Issue number: 806

Provide synchronous SCM polling in the order of dependencies.  For now, to
activate, edit hudson.triggers.SCMTrigger.xml and add
<synchronousPolling>true</synchronousPolling>

This change also relaxes visibility  of Trigger.run()  from protected  to
public.

TODO: connect the UI and provide a global crontab spec setting.  This will
probably happen when I get some feedback on this change.


git-svn-id: https://hudson.dev.java.net/svn/hudson/trunk/hudson/main@4700 71c3de6d-444a-0410-be80-ed276b4c234a

core/src/main/java/hudson/DependencyRunner.java

@@ -0,0 +1,55 @@
+package hudson;
+
+import hudson.model.AbstractProject;
+import hudson.model.Hudson;
+
+import java.util.ArrayList;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * Runs a job on all projects in the order of dependencies
+ */
+public class DependencyRunner implements Runnable {
+    AbstractProject currentProject;
+
+    ProjectRunnable runnable;
+
+    List<AbstractProject> polledProjects = new ArrayList<AbstractProject>();
+
+    @SuppressWarnings("unchecked")
+        public DependencyRunner(ProjectRunnable runnable) {
+            this.runnable = runnable;
+        }
+
+    public void run() {
+        Set<AbstractProject> topLevelProjects = new HashSet<AbstractProject>();
+        // Get all top-level projects
+        for (AbstractProject p : Hudson.getInstance().getAllItems(
+                    AbstractProject.class))
+            if (p.getUpstreamProjects().size() == 0)
+                topLevelProjects.add(p);
+        populate(topLevelProjects);
+        for (AbstractProject p : polledProjects)
+            runnable.run(p);
+    }
+
+    private void populate(Set<AbstractProject> projectList) {
+        for (AbstractProject p : projectList) {
+            if (polledProjects.contains(p))
+                // Project will be readded at the queue, so that we always use
+                // the longest path
+                polledProjects.remove(p);
+
+            polledProjects.add(p);
+
+            // Add all downstream dependencies
+            populate(new HashSet<AbstractProject>(p.getDownstreamProjects()));
+        }
+    }
+
+    public interface ProjectRunnable {
+        void run(AbstractProject p);
+    }
+}