S3Grep – Searching S3 Files and Buckets

On a project we were working on recently it appeared that we had data coming into our Extract, Transform, Load (ETL) processes which should have been filtered out. In this particular case the files which we imported only would exist at max up to 7 days and on any given day we’d have tens of thousands of files that would be created and imported. This presented a difficult problem to trace down if something inside our ETL had gone awry or if we were being fed bad data. Furthermore as the files always would be deleted after importing we didn’t keep where a data point was created from.

Instead of updating our ETL process to track where a specific piece of data originated from we wanted to basically ‘grep’ the files in S3. After looking around it doesn’t look like anyone has built a “Grep for S3”, so we built one. The reason we didn’t simply download the files locally and then process them one at a time is it’d take forever to transfer, then grep each one individual sequentially. Instead we wanted to do the search in parallel and not hold the entire files on the local disk.

With this we came up with our simple S3Grep java app (a pre-built jar is located in the releases) which will search all files in a specific bucket for a specific string. It currently supports both regex or non-regex search strings. You can specify how many threads you want it to use to process the files or it by default will try to use the same number of CPU’s on your machine. It utilizes the S3 Java adapter to read the files as a stream rather than a single transfer, than read from disk. Using the tool is very simple:

A the s3grep.properties file is a config file where you setup what you are searching for. An example:

For the most part this is self explanatory. The log level will default to INFO, however if you specify DEBUG it will output some more information such as what file’s it is currently checking. The logger_pattern parameter defaults to “%d{dd MMM yyyy HH:mm:ss} [%p] %m%n” and can be any pattern you want. For more information on the formatting visit the PatternLayout Documentation.

The default output format would look something like this:

If you want a little less verbose and more of just log lines you can update the logger_pattern to be just %m%n and end up with something similar to:

The format of the output is FILE:LINE_NUMBER:matching_string.

Anyways hope this helps you if you are trying to hunt down what file contains a text string in your S3 buckets. Let us know if you have any questions or if we can help!

Posted In: Amazon AWS, General, Java, Tips n' Tricks

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