gpcweb

gpcweb

More than one supervisor?

I’am new on elixir and I’m building an application that downloads some pdf files from s3. It works just fine using a supervisor and poolboy to manage the process, but I would like to retrieve all the links from a database, I’m seeing ecto but when I used It tells me that I need a supervisor.

This is my current model module

defmodule Pdf.Consumption do
  use Ecto.Schema
  alias Pdf.Consumption
  alias Pdf.Repo

  schema "consumptions" do
    field :invoice_url
  end

  def all do
    Consumption
    |> Repo.all
  end
end 

This is my current application module

defmodule Pdf do
  use Application

  def start(_type, _args) do
    poolboy_config = [
      {:name, {:local, pool_name()}},
      {:worker_module, Pdf.Worker},
      {:size, 2},
      {:max_overflow, 0}
    ]

  children = [:poolboy.child_spec(pool_name(), poolboy_config, [])]

  options = [
   strategy: :one_for_one,
   name: Pdf.Supervisor
  ]

  Supervisor.start_link(children, options)
end

  defp pool_name() do
    :pdf_pool
  end

  defp pdf_pool(link) do
     :poolboy.transaction(
       pool_name(),
       fn(pid) -> :gen_server.call(pid, link) end, :infinity
     )
  end

  def parallel_pool(links) do
    Enum.each( links, fn(link) -> spawn( fn() -> pdf_pool(link) end ) end )
  end
end

And I would like to make this on parallel_pool

def parallel_pool do
  Pdf.Consumption.all
  |>Enum.each( links, fn(link) -> spawn( fn() -> pdf_pool(link) end ) end )
end

So my question is, how can achieve this? I need another module that use Application?

Most Liked

benwilson512

benwilson512

Author of Craft GraphQL APIs in Elixir with Absinthe

So there are really two questions here:

  1. How do you handle multiple supervisors
  2. What’s the best way to download a lot of files concurrently from S3.

I’m gonna answer #2. Poolboy is not the way to do this. The easiest way is to use the Elixir 1.4 Task.async_stream. function:

links
|> Task.async_stream(fn link ->
  process_link(link)
end, max_concurrency: 20)
|> Stream.run

This will download 20 links at a time. It will not return anything, I’m assuming that you’re writing to disk or something with process_link. If you need the results you would just |> Enum.to_list instead of Stream.run

gpcweb

gpcweb

Can you explain me why poolboy is not the way to do this?

NobbZ

NobbZ

Because it adds a dependency while the work can be done with stuff from the std-lib easily.

Where Next?

Popular in Questions Top

RisingFromAshes
I’ve read in another post that it may be possible with a router helper - but I couldn’t find an appropriate one, and tbh, I’m still just ...
New
jononomo
I am trying to figure out how Mix knows whether the environment is test, dev, or prod – where is this set? Thanks.
New
jononomo
For some reason my phoenix channels are working for me in my local dev environment, but as soon as I deploy via Docker, I get a 403 error...
New
Darmani72
If I have a post route which an argument: post /my_post_route/:my_param1, MyController.my_post_handler How would get the post params ...
New
stefanluptak
Hello everybody, usually, I use a 29" ultra-wide monitor for VSCode which can easily accomodate explorer (files panel) + file with code ...
New
siddhant3030
Hi, I have to write a raw query for one of my project. But till now I have used ecto queries and don’t have much experience writing raw ...
New
albydarned
Hello all! I am typing this post from my new MacBook Pro with the M1 chip. I’m loving it so far, and will probably use it as my daily dr...
New

Other popular topics Top

Qqwy
Update: How to use the Blogs & Podcasts section You can post links to your blog posts or podcasts either in one of the Official Blog...
3271 131117 1222
New
minhajuddin
I have seen a lot of code which picks the first element from a list using Enum.at(0) instead of List.first. Is there a reason why people ...
New
vonH
When I run the Plug and I recompile I wind up having to use Ctrl C to quit iex and start again. Witht the help of rlwrap I can use the cu...
New
AstonJ
Seen any cool LiveView demos, sample apps or examples? Please post them here! :003:
New
sergio
Kind of like when jquery came out, it was super necessary. Existing drag and drop libraries have a bunch of baggage to support old browse...
New
jason.o
In the code below, if the create action is not set to accept “extra_key” as an input, it errors out with a message shown above. Is there ...
New

We're in Beta

About us Mission Statement