Pool channels should be created with capacity

[sydhds]

So if the pool is late, items in channels are dropped instead of blocking the emitter

[AurelienFT]

We could start with few thousands on each to be sure. The number should be specified in the config.

[Ben-PH]

Having a look through the code base, It's difficult to see where the entry point to this task is. I'm guessing it's to do with massa_pool_exports::PoolChannels, which currently uses tokio::sync::channel::broadcast sender, and reading the documentation, it looks like capacity is already set:

// massa-node/src/main.rs
    let pool_channels = PoolChannels {
        endorsement_sender: broadcast::channel(pool_config.broadcast_endorsements_channel_capacity)
            .0,
        operation_sender: broadcast::channel(pool_config.broadcast_operations_channel_capacity).0,
        selector: selector_controller.clone(),
    };

Am I missing anything?

[AurelienFT]

This are the channels to broadcast what's going on to be used by other modules (for now used only by grpc API for streaming). The PoolChannels and all XXXChannels structures in the code always define channels that are meant to be exposed and used by other modules.

The internal channels are created in function start_pool_controller looking at them now they already have a size but the three use the same variable. I think, to consider the task done, it would be nice to make a config variable per channel :)