How to use locks in PHP cron jobs to avoid cron overlaps

Cron jobs are hidden building blocks for most of the websites. They are generally used to process/aggregate data in the background. However as a website starts to grow and there is gigabytes of data to be processed by every cron job, chances are that our cron jobs might overlap and possibly corrupt our data. In this blog post, I will demonstrate how can we avoid such overlaps by using simple …

How to build a custom static file serving HTTP server using Libevent in C

Libevent is an event notification library which lays the foundation for immensely successful open source projects like Memcached. As the web advances into a real time mode, more and more websites are using a mix of technologies like HTTP Pub-Sub, HTTP Long-polling and Comet with a custom light weight HTTP servers in the backend to create a real time user experience. In this blog post, I will start with necessary …

How to add content verification using hmac in PHP

Many times a requirement arises where we are supposed to expose an API for intended users, who can use these API endpoints to GET/POST data on our servers. But how do we verify that only the intended users are using these API’s and not any hacker or attacker. In this blog post, I will show you the most elegant way of adding content verification using hash_hmac (Hash-based Message Authentication Code) …

How to use locks for assuring atomic operation in Memcached?

Memcached provide atomic increment and decrement commands to manipulate integer (key,value) pairs. However special care should be taken to ensure application performance and possible race conditions while using memcached. In this blog post, I will first build a facebook style “like” application using atomic increment command of memcached. Also, I will discuss various technical difficulty one would face while ensuring atomicity in this application. Finally, I will demo how to …