Remove with_gossip

[tomaka]

Based on top of #2497. Only the last commit is relevant.

Removes the Service::with_gossip method and turn its usage around the code into individual method calls.

[rphmeier]

Also needs a PR in Polkadot when this is merged.

[gterzian]

What's the rationale for removing the generic with_gossip method with dedicated methods? From the discussion me and @rphmeier had over at #1340 (comment) I took away that we didn't want to bloat the API with too many specific methods...

[tomaka]

Just like the other PRs, I'm trying to make the API less dependant on the threading strategy. To me, passing a closure to with_gossip that gets executed later is strictly worse than doing a "flat call" to a method that does what your closure contains.

[gterzian]

I fail to see how the last commit changes the situation with regards to the dependence on the threading strategy.

We're trading a single with_gossip api endpoint for four specific ones. And those new methods still result in a message being sent across, which will run an "operation" on another task.

The only difference is that every operation we come up with later will require a new method, and message, whereas with_gossip allowed the client to execute a generic operation using gossip.

If what you mean is that you want the "operation" corresponding to the method call to execute immediately, we could still keep with_gossip, and make it a blocking call using a bounded sender, or a lock around gossip.

[rphmeier]

Yeah, I still think with_gossip is still much more robust and we don't have to deal with service API bloat.

[tomaka]

Well, ok. I don't want to spend energy convincing people, so will reopen at a later time on top of other changes when the necessity of that change becomes a bit more obvious.