Adds the latency plugin. Closes #321 (#327)

Author: waldekmastykarz

m365-developer-proxy-abstractions/PluginEvents.cs

@@ -186,8 +186,8 @@ public void RaiseOptionsLoaded(OptionsLoadedArgs args) {
         OptionsLoaded?.Invoke(this, args);
     }
 
-    public void RaiseProxyBeforeRequest(ProxyRequestArgs args) {
-        BeforeRequest?.Invoke(this, args);
+    public async Task RaiseProxyBeforeRequest(ProxyRequestArgs args) {
+        await BeforeRequest?.InvokeAsync(this, args, null);
     }
 
     public async Task RaiseProxyBeforeResponse(ProxyResponseArgs args) {

m365-developer-proxy-plugins/RandomErrors/LatencyPlugin.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.Extensions.Configuration;
+using Microsoft365.DeveloperProxy.Abstractions;
+
+namespace Microsoft365.DeveloperProxy.Plugins.RandomErrors;
+
+public class LatencyConfiguration {
+    public int MinMs { get; set; } = 0;
+    public int MaxMs { get; set; } = 5000;
+}
+
+public class LatencyPlugin : BaseProxyPlugin {
+    private readonly LatencyConfiguration _configuration = new();
+
+    public override string Name => nameof(LatencyPlugin);
+    private readonly Random _random;
+
+    public LatencyPlugin() {
+        _random = new Random();
+    }
+
+    public override void Register(IPluginEvents pluginEvents,
+                         IProxyContext context,
+                         ISet<UrlToWatch> urlsToWatch,
+                         IConfigurationSection? configSection = null) {
+        base.Register(pluginEvents, context, urlsToWatch, configSection);
+
+        configSection?.Bind(_configuration);
+        pluginEvents.BeforeRequest += OnRequest;
+    }
+
+    private async Task OnRequest(object? sender, ProxyRequestArgs e) {
+        if (_urlsToWatch is not null
+            && e.ShouldExecute(_urlsToWatch)) {
+            var delay = _random.Next(_configuration.MinMs, _configuration.MaxMs);
+            _logger?.LogRequest(new[] { $"Delaying request for {delay}ms" }, MessageType.Chaos, new LoggingContext(e.Session));
+            await Task.Delay(delay);
+        }
+    }
+}

m365-developer-proxy/ProxyEngine.cs

@@ -356,13 +356,13 @@ async Task OnRequest(object sender, SessionEventArgs e) {
 
             e.UserData = e.HttpClient.Request;
             _logger.LogRequest(new[] { $"{e.HttpClient.Request.Method} {e.HttpClient.Request.Url}" }, MessageType.InterceptedRequest, new LoggingContext(e));
-            HandleRequest(e);
+            await HandleRequest(e);
         }
     }
 
-    private void HandleRequest(SessionEventArgs e) {
+    private async Task HandleRequest(SessionEventArgs e) {
         ResponseState responseState = new ResponseState();
-        _pluginEvents.RaiseProxyBeforeRequest(new ProxyRequestArgs(e, _throttledRequests, responseState));
+        await _pluginEvents.RaiseProxyBeforeRequest(new ProxyRequestArgs(e, _throttledRequests, responseState));
 
         // We only need to set the proxy header if the proxy has not set a response and the request is going to be sent to the target.
         if (!responseState.HasBeenSet) {

m365-developer-proxy/m365proxyrc.json

@@ -1,5 +1,11 @@
 {
   "plugins": [
+    {
+      "name": "LatencyPlugin",
+      "enabled": false,
+      "pluginPath": "plugins\\m365-developer-proxy-plugins.dll",
+      "configSection": "latencyPlugin"
+    },
     {
       "name": "RetryAfterPlugin",
       "enabled": true,
@@ -137,6 +143,10 @@
   "cachingGuidance": {
     "cacheThresholdSeconds": 5
   },
+  "latencyPlugin": {
+    "minMs": 200,
+    "maxMs": 10000
+  },
   "rate": 50,
   "labelMode": "text",
   "logLevel": "info"