chriseyre2000

chriseyre2000

Concurrent Data Processing In Elixir: Chapter 3 Errata

Towards the end of Chapter 3 (B2) the via function is implemented as:
def via(id) do
{{:via, Registry, {ProducerConsumerRegistry, id}}, []}
end

However the app fails to start unless you change this to:

def via(id) do
{:via, Registry, {ProducerConsumerRegistry, id}}
end

Here is the code that I entered as specified in the book: GitHub - chriseyre2000/scraper: Sample app from chapter 3 of Concurrent Data Processing In Elixir

I did restart this chapter from B1 just in case something had changed/been fixed.

First Post!

svilen

svilen

Author of Concurrent Data Processing in Elixir

Thank you for reporting this Christopher! And thanks for sharing the code, it was super helpful.

Looks like I made a mistake when introducing this. Rather than using {{:via, Registry, {ProducerConsumerRegistry, id}}, []} the book should ask you to modify page_consumer_supervisor.ex and update the subscribe_to options like so:

    opts = [
      strategy: :one_for_one,
      subscribe_to: [
        {OnlinePageProducerConsumer.via("online_page_producer_consumer_1"), []},
        {OnlinePageProducerConsumer.via("online_page_producer_consumer_2"), []}
      ]
    ]

However, you can still keep the code that you have at the moment. You’ll just get a warning message like this:

[warn]  :subscribe_to value with type {:via, module(), term()} is deprecated

I’ll make sure this is fixed in the next version :+1:

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