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
Process.sleep(10)
{:noreply, [], [events | state]}
end
def handle_call(:get, _from, state) do
{:reply, Enum.flat_map(state, & &1), [], state}
end
end
{: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)
ConsumerSpy.call(consumer, :get)
# => [0,1,2,3,...10]