Add a `DataFeed.call_client()` method

Allows for calling an actor local broker client's methods from a remote
actor.

piker/brokers/data.py

@@ -25,7 +25,7 @@ log = get_logger('broker.data')
 
 
 async def wait_for_network(net_func: Callable, sleep: int = 1) -> dict:
-    """Wait until the network comes back up.
+    """Wait until the network (DNS) comes back up.
     """
     down = False
     while True:
@@ -220,7 +220,7 @@ async def get_cached_feed(
     ss = tractor.current_actor().statespace
     feeds = ss.setdefault('feeds', {'_lock': trio.Lock()})
     lock = feeds['_lock']
-    try:
+    feed = None
     try:
         async with lock:
             feed = feeds[brokername]
@@ -241,6 +241,7 @@ async def get_cached_feed(
             feeds[brokername] = feed
         yield feed
     finally:
+        if feed is not None:
             # destroy the API client
             await feed.exit_stack.aclose()
 
@@ -319,9 +320,18 @@ async def start_quote_stream(
             f"Terminating stream quoter task for {feed.mod.name}")
 
 
+async def call_client(
+    broker: str,
+    methname: str,
+    **kwargs,
+):
+    async with get_cached_feed(broker) as feed:
+        return await getattr(feed.client, methname)(**kwargs)
+
+
 class DataFeed:
-    """Data feed client for streaming symbol data from a (remote)
-    ``brokerd`` data daemon.
+    """Data feed client for streaming symbol data from and making API client calls
+    to a (remote) ``brokerd`` daemon.
     """
     _allowed = ('stock', 'option')
 
@@ -400,6 +410,17 @@ class DataFeed:
         ])
         return records, displayables
 
+    async def call_client(self, method, **kwargs):
+        """Call a broker ``Client`` method using RPC and return result.
+        """
+        return await self.portal.run(
+            'piker.brokers.data',
+            'call_client',
+            broker=self.brokermod.name,
+            methname=method,
+            **kwargs
+        )
+
 
 async def stream_to_file(
     watchlist_name: str,