Separate new-style-hash content in DiskCache

DiskCache always stores files in /root/{cas/ac}/digestHash. This change keeps the current behavior, but for new style digest functions inserts a directory between /root/ and {cas/ac} to disambiguate the digest function type.

This prevents issues that could theoretically happen if there were hash collisions between two digest functions sharing the same cache directory.

PiperOrigin-RevId: 554477775
Change-Id: Ibef994e432764c260a3cab821ca6583c231c5b50

(cherry picked from commit f17b280)
Signed-off-by: Brentley Jones <[email protected]>

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

@@ -13,6 +13,7 @@
 // limitations under the License.
 package com.google.devtools.build.lib.remote;
 
+import static com.google.devtools.build.lib.remote.util.DigestUtil.isOldStyleDigestFunction;
 import static com.google.devtools.build.lib.remote.util.RxFutures.toCompletable;
 import static com.google.devtools.build.lib.remote.util.RxFutures.toListenableFuture;
 import static com.google.devtools.build.lib.remote.util.RxFutures.toSingle;
@@ -443,14 +444,6 @@ private static class PathConverterImpl implements PathConverter {
       this.localPaths = localPaths.build();
     }
 
-    private static boolean isOldStyleDigestFunction(DigestFunction.Value digestFunction) {
-      // Old-style digest functions (SHA256, etc) are distinguishable by the length
-      // of their hash alone and do not require extra specification, but newer
-      // digest functions (which may have the same length hashes as the older
-      // functions!) must be explicitly specified in the upload resource name.
-      return digestFunction.getNumber() <= 7;
-    }
-
     @Override
     @Nullable
     public String apply(Path path) {

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

@@ -15,6 +15,7 @@
 
 import static com.google.common.base.Preconditions.checkArgument;
 import static com.google.common.util.concurrent.Futures.immediateVoidFuture;
+import static com.google.devtools.build.lib.remote.util.DigestUtil.isOldStyleDigestFunction;
 import static com.google.devtools.build.lib.remote.util.Utils.getFromFuture;
 import static com.google.devtools.build.lib.remote.util.Utils.waitForBulkTransfer;
 import static java.lang.String.format;
@@ -179,20 +180,12 @@ public ListenableFuture<Void> uploadBlobAsync(
         MoreExecutors.directExecutor());
   }
 
-  private boolean isOldStyleDigestFunction() {
-    // Old-style digest functions (SHA256, etc) are distinguishable by the length
-    // of their hash alone and do not require extra specification, but newer
-    // digest functions (which may have the same length hashes as the older
-    // functions!) must be explicitly specified in the upload resource name.
-    return digestFunction.getNumber() <= 7;
-  }
-
   private String buildUploadResourceName(
       String instanceName, UUID uuid, Digest digest, boolean compressed) {
 
     String resourceName;
 
-    if (isOldStyleDigestFunction()) {
+    if (isOldStyleDigestFunction(digestFunction)) {
       String template =
           compressed ? "uploads/%s/compressed-blobs/zstd/%s/%d" : "uploads/%s/blobs/%s/%d";
       resourceName = format(template, uuid, digest.getHash(), digest.getSizeBytes());

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

@@ -15,6 +15,7 @@
 package com.google.devtools.build.lib.remote;
 
 import static com.google.common.base.Strings.isNullOrEmpty;
+import static com.google.devtools.build.lib.remote.util.DigestUtil.isOldStyleDigestFunction;
 
 import build.bazel.remote.execution.v2.ActionCacheGrpc;
 import build.bazel.remote.execution.v2.ActionCacheGrpc.ActionCacheFutureStub;
@@ -354,14 +355,6 @@ private ListenableFuture<Void> downloadBlob(
         MoreExecutors.directExecutor());
   }
 
-  private static boolean isOldStyleDigestFunction(DigestFunction.Value digestFunction) {
-    // Old-style digest functions (SHA256, etc) are distinguishable by the length
-    // of their hash alone and do not require extra specification, but newer
-    // digest functions (which may have the same length hashes as the older
-    // functions!) must be explicitly specified in the upload resource name.
-    return digestFunction.getNumber() <= 7;
-  }
-
   public static String getResourceName(
       String instanceName, Digest digest, boolean compressed, DigestFunction.Value digestFunction) {
     String resourceName = "";

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

@@ -13,10 +13,13 @@
 // limitations under the License.
 package com.google.devtools.build.lib.remote.disk;
 
+import static com.google.devtools.build.lib.remote.util.DigestUtil.isOldStyleDigestFunction;
+
 import build.bazel.remote.execution.v2.ActionResult;
 import build.bazel.remote.execution.v2.Digest;
 import build.bazel.remote.execution.v2.Directory;
 import build.bazel.remote.execution.v2.Tree;
+import com.google.common.base.Ascii;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.io.ByteStreams;
 import com.google.common.util.concurrent.Futures;
@@ -57,10 +60,17 @@ public class DiskCacheClient implements RemoteCacheClient {
    */
   public DiskCacheClient(
       Path root, boolean verifyDownloads, boolean checkActionResult, DigestUtil digestUtil) {
-    this.root = root;
     this.verifyDownloads = verifyDownloads;
     this.checkActionResult = checkActionResult;
     this.digestUtil = digestUtil;
+
+    if (isOldStyleDigestFunction(digestUtil.getDigestFunction())) {
+      this.root = root;
+    } else {
+      this.root =
+          root.getChild(
+              Ascii.toLowerCase(digestUtil.getDigestFunction().getValueDescriptor().getName()));
+    }
   }
 
   /** Returns {@code true} if the provided {@code key} is stored in the CAS. */

src/main/java/com/google/devtools/build/lib/remote/util/DigestUtil.java

@@ -131,4 +131,12 @@ public static String toString(Digest digest) {
   public static byte[] toBinaryDigest(Digest digest) {
     return HashCode.fromString(digest.getHash()).asBytes();
   }
+
+  public static boolean isOldStyleDigestFunction(DigestFunction.Value digestFunction) {
+    // Old-style digest functions (SHA256, etc) are distinguishable by the length
+    // of their hash alone and do not require extra specification, but newer
+    // digest functions (which may have the same length hashes as the older
+    // functions!) must be explicitly specified in the upload resource name.
+    return digestFunction.getNumber() <= 7;
+  }
 }