Add `open_pikerd()` and `spawn_emsd()`

The direct open is needed for running `pikerd` cmd and
the ems spawn point is the first step toward detaching UI based order
entry from the engine itself.

piker/_daemon.py

@@ -1,7 +1,7 @@
 """
 pikerd daemon lifecylcle & rpc
 """
-from typing import Optional
+from typing import Optional, Dict, Callable
 from contextlib import asynccontextmanager
 
 import tractor
@@ -14,14 +14,41 @@ log = get_logger(__name__)
 
 _root_nursery: Optional[tractor._trionics.ActorNursery] = None
 _root_dname = 'pikerd'
-
 _root_modules = [
     __name__,
-    'piker.exchange._ems',
-    'piker.exchange._client',
+    'piker.clearing._ems',
+    'piker.clearing._client',
 ]
 
 
+@asynccontextmanager
+async def open_pikerd(
+    loglevel: Optional[str] = None
+) -> Optional[tractor._portal.Portal]:
+
+    global _root_nursery
+
+    async with tractor.open_root_actor(
+        name=_root_dname,
+        loglevel=loglevel,
+
+        # TODO: eventually we should be able to avoid
+        # having the root have more then permissions to
+        # spawn other specialized daemons I think?
+        # enable_modules=[__name__],
+        enable_modules=_root_modules
+    ):
+        # init root nursery
+        try:
+            async with tractor.open_nursery() as nursery:
+                _root_nursery = nursery
+                yield nursery
+        finally:
+            # client code may block indefinitely so cancel when
+            # teardown is invoked
+            await nursery.cancel()
+
+
 @asynccontextmanager
 async def maybe_open_pikerd(
     loglevel: Optional[str] = None
@@ -41,20 +68,12 @@ async def maybe_open_pikerd(
             yield portal
 
         else:  # assume role
-            async with tractor.open_root_actor(
-                name=_root_dname,
-                loglevel=loglevel,
-                enable_modules=_root_modules
-            ):
-                # init root nursery
-                try:
-                    async with tractor.open_nursery() as nursery:
-                        _root_nursery = nursery
+            async with open_pikerd(loglevel) as nursery:
+                # in the case where we're starting up the
+                # tractor-piker runtime stack in **this** process
+                # we want to hand off a nursery for starting (as a sub)
+                # whatever actor is requesting pikerd.
                 yield None
-                finally:
-                    # client code may block indefinitely so cancel when
-                    # teardown is invoked
-                    await nursery.cancel()
 
 
 # brokerd enabled modules
@@ -72,10 +91,12 @@ async def spawn_brokerd(
     **tractor_kwargs
 ) -> tractor._portal.Portal:
 
+    log.info(f'Spawning {brokername} broker daemon')
+
     brokermod = get_brokermod(brokername)
     dname = f'brokerd.{brokername}'
-    log.info(f'Spawning {brokername} broker daemon')
-    tractor_kwargs = getattr(brokermod, '_spawnkwargs', {})
+
+    extra_tractor_kwargs = getattr(brokermod, '_spawnkwargs', {})
 
     # TODO: raise exception when _root_nursery == None?
     global _root_nursery
@@ -83,6 +104,32 @@ async def spawn_brokerd(
         dname,
         enable_modules=_data_mods + [brokermod.__name__],
         loglevel=loglevel,
-        **tractor_kwargs
+        **extra_tractor_kwargs
     )
-    return portal
+    return dname
+
+
+async def spawn_emsd(
+    brokername,
+    loglevel: Optional[str] = None,
+    **extra_tractor_kwargs
+) -> tractor._portal.Portal:
+
+    from .clearing import _client
+
+    log.info('Spawning emsd')
+
+    # TODO: raise exception when _root_nursery == None?
+    global _root_nursery
+    assert _root_nursery
+
+    portal = await _root_nursery.start_actor(
+        'emsd',
+        enable_modules=[
+            'piker.clearing._ems',
+            'piker.clearing._client',
+        ],
+        loglevel=loglevel,
+        **extra_tractor_kwargs
+    )
+    return 'emsd'