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Elixir 9 errors

Elixir & Erlang Errors

GenServer timeouts, supervision failures and Mix compilation problems.

Understanding Elixir errors

Elixir errors are shaped by the actor model: a GenServer.call timeout does not mean the server crashed, it means the server was busy for longer than the caller was willing to wait. The right question is usually "what is that process doing?" rather than "why did the call fail?". Because supervisors restart failed processes automatically, transient errors can also hide in the logs while the system appears healthy.

How to debug Elixir errors

  1. Attach to a running node with iex --remsh and inspect the process: Process.info(pid, :message_queue_len). A growing mailbox means the process is the bottleneck.
  2. Use :observer.start() to see the supervision tree, process memory and message queues visually.
  3. Move long-running work out of handle_call. Use handle_cast, a Task, or a dedicated pool so the GenServer stays responsive.
  4. Check restart intensity. A supervisor that exceeds max_restarts takes down its own supervisor, producing a cascade that looks like an unrelated failure at the top.
  5. For compile errors in dependencies, run mix deps.compile --force and check that any required native toolchain (make, gcc, erlang headers) is installed.

Tools worth reaching for

  • :observer.start()
  • iex --remsh
  • Process.info/2
  • mix deps.tree
  • :recon

All 9 Elixir errors

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