1 files changed, 93 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/CacheFileDigestsModule.java b/src/main/java/com/google/devtools/build/lib/runtime/CacheFileDigestsModule.java
new file mode 100644
index 0000000000..1c94bd8a17
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/runtime/CacheFileDigestsModule.java
@@ -0,0 +1,93 @@
+// Copyright 2017 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.runtime;
+
+import com.google.common.cache.CacheStats;
+import com.google.devtools.build.lib.actions.cache.DigestUtils;
+import com.google.devtools.build.lib.buildtool.BuildRequest;
+import com.google.devtools.build.lib.exec.ExecutionOptions;
+import com.google.devtools.build.lib.exec.ExecutorBuilder;
+import com.google.devtools.build.lib.util.Preconditions;
+import java.util.logging.Logger;
+
+/** Enables the caching of file digests in {@link DigestUtils}. */
+public class CacheFileDigestsModule extends BlazeModule {
+
+  private static final Logger log = Logger.getLogger(CacheFileDigestsModule.class.getName());
+
+  /** Stats gathered at the beginning of a command, to compute deltas on completion. */
+  private CacheStats stats;
+
+  /**
+   * Last known size of the cache. Changes to this value cause the cache to be reinitialized. null
+   * if we don't know anything about the last value yet (i.e. before any command has been run).
+   */
+  private Long lastKnownCacheSize;
+
+  public CacheFileDigestsModule() {}
+
+  /**
+   * Adds a line to the log with cache statistics.
+   *
+   * @param message message to prefix to the written line
+   * @param stats the cache statistics to be logged
+   */
+  private static void logStats(String message, CacheStats stats) {
+    log.info(
+        message
+            + ": hit count="
+            + stats.hitCount()
+            + ", miss count="
+            + stats.missCount()
+            + ", hit rate="
+            + stats.hitRate()
+            + ", eviction count="
+            + stats.evictionCount());
+  }
+
+  @Override
+  public void executorInit(CommandEnvironment env, BuildRequest request, ExecutorBuilder builder) {
+    super.executorInit(env, request, builder);
+
+    ExecutionOptions options = request.getOptions(ExecutionOptions.class);
+    if (lastKnownCacheSize == null
+        || options.cacheSizeForComputedFileDigests != lastKnownCacheSize) {
+      log.info("Reconfiguring cache with size=" + options.cacheSizeForComputedFileDigests);
+      DigestUtils.configureCache(options.cacheSizeForComputedFileDigests);
+      lastKnownCacheSize = options.cacheSizeForComputedFileDigests;
+    }
+
+    if (options.cacheSizeForComputedFileDigests == 0) {
+      stats = null;
+      log.info("Disabled cache");
+    } else {
+      stats = DigestUtils.getCacheStats();
+      logStats("Accumulated cache stats before command", stats);
+    }
+  }
+
+  @Override
+  public void afterCommand() {
+    super.afterCommand();
+
+    if (stats != null) {
+      CacheStats newStats = DigestUtils.getCacheStats();
+      Preconditions.checkNotNull(newStats, "The cache is enabled so we must get some stats back");
+      logStats("Accumulated cache stats after command", newStats);
+      logStats("Cache stats for finished command", newStats.minus(stats));
+      stats = null; // Silence stats until next command that uses the executor.
+    }
+  }
+}