PluralKit/PluralKit.Bot/Utils/MiscUtils.cs

using System;
using System.Linq;
using System.Net.Http;
using System.Net.Sockets;
using System.Threading.Tasks;

using Myriad.Rest.Exceptions;

using Newtonsoft.Json;

using Npgsql;

using PluralKit.Core;

using Polly.Timeout;

namespace PluralKit.Bot
{
    public static class MiscUtils
    {
        public static string ProxyTagsString(this PKMember member, string separator = ", ") =>
            string.Join(separator, member.ProxyTags.Select(t => t.ProxyString.AsCode()));

        public static bool IsOurProblem(this Exception e)
        {
            // This function filters out sporadic errors out of our control from being reported to Sentry
            // otherwise we'd blow out our error reporting budget as soon as Discord takes a dump, or something.

            // Occasionally Discord's API will Have A Bad Time and return a bunch of CloudFlare errors (in HTML format).
            // The library tries to parse these HTML responses as JSON and crashes with a consistent exception message.
            if (e is JsonReaderException jre && jre.Message == "Unexpected character encountered while parsing value: <. Path '', line 0, position 0.") return false;

            // And now (2020-05-12), apparently Discord returns these weird responses occasionally. Also not our problem.
            if (e is BadRequestException bre && bre.ResponseBody.Contains("<center>nginx</center>")) return false;
            if (e is NotFoundException ne && ne.ResponseBody.Contains("<center>nginx</center>")) return false;
            if (e is UnauthorizedException ue && ue.ResponseBody.Contains("<center>nginx</center>")) return false;

            // Filter out timeout/ratelimit related stuff
            if (e is TooManyRequestsException) return false;
            if (e is RatelimitBucketExhaustedException) return false;
            if (e is TimeoutRejectedException) return false;

            // 5xxs? also not our problem :^)
            if (e is UnknownDiscordRequestException udre && (int)udre.StatusCode >= 500) return false;

            // Webhook server errors are also *not our problem*
            // (this includes rate limit errors, WebhookRateLimited is a subclass)
            if (e is WebhookExecutionErrorOnDiscordsEnd) return false;

            // Socket errors are *not our problem*
            if (e.GetBaseException() is SocketException) return false;

            // Tasks being cancelled for whatver reason are, you guessed it, also not our problem.
            if (e is TaskCanceledException) return false;

            // Sometimes Discord just times everything out.
            if (e is TimeoutException) return false;

            // HTTP/2 streams are complicated and break sometimes.
            if (e is HttpRequestException) return false;

            // Ignore "Database is shutting down" error
            if (e is PostgresException pe && pe.SqlState == "57P03") return false;

            // Ignore database timing out as well.
            if (e is NpgsqlException tpe && tpe.InnerException is TimeoutException)
                return false;

            // Ignore thread pool exhaustion errors
            if (e is NpgsqlException npe && npe.Message.Contains("The connection pool has been exhausted")) return false;

            // This may expanded at some point.
            return true;
        }
    }
}