Reimplement blaze query using an async evaluation model. Use a concurrent backend for SkyQueryEnvironment's implementation in order to achieve parallelism.

Advantages:
-New design has no flaws that the old design had.
-Code is structured so that deadlocks due to thread starvation are impossible (yup!).

Disadvantages:
-The meat of this change needs to all be in a single CL because every single QueryFunction and QueryExpression needs to be rewritten in the async style.

Still TODO:
-Fully embrace the async model in all QueryFunctions (e.g. 'rdeps', 'allpaths').
-Use concurrency in BlazeQueryEnvironment to achieve parallel evaluation for (non SkyQuery) 'blaze query' and genquery.

--
PiperOrigin-RevId: 148690279
MOS_MIGRATED_REVID=148690279

1 files changed, 0 insertions, 23 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/ThreadSafeCallback.java b/src/main/java/com/google/devtools/build/lib/query2/engine/ThreadSafeCallback.java
deleted file mode 100644
index 950335e38a..0000000000
--- a/src/main/java/com/google/devtools/build/lib/query2/engine/ThreadSafeCallback.java
+++ /dev/null
@@ -1,23 +0,0 @@
-// Copyright 2014 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.query2.engine;
-
-import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
-import com.google.devtools.build.lib.util.ThreadSafeBatchCallback;
-
-/** Marker interface for a {@link Callback} that is {@link ThreadSafe}. */
-@ThreadSafe
-public interface ThreadSafeCallback<T>
-    extends Callback<T>, ThreadSafeBatchCallback<T, QueryException> {
-}