June 2015 Summaries

Open source software can be thought of as a collection of solved problems within a particular problem space, and contributing to such communities provides benefits beyond just better tools, but also strong relationships with other experts working on the same issues. The author, Brian Knox, shares an example from his work at DO, where they used Rsyslog, a logging daemon common on many Linux distributions, in combination with CZMQ, a high-level C binding for ZeroMQ, to solve a problem of safely and securely tailing logs in real-time from remote servers as conveniently as if they were local. This solution was made possible by integrating Rsyslog with CZMQ, which provided certificate-based authentication, libsodium-based encryption, and support for publisher filtered publish-subscribe buses, among other things. The author has contributed the input and output plugins back to Rsyslog, making them available for anyone else with a similar problem, and is looking forward to iterating on this solution and releasing more software around it. By actively taking part in open source development, teams can learn from each other's perspectives, share knowledge gained through direct experience, and work on the core problems their organizations are addressing.

The Redis instances experienced memory pressure due to issues with freeing memory after initial allocation, which was initially misinterpreted as a memory leak. The problem was caused by the interaction between an alternative memory allocator and transparent huge pages. Transparent huge pages allow applications to use large memory pages, but some allocators may not play nicely with this feature. In this case, the `jemalloc` library used by the Redis server process marked ranges of memory as free using `madvise(2)`, which caused problems when combined with transparent huge pages. The operating system was unable to evict pages marked as free because the entire page would have to be unneeded, leading to sustained memory pressure and eventually a Out Of Memory (OOM) kill for the Redis server process.

JavaScript.com is a free online resource for learning JavaScript and staying up-to-date with the latest news, frameworks, and libraries. It's developed in Node.js on DigitalOcean, using CloudFlare as a caching layer to offload traffic from its application servers. The site uses HAProxy load balancers to distribute traffic between multiple servers, with NGINX and Phusion Passenger managing Node processes. A PostgreSQL database handles data storage, with a hot spare server available for read-only access. SaltStack is used for configuration management and scaling out horizontally by spinning up new servers quickly and automatically through DigitalOcean. The site's architecture allows it to scale independently as traffic increases, making it ready to handle a large amount of traffic.

DigitalOcean has announced the launch of Team Accounts, a feature that allows multiple developers to access and manage their account's resources using shared credentials. This new feature aims to simplify infrastructure management for teams of developers and companies working on large-scale applications. With Team Accounts, each team member can have their own secure 2-Factor enabled login, avoiding password sharing and ensuring individual credentials remain secure. The feature also enables easy resource management, allowing development teams to scale infrastructure resources as needed. Additionally, it simplifies billing and expense reporting processes for Dev Shops, enabling them to allocate savings towards other priorities. The launch of Team Accounts is made possible by user feedback during testing and is part of a larger team effort at DigitalOcean.