Fix "Zeno’s paradox" like logic of the progress calculation.

Author: Dmytro Ukhlov

core/src/main/java/jenkins/widgets/RunListProgressiveRendering.java

@@ -27,6 +27,7 @@
 import hudson.model.Run;
 import hudson.util.RunList;
 import java.util.ArrayList;
+import java.util.Iterator;
 import java.util.List;
 import jenkins.util.ProgressiveRendering;
 import net.sf.json.JSON;
@@ -46,7 +47,9 @@ public abstract class RunListProgressiveRendering extends ProgressiveRendering {
      * The first increment will be sized as if this many runs will be in the total,
      * but then like Zeno’s paradox we will never seem to finish until we actually do.
      */
-    private static final double MAX_LIKELY_RUNS = 20;
+    private static final double MAX_LIKELY_RUNS = 20; // if (MAX_LIKELY_RUNS / 2) runs are processed, progress is 0.5
+    private static final int RUN_LIMIT = 1000; // Limit is need because UI doesn't have a pagination
+
     private final List<JSONObject> results = new ArrayList<>();
     private Iterable<? extends Run<?, ?>> builds;
 
@@ -56,18 +59,17 @@ public void setBuilds(Iterable<? extends Run<?, ?>> builds) {
     }
 
     @Override protected void compute() throws Exception {
-        double decay = 1;
-        for (Run<?, ?> build : builds) {
-            if (canceled()) {
-                return;
-            }
+        int processed = 0;
+        Iterator<? extends Run<?, ?>> iter = builds.iterator();
+        while (!canceled() && iter.hasNext() && processed < RUN_LIMIT) {
+            Run<?, ?> build = iter.next();
             JSONObject element = new JSONObject();
             calculate(build, element);
             synchronized (this) {
                 results.add(element);
             }
-            decay *= 1 - 1 / MAX_LIKELY_RUNS;
-            progress(1 - decay);
+            processed++;
+            progress(processed / (processed + MAX_LIKELY_RUNS / 2.0));
         }
     }