Add load time of action cache to statistics.

PiperOrigin-RevId: 583040794
Change-Id: I249afa1769edf76780373a1907a02a4fe5abe74f

src/main/java/com/google/devtools/build/lib/actions/cache/ActionCache.java

@@ -37,6 +37,7 @@
 import com.google.devtools.build.lib.vfs.PathFragment;
 import java.io.IOException;
 import java.io.PrintStream;
+import java.time.Duration;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -434,4 +435,10 @@ public String toString() {
 
   /** Resets the current statistics to zero. */
   void resetStatistics();
+
+  /** Duration it took to load the action cache. Might be null if not loaded in this invocation. */
+  @Nullable
+  default Duration getLoadTime() {
+    return null;
+  }
 }

src/main/java/com/google/devtools/build/lib/actions/cache/CompactPersistentActionCache.java

@@ -47,6 +47,7 @@
 import java.nio.BufferUnderflowException;
 import java.nio.ByteBuffer;
 import java.time.Duration;
+import java.time.Instant;
 import java.util.Collection;
 import java.util.EnumMap;
 import java.util.Map;
@@ -171,6 +172,7 @@ protected void writeValue(byte[] value, DataOutputStream out) throws IOException
   private final PersistentMap<Integer, byte[]> map;
   private final ImmutableMap<MissReason, AtomicInteger> misses;
   private final AtomicInteger hits = new AtomicInteger();
+  private Duration loadTime;
 
   private CompactPersistentActionCache(
       PersistentStringIndexer indexer,
@@ -184,8 +186,14 @@ private CompactPersistentActionCache(
   public static CompactPersistentActionCache create(
       Path cacheRoot, Clock clock, EventHandler reporterForInitializationErrors)
       throws IOException {
-    return create(
-        cacheRoot, clock, reporterForInitializationErrors, /*alreadyFoundCorruption=*/ false);
+    Instant before = clock.now();
+    CompactPersistentActionCache compactPersistentActionCache =
+        create(
+            cacheRoot, clock, reporterForInitializationErrors, /* alreadyFoundCorruption= */ false);
+    Instant after = clock.now();
+    compactPersistentActionCache.loadTime = Duration.between(before, after);
+
+    return compactPersistentActionCache;
   }
 
   private static CompactPersistentActionCache create(
@@ -759,4 +767,14 @@ public void resetStatistics() {
       entry.getValue().set(0);
     }
   }
+
+  @Override
+  @Nullable
+  public Duration getLoadTime() {
+    Duration ret = loadTime;
+    // As a side effect, reset the load time, so it is only reported for the actual invocation that
+    // loaded the action cache.
+    loadTime = null;
+    return ret;
+  }
 }

src/main/java/com/google/devtools/build/lib/buildtool/ExecutionTool.java

@@ -1011,6 +1011,10 @@ private void saveActionCache(@Nullable ActionCache actionCache) {
 
     if (actionCache != null) {
       actionCache.mergeIntoActionCacheStatistics(builder);
+      Duration duration = actionCache.getLoadTime();
+      if (duration != null) {
+        builder.setLoadTimeInMs(duration.toMillis());
+      }
 
       AutoProfiler p =
           GoogleAutoProfilerUtils.profiledAndLogged("Saving action cache", ProfilerTask.INFO);

src/main/protobuf/action_cache.proto

@@ -55,5 +55,9 @@ message ActionCacheStatistics {
   // Breakdown of the cache misses based on the reasons behind them.
   repeated MissDetail miss_details = 5;
 
-  // NEXT TAG: 6
+  // Time it took to load the action cache from disk. Reported as 0 if the
+  // action cache has not been loaded in this invocation.
+  uint64 load_time_in_ms = 6;
+
+  // NEXT TAG: 7
 }