Setup a global aiohttp.ClientSession instance

Author: james-gray

Pipfile

@@ -14,6 +14,7 @@ pytest = "*"
 pytest-cov = "*"
 
 [packages]
+aiohttp = "*"
 cachetools = "*"
 fastapi = "*"
 gunicorn = "*"

app/main.py

@@ -13,6 +13,7 @@
 from .data import data_source
 from .router.v1 import V1
 from .router.v2 import V2
+from .utils.httputils import setup_client_session, teardown_client_session
 
 # ############
 # FastAPI App
@@ -28,6 +29,8 @@
     version="2.0.1",
     docs_url="/",
     redoc_url="/docs",
+    on_startup=[setup_client_session],
+    on_shutdown=[teardown_client_session],
 )
 
 # #####################

app/utils/httputils.py

@@ -0,0 +1,30 @@
+import logging
+
+from aiohttp import ClientSession
+
+
+# Singleton aiohttp.ClientSession instance.
+client_session: ClientSession
+
+
+LOGGER = logging.getLogger(__name__)
+
+
+async def setup_client_session():
+    """Set up the application-global aiohttp.ClientSession instance.
+
+    aiohttp recommends that only one ClientSession exist for the lifetime of an application.
+    See: https://docs.aiohttp.org/en/stable/client_quickstart.html#make-a-request
+
+    """
+    global client_session
+    LOGGER.info("Setting up global aiohttp.ClientSession.")
+    client_session = ClientSession()
+
+
+async def teardown_client_session():
+    """Close the application-global aiohttp.ClientSession.
+    """
+    global client_session
+    LOGGER.info("Closing global aiohttp.ClientSession.")
+    await client_session.close()