Cache account lookup in memory when proxying

PluralKit.Bot/Services/ProxyCacheService.cs

@@ -0,0 +1,82 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Threading.Tasks;
+using Dapper;
+using Microsoft.Extensions.Caching.Memory;
+using Serilog;
+
+namespace PluralKit.Bot
+{
+    public class ProxyCacheService
+    {
+        public class ProxyDatabaseResult
+        {
+            public PKSystem System;
+            public PKMember Member;
+        }
+        
+        private DbConnectionFactory _conn;
+        private IMemoryCache _cache;
+        private ILogger _logger;
+
+        public ProxyCacheService(DbConnectionFactory conn, IMemoryCache cache, ILogger logger)
+        {
+            _conn = conn;
+            _cache = cache;
+            _logger = logger;
+        }
+
+        public Task<IEnumerable<ProxyDatabaseResult>> GetResultsFor(ulong account)
+        {
+            _logger.Debug("Looking up members for account {Account} in cache...", account);
+            return _cache.GetOrCreateAsync(GetKey(account), (entry) => FetchResults(account, entry));
+        }
+
+        public void InvalidateResultsFor(ulong account)
+        {
+            _logger.Information("Invalidating proxy cache for account {Account}", account);
+            _cache.Remove(GetKey(account));
+        }
+        
+        public async Task InvalidateResultsForSystem(PKSystem system)
+        {
+            _logger.Information("Invalidating proxy cache for system {System}", system.Id);
+            using (var conn = await _conn.Obtain())
+                foreach (var accountId in await conn.QueryAsync<ulong>("select uid from accounts where system = @Id", system))
+                    _cache.Remove(GetKey(accountId));
+        }
+
+        private async Task<IEnumerable<ProxyDatabaseResult>> FetchResults(ulong account, ICacheEntry entry)
+        {
+            _logger.Information("Members for account {Account} not in cache, fetching", account);
+            using (var conn = await _conn.Obtain())
+            {
+                var results = (await conn.QueryAsync<PKMember, PKSystem, ProxyDatabaseResult>(
+                    "select members.*, systems.* from members, systems, accounts where members.system = systems.id and accounts.system = systems.id and accounts.uid = @Uid",
+                    (member, system) =>
+                        new ProxyDatabaseResult {Member = member, System = system}, new {Uid = account})).ToList();
+
+                if (results.Count == 0)
+                {
+                    // Long expiry for accounts with no system registered
+                    entry.SetSlidingExpiration(TimeSpan.FromMinutes(5));
+                    entry.SetAbsoluteExpiration(TimeSpan.FromHours(1));
+                }
+                else
+                {
+                    // Shorter expiry if they already have a system
+                    entry.SetSlidingExpiration(TimeSpan.FromMinutes(1));
+                    entry.SetAbsoluteExpiration(TimeSpan.FromMinutes(5));
+                }
+                
+                return results;
+            }
+        }
+
+        private object GetKey(ulong account)
+        {
+            return $"_proxy_account_{account}";
+        }
+    }
+}