Add `mk_` prefix since assignments will use `fqsn`

piker/data/_source.py

@@ -59,6 +59,19 @@ tf_in_1m = {
 }
 
 
+def mk_fqsn(
+    provider: str,
+    symbol: str,
+
+) -> str:
+    '''
+    Generate a "fully qualified symbol name" which is
+    a reverse-hierarchical cross broker/provider symbol
+
+    '''
+    return '.'.join([symbol, provider]).lower()
+
+
 def float_digits(
     value: float,
 ) -> int:
@@ -118,6 +131,12 @@ class Symbol(BaseModel):
             self.key,
         )
 
+    def iterfqsns(self) -> list[str]:
+        return [
+            mk_fqsn(self.key, broker)
+            for broker in self.broker_info.keys()
+        ]
+
 
 @validate_arguments
 def mk_symbol(
@@ -129,7 +148,8 @@ def mk_symbol(
     broker_info: dict[str, Any] = {},
 
 ) -> Symbol:
-    '''Create and return an instrument description for the
+    '''
+    Create and return an instrument description for the
     "symbol" named as ``key``.
 
     '''

piker/data/feed.py

@@ -47,7 +47,12 @@ from ._sharedmem import (
     ShmArray,
 )
 from .ingest import get_ingestormod
-from ._source import base_iohlc_dtype, mk_symbol, Symbol
+from ._source import (
+    base_iohlc_dtype,
+    mk_symbol,
+    Symbol,
+    mk_fqsn,
+)
 from ..ui import _search
 from ._sampling import (
     _shms,
@@ -276,11 +281,20 @@ async def open_feed_bus(
 
     bus._subscribers.setdefault(symbol, [])
 
+    fs = mk_fqsn(symbol, brokername)
+
     # if no cached feed for this symbol has been created for this
     # brokerd yet, start persistent stream and shm writer task in
     # service nursery
     async with bus.task_lock:
         if entry is None:
+
+            if not start_stream:
+                raise RuntimeError(
+                    f'No stream feed exists for {fs}?\n'
+                    f'You may need a `brokerd` started first.'
+                )
+
             init_msg, first_quotes = await bus.nursery.start(
                 partial(
                     allocate_persistent_feed,
@@ -307,6 +321,7 @@ async def open_feed_bus(
     await ctx.started((init_msg, first_quotes))
 
     if not start_stream:
+        log.warning(f'Not opening real-time stream for {fs}')
         await trio.sleep_forever()
 
     async with (
@@ -337,20 +352,19 @@ async def open_feed_bus(
 
         try:
             uid = ctx.chan.uid
-            fqsn = f'{symbol}.{brokername}'
 
             async for msg in stream:
 
                 if msg == 'pause':
                     if sub in subs:
                         log.info(
-                            f'Pausing {fqsn} feed for {uid}')
+                            f'Pausing {fs} feed for {uid}')
                         subs.remove(sub)
 
                 elif msg == 'resume':
                     if sub not in subs:
                         log.info(
-                            f'Resuming {fqsn} feed for {uid}')
+                            f'Resuming {fs} feed for {uid}')
                         subs.append(sub)
                 else:
                     raise ValueError(msg)
@@ -614,8 +628,7 @@ async def maybe_open_feed(
             'loglevel': loglevel,
             'tick_throttle': kwargs.get('tick_throttle'),
             'backpressure': kwargs.get('backpressure'),
-            'backpressure': kwargs.get('backpressure'),
-            'start_stream': kwargs.get('start_stream'),
+            'start_stream': kwargs.get('start_stream', True),
         },
         key=sym,
     ) as (cache_hit, feed):