Distinguish the remote, disk and combined caches in the UI state trac…

…ker.

src/main/java/com/google/devtools/build/lib/remote/GrpcCacheClient.java

@@ -117,6 +117,11 @@ public GrpcCacheClient(
         maxMissingBlobsDigestsPerMessage > 0, "Error: gRPC message size too small.");
   }
 
+  @Override
+  public String getDisplayName() {
+    return "remote-cache";
+  }
+
   private int computeMaxMissingBlobsDigestsPerMessage() {
     final int overhead =
         FindMissingBlobsRequest.newBuilder()

src/main/java/com/google/devtools/build/lib/remote/RemoteCache.java

@@ -95,6 +95,10 @@ public RemoteCache(
     this.options = options;
     this.digestUtil = digestUtil;
   }
+
+  public String getDisplayName() {
+    return cacheProtocol.getDisplayName();
+  }
 
   public CacheCapabilities getCacheCapabilities() throws IOException {
     return cacheProtocol.getCacheCapabilities();

src/main/java/com/google/devtools/build/lib/remote/RemoteExecutionService.java

@@ -289,6 +289,15 @@ private static boolean useDiskCache(RemoteOptions options) {
     return options.diskCache != null && !options.diskCache.isEmpty();
   }
 
+  /**
+   * If using a disk, remote or combined cache, returns the display name for the cache. Otherwise,
+   * returns null.
+   */
+  @Nullable
+  public String getCacheDisplayName() {
+    return remoteCache != null ? remoteCache.getDisplayName() : null;
+  }
+
   public CachePolicy getReadCachePolicy(Spawn spawn) {
     if (remoteCache == null) {
       return CachePolicy.NO_CACHE;

src/main/java/com/google/devtools/build/lib/remote/RemoteSpawnCache.java

@@ -13,6 +13,7 @@
 // limitations under the License.
 package com.google.devtools.build.lib.remote;
 
+import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.base.Strings.isNullOrEmpty;
 import static com.google.devtools.build.lib.profiler.ProfilerTask.REMOTE_DOWNLOAD;
 import static com.google.devtools.build.lib.remote.util.Utils.createSpawnResult;
@@ -46,6 +47,7 @@
 import com.google.devtools.build.lib.vfs.Path;
 import java.io.IOException;
 import java.util.NoSuchElementException;
+import java.util.concurrent.ConcurrentHashMap;
 
 /** A remote {@link SpawnCache} implementation. */
 @ThreadSafe // If the RemoteActionCache implementation is thread-safe.
@@ -60,6 +62,10 @@ final class RemoteSpawnCache implements SpawnCache {
   private final DigestUtil digestUtil;
   private final boolean verboseFailures;
 
+  // Maps cache display names to lazily-initialized, reusable singleton events, to reduce garbage.
+  private static final ConcurrentHashMap<String, SpawnCheckingCacheEvent> EVENT_MAP =
+      new ConcurrentHashMap<>();
+
   RemoteSpawnCache(
       Path execRoot,
       RemoteOptions options,
@@ -101,7 +107,7 @@ public CacheHandle lookup(Spawn spawn, SpawnExecutionContext context)
 
     Profiler prof = Profiler.instance();
     if (shouldAcceptCachedResult) {
-      context.report(SPAWN_CHECKING_CACHE_EVENT);
+      reportSpawnCheckingCacheEvent(context);
       // Metadata will be available in context.current() until we detach.
       // This is done via a thread-local variable.
       try {
@@ -212,6 +218,13 @@ private void checkForConcurrentModifications()
     }
   }
 
+  private void reportSpawnCheckingCacheEvent(SpawnExecutionContext context) {
+    String displayName = checkNotNull(remoteExecutionService.getCacheDisplayName());
+    SpawnCheckingCacheEvent event = EVENT_MAP.computeIfAbsent(displayName,
+        SpawnCheckingCacheEvent::create);
+    context.report(event);
+  }
+
   @Override
   public boolean usefulInDynamicExecution() {
     return false;

src/main/java/com/google/devtools/build/lib/remote/common/RemoteCacheClient.java

@@ -33,6 +33,9 @@
  * <p>Implementations must be thread-safe.
  */
 public interface RemoteCacheClient extends MissingDigestsFinder {
+
+  String getDisplayName();
+
   CacheCapabilities getCacheCapabilities() throws IOException;
 
   ListenableFuture<String> getAuthority();

src/main/java/com/google/devtools/build/lib/remote/disk/DiskAndRemoteCacheClient.java

@@ -49,6 +49,11 @@ public DiskAndRemoteCacheClient(DiskCacheClient diskCache, RemoteCacheClient rem
     this.remoteCache = Preconditions.checkNotNull(remoteCache);
   }
 
+  @Override
+  public String getDisplayName() {
+    return "combined-cache";
+  }
+
   @Override
   public ListenableFuture<Void> uploadActionResult(
       RemoteActionExecutionContext context, ActionKey actionKey, ActionResult actionResult) {

src/main/java/com/google/devtools/build/lib/remote/disk/DiskCacheClient.java

@@ -84,6 +84,11 @@ public DiskCacheClient(Path root, boolean verifyDownloads, DigestUtil digestUtil
     this.root.createDirectoryAndParents();
   }
 
+  @Override
+  public String getDisplayName() {
+    return "disk-cache";
+  }
+
   /**
    * If the given path exists, updates its mtime and returns true. Otherwise, returns false.
    *

src/main/java/com/google/devtools/build/lib/remote/http/HttpCacheClient.java

@@ -300,6 +300,11 @@ public void channelCreated(Channel ch) {
     this.retrier = retrier;
   }
 
+  @Override
+  public String getDisplayName() {
+    return "remote-cache";
+  }
+
   @SuppressWarnings("FutureReturnValueIgnored")
   private Promise<Channel> acquireUploadChannel() {
     Promise<Channel> channelReady = eventLoop.next().newPromise();

src/test/java/com/google/devtools/build/lib/remote/RemoteSpawnCacheTest.java

@@ -288,6 +288,8 @@ public final void setUp() throws Exception {
     remotePathResolver = RemotePathResolver.createDefault(execRoot);
 
     fakeFileCache.createScratchInput(simpleSpawn.getInputFiles().getSingleton(), "xyz");
+
+    when(remoteCache.getDisplayName()).thenReturn("remote-cache");
   }
 
   @Test

src/test/java/com/google/devtools/build/lib/remote/util/InMemoryCacheClient.java

@@ -59,6 +59,11 @@ public InMemoryCacheClient(Map<Digest, byte[]> casEntries) {
     }
   }
 
+  @Override
+  public String getDisplayName() {
+    return "in-memory-cache";
+  }
+
   public InMemoryCacheClient() {
     this.cas = new ConcurrentHashMap<>();
   }