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Datasource, my 2nd Hex-Package
– , 2018-09-03

After publishing Bucketier, a simple KV store for Elixir as a Hex-package about a month ago, today let me announce Datasource.

Datasource is a side project used in my Raspberry Experiments and as a handler of client-activities in my work-project.

A continues stream of data from any source

The Datasource is a straightforward module providing one function next() which returns the next value from a given source.

Sources can be from simple “endless counters” to “clocks,” “files,” but also sensors and triggers in a Nerves-project.

Datasource also provides a module Datasource.DataStage which can be used as GenStage producer, reading data from a Datasource on demand.

# Rememnber consumed events in state
defmodule ConsumerSpy do
  use GenStage

  def start_link(), do: GenStage.start_link(ConsumerSpy, [])
  def init(state), do: {:consumer, state}

  def handle_events(events, _from, state) do
    # Simulate load
    {:noreply, [], [events | state]}

  def handle_call(:get, _from, state) do
    {:reply, Enum.flat_map(state, & &1), [], state}

{:ok, datasource} = Datasource.start_link( 0, fn(state) -> { state, state + 1 } end)
{:ok, producer} = Datasource.DataStage.start_link(datasource)
{:ok, consumer} = ConsumerSpy.start_link()

GenStage.sync_subscribe(consumer, to: producer, max_demand: 1)
Process.sleep(100), :get)
# => [0,1,2,3,...10]