Make block time configurable

[cmichi]

@xgreenx came up with this idea.

We should look into making the block time here configurable for CI/testing purposes. In those environments most often only a standalone node is used anyway (so no consensus issues) and in the case of e.g. ink-waterfall the tests are often blocked waiting for the next block.

substrate-contracts-node/runtime/src/lib.rs

Lines 107 to 113 in 82834b3

	/// This determines the average expected block time that we are targeting.
	/// Blocks will be produced at a minimum duration defined by `SLOT_DURATION`.
	/// `SLOT_DURATION` is picked up by `pallet_timestamp` which is in turn picked
	/// up by `pallet_aura` to implement `fn slot_duration()`.
	///
	/// Change this to adjust the block time.
	pub const MILLISECS_PER_BLOCK: u64 = 6000;

By decreasing this to a way smaller value the CI's which are using this node could be sped up significantly.

[HCastano]

Instead of doing this why not use manual seal/instant seal? That way blocks are produced when transactions are submitted to the node, regardless of the time

[gabriel-viviani]

I'm VERY new to blockchain world. I think if discussion goes in the using manual/instant seal it would be an advanced topic/implementation. Should I wait for you guys to discuss it or go ahead and trying to help with the configurable opt?!

[xgreenx]

Instead of doing this why not use manual seal/instant seal? That way blocks are produced when transactions are submitted to the node, regardless of the time

Creating blocks on-demand after each transaction will be cool. But it requires changes from substrate and it maybe it's not easy to implement. But to have that feature(blocks on demand) configurable will be perfect for testing.

[cmichi]

I didn't know about manual seal/instant seal and skimmed https://github.com/paritytech/substrate/pull/4143/files quickly. It's a different consensus engine, so would require making the engine switchable altogether ‒ thus resulting in more complexity in this node. I'd like to keep the repo as simple as possible, making it easy for us to maintain and grasp for people looking how to integrate pallet-contracts. Right now, it's really only a minimal diff to Substrate's node-template.

So my preference would be to just make this variable configurable.

[HCastano]

I haven't looked at the manual seal stuff since it was merged, but I don't imagine it should be that hard to integrate it into a node.

For development it makes a lot of sense to have it though. I say the extra complexity is worth is, especially since that's code that wouldn't change very often.

Not to put any pressure on you @gabriel-viviani, but maybe as a good starting point can you go through the Substrate Seminar related to manual seal and see what's required to integrate it into a node?

[HCastano]

@gabriel-viviani Hey! Any updates here 😃?

[cmichi]

Closed via #42.

[themartto]

so what now if I need to go back to the normal aura/grandpa block production?