Improper Resource Allocation - Memory Leak - Elixir

Need

To avoid exhausting system resources due to memory leaks

Context

1. Usage of Elixir 1.12 for building scalable and concurrent applications
2. Usage of Phoenix Framework 1.6 for web development

Description

Insecure Code Example

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

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

Secure Code Example

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

Last updated

2023/09/18