Remove runtime from secret_store.

[c0gent]

• Remove the independent runtimes from KeyServerHttpListener and
  KeyServerCore and instead require a parity_runtime::Executor
  to be passed upon creation of each.

• Remove the threads parameter from both ClusterConfiguration structs.

• Implement the future::Executor trait for parity_runtime::Executor.

• Update tests.

  • Update the loop_until function to instead use a oneshot to signal
    completion.
  • Modify the make_key_servers function to create and return a runtime.

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[lexfrl]

the PR makes sense to me, in general, but couldn't you provide the actual use-case (example) also and some more rationale on why it is important to merge essentially?

[lexfrl]

BTW, how necessary it is to update the cargo.lock in this PR?

[niklasad1]

@fckt basically this PR changes secret_store to use parity_runtime::Executor instead of tokio::Executor so I would say that Cargo.lock must be updated in order to do so!

[c0gent]

... couldn't you provide the actual use-case (example) also and some more rationale on why it is important to merge essentially?

This PR is a follow up to #9657 and simply removes an unnecessary extra runtime. (I had been waiting to submit this until #9807 was resolved.) It's possible that there is a tiny performance benefit but this change primarily falls under the category of simplification.

The only changes to usage are that a parity_runtime::Executor must be passed to secret_store::start and KeyServerHttpListener::start.

In terms of potential impact, by consolidating the runtime usage, secret_store tasks now share threads with other tasks spawned within Parity which is, if anything, a slight optimization.

[niklasad1]

It doesn't compile

$ cargo check --features secretstore
 error[E0412]: cannot find type `Executor` in this scope                                                                                                                                                                                        
   --> parity/secretstore.rs:140:69                                                                                                                                                                                                            
    |                                                                                                                                                                                                                                          
140 |         pub fn new(mut conf: Configuration, deps: Dependencies, executor: Executor) -> Result<Self, String> {                                                                                                                            
    |                                                                           ^^^^^^^^ not found in this scope                                                                                                                               
help: possible candidates are found in other modules, you can import them into scope                                                                                                                                                           
    |                                                                                                                                                                                                                                          
119 |     use futures::executor::Executor;                                                                                                                                                                                                     
    |                                                                                                                                                                                                                                          
119 |     use parity_rpc::informant::Executor;                                                                                                                                                                                                 
    |                                                                                                                                                                                                                                          
119 |     use parity_rpc::ws::tokio::executor::Executor;                                                                                                                                                                                       
    |                                                                                                                                                                                                                                          
119 |     use parity_rpc::ws::tokio::prelude::future::Executor;                                                                                                                                                                                
    |                                                                                                                                                                                                                                          
and 2 other candidates                                                                                                                                                                                                                         
                                                                                                                                                                                                                                               
error: aborting due to previous error    

Please fix by adding
use super::{Configuration, Dependencies, NodeSecretKey, ContractAddress, Executor}; on https://github.com/paritytech/parity-ethereum/blob/master/parity/secretstore.rs#L123

[svyatonik]

Is this this parameter still actual after this PR? Could you please remove it if not?

[c0gent]

I'll sort out the outstanding issues first thing tomorrow.

[c0gent]

Updated. All items should be addressed.

I went ahead removed one other extra runtime that I was going to leave for a later PR but it's cleaner to do all at once.

[sorpaas]

Mostly LGTM. A small grumble.

[c0gent]

Made a minor documentation tweak.