Shutdown runtime after task is completed

[jaspervdm]

Each request was spawning its own multithreaded runtime that kept running even after the request was done, taking up resources unnecessarily. This PR addresses that, by using a runtime that runs in the current thread.
Ideally we would have a single multithreaded runtime to spawn all requests on, but that is a larger refactor that I'm planning on doing later on.

Small side note is that the current-thread runtime is only active until the future completes and any unfinished tasks that were spawned by this future aren't polled anymore. Since we are not spawning any tasks that outlive our future this shouldn't have any effect but it is something to keep in the back of our minds.

Fixes #330

[fentanyluser]

with this i am receiving these errors

20200213 00:14:35.309 ERROR grin_util::logger -
thread 'tokio-runtime-worker-0' panicked at 'Multiple executors at once: EnterError { reason: "attempted to run an executor while another executor is already running" }': src/libcore/result.rs:1165stack backtrace:
0: grin_util::logger::send_panic_to_log::{{closure}}
1: std::panicking::rust_panic_with_hook
at src/libstd/panicking.rs:468
2: std::panicking::continue_panic_fmt
at src/libstd/panicking.rs:373
3: rust_begin_unwind
at src/libstd/panicking.rs:302
4: core::panicking::panic_fmt
at src/libcore/panicking.rs:139
5: core::result::unwrap_failed
at src/libcore/result.rs:1165
6: tokio::runtime::current_thread::runtime::Runtime::block_on
7: grin_wallet_impls::client_utils::client::Client::send_request
8: grin_wallet_impls::client_utils::client::Client::get
9: <grin_wallet_impls::node_clients::http::HTTPNodeClient as grin_wallet_libwallet::types::NodeClient>::get_chain_tip
10: grin_wallet_libwallet::api_impl::owner::node_height
11: grin_wallet_api::owner::Owner<L,C,K>::node_height
12: <grin_wallet_api::owner::Owner<L,C,K> as grin_wallet_api::owner_rpc::OwnerRpc>::node_height
13: ::handle
14: easy_jsonrpc_mw::handle_call
15: easy_jsonrpc_mw::handle_parsed_request
16: easy_jsonrpc_mw::Handler::handle_request
17: futures::future::chain::Chain<A,B,C>::poll
18: <futures::future::and_then::AndThen<A,B,F> as futures::future::Future>::poll
19: futures::future::chain::Chain<A,B,C>::poll
20: <futures::future::and_then::AndThen<A,B,F> as futures::future::Future>::poll
21: futures::future::chain::Chain<A,B,C>::poll
22: <futures::future::or_else::OrElse<A,B,F> as futures::future::Future>::poll
23: <hyper::proto::h1::dispatch::Server as hyper::proto::h1::dispatch::Dispatch>::poll_msg
24: <futures::future::either::Either<A,B> as futures::future::Future>::poll
25: <hyper::server::conn::upgrades::UpgradeableConnection<I,S,E> as futures::future::Future>::poll
26: <hyper::server::conn::spawn_all::NewSvcTask<I,N,S,E,W> as futures::future::Future>::poll
27: futures::task_impl::std::set
28: std::panicking::try::do_call
29: __rust_maybe_catch_panic
at src/libpanic_unwind/lib.rs:78
30: tokio_threadpool::task::Task::run
31: tokio_threadpool::worker::Worker::run_task
32: tokio_threadpool::worker::Worker::run
33: tokio_reactor::with_default
34: tokio::runtime::builder::Builder::build::{{closure}}
35: std::thread::local::LocalKey::with
36: std::thread::local::LocalKey::with
37: std::sys_common::backtrace::__rust_begin_short_backtrace
38: std::panicking::try::do_call
39: __rust_maybe_catch_panic
at src/libpanic_unwind/lib.rs:78
40: core::ops::function::FnOnce::call_once{{vtable.shim}}
41: <alloc::boxed::Box as core::ops::function::FnOnce>::call_once
at /rustc/73528e339aae0f17a15ffa49a8ac608f50c6cf14/src/liballoc/boxed.rs:942
42: <alloc::boxed::Box as core::ops::function::FnOnce>::call_once
at /rustc/73528e339aae0f17a15ffa49a8ac608f50c6cf14/src/liballoc/boxed.rs:942
std::sys_common::thread::start_thread
at src/libstd/sys_common/thread.rs:13
std::sys::unix::thread::Thread::new::thread_start
at src/libstd/sys/unix/thread.rs:79
43: start_thread
44: clone

Thread 'tokio-runtime-worker-0' panicked with message:
"Multiple executors at once: EnterError { reason: "attempted to run an executor while another executor is already running" }"
See .grin/main/grin-wallet.log for further details.

[jaspervdm]

Hmm, I'll investigate tomorrow

[jaspervdm]

@fentanyluser Should be fixed now, I tested the owner api and it no longer panics with latest commit in this PR. The original issue should also be fixed since we wait for shutdown of runtime before returning.

[yeastplume]

LGTM, test failures unrelated so merging.

[aleqx]

Getting a error[E0658]: non exhaustive is an experimental feature when trying to compile master with this commit. Does it need a rustup to nightly?

EDIT: Ignore me - I thought I was running the latest stable rustc but in fact it was quite old. My apologies

[quentinlesceller]

Which version of rust are you using? @aleqx I'm not getting this on 1.41.

[fentanyluser]

It appears to be still having the same issue #330