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From mjac...@apache.org
Subject [1/2] incubator-impala git commit: IMPALA-4611: Checking perms on S3 files is a very expensive no-op
Date Tue, 13 Dec 2016 03:13:25 GMT
Repository: incubator-impala
Updated Branches:
  refs/heads/master 2414d4c9c -> 73e41cea1


IMPALA-4611: Checking perms on S3 files is a very expensive no-op

We call getPermissions() on partition directories to find out if
Impala has access to those files. On S3, this currently is a no-op
as the S3A connector does not try to set/get the permissions for S3
objects. So, it always returns the default set of permissions -> 777.
However, it still makes a roundtrip to S3 causing a slow down in the
Catalog.

We can return the READ_WRITE permission immediately if we know we are
accessing an S3 file, thereby avoiding the round trip to S3 for every
partition. This will greatly speedup metadata operations for S3 tables
and partitions, which is already known to be a big bottleneck.

If and when the S3A connector is able to manage permissions in
the future, we need to revisit this code. However, as permissions on
S3 are unsupported by Impala right now, we might as well gain on perf.

Change-Id: If9d1072c185a6162727019cdf1cb34d7f3f1c75c
Reviewed-on: http://gerrit.cloudera.org:8080/5449
Reviewed-by: Sailesh Mukil <sailesh@cloudera.com>
Tested-by: Impala Public Jenkins


Project: http://git-wip-us.apache.org/repos/asf/incubator-impala/repo
Commit: http://git-wip-us.apache.org/repos/asf/incubator-impala/commit/ffbdeda9
Tree: http://git-wip-us.apache.org/repos/asf/incubator-impala/tree/ffbdeda9
Diff: http://git-wip-us.apache.org/repos/asf/incubator-impala/diff/ffbdeda9

Branch: refs/heads/master
Commit: ffbdeda9469997dce6c6c3a80c78877486a3bdd9
Parents: 2414d4c
Author: Sailesh Mukil <sailesh@cloudera.com>
Authored: Fri Dec 9 15:12:25 2016 -0800
Committer: Impala Public Jenkins <impala-public-jenkins@gerrit.cloudera.org>
Committed: Tue Dec 13 01:56:28 2016 +0000

----------------------------------------------------------------------
 fe/src/main/java/org/apache/impala/catalog/HdfsTable.java | 10 ++++++++++
 1 file changed, 10 insertions(+)
----------------------------------------------------------------------


http://git-wip-us.apache.org/repos/asf/incubator-impala/blob/ffbdeda9/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
----------------------------------------------------------------------
diff --git a/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java b/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
index ae5e811..c2c569f 100644
--- a/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
+++ b/fe/src/main/java/org/apache/impala/catalog/HdfsTable.java
@@ -795,9 +795,19 @@ public class HdfsTable extends Table {
    * permissions Impala has on the given path. If the path does not exist, recurses up
    * the path until a existing parent directory is found, and inherit access permissions
    * from that.
+   * Always returns READ_WRITE for S3 files.
    */
   private TAccessLevel getAvailableAccessLevel(FileSystem fs, Path location)
       throws IOException {
+
+    // Avoid calling getPermissions() on file path for S3 files, as that makes a round
+    // trip to S3. Also, the S3A connector is currently unable to manage S3 permissions,
+    // so for now it is safe to assume that all files(objects) have READ_WRITE
+    // permissions, as that's what the S3A connector will always return too.
+    // TODO: Revisit if the S3A connector is updated to be able to manage S3 object
+    // permissions. (see HADOOP-13892)
+    if (FileSystemUtil.isS3AFileSystem(fs)) return TAccessLevel.READ_WRITE;
+
     FsPermissionChecker permissionChecker = FsPermissionChecker.getInstance();
     while (location != null) {
       if (fs.exists(location)) {


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