Stop accepting JsonRpc requests during shutdown (#7818)

Author: benaadams

src/Nethermind/Nethermind.Config/IProcessExitSource.cs

@@ -16,6 +16,7 @@ public interface IProcessExitSource
 
 public class ProcessExitSource : IProcessExitSource
 {
+    private static readonly CancellationToken _cancelledToken = new(canceled: true);
     private CancellationTokenSource _cancellationTokenSource;
     private readonly TaskCompletionSource _exitResult = new();
 
@@ -38,5 +39,5 @@ public void Exit(int exitCode)
 
     public Task ExitTask => _exitResult.Task;
 
-    public CancellationToken Token => _cancellationTokenSource.Token;
+    public CancellationToken Token => _cancellationTokenSource?.Token ?? _cancelledToken;
 }

src/Nethermind/Nethermind.JsonRpc/IJsonRpcProcessor.cs

@@ -3,10 +3,12 @@
 
 using System.Collections.Generic;
 using System.IO.Pipelines;
+using System.Threading;
 
 namespace Nethermind.JsonRpc;
 
 public interface IJsonRpcProcessor
 {
     IAsyncEnumerable<JsonRpcResult> ProcessAsync(PipeReader stream, JsonRpcContext context);
+    CancellationToken ProcessExit { get; }
 }

src/Nethermind/Nethermind.JsonRpc/JsonRpcProcessor.cs

@@ -16,6 +16,7 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Connections;
 using Microsoft.AspNetCore.Http;
+using Nethermind.Config;
 using Nethermind.Core.Collections;
 using Nethermind.Core.Extensions;
 using Nethermind.Core.Resettables;
@@ -30,15 +31,18 @@ public class JsonRpcProcessor : IJsonRpcProcessor
     private readonly ILogger _logger;
     private readonly IJsonRpcService _jsonRpcService;
     private readonly Recorder _recorder;
+    private readonly IProcessExitSource? _processExitSource;
 
-    public JsonRpcProcessor(IJsonRpcService jsonRpcService, IJsonRpcConfig jsonRpcConfig, IFileSystem fileSystem, ILogManager logManager)
+    public JsonRpcProcessor(IJsonRpcService jsonRpcService, IJsonRpcConfig jsonRpcConfig, IFileSystem fileSystem, ILogManager logManager, IProcessExitSource? processExitSource = null)
     {
         _logger = logManager?.GetClassLogger() ?? throw new ArgumentNullException(nameof(logManager));
         ArgumentNullException.ThrowIfNull(fileSystem);
 
         _jsonRpcService = jsonRpcService ?? throw new ArgumentNullException(nameof(jsonRpcService));
         _jsonRpcConfig = jsonRpcConfig ?? throw new ArgumentNullException(nameof(jsonRpcConfig));
 
+        _processExitSource = processExitSource;
+
         if (_jsonRpcConfig.RpcRecorderState != RpcRecorderState.None)
         {
             if (_logger.IsWarn) _logger.Warn("Enabling JSON RPC diagnostics recorder - this will affect performance and should be only used in a diagnostics mode.");
@@ -47,6 +51,9 @@ public JsonRpcProcessor(IJsonRpcService jsonRpcService, IJsonRpcConfig jsonRpcCo
         }
     }
 
+    public CancellationToken ProcessExit
+        => _processExitSource?.Token ?? default;
+
     private (JsonRpcRequest? Model, ArrayPoolList<JsonRpcRequest>? Collection) DeserializeObjectOrArray(JsonDocument doc)
     {
         JsonValueKind type = doc.RootElement.ValueKind;
@@ -120,6 +127,12 @@ private ArrayPoolList<JsonRpcRequest> DeserializeArray(JsonElement element) =>
 
     public async IAsyncEnumerable<JsonRpcResult> ProcessAsync(PipeReader reader, JsonRpcContext context)
     {
+        if (ProcessExit.IsCancellationRequested)
+        {
+            JsonRpcErrorResponse response = _jsonRpcService.GetErrorResponse(ErrorCodes.ResourceUnavailable, "Shutting down");
+            yield return JsonRpcResult.Single(RecordResponse(response, new RpcReport("Shutdown", 0, false)));
+        }
+
         reader = await RecordRequest(reader);
         long startTime = Stopwatch.GetTimestamp();
         CancellationTokenSource timeoutSource = new(_jsonRpcConfig.Timeout);

src/Nethermind/Nethermind.Runner/Ethereum/Steps/StartRpc.cs

@@ -50,7 +50,8 @@ public async Task Execute(CancellationToken cancellationToken)
                     jsonRpcService,
                     jsonRpcConfig,
                     _api.FileSystem,
-                    _api.LogManager);
+                    _api.LogManager,
+                    _api.ProcessExit);
 
 
                 if (initConfig.WebSocketsEnabled)

src/Nethermind/Nethermind.Runner/JsonRpc/Startup.cs

@@ -146,6 +146,12 @@ public void Configure(IApplicationBuilder app, IWebHostEnvironment env, IJsonRpc
                 return;
             }
 
+            if (jsonRpcProcessor.ProcessExit.IsCancellationRequested)
+            {
+                ctx.Response.StatusCode = (int)HttpStatusCode.ServiceUnavailable;
+                return;
+            }
+
             if (!jsonRpcUrlCollection.TryGetValue(ctx.Connection.LocalPort, out JsonRpcUrl jsonRpcUrl) ||
                 !jsonRpcUrl.RpcEndpoint.HasFlag(RpcEndpoint.Http))
             {