Adds caching guidance (#259)

Author: waldekmastykarz

msgraph-developer-proxy-plugins/Guidance/CachingGuidancePlugin.cs

@@ -0,0 +1,64 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Microsoft.Extensions.Configuration;
+using Microsoft.Graph.DeveloperProxy.Abstractions;
+using Titanium.Web.Proxy.Http;
+
+namespace Microsoft.Graph.DeveloperProxy.Plugins.Guidance;
+
+public class CachingGuidancePluginConfiguration
+{
+  public int CacheThresholdSeconds { get; set; } = 5;
+}
+
+public class CachingGuidancePlugin : BaseProxyPlugin
+{
+  public override string Name => nameof(CachingGuidancePlugin);
+  private readonly CachingGuidancePluginConfiguration _configuration = new();
+  private IDictionary<string, DateTime> _interceptedRequests = new Dictionary<string, DateTime>();
+
+  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 += BeforeRequest;
+  }
+
+  private async Task BeforeRequest(object? sender, ProxyRequestArgs e)
+  {
+    if (_urlsToWatch is null || !e.HasRequestUrlMatch(_urlsToWatch))
+    {
+      return;
+    }
+
+    Request request = e.Session.HttpClient.Request;
+    var url = request.RequestUri.AbsoluteUri;
+    var now = DateTime.Now;
+
+    if (!_interceptedRequests.ContainsKey(url))
+    {
+      _interceptedRequests.Add(url, now);
+      return;
+    }
+
+    var lastIntercepted = _interceptedRequests[url];
+    var secondsSinceLastIntercepted = (now - lastIntercepted).TotalSeconds;
+    if (secondsSinceLastIntercepted <= _configuration.CacheThresholdSeconds)
+    {
+      _logger?.LogRequest(BuildCacheWarningMessage(request, _configuration.CacheThresholdSeconds, lastIntercepted), MessageType.Warning, new LoggingContext(e.Session));
+    }
+
+    _interceptedRequests[url] = now;
+  }
+
+  private static string[] BuildCacheWarningMessage(Request r, int _warningSeconds, DateTime lastIntercepted) => new[] {
+    $"Another request to {r.RequestUri.PathAndQuery} intercepted within {_warningSeconds} seconds.",
+    $"Last intercepted at {lastIntercepted}.",
+    "Consider using cache to avoid calling the API too often."
+  };
+}

msgraph-developer-proxy/mgdprc.json

@@ -61,6 +61,12 @@
         "https://microsoftgraph.chinacloudapi.cn/beta/*"
       ]
     },
+    {
+      "name": "CachingGuidancePlugin",
+      "enabled": true,
+      "pluginPath": "GraphProxyPlugins\\msgraph-developer-proxy-plugins.dll",
+      "configSection": "cachingGuidance"
+    },
     {
       "name": "RateLimitingPlugin",
       "enabled": false,
@@ -109,6 +115,9 @@
   "executionSummaryPlugin": {
     "groupBy": "url"
   },
+  "cachingGuidance": {
+    "cacheThresholdSeconds": 5
+  },
   "rate": 50,
   "labelMode": "text",
   "logLevel": "info"