workers: basic event loop (#3828)

* establish basic event loop for workers
* make "self.close()" inside worker
* remove "runWorkerMessageLoop() - instead manually call global function 
  in Rust when message arrives. This is done in preparation for structured clone
* refactor "WorkerChannel" and use distinct structs for internal 
  and external channels;  "WorkerChannelsInternal" and "WorkerHandle"
* move "State.worker_channels_internal" to "Worker.internal_channels"
* add "WorkerEvent" enum for child->host communication; 
  currently "Message(Buf)" and  "Error(ErrBox)" variants are supported
* add tests for nested workers
* add tests for worker throwing error on startup

1 files changed, 3 insertions, 7 deletions

diff --git a/cli/state.rs b/cli/state.rs
index 4e2f47e62..b9ef62053 100644
--- a/cli/state.rs
+++ b/cli/state.rs
@@ -8,8 +8,7 @@ use crate::metrics::Metrics;
 use crate::ops::JsonOp;
 use crate::ops::MinimalOp;
 use crate::permissions::DenoPermissions;
-use crate::worker::WorkerChannelsExternal;
-use crate::worker::WorkerChannelsInternal;
+use crate::worker::WorkerHandle;
 use deno_core::Buf;
 use deno_core::CoreOp;
 use deno_core::ErrBox;
@@ -55,8 +54,7 @@ pub struct StateInner {
   pub import_map: Option<ImportMap>,
   pub metrics: Metrics,
   pub global_timer: GlobalTimer,
-  pub workers: HashMap<u32, WorkerChannelsExternal>,
-  pub worker_channels_internal: Option<WorkerChannelsInternal>,
+  pub workers: HashMap<u32, WorkerHandle>,
   pub next_worker_id: AtomicUsize,
   pub start_time: Instant,
   pub seeded_rng: Option<StdRng>,
@@ -232,7 +230,6 @@ impl State {
       import_map,
       metrics: Metrics::default(),
       global_timer: GlobalTimer::new(),
-      worker_channels_internal: None,
       workers: HashMap::new(),
       next_worker_id: AtomicUsize::new(0),
       start_time: Instant::now(),
@@ -269,7 +266,6 @@ impl State {
       import_map: None,
       metrics: Metrics::default(),
       global_timer: GlobalTimer::new(),
-      worker_channels_internal: None,
       workers: HashMap::new(),
       next_worker_id: AtomicUsize::new(0),
       start_time: Instant::now(),
@@ -282,7 +278,7 @@ impl State {
     Ok(Self(state))
   }
 
-  pub fn add_child_worker(&self, handle: WorkerChannelsExternal) -> u32 {
+  pub fn add_child_worker(&self, handle: WorkerHandle) -> u32 {
     let mut inner_state = self.borrow_mut();
     let worker_id =
       inner_state.next_worker_id.fetch_add(1, Ordering::Relaxed) as u32;