[jira] [Created] (HBASE-28042) Snapshot corruptions due to non-atomic rename within same filesystem

["Viraj Jasani (Jira)" <ji...@apache.org>]

Viraj Jasani created HBASE-28042:
------------------------------------

             Summary: Snapshot corruptions due to non-atomic rename within same filesystem
                 Key: HBASE-28042
                 URL: https://issues.apache.org/jira/browse/HBASE-28042
             Project: HBase
          Issue Type: Bug
            Reporter: Viraj Jasani
            Assignee: Viraj Jasani
             Fix For: 2.6.0, 2.4.18, 2.5.6, 3.0.0-beta-1


Sequence of events that can lead to snapshot corruptions:
 # Create snapshot using admin command
 # Active master triggers async snapshot creation
 # If the snapshot operation doesn't complete within 5 min, client gets exception

{code:java}
org.apache.hadoop.hbase.snapshot.SnapshotCreationException: Snapshot 'T1_1691888405683_1691888440827_1' wasn't completed in expectedTime:600000 ms   {code}
 # Client initiates snapshot deletion after this error
 # In the snapshot completion/commit phase, the files are moved from tmp to final dir.
 # Snapshot delete and snapshot commit operations can cause corruption by leaving incomplete metadata:

 * [Snapshot commit] create "/hbase/.hbase-snapshot/T1_1691888405683_1691888440827_1/.snapshotinfo"
 * [Snapshot delete from client]  delete "/hbase/.hbase-snapshot/T1_1691888405683_1691888440827_1/.snapshotinfo"
 * [Snapshot commit]  create "/hbase/.hbase-snapshot/T1_1691888405683_1691888440827_1/data-manifest"

 

The changes introduced by HBASE-21098 performs atomic rename for hbase 1 but not for hbase 2
{code:java}
  public static void completeSnapshot(Path snapshotDir, Path workingDir, FileSystem fs,
    FileSystem workingDirFs, final Configuration conf)
    throws SnapshotCreationException, IOException {
    LOG.debug(
      "Sentinel is done, just moving the snapshot from " + workingDir + " to " + snapshotDir);
    URI workingURI = workingDirFs.getUri();
    URI rootURI = fs.getUri();
    if (
      (!workingURI.getScheme().equals(rootURI.getScheme()) || workingURI.getAuthority() == null
        || !workingURI.getAuthority().equals(rootURI.getAuthority())
        || workingURI.getUserInfo() == null //always true for hdfs://{cluster}
        || !workingURI.getUserInfo().equals(rootURI.getUserInfo())
        || !fs.rename(workingDir, snapshotDir)) //this condition isn't even evaluated due to short circuit above
        && !FileUtil.copy(workingDirFs, workingDir, fs, snapshotDir, true, true, conf) // non-atomic rename operation
    ) {
      throw new SnapshotCreationException("Failed to copy working directory(" + workingDir
        + ") to completed directory(" + snapshotDir + ").");
    }
  } {code}
whereas for hbase 1
{code:java}
// check UGI/userInfo
if (workingURI.getUserInfo() == null && rootURI.getUserInfo() != null) {
  return true;
}
if (workingURI.getUserInfo() != null &&
    !workingURI.getUserInfo().equals(rootURI.getUserInfo())) {
  return true;
}
 {code}
this causes shouldSkipRenameSnapshotDirectories() to return false if workingURI and rootURI share the same filesystem, which would always lead to atomic rename:
{code:java}
if ((shouldSkipRenameSnapshotDirectories(workingURI, rootURI)
    || !fs.rename(workingDir, snapshotDir))
     && !FileUtil.copy(workingDirFs, workingDir, fs, snapshotDir, true, true, conf)) {
  throw new SnapshotCreationException("Failed to copy working directory(" + workingDir
      + ") to completed directory(" + snapshotDir + ").");
} {code}
 



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