Add sequence diagram

Author: fcollonval

README.md

@@ -34,6 +34,83 @@ that the server extension is enabled:
 jupyter server extension list
 ```
 
+## How does it works
+
+### Generic case
+
+Execution of a Python code snippet: `print("hello")`
+
+```mermaid
+sequenceDiagram
+    Frontend->>+Server: POST /api/kernels/<id>/execute
+    Server->>+ExecutionStack: Create asyncio.Task
+    ExecutionStack->>Kernel: Execute request msg
+    activate Kernel
+    ExecutionStack-->>Server: Task uid
+    Server-->>-Frontend: Returns task uid
+    loop Running
+        Kernel->>Shared Document: Add output
+        Shared Document->>Frontend: Document update
+    end
+    loop While status is 202
+        Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+        Server->>ExecutionStack: Get task result
+        ExecutionStack-->>Server: null
+        Server-->>-Frontend: Request status 202
+    end
+    Kernel-->>ExecutionStack: Execution reply
+    deactivate Kernel
+    Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+    Server->>ExecutionStack: Get task result
+    ExecutionStack-->>Server: Result
+    Server-->>-Frontend: Status 200 & result
+```
+
+### With input case
+
+
+Execution of a Python code snippet: `input("Age:")`
+
+```mermaid
+sequenceDiagram
+    Frontend->>+Server: POST /api/kernels/<id>/execute
+    Server->>+ExecutionStack: Create asyncio.Task
+    ExecutionStack->>Kernel: Execute request msg
+    activate Kernel
+    ExecutionStack-->>Server: Task uid
+    Server-->>-Frontend: Returns task uid
+    loop Running
+        Kernel->>Shared Document: Add output
+        Shared Document->>Frontend: Document update
+    end
+    loop While status is 202
+        Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+        Server->>ExecutionStack: Get task result
+        ExecutionStack-->>Server: null
+        Server-->>-Frontend: Request status 202
+    end
+    Kernel->>ExecutionStack: Set pending input
+    Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+    Server->>ExecutionStack: Get task result
+    ExecutionStack-->>Server: Pending input
+    Server-->>-Frontend: Status 300 & Pending input
+    Frontend->>+Server: POST /api/kernels/<id>/input
+    Server->>Kernel: Send input msg
+    Server-->>-Frontend: 
+    loop While status is 202
+        Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+        Server->>ExecutionStack: Get task result
+        ExecutionStack-->>Server: null
+        Server-->>-Frontend: Request status 202
+    end
+    Kernel-->>ExecutionStack: Execution reply
+    deactivate Kernel
+    Frontend->>+Server: GET /api/kernels/<id>/requests/<uid>
+    Server->>ExecutionStack: Get task result
+    ExecutionStack-->>Server: Result
+    Server-->>-Frontend: Status 200 & result
+```
+
 ## Contributing
 
 ### Development install
@@ -46,7 +123,6 @@ jupyter server extension list
 pip install -e .
 ```
 
-
 You can watch the source directory and run your Jupyter Server-based application at the same time in different terminals to watch for changes in the extension's source and automatically rebuild the extension.  For example,
 when running JupyterLab:
 

jupyter_server_nbmodel/handlers.py

@@ -111,7 +111,7 @@ def _stdin_hook(self, kernel_id: str, msg: dict) -> None:
 
         It will register the pending input as temporary answer to the execution request.
         """
-        get_logger().info(f"Execution request {kernel_id} received a input request {msg!s}")
+        get_logger().debug(f"Execution request {kernel_id} received a input request.")
         if kernel_id in self.__pending_inputs:
             get_logger().error(
                 f"Execution request {kernel_id} received a input request while waiting for an input.\n{msg}"  # noqa: E501
@@ -186,11 +186,11 @@ async def _execute_snippet(
         reply_content = reply["content"]
 
         if ycell is not None:
-            ycell["execution_count"] = reply_content["execution_count"]
+            ycell["execution_count"] = reply_content.get("execution_count")
 
         return {
             "status": reply_content["status"],
-            "execution_count": reply_content["execution_count"],
+            "execution_count": reply_content.get("execution_count"),
             # FIXME quid for buffers
             "outputs": json.dumps(outputs),
         }