[HADOOP-12046] Avoid creating "._COPYING_" temporary file when copying file to Swift file system

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Duplicate
• Affects Version/s: 2.7.0
• Component/s: fs/swift
• Assignee: Chen He
• Reporter: Chen He
• Created: 01/Jun/15 03:03
• Updated: 14/Mar/19 14:26
• Resolved: 14/Mar/19 14:26

Description

When copy file from HDFS or local to another file system implementation, in CommandWithDestination.java, it creates a temp file by adding suffix ".COPYING". Once file is successfully copied, it will remove the suffix by rename().

try

{ PathData tempTarget = target.suffix("._COPYING_"); targetFs.setWriteChecksum(writeChecksum); targetFs.writeStreamToFile(in, tempTarget, lazyPersist); targetFs.rename(tempTarget, target); }

finally

{ targetFs.close(); // last ditch effort to ensure temp file is removed }

It is not costly in HDFS. However, if copy to Swift file system, the rename process is to create a new file. It is not efficient if users copy a lot of files to swift file system. I did some tests, for a 1G file copying to swift, it will take 10% more time. We should only do the copy one time for Swift file system. Changes should be limited to the Swift driver level.

Issue Links

• depends upon: HADOOP-12057 swiftfs rename on partitioned file attempts to consolidate partitions
• is related to: HADOOP-12038 SwiftNativeOutputStream should check whether a file exists or not before deleting
• is superceded by: HADOOP-15281 Distcp to add no-rename copy option
• relates to: HADOOP-12109 Distcp of file > 5GB to swift fails with HTTP 413 error
• relates to: HDFS-8673 HDFS reports file already exists if there is a file/dir name end with ._COPYING_
• relates to: HADOOP-9565 Add a Blobstore interface to add to blobstore FileSystems