run_emulator_client retries.

api/src/opentrons/hardware_control/emulation/app.py

@@ -1,5 +1,6 @@
 import asyncio
 import logging
+from enum import Enum
 
 from opentrons.hardware_control.emulation.module_server import ModuleStatusServer
 from opentrons.hardware_control.emulation.parser import Parser
@@ -11,6 +12,14 @@
 logger = logging.getLogger(__name__)
 
 
+class ModuleType(str, Enum):
+    """Module type enumeration."""
+    Magnetic = "magnetic"
+    Temperature = "temperature"
+    Thermocycler = "thermocycler"
+    Heatershaker = "heatershaker"
+
+
 class Application:
     """The emulator application."""
 
@@ -26,16 +35,16 @@ def __init__(self, settings: Settings) -> None:
             parser=Parser(), settings=settings.smoothie
         )
         self._magdeck = Proxy(
-            "magdeck", self._status_server, self._settings.magdeck_proxy
+            ModuleType.Magnetic, self._status_server, self._settings.magdeck_proxy
         )
         self._temperature = Proxy(
-            "temperature", self._status_server, self._settings.temperature_proxy
+            ModuleType.Temperature, self._status_server, self._settings.temperature_proxy
         )
         self._thermocycler = Proxy(
-            "thermocycler", self._status_server, self._settings.thermocycler_proxy
+            ModuleType.Thermocycler, self._status_server, self._settings.thermocycler_proxy
         )
         self._heatershaker = Proxy(
-            "heatershaker", self._status_server, self._settings.heatershaker_proxy
+            ModuleType.Heatershaker, self._status_server, self._settings.heatershaker_proxy
         )
 
     async def run(self) -> None:

api/src/opentrons/hardware_control/emulation/module_server.py

@@ -73,7 +73,7 @@ def on_server_disconnected(self, identifier: str) -> None:
             log.exception("Failed to find identifier")
 
     async def run(self) -> None:
-        """"""
+        """Run the server."""
         server = await asyncio.start_server(
             self._handle_connection, host=self._settings.host, port=self._settings.port
         )

api/src/opentrons/hardware_control/emulation/run_emulator.py

@@ -1,22 +1,56 @@
 import asyncio
 import logging
+from typing import Optional
 
 from opentrons.hardware_control.emulation.abstract_emulator import AbstractEmulator
 from opentrons.hardware_control.emulation.connection_handler import ConnectionHandler
 
 log = logging.getLogger(__name__)
 
 
-async def run_emulator_client(host: str, port: int, emulator: AbstractEmulator) -> None:
-    """Run an emulator as a client."""
+async def run_emulator_client(host: str, port: int, emulator: AbstractEmulator, retries: int = 3, interval_seconds:float=0.1) -> None:
+    """Run an emulator as a client.
+
+    Args:
+        host: Host to connect to.
+        port: Port to connect on.
+        emulator: The emulator instance.
+        retries: Number of retries on a failed connection attempt.
+        interval_seconds: How long to wait between retries.
+
+    Returns:
+        None
+    """
     log.info(f"Connecting to {emulator.__class__.__name__} at {host}:{port}")
-    r, w = await asyncio.open_connection(host, port)
+
+    r: Optional[asyncio.StreamReader] = None
+    w: Optional[asyncio.StreamWriter] = None
+    for i in range(retries):
+        try:
+            r, w = await asyncio.open_connection(host, port)
+            break
+        except IOError:
+            log.error(f"{emulator.__class__.__name__} failed to connect on try {i + 1}. Retrying in {interval_seconds} seconds.")
+            await asyncio.sleep(interval_seconds)
+
+    if r is None or w is None:
+        raise IOError(f"Failed to connect to {emulator.__class__.__name__} at {host}:{port} after {retries} retries.")
+
     connection = ConnectionHandler(emulator)
     await connection(r, w)
 
 
 async def run_emulator_server(host: str, port: int, emulator: AbstractEmulator) -> None:
-    """Run an emulator as a server."""
+    """Run an emulator as a server.
+
+    Args:
+        host: Host to listen on.
+        port: Port to listen on.
+        emulator: Emaulator instance.
+
+    Returns:
+        None
+    """
     log.info(f"Starting {emulator.__class__.__name__} at {host}:{port}")
     server = await asyncio.start_server(ConnectionHandler(emulator), host, port)
     await server.serve_forever()