experimental UI: track touched packages during loading/analysis

To give a better understanding of which packages are on the critical
path during loading and analysis, provide information in the same way
as during execution: show the earliest started, but not yet completed
package. As not all packages looked at during the analysis phase are
reported to the progress receiver, use a custom class to aggregate those
data.

--
Change-Id: I03c25efdecb4124e1bc06fce8be9175dc56b5500
Reviewed-on: https://bazel-review.googlesource.com/#/c/3700
MOS_MIGRATED_REVID=123408689

1 files changed, 73 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/PackageProgressReceiver.java b/src/main/java/com/google/devtools/build/lib/skyframe/PackageProgressReceiver.java
new file mode 100644
index 0000000000..4faf952dd9
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/PackageProgressReceiver.java
@@ -0,0 +1,73 @@
+// Copyright 2016 The Bazel Authors. All rights reserved.
+//
+// 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.google.devtools.build.lib.skyframe;
+
+import com.google.devtools.build.lib.cmdline.PackageIdentifier;
+
+import com.google.devtools.build.lib.util.Pair;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+
+/**
+ * A class that, when beeing told about start and end of a package
+ * being loaded, keeps track of the loading progress and provides it
+ * as a human-readable string intened for the progress bar.
+ */
+public class PackageProgressReceiver {
+
+  private int packagesCompleted;
+  private Deque<PackageIdentifier> pending = new ArrayDeque<>();
+
+  /**
+   * Register that loading a package has started.
+   */
+  public synchronized void startReadPackage(PackageIdentifier packageId) {
+    pending.addLast(packageId);
+  }
+
+  /**
+   * Register that loding a package has completed.
+   */
+  public synchronized void doneReadPackage(PackageIdentifier packageId) {
+    packagesCompleted++;
+    pending.remove(packageId);
+  }
+
+  /**
+   * Reset all instance variables of this object to a state equal to that of a newly
+   * constructed object.
+   */
+  public synchronized void reset() {
+    packagesCompleted = 0;
+    pending = new ArrayDeque<>();
+  }
+
+  /**
+   * Return the ordered pair of a consistent snapshot of the state, consisting of a human-readable
+   * description of the progress achieved so far and a human readable description of the currently
+   * running activities. The later always include the oldest loading package not finished loading.
+   */
+  public synchronized Pair<String, String> progressState() {
+    String progress = "" + packagesCompleted + " packages loaded";
+    StringBuffer activity = new StringBuffer();
+    if (pending.size() > 0) {
+      activity.append("currently loading: ").append(pending.peekFirst().toString());
+      if (pending.size() > 1) {
+        activity.append(" ... (" + pending.size() + " packages)");
+      }
+    }
+    return new Pair<String, String>(progress, activity.toString());
+  }
+}