[JENKINS-42556] Improved logging for Queue.

core/src/main/java/hudson/model/Queue.java

@@ -728,7 +728,11 @@ public boolean cancel(Task p) {
    }

    private void updateSnapshot() {
        snapshot = new Snapshot(waitingList, blockedProjects, buildables, pendings);
        Snapshot revised = new Snapshot(waitingList, blockedProjects, buildables, pendings);
        if (LOGGER.isLoggable(Level.FINEST)) {
            LOGGER.log(Level.FINEST, "{0} → {1}; leftItems={2}", new Object[] {snapshot, revised, leftItems.asMap()});
        }
        snapshot = revised;
    }

    public boolean cancel(Item item) {
@@ -1443,9 +1447,11 @@ public void maintain() {
                }
                // pending -> buildable
                for (BuildableItem p: lostPendings) {
                    LOGGER.log(Level.FINE,
                    if (LOGGER.isLoggable(Level.FINE)) {
                        LOGGER.log(Level.FINE,
                            "BuildableItem {0}: pending -> buildable as the assigned executor disappeared",
                            p.task.getFullDisplayName());
                    }
                    p.isPending = false;
                    pendings.remove(p);
                    makeBuildable(p); // TODO whatever this is for, the return value is being ignored, so this does nothing at all
@@ -1464,7 +1470,7 @@ public void maintain() {
                    Collections.sort(blockedItems, QueueSorter.DEFAULT_BLOCKED_ITEM_COMPARATOR);
                }
                for (BlockedItem p : blockedItems) {
                    String taskDisplayName = p.task.getFullDisplayName();
                    String taskDisplayName = LOGGER.isLoggable(Level.FINEST) ? p.task.getFullDisplayName() : null;
                    LOGGER.log(Level.FINEST, "Current blocked item: {0}", taskDisplayName);
                    if (!isBuildBlocked(p) && allowNewBuildableTask(p.task)) {
                        LOGGER.log(Level.FINEST,
@@ -1499,7 +1505,7 @@ public void maintain() {
                if (!isBuildBlocked(top) && allowNewBuildableTask(p)) {
                    // ready to be executed immediately
                    Runnable r = makeBuildable(new BuildableItem(top));
                    String topTaskDisplayName = top.task.getFullDisplayName();
                    String topTaskDisplayName = LOGGER.isLoggable(Level.FINEST) ? top.task.getFullDisplayName() : null;
                    if (r != null) {
                        LOGGER.log(Level.FINEST, "Executing runnable {0}", topTaskDisplayName);
                        r.run();