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Using the MapReduce Technique to Process 500GB of Server Logs 4

Posted by Stuart McGarrity,

Here I’m using the MapReduce functionality in Parallel Processing Toolbox to process several hundred GBs of server logs from our web site. I want to be able to visualize the counts per minute of certain quantities and also filter the data to look for certain special requests to our website. I start small, getting my algorithm to work with one file first and without parallel processing. But MapReduce lets you write it in a way that it will work on any size and with parallel processing.

It eventually took 50 min to process one day’s worth of data (72GB) and about 14hrs to do 8 days (562GB). I think I’ll profile the small dataset problem to see where its spending the time, but suspect it is all file I/O.

>> sum(minuteResults.totalRequests)
ans =
   1.3388e+09
>> bar(minuteResults.timeMinute ,minuteResults.totalRequests)


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4 CommentsOldest to Newest

Francisco replied on : 3 of 4
Very useful, thanks. I guess the same analysis could be done with Tall arrays + findgroups() + splitapply() + gather() If so, what do you think would be the advantages/disadvantages of this alternative workflow in terms of performance, code simplicity, etc? Thanks, Francisco
Stuart McGarrity replied on : 4 of 4
Hi Francisco, In my opinion, its a simplicity vs control, or a high-level vs low-level trade-off. First of all, not all operations are supported with tall arrays. But if you can express what you need to do as tall arrays, it results in a simpler implementation. With Map Reduce you have to do more work to code it but it gives you more control, useful for more complex problems. I did originally try this with tall arrays but found I needed to handle a lot or missing data and edge cases that didn't fit into the TA model. I needed the control of MR.

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