Shell Tips !

JETM stand for Java™ Execution Time Measurement Library, it’s an useful library to monitor your java application in a smart and easy way. Here is an overview on how to use JETM with a Spring application like in Red5.

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My previous post was made a long time ago, so here is a draft that I finally decide to post. Let’s see how to secure some of your data with an encrypted block device using losetup and dd.

Steps will be :

1. Create an image with dd
2. Build a new device using the image with an encrypt algorythm by using losetup
3. Format the device using mkfs.ext3
4. Mount the device and start using it !

Of course, when you have mounted the device, your data are readable to anyone who have access to the mounted directory.

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Here is a quick picture about the impact of MySQL indexes misuse. At work, our developers made a new release of their search engine using MySQL fulltext indexes, unfortunately they didn’t implement it correctly. The impact was a huge load on all our database servers. To find the trouble, I had to redirect the SQL search flow to a specific server and check for the slow queries then reproduce it with EXPLAIN. Don’t need a long time to find that the search query did an invalid usage of the fulltext index and the “Match / Against” syntax. In fact, the fulltext index was a multiple column fulltext index. As far as I know, it’s the same behavior for any other kind of multiple column index : You have to specify ALL the column present in your index, else index won’t be used by MySQL…