Elixir Q & A


How to debug Elixir applications?

Debugging Elixir applications involves a combination of tools, techniques, and best practices to identify and resolve issues efficiently. Here are some key strategies for debugging Elixir applications:


  1. IO.inspect/2: One of the simplest yet effective debugging tools in Elixir is the `IO.inspect/2` function. You can insert `IO.inspect/2` calls at various points in your code to inspect the values of variables and data structures. This allows you to print out information for analysis during runtime.


  1. Logger: Elixir’s built-in Logger module provides a more structured way to capture and output logs. You can use different log levels (e.g., `:info`, `:warn`, `:error`) to categorize log messages. Configure the Logger to output logs to the console or log files as needed.


  1. ExUnit and Mix Tasks: Elixir’s test framework, ExUnit, is not just for testing but also for debugging. You can write custom assertions and use ExUnit to run specific test cases or even write custom Mix tasks to automate debugging routines.


  1. Erlang’s Observer: Elixir runs on the Erlang virtual machine, which includes powerful debugging tools like Observer. You can use Observer to inspect processes, memory usage, and system information. Start it with `:observer.start` in an IEx session to access these features.


  1. IEx (Interactive Elixir): IEx is an interactive REPL (Read-Eval-Print Loop) for Elixir. You can start an IEx session within your running application using `iex -S mix` or attach to a running node. This allows you to interactively explore and debug your application’s state and code.


  1. ExDebug: ExDebug is an external debugging tool for Elixir that provides features like breakpoints, step-by-step execution, and inspection of processes and variables. You can integrate it into your project to facilitate more advanced debugging.


  1. Distributed Tracing: Elixir supports distributed tracing with libraries like OpenTelemetry and Telemetry. These tools allow you to trace the flow of requests across processes and nodes, making it easier to identify bottlenecks and issues in distributed systems.


  1. Error Handling: Proper error handling using try/catch, case statements, and error supervisors is essential. Catching and logging errors can help you diagnose issues and prevent application crashes.


Debugging Elixir applications involves a mix of built-in functions like `IO.inspect/2`, structured logging with Logger, interactive exploration using IEx, and advanced tools like Observer and ExDebug. Additionally, writing tests and utilizing distributed tracing can help identify and prevent issues early in the development process, making debugging more efficient and effective.


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Tech Lead in Elixir with 3 years' experience. Passionate about Elixir/Phoenix and React Native. Full Stack Engineer, Event Organizer, Systems Analyst, Mobile Developer.