View Source GenStage.BroadcastDispatcher (gen_stage v1.2.1)
A dispatcher that accumulates demand from all consumers before broadcasting events to all of them.
This dispatcher guarantees that events are dispatched to all consumers without exceeding the demand of any given consumer.
If a producer uses GenStage.BroadcastDispatcher
, its subscribers
can specify an optional :selector
function that receives the event
and returns a boolean in the subscription options.
Assume producer
and consumer
are stages exchanging events of type
%{:key => String.t, any => any}
, then by calling
GenStage.sync_subscribe(consumer,
to: producer,
selector: fn %{key: key} -> String.starts_with?(key, "foo-") end)
consumer
will receive only the events broadcast from producer
for which the selector function returns a truthy value.
The :selector
option can be specified in sync and async subscriptions,
as well as in the :subscribe_to
list in the return tuple of
GenStage.init/1
. For example:
def init(:ok) do
{:consumer, :ok, subscribe_to:
[{producer, selector: fn %{key: key} -> String.starts_with?(key, "foo-") end}]}
end