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Paratize

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Elixir library providing some handy parallel processing facilities that supports configuring number of workers and timeout.

This library is inspired by Parex.

Documentation

API documentation is available at http://hexdocs.pm/paratize

Adding Paratize To Your Project

To use Paratize with your projects, edit your mix.exs file and add it as a dependency:

defp deps do
  [
    {:paratize, "~> x.x.x"},
  ]
end

Examples

Paratize is designed to run slow tasks in parallel. There are two processor implementatons, first the chunk based implementation Paratize.Chunk and the second the worker pool based implementation Paratize.Pool. Both modules have the same API.

  • parallel_exec(fun_list, task_options)
  • parallel_map(arg_list, fun, task_options)
  • parallel_each(arg_list, fun, task_options)

To execute a list of functions in parallel,

import Paratize.Pool

function_list = [
  fn -> Math.fib(40) end,
  fn -> :timer.sleep(5000) end,
  fn -> HTTPotion.get("http://wwww.reddit.com") end
]

parallel_exec(function_list) # => [102334155, :ok, %HTTPotion.Response{body...}]

function_keyword_list = [
  fib: fn -> Math.fib(40) end,
  hang: fn -> :timer.sleep(5000) end,
  web_request: fn -> HTTPotion.get("http://wwww.reddit.com") end
]

parallel_exec(function_keyword_list) # => [fib: 102334155, hang: :ok, web_request: %HTTPotion.Response{body...}]

To execute a map in parallel,
(useful when results are needed for further processing)

import Paratize.Pool

slow_func = fn arg -> :timer.sleep(1000); arg + 1 end
workload = 1..100

{time, result} = :timer.tc fn -> workload |> parallel_map(slow_func) |> Enum.join(", ") end
time # => 13034452 (8 CPU cores system, running 8 workers)

To execute a each in parallel,
(useful when resultset is large, and can be processed individually to prevent memory hog)

import Paratize.Pool

lots_of_urls |> parallel_each(fn url ->
  HTTPotion.get(url) |> parse_page |> save_meta_data
end)

Task Options

Each function accepts task options to customize the parallel processing.

  • size - the number of parallel workers, defaults to the number of system cores given by :erlang.system_info(:schedulers)
  • timeout - in milliseconds, the minimum time given for a function to complete, defaults to 5000. If timeout happens, the entire parallel processing crashes with exit(:timeout,...). To disable timeout, use :infinity.

Considerations

To achieve maximum parallelism, %Paratize.TaskOptions{} size should be set to size of your workload,

alias Paratize.Pool

slow_func = fn arg -> :timer.sleep(1000); arg + 1 end
workload = 1..100

{time, result} = :timer.tc fn ->
    workload |> Pool.parallel_map(slow_func, size: Enum.count(workload)) |> Enum.join(", ")
end
time # => 1004370 (Running 100 workers)

The %Paratize.TaskOptions{} timeout should not be relied upon for precise timing out of each workload, because it is not strictly enforced. It is an implementation detail that reasonably crashes the processor if no further work is completed after the timeout period has lapsed.

LICENSE

This software is licensed under MIT LICENSE.


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