guides/features: add document for how to gracefully shutdown server

content/en/docs/guides/server-graceful-stop.md

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+---
+title: Gracefully stopping a server
+description: >-
+  Explains how to gracefully stop/shutdown a gRPC server.
+---
+
+### Overview
+
+gRPC servers often need to shut down gracefully, ensuring that in-flight RPCs
+are completed within a reasonable timeframe and new RPCs are no longer
+accepted. The "Graceful shutdown function" facilitates this process, allowing
+the server to transition smoothly without abruptly terminating active
+connections.
+
+When the "Graceful shutdown function" is called, the server immediately stops
+accepting new RPCs. In-flight RPCs are allowed to continue until they complete
+or a specified deadline is reached. Once all active RPCs finish or the deadline
+expires, the server shuts down completely.
+
+### How to do Graceful Server Shutdown
+
+The exact implementation of the "Graceful shutdown function" varies depending on
+the programming language you are using. However, the general pattern
+involves:
+
+- Initiating the graceful shutdown process by calling "Graceful shutdown
+  Function" on your gRPC server object. This function blocks until all
+  currently running RPCs complete. This ensures that in-flight requests are
+  allowed to finish processing.
+- Specify a timeout period to limit the time allowed for in-progress RPCs to
+  finish. It's crucial to call the "Forceful shutdown function" on the server
+  object with a timeout before calling the "Graceful shutdown function". This
+  acts as a safety net, ensuring that the server eventually shuts down even if
+  some in-flight RPCs don't complete within a reasonable timeframe. This
+  prevents indefinite blocking.
+
+The following shows the sequence of events that occur, when a server's graceful
+stop is invoked, in-flight RPCs continue to prorcess, but new RPCs are
+rejected. If some in-flight RPCs are not finished in time, server is forcefully
+shutdown.
+```mermaid
+sequenceDiagram
+Client->>Server: New RPC Request 1
+Client->>Server: New RPC Request 2
+Server->>Client: Processing RPC 1
+Server->>Client: Processing RPC 2
+Server-->>Server: Graceful Stop Invoked
+Server->>Client: Continues Processing In-Flight RPCs
+Client->>Server: New RPC Request 3 (Rejected)
+alt RPCs complete within timeout
+    Server->>Client: Completes RPC 1
+    Server->>Client: Completes RPC 2
+    Server-->>Server: Shutdown Complete
+    Client->>Server: New RPC Request 4 (Rejected)
+else Timeout reached
+    Server->>Client: RPC 2 and other pending RPCs forcefully terminated
+    Server-->>Server: Shutdown Complete
+    Client->>Server: New RPC Request 4 (Rejected)
+end
+```
+The following is a state based view
+```mermaid
+stateDiagram-v2
+    [*] --> RUNNING : Server Started
+    RUNNING --> GRACEFUL_STOP_INITIATED : GracefulStop() Called (with Timeout)
+    GRACEFUL_STOP_INITIATED --> GRACEFUL_STOPPING : Reject New RPCs
+    GRACEFUL_STOPPING --> TERMINATED : Complete In-Flight RPCs (Before Timeout)
+    GRACEFUL_STOPPING --> FORCE_STOP : Timeout Reached
+    FORCE_STOP --> TERMINATED : Force Terminate Pending RPCs and Shutdown
+```
+
+### Alternatives
+
+- Forceful Shutdown: Immediately terminates the server using "Forceful Shutdown
+  Function" on server object, potentially interrupting active RPCs and leading
+  to errors on the client-side. Use only as a last resort.
+
+### Language Support
+
+| Language | Example           |
+|----------|-------------------|
+| Java     |                   |
+| Go       | [Go example]      |
+| Python   |                   |
+
+[Go example]: https://github.com/grpc/grpc-go/tree/master/examples/features/gracefulstop