This is the beginning of Learn You Some Erlang for Great Good! Reading this tutorial should be one of your first steps in learning Erlang, so let's talk about it a bit.
Erlang logo
First of all, I began growing the idea of writing this after reading Miran Lipovača's Learn You a Haskell for great Good! (LYAH) tutorial; I thought he did a great job making the language attractive and the learning experience friendly. As I already knew him, I asked him how he felt about me writing an Erlang version of his book. He liked the idea, being somewhat interested in Erlang.
So here I am typing this. Of course there were other sources to my motivation: I mainly find the entry to the language to be hard (the web has sparse documentation and otherwise you need to buy books), and I thought the community would benefit from a LYAH-like guide. Less importantly, I've seen people attributing Erlang too much or not enough merit sometimes based on sweeping generalizations. Then there are people who sure as hell believe Erlang is nothing but hype. If I'd like to convince them otherwise, I know they're not likely to read this in the first place.
This book thus wants itself to be a way to learn Erlang for people who have basic knowledge of programming in imperative languages (such as C/C++, Java, Python, Ruby, etc) and may or may not know functional programming (Haskell, Scala, Erlang, Clojure, OCaml...). I also want to write this book in a honest manner, selling Erlang for what it is, acknowledging its weaknesses and strengths.
Partisan is a scalable and flexible, TCP-based membership system and distribution layer for the BEAM. It bypasses the use of Distributed Erlang for manual connection management via TCP, and has several pluggable backends for different deployment scenarios.
Partisan is a runtime system that enables greater scalability and reduced latency for distributed actor applications.
- Partisan improves scalability by allowing the application developer to specialize the overlay network to the application’s communication patterns.
- Partisan achieves lower latency by leveraging several predominately automatic optimizations that result in the efficient scheduling of messages.
- Bring Your Own Overlay - Partisan exposes an API for users to implement their own overlays; application developers must simply implement the membership_strategy interface for handling messages. Partisan automatically uses this membership strategy for processing incoming and outgoing messages to the system – the application developer only needs to handle internal state transitions and supplying the system with an updated list of members. Partisan automatically sets up required connections, serializes and deserializes messages, performs failure detection, and message forwarding. This makes it possible to implement protocols with very little code; our implementation of the full-mesh membership protocol is 152 LOC.
- Partisan is the first distributed actor system to expose this level of control to the application developer, improving the performance of existing actor application and enabling new types of actor applications.
amnesia wraps everything exposed by mnesia, from fragments to fragment hash, access and backup behaviors.
It provides a simplified table and database definition with some macros and allows you to use the nice Enum functions on tables by implementing the Enum.Iterator protocol.
Everything is documented and specced, even the unspecced and undocumented parts of mnesia that have been wrapped.
The documentation often refers to mnesia functions, I strongly suggest you read mnesia's documentation too, since it has a lot of valuable information.
At a high level, Mnesia is a Database Management System (DBMS) that is baked into OTP. Thus, if you are using Elixir or Erlang, you have the ability to leverage Mnesia out-of-the-box. No additional dependencies need to be installed and no separate systems need to be running. Before considering migrating everything from your existing database to Mnesia, let's discuss what Mnesia was designed for and what problems it aims to solve.
Mnesia was largely designed to solve the problems that existed in the telecommunications problem space. Specifically, some of the following requirements needed to be fulfilled (check out this research paper for more details):
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Fast key/value lookup times where you need soft real-time latency guarantees. A soft real-time system is one where the system should be able to service the majority of its requests within a given time frame and a failure to do so generally means degradation of service (i.e the data is no longer useful after the time frame has passed). A hard real-time system, on the other hand, is a system that must respond within a given time frame or else it is considered a system failure.
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The ability to perform complex queries (like you would in SQL for example), but without soft real-time latency guarantees
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A high level of fault tolerance
The holy cow of servers.
Ranch is a socket acceptor pool for building awesome TCP and TLS servers
Small, fast, modern HTTP server.
Cowboy is the ultimate server for the modern Web with support for Websocket, HTTP/2 and REST.
Like many people, I recently have been re-discovering the XMPP messaging protocol and ended up running my own server. In fact, this blog is essentially a result of that effort, though it functions independently from the XMPP service.
This is the code that powers https://webbkoll.dataskydd.net – an online tool that checks how a webpage is doing with regards to privacy.
It attempts to simulate what happens when a user visits a specified page with a typical browser without clicking on anything, with the browser having no particular extensions installed, and with Do Not Track (DNT) disabled (as this is the default setting in most browsers).
In short: this tool, which runs the user-facing web service (built with Elixir and Phoenix), asks a simple Node.js backend to visit a page with Chromium. The backend uses Puppeteer to control Chromium; it visits and renders the page, collects various data (requests made, cookies, response headers, etc.), and sends it back as JSON to this tool which then analyzes the data and presents the results on a webpage along with explanations and advice.
Webbkoll is multilingual and currently supports English and Swedish. If you want to help us translate Webbkoll into more languages, see TRANSLATIONS.md.
Jumbo is used for job processing, and some basic rate limiting is done with ex_rated. Multiple backends can be configured. ConCache is used to store results in an in-memory ETS table for a limited time. Other than the Node.js backend, there are no external dependencies, and nothing is saved to disk.
Please note that this is still a work in progress. Expect bugs and messy code in places. Only a few basic tests are in place.
Also note that this tool is mainly meant to be used as a starting point for web developers. For more rigorous and systematic testing we recommend that you check out OpenWPM, which we used to analyze the websites of Sweden's municipalities (site, code). You might also want to have a look at PrivacyScore, which is a bit more comprehensive than Webbkoll (additionally checks e.g. email and TLS/SSL configuration) and also lets you compare/rank lists of sites.
This is a project by Dataskydd.net. See Webbkoll's About page for more information.
Webbkoll hilft Dir festzustellen, welche datenschutzrechtlichen Maßnahmen eine Website ergriffen hat, um Dir die Kontrolle über Deine Privatsphäre zu geben.
Bitte beachte:
1. Dieses Tool simuliert einen normalen Browser mit ausgeschalteter "Do Not Track" Funktion (ist bei den meisten die Standardeinstellung) und ohne Erweiterungen.
2. Auch wenn Du https:// eingibst, prüfen wir http:// und ob es automatisch auf eine https:// Seite weiter leitet (Weiterleitungen wird gefolgt).
3. Im Allgemeinen sollte alles funktionieren, manchmal kann es jedoch vorkommen, dass einzelne Seiten aus den verschiedensten Gründen nicht funktionieren.
4. Das Back-End läuft derzeit auf einem einzelnen Server mit begrenzten Ressourcen. In Spitzenzeiten kann ein Durchlauf daher etwas dauern. (Wenn Du willst, kannst Du Webbkoll in einer eigenen Instanz betreiben!)
5. Feedback ist willkommen: Sende uns eine Email oder berichte einen Fehler.
Elixir is a dynamic, functional language designed for building scalable and maintainable applications.
Elixir leverages the Erlang VM, known for running low-latency, distributed and fault-tolerant systems, while also being successfully used in web development and the embedded software domain.
To learn more about Elixir, check our getting started guide and our learning page for other resources. Or keep reading to get an overview of the platform, language and tools.
