Improper Resource Allocation - Memory Leak

Need

To avoid exhausting system resources due to memory leaks

Context

• Usage of Elixir 1.12 for building scalable and concurrent applications
• Usage of Phoenix Framework 1.6 for web development

Description

Non compliant code

defmodule MemoryLeak do
  def leak_memory do
    spawn(fn ->
      Process.flag(:trap_exit, true)
      accumulate([])
    end)
  end

  defp accumulate(list) do
    new_list = [0 | list]
    accumulate(new_list)
  end
end

The following code demonstrates a memory leak situation in Elixir. A process is spawned that starts a large data structure (a list), which is continually appended with elements. However, these elements are never released and accumulate over time, leading to increased memory usage.

Steps

• Monitor your processes and identify those that continue to consume memory over time
• Limit the lifetime of processes that create large data structures
• Consider making use of Elixir's garbage collection features to manually trigger garbage collection in certain situations

Compliant code

defmodule MemoryLeak do
  def leak_memory do
    spawn(fn ->
      Process.flag(:trap_exit, true)
      accumulate([])
      Process.sleep(10000)
      :ok
    end)
  end

  defp accumulate(list) when length(list) < 1_000_000 do
    new_list = [0 | list]
    accumulate(new_list)
  end

  defp accumulate(_list), do: :ok
end

In this solution, the process is set to terminate after a certain period of time, ensuring that the large data structure it has created is released from memory.

References

• 317.Improper resource allocation - Memory leak