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interface `LeaseRecoverable`

hadoop-common-project/hadoop-common/src/site/markdown/filesystem/leaserecoverable.md

2.0.5-alpha-rc22.1 KB
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<a name="LeaseRecoverable"></a> interface LeaseRecoverable

The LeaseRecoverable interface tells whether a given path of current filesystem can perform lease recovery for open file that a lease is not explicitly renewed or the client holding it goes away.

This interface should be implemented accordingly when necessary to any Filesystem that supports lease recovery, e.g. DistributedFileSystem (HDFS) and ViewDistributedFileSystem.

java
public interface LeaseRecoverable {
  boolean recoverLease(Path file) throws IOException;
  boolean isFileClosed(Path file) throws IOException;
}

There are two main functions of this interface, one performs lease recovery and another one verifies if a file has been closed.

boolean recoverLease(Path file)

This function performs the lease recovery for the given file path, and it does not support directory path recovery.

  1. Return true, if the file has already closed, or does not require lease recovery.
  2. Return false, if the lease recovery is yet completed.
  3. Throw IOException if a directory path is given as input.

boolean isFileClosed(Path file)

This function only checks if the give file path has been closed, and it does not support directory verification.

  1. Return true, if the file has been closed.
  2. Return false, if the file is still open.
  3. Throw IOException if a directory path is given as input.

Path Capabilities SHOULD BE declared

If a filesystem supports LeaseRecoverable, it should return true to PathCapabilities.hasPathCapability(path, "fs.capability.lease.recoverable") for a given path.