[MAPREDUCE-7233] MapReduce Input Path Should Ignore Path Ends With '/*' When Job Submit

• Type: Bug
• Status: Open
• Priority: Major
• Resolution: Unresolved
• Affects Version/s: 2.7.2
• Component/s: job submission, performance
• Assignee: Unassigned
• Reporter: Victor Zhang
• Created: 20/Aug/19 09:09
• Updated: 20/Nov/19 02:13

Description

We have a public and shared hadoop cluster that runs so many MR job from different department.

 

I found that job submission very slow once the input path of the job set to a path ends with "/*", like "/my/path/*", but "/my/path" or "/my/path/" works fine.

 

After read the code. I think the problem lies in the process of splits calculation.

 

FileInputFormat#singleThreadedListStatus() method get a array of FileStatus first. If the input path ends with "/*", and the result is all file/directory FileStatus object in the input path. But only one FileStatus object(the input path) if the input path not ends with "/*".

 

The next step is find the LocatedFileStatus of each FileStatus object. so, only the directory FileStatus do searching the LocatedFileStatus(dfs.listPaths(), batch).

 

Finally, when calculate job split like FileInputFormat#getSplits() method. If the FileStatus is not LocatedFileStatus object, then use fs.getFileBlockLocations() method to fetch. Which could lead a lot of RPC requests when many files in the input path. CombineFileInputFormat do this also in the construction method of OneFileInfo.

 

So, in this case, some job take a few minutes/hours to submit.

 

I tried to remove the suffix of the input path that ends with "/*" before the code that get file status, but I don't confirm if this will cause other problems.