Dealing with Corrupt Files in Hadoop

As I've been working with Hadoop a lot in the last several months, I've come to realize that it doesn't deal gracefully with corrupt files (e.g., mal-formed gzip files). I would throw a cluster at a couple hundred thousand files (of which one or two were bad) and the job would die two hours into execution, throwing EOFException errors all over the place. If I was only processing one file, I suppose that's a reasonably acceptable outcome. But when 99.9% of your files are fine, and the corrupt ones aren't recoverable anyway, there's no sense in blowing up the whole job just because a trivial portion of the data was bad.

elephant loses balance

Hadoop's relatively unknown LostBalance exception.

Turns out, it's not too hard to catch those exceptions within a custom record reader, log a warning message, gracefully ignore the files in question, and go about your business. Here's how to do it.

Continue reading