.Net Core 快取方式（二）AddStackExchangeRedisCache實現（3）
阿新 • • 發佈：2020-08-26
.Net Core 快取方式（二）AddStackExchangeRedisCache實現（3）
Distributed Redis Cache 是什麼
Redis是一種開源的記憶體中資料儲存，通常用作分散式快取
使用方式
- Startup.ConfigureServices
nuget Microsoft.Extensions.Caching.StackExchangeRedis
services.AddStackExchangeRedisCache(options => { options.Configuration = "localhost"; options.InstanceName = "SampleInstance"; });
原始碼以及實現
依賴注入 StackExchangeRedisCacheServiceCollectionExtensions.cs
public static IServiceCollection AddStackExchangeRedisCache(this IServiceCollection services, Action<RedisCacheOptions> setupAction) { if (services == null) { throw new ArgumentNullException(nameof(services)); } if (setupAction == null) { throw new ArgumentNullException(nameof(setupAction)); } services.AddOptions(); services.Configure(setupAction); services.Add(ServiceDescriptor.Singleton<IDistributedCache, RedisCache>()); return services; }
實現IDistributedCache RedisCache.cs
// Licensed to the .NET Foundation under one or more agreements. // The .NET Foundation licenses this file to you under the MIT license. // See the LICENSE file in the project root for more information. using System; using System.Threading; using System.Threading.Tasks; using Microsoft.Extensions.Caching.Distributed; using Microsoft.Extensions.Options; using StackExchange.Redis; namespace Microsoft.Extensions.Caching.StackExchangeRedis { public class RedisCache : IDistributedCache, IDisposable { // KEYS[1] = = key // ARGV[1] = absolute-expiration - ticks as long (-1 for none) // ARGV[2] = sliding-expiration - ticks as long (-1 for none) // ARGV[3] = relative-expiration (long, in seconds, -1 for none) - Min(absolute-expiration - Now, sliding-expiration) // ARGV[4] = data - byte[] // this order should not change LUA script depends on it private const string SetScript = (@" redis.call('HMSET', KEYS[1], 'absexp', ARGV[1], 'sldexp', ARGV[2], 'data', ARGV[4]) if ARGV[3] ~= '-1' then redis.call('EXPIRE', KEYS[1], ARGV[3]) end return 1"); private const string AbsoluteExpirationKey = "absexp"; private const string SlidingExpirationKey = "sldexp"; private const string DataKey = "data"; private const long NotPresent = -1; private volatile ConnectionMultiplexer _connection; private IDatabase _cache; private readonly RedisCacheOptions _options; private readonly string _instance; private readonly SemaphoreSlim _connectionLock = new SemaphoreSlim(initialCount: 1, maxCount: 1); public RedisCache(IOptions<RedisCacheOptions> optionsAccessor) { if (optionsAccessor == null) { throw new ArgumentNullException(nameof(optionsAccessor)); } _options = optionsAccessor.Value; // This allows partitioning a single backend cache for use with multiple apps/services. _instance = _options.InstanceName ?? string.Empty; } public byte[] Get(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } return GetAndRefresh(key, getData: true); } public async Task<byte[]> GetAsync(string key, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } token.ThrowIfCancellationRequested(); return await GetAndRefreshAsync(key, getData: true, token: token).ConfigureAwait(false); } public void Set(string key, byte[] value, DistributedCacheEntryOptions options) { if (key == null) { throw new ArgumentNullException(nameof(key)); } if (value == null) { throw new ArgumentNullException(nameof(value)); } if (options == null) { throw new ArgumentNullException(nameof(options)); } Connect(); var creationTime = DateTimeOffset.UtcNow; var absoluteExpiration = GetAbsoluteExpiration(creationTime, options); var result = _cache.ScriptEvaluate(SetScript, new RedisKey[] { _instance + key }, new RedisValue[] { absoluteExpiration?.Ticks ?? NotPresent, options.SlidingExpiration?.Ticks ?? NotPresent, GetExpirationInSeconds(creationTime, absoluteExpiration, options) ?? NotPresent, value }); } public async Task SetAsync(string key, byte[] value, DistributedCacheEntryOptions options, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } if (value == null) { throw new ArgumentNullException(nameof(value)); } if (options == null) { throw new ArgumentNullException(nameof(options)); } token.ThrowIfCancellationRequested(); await ConnectAsync(token).ConfigureAwait(false); var creationTime = DateTimeOffset.UtcNow; var absoluteExpiration = GetAbsoluteExpiration(creationTime, options); await _cache.ScriptEvaluateAsync(SetScript, new RedisKey[] { _instance + key }, new RedisValue[] { absoluteExpiration?.Ticks ?? NotPresent, options.SlidingExpiration?.Ticks ?? NotPresent, GetExpirationInSeconds(creationTime, absoluteExpiration, options) ?? NotPresent, value }).ConfigureAwait(false); } public void Refresh(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } GetAndRefresh(key, getData: false); } public async Task RefreshAsync(string key, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } token.ThrowIfCancellationRequested(); await GetAndRefreshAsync(key, getData: false, token: token).ConfigureAwait(false); } private void Connect() { if (_cache != null) { return; } _connectionLock.Wait(); try { if (_cache == null) { if (_options.ConfigurationOptions != null) { _connection = ConnectionMultiplexer.Connect(_options.ConfigurationOptions); } else { _connection = ConnectionMultiplexer.Connect(_options.Configuration); } _cache = _connection.GetDatabase(); } } finally { _connectionLock.Release(); } } private async Task ConnectAsync(CancellationToken token = default(CancellationToken)) { token.ThrowIfCancellationRequested(); if (_cache != null) { return; } await _connectionLock.WaitAsync(token).ConfigureAwait(false); try { if (_cache == null) { if (_options.ConfigurationOptions != null) { _connection = await ConnectionMultiplexer.ConnectAsync(_options.ConfigurationOptions).ConfigureAwait(false); } else { _connection = await ConnectionMultiplexer.ConnectAsync(_options.Configuration).ConfigureAwait(false); } _cache = _connection.GetDatabase(); } } finally { _connectionLock.Release(); } } private byte[] GetAndRefresh(string key, bool getData) { if (key == null) { throw new ArgumentNullException(nameof(key)); } Connect(); // This also resets the LRU status as desired. // TODO: Can this be done in one operation on the server side? Probably, the trick would just be the DateTimeOffset math. RedisValue[] results; if (getData) { results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey, DataKey); } else { results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey); } // TODO: Error handling if (results.Length >= 2) { MapMetadata(results, out DateTimeOffset? absExpr, out TimeSpan? sldExpr); Refresh(key, absExpr, sldExpr); } if (results.Length >= 3 && results[2].HasValue) { return results[2]; } return null; } private async Task<byte[]> GetAndRefreshAsync(string key, bool getData, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } token.ThrowIfCancellationRequested(); await ConnectAsync(token).ConfigureAwait(false); // This also resets the LRU status as desired. // TODO: Can this be done in one operation on the server side? Probably, the trick would just be the DateTimeOffset math. RedisValue[] results; if (getData) { results = await _cache.HashMemberGetAsync(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey, DataKey).ConfigureAwait(false); } else { results = await _cache.HashMemberGetAsync(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey).ConfigureAwait(false); } // TODO: Error handling if (results.Length >= 2) { MapMetadata(results, out DateTimeOffset? absExpr, out TimeSpan? sldExpr); await RefreshAsync(key, absExpr, sldExpr, token).ConfigureAwait(false); } if (results.Length >= 3 && results[2].HasValue) { return results[2]; } return null; } public void Remove(string key) { if (key == null) { throw new ArgumentNullException(nameof(key)); } Connect(); _cache.KeyDelete(_instance + key); // TODO: Error handling } public async Task RemoveAsync(string key, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } await ConnectAsync(token).ConfigureAwait(false); await _cache.KeyDeleteAsync(_instance + key).ConfigureAwait(false); // TODO: Error handling } private void MapMetadata(RedisValue[] results, out DateTimeOffset? absoluteExpiration, out TimeSpan? slidingExpiration) { absoluteExpiration = null; slidingExpiration = null; var absoluteExpirationTicks = (long?)results[0]; if (absoluteExpirationTicks.HasValue && absoluteExpirationTicks.Value != NotPresent) { absoluteExpiration = new DateTimeOffset(absoluteExpirationTicks.Value, TimeSpan.Zero); } var slidingExpirationTicks = (long?)results[1]; if (slidingExpirationTicks.HasValue && slidingExpirationTicks.Value != NotPresent) { slidingExpiration = new TimeSpan(slidingExpirationTicks.Value); } } private void Refresh(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr) { if (key == null) { throw new ArgumentNullException(nameof(key)); } // Note Refresh has no effect if there is just an absolute expiration (or neither). TimeSpan? expr = null; if (sldExpr.HasValue) { if (absExpr.HasValue) { var relExpr = absExpr.Value - DateTimeOffset.Now; expr = relExpr <= sldExpr.Value ? relExpr : sldExpr; } else { expr = sldExpr; } _cache.KeyExpire(_instance + key, expr); // TODO: Error handling } } private async Task RefreshAsync(string key, DateTimeOffset? absExpr, TimeSpan? sldExpr, CancellationToken token = default(CancellationToken)) { if (key == null) { throw new ArgumentNullException(nameof(key)); } token.ThrowIfCancellationRequested(); // Note Refresh has no effect if there is just an absolute expiration (or neither). TimeSpan? expr = null; if (sldExpr.HasValue) { if (absExpr.HasValue) { var relExpr = absExpr.Value - DateTimeOffset.Now; expr = relExpr <= sldExpr.Value ? relExpr : sldExpr; } else { expr = sldExpr; } await _cache.KeyExpireAsync(_instance + key, expr).ConfigureAwait(false); // TODO: Error handling } } private static long? GetExpirationInSeconds(DateTimeOffset creationTime, DateTimeOffset? absoluteExpiration, DistributedCacheEntryOptions options) { if (absoluteExpiration.HasValue && options.SlidingExpiration.HasValue) { return (long)Math.Min( (absoluteExpiration.Value - creationTime).TotalSeconds, options.SlidingExpiration.Value.TotalSeconds); } else if (absoluteExpiration.HasValue) { return (long)(absoluteExpiration.Value - creationTime).TotalSeconds; } else if (options.SlidingExpiration.HasValue) { return (long)options.SlidingExpiration.Value.TotalSeconds; } return null; } private static DateTimeOffset? GetAbsoluteExpiration(DateTimeOffset creationTime, DistributedCacheEntryOptions options) { if (options.AbsoluteExpiration.HasValue && options.AbsoluteExpiration <= creationTime) { throw new ArgumentOutOfRangeException( nameof(DistributedCacheEntryOptions.AbsoluteExpiration), options.AbsoluteExpiration.Value, "The absolute expiration value must be in the future."); } var absoluteExpiration = options.AbsoluteExpiration; if (options.AbsoluteExpirationRelativeToNow.HasValue) { absoluteExpiration = creationTime + options.AbsoluteExpirationRelativeToNow; } return absoluteExpiration; } public void Dispose() { if (_connection != null) { _connection.Close(); } } } }
Get =》 GetAndRefresh
private byte[] GetAndRefresh(string key, bool getData)
{
if (key == null)
{
throw new ArgumentNullException(nameof(key));
}
Connect();
// This also resets the LRU status as desired.
// TODO: Can this be done in one operation on the server side? Probably, the trick would just be the DateTimeOffset math.
RedisValue[] results;
if (getData)
{
results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey, DataKey);
}
else
{
results = _cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey);
}
// TODO: Error handling
if (results.Length >= 2)
{
MapMetadata(results, out DateTimeOffset? absExpr, out TimeSpan? sldExpr);
Refresh(key, absExpr, sldExpr);
}
if (results.Length >= 3 && results[2].HasValue)
{
return results[2];
}
return null;
}
private IDatabase _cache 來自擴充套件方法 RedisExtensions.cs 實現
_cache.HashMemberGet(_instance + key, AbsoluteExpirationKey, SlidingExpirationKey)
internal static class RedisExtensions
{
private const string HmGetScript = (@"return redis.call('HMGET', KEYS[1], unpack(ARGV))");
internal static RedisValue[] HashMemberGet(this IDatabase cache, string key, params string[] members)
{
var result = cache.ScriptEvaluate(
HmGetScript,
new RedisKey[] { key },
GetRedisMembers(members));
// TODO: Error checking?
return (RedisValue[])result;
}
internal static async Task<RedisValue[]> HashMemberGetAsync(
this IDatabase cache,
string key,
params string[] members)
{
var result = await cache.ScriptEvaluateAsync(
HmGetScript,
new RedisKey[] { key },
GetRedisMembers(members)).ConfigureAwait(false);
// TODO: Error checking?
return (RedisValue[])result;
}
private static RedisValue[] GetRedisMembers(params string[] members)
{
var redisMembers = new RedisValue[members.Length];
for (int i = 0; i < members.Length; i++)
{
redisMembers[i] = (RedisValue)members[i];
}
return redisMembers;
}
}