From 5ab2cc0155c2dfe0c0233747cd313aee8aa7bc30 Mon Sep 17 00:00:00 2001
From: Kafonek <matt.kafonek@noteable.io>
Date: Thu, 25 Aug 2022 15:41:59 -0400
Subject: [PATCH 1/4] Add a sleep in Jupyter Backend poll loop

---
 CHANGELOG.md                |  1 +
 sending/backends/jupyter.py | 13 ++++++++++++-
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 93abeec..7197e6a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - Use `managed_service_fixtures` for Redis tests
 - `WebsocketManager` backend uses vanilla `logging` instead of `structlog`, remove need for `structlog` dependency once `managed-service-fixtures` also drops it
+- `JupyterBackend` introduce a short sleep in its poll loop while investigating 100% CPU usage
 
 ## [0.2.2] - 2022-07-28
 ### Changed
diff --git a/sending/backends/jupyter.py b/sending/backends/jupyter.py
index 65f8c96..e3b32d2 100644
--- a/sending/backends/jupyter.py
+++ b/sending/backends/jupyter.py
@@ -1,7 +1,9 @@
+import asyncio
 from queue import Empty
 from typing import Optional, Union
 
 from jupyter_client import AsyncKernelClient
+from jupyter_client.channels import ZMQSocketChannel
 from zmq import NOBLOCK, Event, Socket, SocketOption, pyzmq_version, zmq_version
 from zmq.asyncio import Context
 from zmq.utils.monitor import recv_monitor_message
@@ -93,7 +95,7 @@ def _cycle_socket(self, topic):
 
     async def _poll(self):
         for topic_name in self.subscribed_topics:
-            channel_obj = getattr(self._client, f"{topic_name}_channel")
+            channel_obj: ZMQSocketChannel = getattr(self._client, f"{topic_name}_channel")
 
             while True:
                 try:
@@ -117,3 +119,12 @@ async def _poll(self):
             # when it violates some constraint such as the max message size.
             logger.info(f"ZMQ disconnected for topic '{topic}', cycling socket")
             self._cycle_socket(topic)
+
+    async def _poll_loop(self):
+        while True:
+            try:
+                await self._poll()
+            except Exception:
+                logger.exception("Uncaught exception encountered while polling backend")
+            finally:
+                await asyncio.sleep(0.001)

From 2ff0a0dd256488a4ec46d714492ff8a18021f1a1 Mon Sep 17 00:00:00 2001
From: Kafonek <matt.kafonek@noteable.io>
Date: Thu, 25 Aug 2022 15:47:44 -0400
Subject: [PATCH 2/4] docstring

---
 sending/backends/jupyter.py | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sending/backends/jupyter.py b/sending/backends/jupyter.py
index e3b32d2..cfe37cd 100644
--- a/sending/backends/jupyter.py
+++ b/sending/backends/jupyter.py
@@ -121,6 +121,11 @@ async def _poll(self):
             self._cycle_socket(topic)
 
     async def _poll_loop(self):
+        """
+        Override base Manager _poll_loop to switch the final asyncio.sleep from 0 to 0.001.
+        While observing JupyterManager in real world, containers are using 100% CPU.
+        Possibly due to this loop being too aggressive?
+        """
         while True:
             try:
                 await self._poll()

From 9b30731bc7571daf68300d493fe2a10c2e9aeca7 Mon Sep 17 00:00:00 2001
From: Kafonek <matt.kafonek@noteable.io>
Date: Thu, 25 Aug 2022 15:57:06 -0400
Subject: [PATCH 3/4] make the sleep time a class attribute so we can change it
 in PA

---
 sending/backends/jupyter.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/sending/backends/jupyter.py b/sending/backends/jupyter.py
index cfe37cd..11ec0bf 100644
--- a/sending/backends/jupyter.py
+++ b/sending/backends/jupyter.py
@@ -13,11 +13,18 @@
 
 
 class JupyterKernelManager(AbstractPubSubManager):
-    def __init__(self, connection_info: dict, *, max_message_size: int = None):
+    def __init__(
+        self,
+        connection_info: dict,
+        *,
+        max_message_size: int = None,
+        sleep_between_polls: float = 0.005,
+    ):
         super().__init__()
         self.connection_info = connection_info
         self._monitor_sockets_for_topic: dict[str, Socket] = {}
         self.max_message_size = max_message_size
+        self.sleep_between_polls = sleep_between_polls
 
     async def initialize(
         self, *, queue_size=0, inbound_workers=1, outbound_workers=1, poll_workers=1
@@ -132,4 +139,4 @@ async def _poll_loop(self):
             except Exception:
                 logger.exception("Uncaught exception encountered while polling backend")
             finally:
-                await asyncio.sleep(0.001)
+                await asyncio.sleep(self.sleep_between_polls)

From 671167b54362f8487bc9103ba95d3c32ef43fc0a Mon Sep 17 00:00:00 2001
From: Kafonek <matt.kafonek@noteable.io>
Date: Thu, 25 Aug 2022 16:06:02 -0400
Subject: [PATCH 4/4] fix docstring

---
 sending/backends/jupyter.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sending/backends/jupyter.py b/sending/backends/jupyter.py
index 11ec0bf..5016d32 100644
--- a/sending/backends/jupyter.py
+++ b/sending/backends/jupyter.py
@@ -129,7 +129,8 @@ async def _poll(self):
 
     async def _poll_loop(self):
         """
-        Override base Manager _poll_loop to switch the final asyncio.sleep from 0 to 0.001.
+        Override base Manager _poll_loop to switch the final asyncio.sleep from 0 to
+        something more than that (definable at init or after instantiation, default 0.005).
         While observing JupyterManager in real world, containers are using 100% CPU.
         Possibly due to this loop being too aggressive?
         """