The right way to use Spark and JDBC

A while ago I had to read data from a MySQL table, do a bit of manipulations on that data and store the results on the disk. The obvious choice was to use Spark, I was already using it for other stuff and it seemed super easy to implement. This is more or less what I had to do (I removed the part which does the manipulation for the sake of simplicity): Looks good, only it didn’t quite work. Either it was super slow or it totally crashed depends on the size of the table. Tuning Spark and the cluster properties helped a bit, but it didn’t solve the problems. Since I was using AWS EMR, it made sense to give Sqoop a try since it is a part of the applications supported on EMR. Sqoop performed so much better almost instantly, all you needed to do is to set the number of mappers according to the size of the data and it was working perfectly. Since both Spark and Sqoop are a based on Hadoop map-reduce framework, it was clear that Spark can work at least as good as Sqoop, I only needed to find out how to do Continue reading The right way to use Spark and JDBC

How to properly collect AWS EMR metrics?

Working with AWS EMR has a lot of benefits. But when it comes to metrics, AWS currently does not supply a proper solution for collecting cluster metrics from EMRs. Well, there is AWS Cloudwatch of course, which works out of the box and gives you loads of EMR metrics. The problem with CloudWatch is that it doesn’t give you the ability to follow metrics per a business unit, or a tag, only per a specific EMR id. This simply means you can not compare the metrics over time, only for specific EMRs. Let me explain again the problem. A common use of EMR, is that you write some kind of code that will be executed inside an EMR, and will be triggered every given amount of time, lets say every 5 hours. This means that every 5 hours a new EMR, with a new ID will be spawned. In CloudWatch you can see each of these EMRs individually but not in a single graph, which is defiantly a disadvantage. Just to note, I am referring only to machine metrics, like memory, cpu and disk. Other metrics like jvm metrics or business metrics, are usually collected by the process itself and Continue reading How to properly collect AWS EMR metrics?

Best code convention syndrome

Developers often tend to think that one coding convention is better than another in terms of readability. Some people think that adding a break before the curly braces is more coherent. Some like camelCase, some hate it. The fact of the matter is, there isn’t any proof that one convention gives better readability than another. Now don’t misunderstand me, I am all for coding conventions, coding conventions are a good thing, but the holy wars for which convention is better seems redundant to me. If indeed one format is better than the other, it has a lot less affect on your performance than you would like to think. The truth is that the convention you prefer gives you better performance simply because you are used to it. The best format to use, the one that would give best results, is the one that you are most comfortable with, even if it is not the best one (if there is indeed a best one). The way our brain works is it always searches for familiar structures to make it work less. When you read a piece of code, your mind finds templates which exists in your memory to ease the job Continue reading Best code convention syndrome

jQuery Deferred – one step closer to desktop apps

Every time I forget why I like jQuery, they keep reminding me. Not too long ago I came across jQuery deferred (even though it was added already in JQuery 1.5) and I immediately liked it. I feel this feature brings the web application development a bit closer to the desktop development. Deferreds simply let you add multiple callback to long lasting operation calls like Ajax requests. Long lasting operations without JQuery Deferred If you haven’t used deferreds, this is probably how you had done long lasting actions like ajax calls. Long lasting operations like ajax require a callback function. In this case the callback is given as a parameter to the caller. This is fine, but there is a way to add a callback separately from the call. Try it This is actually the simplest example of using Deferreds. JQuery ajax methods (get,post,ajax…) return an object which you can add callback methods to it. Why is it better? Simply because it lets you keep the logic of execution and the logic of the result separated. This makes a more readable and maintainable code. So what is a ‘Deferred’? Deferred is an object which lets you add multiple callback methods to Continue reading jQuery Deferred – one step closer to desktop apps