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Releases

The main feature in Elixir v1.9 is the addition of releases. A release is a self-contained directory that consists of your application code, all of its dependencies, plus the whole Erlang Virtual Machine (VM) and runtime. Once a release is assembled, it can be packaged and deployed to a target as long as the target runs on the same operating system (OS) distribution and version as the machine running the mix release command.

You can start a new project and assemble a release for it in three easy steps:

$ mix new my_app
$ cd my_app
$ MIX_ENV=prod mix release

A release will be assembled in _build/prod/rel/my_app. Inside the release, there will be a bin/my_app file which is the entry point to your system. It supports multiple commands, such as:

• bin/my_app start, bin/my_app start_iex, bin/my_app restart, and bin/my_app stop - for general management of the release

• bin/my_app rpc COMMAND and bin/my_app remote - for running commands on the running system or to connect to the running system

• bin/my_app eval COMMAND - to start a fresh system that runs a single command and then shuts down

• bin/my_app daemon and bin/my_app daemon_iex - to start the system as a daemon on Unix-like systems

• bin/my_app install - to install the system as a service on Windows machines

Why releases?

Releases allow developers to precompile and package all of their code and the runtime into a single unit. The benefits of releases are:

• Code preloading. The VM has two mechanisms for loading code: interactive and embedded. By default, it runs in the interactive mode which dynamically loads modules when they are used for the first time. The first time your application calls Enum.map/2, the VM will find the Enum module and load it. There’s a downside. When you start a new server in production, it may need to load many other modules, causing the first requests to have an unusual spike in response time. Releases run in embedded mode, which loads all available modules upfront, guaranteeing your system is ready to handle requests after booting.

• Configuration and customization. Releases give developers fine grained control over system configuration and the VM flags used to start the system.

• Self-contained. A release does not require the source code to be included in your production artifacts. All of the code is precompiled and packaged. Releases do not even require Erlang or Elixir in your servers, as they include the Erlang VM and its runtime by default. Furthermore, both Erlang and Elixir standard libraries are stripped to bring only the parts you are actually using.

• Multiple releases. You can assemble different releases with different configuration per application or even with different applications altogether.

Hooks and Configuration

Releases also provide built-in hooks for configuring almost every need of the production system:

• config/config.exs (and config/prod.exs) - provides build-time application configuration, which is executed when the release is assembled

• config/releases.exs - provides runtime application configuration. It is executed every time the release boots and is further extensible via config providers

• rel/vm.args.eex - a template file that is copied into every release and provides static configuration of the Erlang Virtual Machine and other runtime flags

• rel/env.sh.eex and rel/env.bat.eex - template files that are copied into every release and executed on every command to set up environment variables, including ones specific to the VM, and the general environment

We have written extensive documentation on releases, so we recommend checking it out for more information.

Configuration overhaul

A new Config module has been added to Elixir. The previous configuration API, Mix.Config, was part of the Mix build tool. But since releases provide runtime configuration and Mix is not included in releases, we ported the Mix.Config API to Elixir. In other words, use Mix.Config has been soft-deprecated in favor of import Config.

Another important change related to configuration is that mix new will no longer generate a config/config.exs file. Relying on configuration is undesired for most libraries and the generated config files pushed library authors in the wrong direction. Furthermore, mix new --umbrella will no longer generate a configuration for each child app, instead all configuration should be declared in the umbrella root. That's how it has always behaved, we are now making it explicit.

Other enhancements

There are many other enhancements. The Elixir CLI got a handful of new options in order to best support releases. Logger now computes its sync/async/discard thresholds in a decentralized fashion, reducing contention. EEx templates support more complex expressions than before. Finally, there is a new ~U sigil for working with UTC DateTimes as well as new functions in the File, Registry, and System modules.

v1.9.0 (2019-06-24)

1. Enhancements

EEx

• EEx Allow more complex mixed expressions when tokenizing

Elixir

• Access Allow Access.at/1 to handle negative index
• CLI Add support for --boot, --boot-var, --erl-config, --pipe-to, --rpc-eval, and --vm-args options
• Code Add static_atom_encoder option to Code.string_to_quoted/2
• Code Support :force_do_end_blocks on Code.format_string!/2 and Code.format_file!/2
• Code Do not raise on deadlocks on Code.ensure_compiled/1
• Config Add Config, Config.Reader, and Config.Provider modules for working with configuration
• File Add File.rename!/2
• Inspect Add :inspect_fun and :custom_options to Inspect.Opts
• Kernel Add ~U sigil for UTC date times
• Kernel Optimize &super/arity and &super(&1)
• Kernel Optimize generated code for with with a catch-all clause
• Kernel Validate __struct__ key in map returned by __struct__/0,1
• Module Add Module.get_attribute/3
• Protocol Improve Protocol.UndefinedError messages to also include the type that was attempted to dispatch on
• Protocol Optimize performance of dynamic dispatching for non-consolidated protocols
• Record Include field names in generated type for records
• Regex Automatically recompile regexes
• Registry Add Registry.select/2
• System Add System.restart/0, System.pid/0 and System.no_halt/1
• System Add System.get_env/2, System.fetch_env/1, and System.fetch_env!/1
• System Support SOURCE_DATE_EPOCH for reproducible builds

ExUnit

• ExUnit Allow multiple :exclude on configuration/CLI
• ExUnit.DocTest No longer wrap doctest errors in custom exceptions. They ended-up hiding more information than showing
• ExUnit.DocTest Display the actual doctest code when doctest fails

IEx

• IEx.CLI Copy ticktime from remote node on IEx --remsh
• IEx.CLI Automatically add a host on node given to --remsh

Logger

• Logger Use a decentralized mode computation for Logger which allows overloads to be detected more quickly
• Logger Use persistent_term to store configuration whenever available for performance

Mix

• Mix Follow XDG base dir specification in Mix for temporary and configuration files
• Mix.Generator Add copy_file/3, copy_template/4, and overwite?/2
• Mix.Project Add preferred_cli_target that works like preferred_cli_env
• mix archive.uninstall Allow mix archive.uninstall APP to uninstall any installed version of APP
• mix new No longer generate a config/ directory for mix new
• mix release Add support for releases
• mix release.init Add templates for release configuration
• mix test Allow running tests for a given umbrella app from the umbrella root with mix test apps/APP/test. Test failures also include the apps/APP prefix in the test location

2. Bug fixes

EEx

• EEx Consistently trim newlines when you have a single EEx expression per line on multiple lines

Elixir

• Code Quote :: in Code.format_string!/1 to avoid ambiguity
• Code Do not crash formatter on false positive sigils
• Enum Ensure the first equal entry is returned by Enum.min/2 and Enum.max/2
• Kernel Improve error message when string interpolation is used in a guard
• Kernel Properly merge and handle docs for callbacks with multiple clauses
• Kernel Guarantee reproducible builds on modules with dozens of specs
• Kernel Resolve __MODULE__ accordingly in nested defmodule to avoid double nesting
• Kernel Type variables starting with an underscore (_foo) should not raise compile error
• Kernel Keep order of elements when macro in/2 is expanded with a literal list on the right-hand side
• Kernel Print proper location on undefined function error from dynamically generated functions
• System Make sure :init.get_status/0 is set to {:started, :started} once the system starts
• Path Do not expand ~ in Path.expand/2 when not followed by a path separator
• Protocol Ensure debug_info is kept in protocols
• Regex Ensure inspect returns valid ~r// expressions when they are manually compiled with backslashes
• Registry Fix ETS leak in Registry.register/2 for already registered calls in unique registries while the process is still alive

ExUnit

• ExUnit Raise error if attempting to run single line tests on multiple files
• ExUnit Return proper error on duplicate child IDs on start_supervised

IEx

• IEx Automatically shut down IEx if we receive EOF

Logger

• Logger Don't discard Logger messages from other nodes as to leave a trail on both systems

Mix

• mix compile Ensure Erlang-based Mix compilers (erlang, leex, yecc) set valid position on diagnostics
• mix compile Ensure compilation halts in an umbrella project if one of the siblings fail to compile
• mix deps Raise an error if the umbrella app's dir name and mix.exs app name don't match
• mix deps.compile Fix subcommand splitting bug in rebar3
• mix test Do not consider modules that are no longer cover compiled when computing coverage report, which could lead to flawed reports

3. Soft-deprecations (no warnings emitted)

Mix

• Mix.Config Mix.Config has been deprecated in favor of the Config module that now ships as part of Elixir itself. Reading configuration files should now be done by the Config.Reader module

4. Hard-deprecations

Elixir

• CLI Deprecate --detached option, use --erl "-detached" instead
• Map Deprecate Enumerable keys in Map.drop/2, Map.split/2, and Map.take/2
• String The :insert_replaced option in String.replace/4 has been deprecated. Instead you may pass a function as a replacement or use :binary.replace/4 if you need to support earlier Elixir versions

Mix

• Mix.Project Deprecate Mix.Project.load_paths/1 in favor of Mix.Project.compile_path/1

Checksums

• Precompiled.zip SHA1: e9847341ca0484da0ade831bf5d714d9094629c1
• Precompiled.zip SHA512: 89686dd150abbc3c65be373dedf60971801063537a3b32cccdcd7eda18e5a9b3b78012b11a2f06575824e0164fbf0b80178a7de943f508ec90ad9a74d8a1da05
• Docs.zip SHA1: d53d941dde32066e3f8d7aea6a5c85b77e32810d
• Docs.zip SHA512: a63ae1c11f0e2c787a18309fcf02e5eba579b7161d552fa70e0d9987e3a2407109b7cbc3ac8e9a9bca50c3a185f1d9f16e0dd3354c28f9aaf93211e1db054226