Phoenix a Rails successorINTRODUCTION TO ELIXIR AND ITS POWERFUL WEB FRAMEWORK

Tanuj Soni | mail@tanuj.in

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What is Phoenix?

It’s a web framework that is written in Elixir programing language and runs on Erlang virtual machine.

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How does it came to existence

Chris Mccord (the creator of Phoenix) was working on a realtime application in which clients had to open long connections with the server and needed to have data flowing full duplex mode.And developing scalable realtime applications was hard because the clients will maintain long connections with server and will block the resources of the server till the connection ends.While he was trying to figure out the problem he heard WhatsApp case. WhatsApp guys were maintaining 2 Million connections on a single machine.

Blog post describing the case..http://blog.whatsapp.com/index.php/2012/01/1-million-is-so-2011/

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WhatsApp Server configuration

Intel(R) Xeon(R) CPU X5675 @ 3.07GHz 24 CPU Cores96 GB RAM

Only 40% of RAM and CPU were utilized…..

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● It was designed by Ericsson for its telecommunication systems in 1986.

● It’s Distributed, Fault-tolerant and Hot swappable language. These features met all telecommunication requirements.

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● Elixir is a functional, concurrent, general-purpose programming language that runs on the Erlang virtual machine (BEAM).

● José Valim is the creator of the Elixir programming language, a R&D project of Plataformatec. His goals were to enable higher extensibility and productivity in the Erlang VM while keeping compatibility with Erlang's tools and ecosystem.

● José added a lot of syntactic sugar to make look similar to Ruby.

Ref- https://en.wikipedia.org/wiki/Elixir_(programming_language)

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What is new in that?Isn't that’s similar to Node or EM Websocket Ruby?

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The difference is about scaling!

● The clock speed of newer CPUs are not getting faster instead they having multiple cores.

● Ruby and Node both are not able to utilize the resources in a way these are utilized by Elixir.

● As we have seen the WhatsApp case we know the Elixir can scale vertically and it scales very well.

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So what happens if we can not further scale vertically?

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We start scaling it horizontally

● If a single powerful machine is not capable, we can simply turn on another machine and tell this new machine how to find other machines.

● Erlang is distributed so is Elixir as the system is designed around message passing, the Erlang VM abstracts the message passing in a such a way that it doesn’t matter if the recipient of the message is in the same machine or in another node in the same network.

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Scaling vertically by adding more powerful hardware was a thing of the past. We scaled horizontally, by adding more commodity hardware. With the coming of age of mega-core architectures, we have the choice of either adding more hardware or more cores, or both. Erlang style concurrency puts Elixir/Phoenix ahead of the game when it comes to scaling with both approaches.

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● Whenever a socket is initiated a new process is created to handle it. Don’t worry the are Erlang virtual machine processes not operating system processes.

● And for every channel that is created within this channel separate processes are created.

● Erlang VM processes are very isolated that means a buggy or faulty channel will not affect any other thing in the system.

● All the processes are concurrent so none of the process is going to block anything in the system.

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Problem with Node

Despite its asynchronous event model, by nature it is single threaded. When you launch a Node process, you are running a single process with a single thread on a single core. So your code will not be executed in parallel, only I/O operations are parallel because they are executed asynchronous. As such, long running CPU tasks will block the whole server and are usually a bad way to do things.

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Problem with Rails 5 ActionCable

One of Rails screencast suggested that “You should not do any processing in action cable channels because they are not concurrent , if you do they will block everything.” and that is true.What Rails actually does is that it puts the actions in a queue after some time it will be fetched, processed and broadcasted afterwards.

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This was a brief introduction about how it came to existence.

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With Elixir Phoenix we can be as much productive as we were with Rails best part is that the developed things are going to be multiple times efficient.Let’s see other benchmarks and features of Phoenix.

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The Road to 2 Million Websocket Connections in Phoenix

● Phoenix guys started to benchmark the framework developed on a  128GB RAM and 40 cores.

● And they were able to open 2 Million connections using 80 GB of RAM. CPUs were ideal as none of the data was flowing.

● They broadcasted a Wikipedia article to 2 million connection and it took only 3 seconds.

Ref-http://www.phoenixframework.org/blog/the-road-to-2-million-websocket-connections

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How regular applications benefit from Elixir Phoenix?

Phoenix allocates a separate dedicated Erlang VM process for every http request and serves them concurrently.

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● Data for each request is isolated.● Garbage Collector is per process based. ● Most of the time it is not required to Garbage collect as once the

request is served the data is scraped, no GC is required and this also saves the CPU cycles.

● Node, Ruby, Python have global GCs and when the servers starts getting heavy load the GC starts running very frequently that increases the response time of requests.

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● Ref- https://github.com/mroth/phoenix-showdown

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Productivity

➢Short-term Productivity- Documentation/Guides- Workflows/Generators

➢Long-term Productivity- Introspection- Maintainability

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Generators

mix phoenix.gen.htmlmix phoenix.gen.jsonmix phoenix.gen.channel

These generates highly documented code.

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Some more development addons.

● Live Reloads.● ES6 as default.● Pretty error pages.● Concurrency test tools.● (HEX) Packages and dependency resolution tool.● Uses all cores for compiling code.● Uses all cores to run tests.● Debuggers: IEx.pry, Debugger(GUI).

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Observer Tool

Observer allows us to open multiple windows with information on the whole system's statistics or even an individual process of that running system.It makes it easy to identify the bottlenecks of the application just by looking in to the stats of resources consumed by multiple processes.We can simulate an error by manually killing process or by killing DB connection pools.

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Related links

● https://github.com/h4cc/awesome-elixir● https://hex.pm/● https://github.com/doomspork/elixir-companies● http://elixir-lang.org/docs.html● https://hexdocs.pm/phoenix/Phoenix.html

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Tanuj Sonimail@tanuj.inhttps://www.linkedin.com/in/tanujsoni

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Contact me on the below details for any question or suggestion.