Created
May 9, 2021 23:53
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| defmodule Producer do | |
| use GenStage | |
| @behaviour Broadway.Producer | |
| def init(_opts) do | |
| {:producer, 0} | |
| end | |
| def handle_demand(demand, stored_demand) do | |
| total_demand = demand + stored_demand | |
| messages = | |
| total_demand | |
| |> BlockingBuffer.drain() | |
| |> Enum.map(&%Broadway.Message{data: &1, acknowledger: {Broadway.NoopAcknowledger, nil, nil}}) # Create a broadway message from the kafka message | |
| message_count = length(messages) | |
| # If we've run out of messages, we need to kickstart the pipeline again | |
| # so, try drain again soon | |
| if message_count < total_demand do | |
| Process.send_after(self(), :kick_start, 1_000) | |
| end | |
| {:noreply, messages, total_demand - message_count} | |
| end | |
| def handle_info(:kick_start, stored_demand) do | |
| handle_demand(0, stored_demand) | |
| end | |
| end |
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