Extends GenericRandomErrorPlugin with request matching. Closes #818 (#819)

Author: waldekmastykarz

dev-proxy-plugins/GenericErrorResponse.cs

@@ -1,13 +1,40 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT License.
 
-using Microsoft.DevProxy.Abstractions;
-
 namespace Microsoft.DevProxy.Plugins;
 
 public class GenericErrorResponse
 {
-    public int StatusCode { get; set; }
-    public List<MockResponseHeader>? Headers { get; set; }
+    public GenericErrorResponseRequest? Request { get; set; }
+    public GenericErrorResponseResponse[]? Responses { get; set; }
+}
+
+public class GenericErrorResponseRequest
+{
+    public string Url { get; set; } = string.Empty;
+    public string Method { get; set; } = "GET";
+    public string? BodyFragment { get; set; }
+}
+
+public class GenericErrorResponseResponse
+{
+    public int? StatusCode { get; set; } = 400;
     public dynamic? Body { get; set; }
+    public List<GenericErrorResponseHeader>? Headers { get; set; }
+}
+
+public class GenericErrorResponseHeader
+{
+    public string Name { get; set; } = string.Empty;
+    public string Value { get; set; } = string.Empty;
+
+    public GenericErrorResponseHeader()
+    {
+    }
+
+    public GenericErrorResponseHeader(string name, string value)
+    {
+        Name = name;
+        Value = value;
+    }
 }

dev-proxy-plugins/RandomErrors/GenericErrorResponsesLoader.cs

@@ -26,7 +26,7 @@ public void LoadResponses()
         if (!File.Exists(_errorsFile))
         {
             _logger.LogWarning("File {configurationFile} not found in the current directory. No error responses will be loaded", _configuration.ErrorsFile);
-            _configuration.Responses = Array.Empty<GenericErrorResponse>();
+            _configuration.Errors = Array.Empty<GenericErrorResponse>();
             return;
         }
 
@@ -36,10 +36,10 @@ public void LoadResponses()
             using var reader = new StreamReader(stream);
             var responsesString = reader.ReadToEnd();
             var responsesConfig = JsonSerializer.Deserialize<GenericRandomErrorConfiguration>(responsesString, ProxyUtils.JsonSerializerOptions);
-            IEnumerable<GenericErrorResponse>? configResponses = responsesConfig?.Responses;
+            IEnumerable<GenericErrorResponse>? configResponses = responsesConfig?.Errors;
             if (configResponses is not null)
             {
-                _configuration.Responses = configResponses;
+                _configuration.Errors = configResponses;
                 _logger.LogInformation("{configResponseCount} error responses loaded from {errorFile}", configResponses.Count(), _configuration.ErrorsFile);
             }
         }

dev-proxy-plugins/RandomErrors/GenericRandomErrorPlugin.cs

@@ -10,6 +10,7 @@
 using Titanium.Web.Proxy.Models;
 using Microsoft.DevProxy.Plugins.Behavior;
 using Microsoft.Extensions.Logging;
+using System.Text.RegularExpressions;
 
 namespace Microsoft.DevProxy.Plugins.RandomErrors;
 internal enum GenericRandomErrorFailMode
@@ -23,7 +24,7 @@ public class GenericRandomErrorConfiguration
 {
     public string? ErrorsFile { get; set; }
     public int RetryAfterInSeconds { get; set; } = 5;
-    public IEnumerable<GenericErrorResponse> Responses { get; set; } = Array.Empty<GenericErrorResponse>();
+    public IEnumerable<GenericErrorResponse> Errors { get; set; } = Array.Empty<GenericErrorResponse>();
 }
 
 public class GenericRandomErrorPlugin : BaseProxyPlugin
@@ -43,11 +44,16 @@ public GenericRandomErrorPlugin(IPluginEvents pluginEvents, IProxyContext contex
     // uses config to determine if a request should be failed
     private GenericRandomErrorFailMode ShouldFail(ProxyRequestArgs e) => _random.Next(1, 100) <= Context.Configuration.Rate ? GenericRandomErrorFailMode.Random : GenericRandomErrorFailMode.PassThru;
 
-    private void FailResponse(ProxyRequestArgs e, GenericRandomErrorFailMode failMode)
+    private void FailResponse(ProxyRequestArgs e)
     {
-        // pick a random error response for the current request
-        var error = _configuration.Responses.ElementAt(_random.Next(0, _configuration.Responses.Count()));
-        UpdateProxyResponse(e, error);
+        var matchingResponse = GetMatchingErrorResponse(e.Session.HttpClient.Request);
+        if (matchingResponse is not null &&
+            matchingResponse.Responses is not null)
+        {
+            // pick a random error response for the current request
+            var error = matchingResponse.Responses.ElementAt(_random.Next(0, matchingResponse.Responses.Length));
+            UpdateProxyResponse(e, error);
+        }
     }
 
     private ThrottlingInfo ShouldThrottle(Request request, string throttlingKey)
@@ -56,16 +62,76 @@ private ThrottlingInfo ShouldThrottle(Request request, string throttlingKey)
         return new ThrottlingInfo(throttleKeyForRequest == throttlingKey ? _configuration.RetryAfterInSeconds : 0, "Retry-After");
     }
 
-    private void UpdateProxyResponse(ProxyRequestArgs e, GenericErrorResponse error)
+    private GenericErrorResponse? GetMatchingErrorResponse(Request request)
+    {
+        if (_configuration.Errors is null ||
+            !_configuration.Errors.Any())
+        {
+            return null;
+        }
+
+        var errorResponse = _configuration.Errors.FirstOrDefault(errorResponse =>
+        {
+            if (errorResponse.Request is null) return false;
+            if (errorResponse.Responses is null) return false;
+
+            if (errorResponse.Request.Method != request.Method) return false;
+            if (errorResponse.Request.Url == request.Url &&
+                HasMatchingBody(errorResponse, request))
+            {
+                return true;
+            }
+
+            // check if the URL contains a wildcard
+            // if it doesn't, it's not a match for the current request for sure
+            if (!errorResponse.Request.Url.Contains('*'))
+            {
+                return false;
+            }
+
+            // turn mock URL with wildcard into a regex and match against the request URL
+            var errorResponseUrlRegex = Regex.Escape(errorResponse.Request.Url).Replace("\\*", ".*");
+            return Regex.IsMatch(request.Url, $"^{errorResponseUrlRegex}$") &&
+                HasMatchingBody(errorResponse, request);
+        });
+
+        return errorResponse;
+    }
+
+    private bool HasMatchingBody(GenericErrorResponse errorResponse, Request request)
+    {
+        if (request.Method == "GET")
+        {
+            // GET requests don't have a body so we can't match on it
+            return true;
+        }
+
+        if (errorResponse.Request?.BodyFragment is null)
+        {
+            // no body fragment to match on
+            return true;
+        }
+
+        if (!request.HasBody || string.IsNullOrEmpty(request.BodyString))
+        {
+            // error response defines a body fragment but the request has no body
+            // so it can't match
+            return false;
+        }
+
+        return request.BodyString.Contains(errorResponse.Request.BodyFragment, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private void UpdateProxyResponse(ProxyRequestArgs e, GenericErrorResponseResponse error)
     {
         SessionEventArgs session = e.Session;
         Request request = session.HttpClient.Request;
-        var headers = new List<MockResponseHeader>();
+        var headers = new List<GenericErrorResponseHeader>();
         if (error.Headers is not null)
         {
             headers.AddRange(error.Headers);
         }
-        
+
         if (error.StatusCode == (int)HttpStatusCode.TooManyRequests &&
             error.Headers is not null &&
             error.Headers.FirstOrDefault(h => h.Name == "Retry-After" || h.Name == "retry-after")?.Value == "@dynamic")
@@ -83,7 +149,7 @@ error.Headers is not null &&
             headers.Add(new("Retry-After", _configuration.RetryAfterInSeconds.ToString()));
         }
 
-        var statusCode = (HttpStatusCode)error.StatusCode;
+        var statusCode = (HttpStatusCode)(error.StatusCode ?? 400);
         var body = error.Body is null ? string.Empty : JsonSerializer.Serialize(error.Body, ProxyUtils.JsonSerializerOptions);
         // we get a JSON string so need to start with the opening quote
         if (body.StartsWith("\"@"))
@@ -146,7 +212,7 @@ private Task OnRequest(object? sender, ProxyRequestArgs e)
             {
                 return Task.CompletedTask;
             }
-            FailResponse(e, failMode);
+            FailResponse(e);
             state.HasBeenSet = true;
         }
 

dev-proxy/devproxy-errors.json

@@ -1,67 +1,74 @@
 {
   "$schema": "https://raw.githubusercontent.com/microsoft/dev-proxy/main/schemas/v0.20.0/genericrandomerrorplugin.schema.json",
-  "responses": [
+  "errors": [
     {
-      "statusCode": 400,
-      "body": {
-        "message": "Bad Request",
-        "details": "The server cannot process the request due to invalid syntax."
-      }
-    },
-    {
-      "statusCode": 401,
-      "body": {
-        "message": "Unauthorized",
-        "details": "The request requires user authentication."
-      }
-    },
-    {
-      "statusCode": 403,
-      "body": {
-        "message": "Forbidden",
-        "details": "The server understood the request, but refuses to authorize it."
-      }
-    },
-    {
-      "statusCode": 404,
-      "body": {
-        "message": "Not Found",
-        "details": "The requested resource could not be found."
-      }
-    },
-    {
-      "statusCode": 418,
-      "body": {
-        "message": "I'm a teapot",
-        "details": "The server refuses the attempt to brew coffee with a teapot."
-      }
-    },
-    {
-      "statusCode": 429,
-      "body": {
-        "message": "Too Many Requests",
-        "details": "The user has sent too many requests in a given amount of time (\"rate limiting\")."
+      "request": {
+        "url": "https://jsonplaceholder.typicode.com/*"
       },
-      "headers": [
+      "responses": [
+        {
+          "statusCode": 400,
+          "body": {
+            "message": "Bad Request",
+            "details": "The server cannot process the request due to invalid syntax."
+          }
+        },
+        {
+          "statusCode": 401,
+          "body": {
+            "message": "Unauthorized",
+            "details": "The request requires user authentication."
+          }
+        },
         {
-          "name": "Retry-After",
-          "value": "@dynamic"
+          "statusCode": 403,
+          "body": {
+            "message": "Forbidden",
+            "details": "The server understood the request, but refuses to authorize it."
+          }
+        },
+        {
+          "statusCode": 404,
+          "body": {
+            "message": "Not Found",
+            "details": "The requested resource could not be found."
+          }
+        },
+        {
+          "statusCode": 418,
+          "body": {
+            "message": "I'm a teapot",
+            "details": "The server refuses the attempt to brew coffee with a teapot."
+          }
+        },
+        {
+          "statusCode": 429,
+          "body": {
+            "message": "Too Many Requests",
+            "details": "The user has sent too many requests in a given amount of time (\"rate limiting\")."
+          },
+          "headers": [
+            {
+              "name": "Retry-After",
+              "value": "@dynamic"
+            }
+          ]
+        },
+        {
+          "statusCode": 500,
+          "body": {
+            "message": "Internal Server Error",
+            "details": "The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application."
+          }
+        },
+        {
+          "statusCode": 503,
+          "body": {
+            "message": "Service Unavailable",
+            "details": "The server is currently unable to handle the request due to a temporary overload or maintenance. Please try again later."
+          }
         }
       ]
-    },
-    {
-      "statusCode": 500,
-      "body": {
-        "message": "Internal Server Error",
-        "details": "The server encountered an internal error and was unable to complete your request. Either the server is overloaded or there is an error in the application."
-      }
-    },
-    {
-      "statusCode": 503,
-      "body": {
-        "message": "Service Unavailable",
-        "details": "The server is currently unable to handle the request due to a temporary overload or maintenance. Please try again later."
-      }
     }
   ]
 }