Re-implement client caching using `maybe_open_ctx`

piker/_cacheables.py

@@ -79,59 +79,6 @@ def async_lifo_cache(maxsize=128):
 _cache: dict[str, 'Client'] = {}  # noqa
 
 
-# XXX: this mis mostly an alt-implementation of
-# maybe_open_ctx() below except it uses an async exit statck.
-# ideally wer pick one or the other.
-@asynccontextmanager
-async def open_cached_client(
-    brokername: str,
-) -> 'Client':  # noqa
-    '''Get a cached broker client from the current actor's local vars.
-
-    If one has not been setup do it and cache it.
-    '''
-    global _cache
-
-    clients = _cache.setdefault('clients', {'_lock': trio.Lock()})
-
-    # global cache task lock
-    lock = clients['_lock']
-
-    client = None
-
-    try:
-        log.info(f"Loading existing `{brokername}` client")
-
-        async with lock:
-            client = clients[brokername]
-            client._consumers += 1
-
-        yield client
-
-    except KeyError:
-        log.info(f"Creating new client for broker {brokername}")
-
-        async with lock:
-            brokermod = get_brokermod(brokername)
-            exit_stack = AsyncExitStack()
-
-            client = await exit_stack.enter_async_context(
-                brokermod.get_client()
-            )
-            client._consumers = 0
-            client._exit_stack = exit_stack
-            clients[brokername] = client
-
-        yield client
-
-    finally:
-        if client is not None:
-            # if no more consumers, teardown the client
-            client._consumers -= 1
-            if client._consumers <= 0:
-                await client._exit_stack.aclose()
-
-
 class cache:
     '''Globally (processs wide) cached, task access to a
     kept-alive-while-in-use async resource.
@@ -227,3 +174,20 @@ async def maybe_open_ctx(
 
                 # terminate mngr nursery
                 cache.no_more_users.set()
+
+
+@asynccontextmanager
+async def open_cached_client(
+    brokername: str,
+) -> 'Client':  # noqa
+    '''Get a cached broker client from the current actor's local vars.
+
+    If one has not been setup do it and cache it.
+
+    '''
+    brokermod = get_brokermod(brokername)
+    async with maybe_open_ctx(
+        key=brokername,
+        mngr=brokermod.get_client(),
+    ) as (cache_hit, client):
+        yield client