[GitHub] [hadoop] steveloughran commented on a change in pull request #2038: HADOOP-17022 Tune S3AFileSystem.listFiles() api.

[GitBox <gi...@apache.org>]

steveloughran commented on a change in pull request #2038:
URL: https://github.com/apache/hadoop/pull/2038#discussion_r450298495



##########
File path: hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java
##########
@@ -4181,79 +4181,114 @@ public LocatedFileStatus next() throws IOException {
     Path path = qualify(f);
     LOG.debug("listFiles({}, {})", path, recursive);
     try {
-      // if a status was given, that is used, otherwise
-      // call getFileStatus, which triggers an existence check
-      final S3AFileStatus fileStatus = status != null
-          ? status
-          : (S3AFileStatus) getFileStatus(path);
-      if (fileStatus.isFile()) {
+      // if a status was given and it is a file.
+      if (status != null && status.isFile()) {
         // simple case: File
         LOG.debug("Path is a file");
         return new Listing.SingleStatusRemoteIterator(
-            toLocatedFileStatus(fileStatus));
-      } else {
-        // directory: do a bulk operation
-        String key = maybeAddTrailingSlash(pathToKey(path));
-        String delimiter = recursive ? null : "/";
-        LOG.debug("Requesting all entries under {} with delimiter '{}'",
-            key, delimiter);
-        final RemoteIterator<S3AFileStatus> cachedFilesIterator;
-        final Set<Path> tombstones;
-        boolean allowAuthoritative = allowAuthoritative(f);
-        if (recursive) {
-          final PathMetadata pm = metadataStore.get(path, true);
-          // shouldn't need to check pm.isDeleted() because that will have
-          // been caught by getFileStatus above.
-          MetadataStoreListFilesIterator metadataStoreListFilesIterator =
-              new MetadataStoreListFilesIterator(metadataStore, pm,
-                  allowAuthoritative);
-          tombstones = metadataStoreListFilesIterator.listTombstones();
-          // if all of the below is true
-          //  - authoritative access is allowed for this metadatastore for this directory,
-          //  - all the directory listings are authoritative on the client
-          //  - the caller does not force non-authoritative access
-          // return the listing without any further s3 access
-          if (!forceNonAuthoritativeMS &&
-              allowAuthoritative &&
-              metadataStoreListFilesIterator.isRecursivelyAuthoritative()) {
-            S3AFileStatus[] statuses = S3Guard.iteratorToStatuses(
-                metadataStoreListFilesIterator, tombstones);
-            cachedFilesIterator = listing.createProvidedFileStatusIterator(
-                statuses, ACCEPT_ALL, acceptor);
-            return listing.createLocatedFileStatusIterator(cachedFilesIterator);
-          }
-          cachedFilesIterator = metadataStoreListFilesIterator;
-        } else {
-          DirListingMetadata meta =
-              S3Guard.listChildrenWithTtl(metadataStore, path, ttlTimeProvider,
-                  allowAuthoritative);
-          if (meta != null) {
-            tombstones = meta.listTombstones();
-          } else {
-            tombstones = null;
-          }
-          cachedFilesIterator = listing.createProvidedFileStatusIterator(
-              S3Guard.dirMetaToStatuses(meta), ACCEPT_ALL, acceptor);
-          if (allowAuthoritative && meta != null && meta.isAuthoritative()) {
-            // metadata listing is authoritative, so return it directly
-            return listing.createLocatedFileStatusIterator(cachedFilesIterator);
-          }
+            toLocatedFileStatus(status));
+      }
+      // Assuming the path to be a directory
+      // do a bulk operation.
+      RemoteIterator<S3ALocatedFileStatus> listFilesAssumingDir =
+              getListFilesAssumingDir(path,
+                      recursive,
+                      acceptor,
+                      collectTombstones,
+                      forceNonAuthoritativeMS);
+      // If there are no list entries present, we
+      // fallback to file existence check as the path
+      // can be a file or empty directory.
+      if (!listFilesAssumingDir.hasNext()) {
+        final S3AFileStatus fileStatus = (S3AFileStatus) getFileStatus(path);

Review comment:
       yea, but an empty dir is that HEAD marker. So no list, right?
   
   Don't worry about it -my dir marker tuning changes things anyway, replacing the HEAD + / with a list.




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