Execute webhooks directly rather than through D.NET

PluralKit.Bot/PluralKit.Bot.csproj

@@ -10,7 +10,6 @@
     </ItemGroup>
 
     <ItemGroup>
-      <PackageReference Include="Discord.Net.Webhook" Version="2.1.1" />
       <PackageReference Include="Discord.Net.WebSocket" Version="2.1.1" />
       <PackageReference Include="Humanizer.Core" Version="2.6.2" />
       <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="2.2.0" />

PluralKit.Bot/Services/WebhookCacheService.cs

@@ -4,7 +4,6 @@ using System.Linq;
 using System.Net.Http;
 using System.Threading.Tasks;
 using Discord;
-using Discord.Webhook;
 using Discord.WebSocket;
 
 using Serilog;

PluralKit.Bot/Services/WebhookExecutorService.cs

@@ -3,11 +3,14 @@ using System.Net.Http;
 using System.Text.RegularExpressions;
 using System.Threading.Tasks;
 using App.Metrics;
-using App.Metrics.Logging;
+
 using Discord;
-using Discord.Net;
+
-using Discord.Webhook;
+using Humanizer;
-using Microsoft.Extensions.Caching.Memory;
+
+using Newtonsoft.Json;
+using Newtonsoft.Json.Linq;
+
 using Serilog;
 
 namespace PluralKit.Bot
@@ -15,14 +18,12 @@ namespace PluralKit.Bot
     public class WebhookExecutorService: IDisposable
     {
         private WebhookCacheService _webhookCache;
-        private IMemoryCache _cache;
         private ILogger _logger;
         private IMetrics _metrics;
         private HttpClient _client;
 
-        public WebhookExecutorService(IMemoryCache cache, IMetrics metrics, WebhookCacheService webhookCache, ILogger logger)
+        public WebhookExecutorService(IMetrics metrics, WebhookCacheService webhookCache, ILogger logger)
         {
-            _cache = cache;
             _metrics = metrics;
             _webhookCache = webhookCache;
             _logger = logger.ForContext<WebhookExecutorService>();
@@ -48,72 +49,44 @@ namespace PluralKit.Bot
         private async Task<ulong> ExecuteWebhookInner(IWebhook webhook, string name, string avatarUrl, string content,
             IAttachment attachment, bool hasRetried = false)
         {
-            var client = await GetClientFor(webhook);
 
-            try
+            var mfd = new MultipartFormDataContent();
+            mfd.Add(new StringContent(content.Truncate(2000)), "content");
+            mfd.Add(new StringContent(FixClyde(name).Truncate(80)), "username");
+            if (avatarUrl != null) mfd.Add(new StringContent(avatarUrl), "avatar_url");
+
+            if (attachment != null)
             {
-                // If we have an attachment, use the special SendFileAsync method
+                var attachmentResponse = await _client.GetAsync(attachment.Url);
-                if (attachment != null)
+                var attachmentStream = await attachmentResponse.Content.ReadAsStreamAsync();
-                    using (var attachmentStream = await _client.GetStreamAsync(attachment.Url))
+                mfd.Add(new StreamContent(attachmentStream), "file", attachment.Filename);
-                    using (_metrics.Measure.Timer.Time(BotMetrics.WebhookResponseTime))
-                        return await client.SendFileAsync(attachmentStream, attachment.Filename, content,
-                            username: FixClyde(name),
-                            avatarUrl: avatarUrl);
-
-                // Otherwise, send normally
-                return await client.SendMessageAsync(content, username: FixClyde(name), avatarUrl: avatarUrl);
             }
-            catch (HttpException e)
+
+            HttpResponseMessage response;
+            using (_metrics.Measure.Timer.Time(BotMetrics.WebhookResponseTime))
+                response = await _client.PostAsync($"{DiscordConfig.APIUrl}webhooks/{webhook.Id}/{webhook.Token}?wait=true", mfd);
+
+            // TODO: are there cases where an error won't also return a parseable JSON object?
+            var responseJson = JsonConvert.DeserializeObject<JObject>(await response.Content.ReadAsStringAsync());
+            if (responseJson.ContainsKey("code"))
             {
-                // If we hit an error, just retry (if we haven't already)
+                if (responseJson["code"].Value<int>() == 10015 && !hasRetried)
-                if (e.DiscordCode == 10015 && !hasRetried) // Error 10015 = "Unknown Webhook"
                 {
-                    _logger.Warning(e, "Error invoking webhook {Webhook} in channel {Channel}", webhook.Id, webhook.ChannelId);
+                    // Error 10015 = "Unknown Webhook" - this likely means the webhook was deleted
+                    // but is still in our cache. Invalidate, refresh, try again
+                    _logger.Warning("Error invoking webhook {Webhook} in channel {Channel}", webhook.Id, webhook.ChannelId);
                     return await ExecuteWebhookInner(await _webhookCache.InvalidateAndRefreshWebhook(webhook), name, avatarUrl, content, attachment, hasRetried: true);
                 }
-
+                
-                throw;
+                // TODO: look into what this actually throws, and if this is the correct handling
+                response.EnsureSuccessStatusCode();
             }
-        }
-        
-        private async Task<DiscordWebhookClient> GetClientFor(IWebhook webhook)
-        {
-            _logger.Verbose("Looking for client for webhook {Webhook} in cache", webhook.Id);
-            return await _cache.GetOrCreateAsync($"_webhook_client_{webhook.Id}",
-                (entry) => MakeCachedClientFor(entry, webhook));
-        }
-
-        private Task<DiscordWebhookClient> MakeCachedClientFor(ICacheEntry entry, IWebhook webhook) {
-            _logger.Information("Client for {Webhook} not found in cache, creating", webhook.Id);
             
-            // Define expiration for the client cache
+            // At this point we're sure we have a 2xx status code, so just assume success
-            // 10 minutes *without a query* and it gets yoten
+            // TODO: can we do this without a round-trip to a string?
-            entry.SlidingExpiration = TimeSpan.FromMinutes(10);
+            return responseJson["id"].Value<ulong>();
-
-            // IMemoryCache won't automatically dispose of its values when the cache gets evicted
-            // so we register a hook to do so here.
-            entry.RegisterPostEvictionCallback((key, value, reason, state) => (value as IDisposable)?.Dispose());
-            
-            // DiscordWebhookClient has a sync network call in its constructor (!!!)
-            // and we want to punt that onto a task queue, so we do that.
-            return Task.Run(async () =>
-            {
-                try
-                {
-                    return new DiscordWebhookClient(webhook);
-                }
-                catch (InvalidOperationException)
-                {
-                    // TODO: does this leak stuff inside the DiscordWebhookClient created above?
-                    
-                    // Webhook itself was found in cache, but has been deleted on the channel
-                    // We request a new webhook instead
-                    return new DiscordWebhookClient(await _webhookCache.InvalidateAndRefreshWebhook(webhook));
-                }
-
-            });
         }
-        
+
         private string FixClyde(string name)
         {
             // Check if the name contains "Clyde" - if not, do nothing