) {
+                        LOGGER.log(Level.WARNING, taskName + " failed perhaps due to plugin dependency issues", x);
+                    } else {
+                        throw x;
+                    }
                 } finally {
                     t.setName(name);
                     SecurityContextHolder.clearContext();
                 }
             }
+            private boolean containsLinkageError(Throwable x) {
+                if (x instanceof LinkageError) {
+                    return true;
+                }
+                Throwable x2 = x.getCause();
+                return x2 != null && containsLinkageError(x2);
+            }
         };
 
         new InitReactorRunner() {
@@ -3022,15 +3035,15 @@ public class Jenkins extends AbstractCIBase implements DirectlyModifiableTopLeve
                 final Level level = Level.parse(Configuration.getStringConfigParameter("termLogLevel", "FINE"));
 
                 public void onTaskStarted(Task t) {
-                    LOGGER.log(level, "Started " + t.getDisplayName());
+                    LOGGER.log(level, "Started {0}", InitReactorRunner.getDisplayName(t));
                 }
 
                 public void onTaskCompleted(Task t) {
-                    LOGGER.log(level, "Completed " + t.getDisplayName());
+                    LOGGER.log(level, "Completed {0}", InitReactorRunner.getDisplayName(t));
                 }
 
                 public void onTaskFailed(Task t, Throwable err, boolean fatal) {
-                    LOGGER.log(SEVERE, "Failed " + t.getDisplayName(), err);
+                    LOGGER.log(SEVERE, "Failed " + InitReactorRunner.getDisplayName(t), err);
                 }
 
                 public void onAttained(Milestone milestone) {