![]() I hope you found this run-through of hot code reloading useful. In the next part of the series, I'll delve into the world of supervisors in Elixir. Upgrading an individual process, together with its callback module,Ĭan be used as a 'tactical weapon' to fix localized bugs orīut updating a system at a greater scale, on a regular basis, requires more powerful tools. We've also demonstrated how to upgrade a single Now, let's roll back to the first shell: User switch command -> c 1. Create a new variable called hello and assign some value to it: hello :world. The command above will start a new shell and connect to it. In the first part of this series, we've seen that a GenServer implementation is neededįor effective hot code upgrades. User switch command -> s 'Elixir.IEx' -> c. Iex(3 ) > :code.load_file( CodePurge.Pi ) iex(11 ) > :sys.change_code( pid, CodePurge.PiGs, nil, ) :ok iex(12 ) > :sys.resume( pid ) :ok iex(13 ) > ( pid ) 3.14 iex(14 ) > :sys.get_state( pid ) Įverything works fine, and the last call to :sys.get_state demonstrates that the What happens if we want to upgrade code two or more times? How GenServer helps us make such a transition seamlesslyĪt this point, I'd like to highlight one important concept in-depth: code purge.The importance of external calls, which make it possible to transition from old code to new code.How two versions of code exist after loading a new version of the module: new code and old code.Hot Code Upgrades: The BasicsĪ good starting point to understand hot code reload is ![]() Only for systems built according to OTP principles. How Are OTP and Hot Code Upgrades Related?Īs we will see, hot code upgrades on a larger scale (application and release levels) work In this article, we will consider application OTP offers tools for upgrading at any scale. a whole running instance (a release in terms of OTP).a package (an application in terms of OTP).Uncertainty comes in with scaling - the question is if we can upgrade: For example, we may change the behavior of a process that holdsĪ TCP connection without terminating this connection. Without any negative impact on that process. When we speak of hot code reload or hot code upgrade, we usually mean an ability to change a running process behavior There is a bit of uncertainty about this concept. Hot Code Reload: Tackling the Uncertainties Informally, OTP often denotes a set of principles to build robust apps in Erlang and theĬorresponding set of built-in libraries. a set of libraries, compilers and a VM implementation. Is a specific implementation of Erlang Runtime System, i.e. But before we dive in, let's quickly define OTP. This article will focus on hot code reloading and upgrades. function iex> recompile Recompiles the current project on the fly. In this series, we will examine how to make the most of these benefits in your production code upgrades. iex Interactive Elixir - press Ctrl+C to exit (type h() ENTER for help) iex> h. When building software, Elixir (or Erlang) offers great benefits, including concurrency, scalability and reliability.
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