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一、下载源码
在github上，地址https://github.com/allegro/bigcache，我们可以把代码源码clone到本地。
这里选择分支v3.1.0的代码。
二、源码目录
我们打开源码
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | .├── LICENSE├── README.md├── assert_test.go├── bigcache.go├── bigcache_bench_test.go├── bigcache_test.go├── bytes.go├── bytes_appengine.go├── clock.go├── config.go├── encoding.go├── encoding_test.go├── entry_not_found_error.go├── examples_test.go├── fnv.go├── fnv_bench_test.go├── fnv_test.go├── go.mod├── go.sum├── hash.go├── hash_test.go├── iterator.go├── iterator_test.go├── logger.go├── queue│ ├── bytes_queue.go│ └── bytes_queue_test.go├── server│ ├── README.md│ ├── cache_handlers.go│ ├── middleware.go│ ├── middleware_test.go│ ├── server.go│ ├── server_test.go│ └── stats_handler.go├── shard.go├── stats.go└── utils.go2 directories, 36 files |
比较重要的几个文件
queue目录
shard.go 分片
fnv.go Fnv hash算法
bigcache.go 初始化new结构体，以及set，get方法。
我们可以看上篇文档的示例：
1 2 3 4 5 6 7 8 9 10 11 12 13 | func TestSetGet(t *testing.T) { // new一个bigCache对象 cache, _ := bigcache.New(context.Background(), bigcache.DefaultConfig(10*time.Minute)) // get获取一个无值的key vNil, err := cache.Get("key") t.Log(vNil, err) // [] Entry not found 值为空的[]字节slice // set 存储数据 cache.Set("key", []byte("value")) // get 获取数据 v, _ := cache.Get("key") t.Log(v) // 输出 [118 97 108 117 101] t.Log(string(v)) // 输出 value} |
那么我们先找到这个，第一行对应的
1 | cache, _ := bigcache.New(context.Background(), bigcache.DefaultConfig(10*time.Minute)) |
在源码的代码如下:
1 2 3 4 5 | // New initialize new instance of BigCache// New用来初始化一个新的BigCache实例。func New(ctx context.Context, config Config) (*BigCache, error) { return newBigCache(ctx, config, &systemClock{})} |
我们在使用的时候，主要又涉及到一个 bigcache.DefaultConfig(10*time.Minute))我们看一下他的方法：
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | // DefaultConfig initializes config with default values.// DefaultConfig 初始化Config，给定默认值。// When load for BigCache can be predicted in advance then it is better to use custom config.// 当load加载 BigCache 的时候，如果在使用之前就能预估到使用量，然后预设置config，它好于使用默认config。func DefaultConfig(eviction time.Duration) Config { return Config{ Shards: 1024, LifeWindow: eviction, CleanWindow: 1 * time.Second, MaxEntriesInWindow: 1000 * 10 * 60, MaxEntrySize: 500, StatsEnabled: false, Verbose: true, Hasher: newDefaultHasher(), HardMaxCacheSize: 0, Logger: DefaultLogger(), }} |
设计一个Config结构体
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 | // Config for BigCachetype Config struct { // Number of cache shards, value must be a power of two Shards int // Time after which entry can be evicted // LifeWindow后,缓存对象被认为不活跃,但并不会删除对象 LifeWindow time.Duration // Interval between removing expired entries (clean up). // If set to <= 0 then no action is performed. Setting to < 1 second is counterproductive — bigcache has a one second resolution. // CleanWindow后，会删除被认为不活跃的对象（超过LifeWindow时间的对象），0代表不操作； CleanWindow time.Duration // Max number of entries in life window. Used only to calculate initial size for cache shards. // When proper value is set then additional memory allocation does not occur. // 设置最大存储对象数量，仅在初始化时可以设置 MaxEntriesInWindow int // Max size of entry in bytes. Used only to calculate initial size for cache shards. // 缓存对象的最大字节数，仅在初始化时可以设置 MaxEntrySize int // StatsEnabled if true calculate the number of times a cached resource was requested. StatsEnabled bool // Verbose mode prints information about new memory allocation // 是否打印内存分配信息 Verbose bool // Hasher used to map between string keys and unsigned 64bit integers, by default fnv64 hashing is used. Hasher Hasher // HardMaxCacheSize is a limit for BytesQueue size in MB. // It can protect application from consuming all available memory on machine, therefore from running OOM Killer. // Default value is 0 which means unlimited size. When the limit is higher than 0 and reached then // the oldest entries are overridden for the new ones. The max memory consumption will be bigger than // HardMaxCacheSize due to Shards' s additional memory. Every Shard consumes additional memory for map of keys // and statistics (map[uint64]uint32) the size of this map is equal to number of entries in // cache ~ 2×(64+32)×n bits + overhead or map itself. // 设置缓存最大值(单位为MB),0表示无限制 HardMaxCacheSize int // OnRemove is a callback fired when the oldest entry is removed because of its expiration time or no space left // for the new entry, or because delete was called. // Default value is nil which means no callback and it prevents from unwrapping the oldest entry. // ignored if OnRemoveWithMetadata is specified. // 在缓存过期或者被删除时,可设置回调函数，参数是(key、val)，默认是nil不设置 OnRemove func(key string, entry []byte) // OnRemoveWithMetadata is a callback fired when the oldest entry is removed because of its expiration time or no space left // for the new entry, or because delete was called. A structure representing details about that specific entry. // Default value is nil which means no callback and it prevents from unwrapping the oldest entry. OnRemoveWithMetadata func(key string, entry []byte, keyMetadata Metadata) // OnRemoveWithReason is a callback fired when the oldest entry is removed because of its expiration time or no space left // for the new entry, or because delete was called. A constant representing the reason will be passed through. // Default value is nil which means no callback and it prevents from unwrapping the oldest entry. // Ignored if OnRemove is specified. // 在缓存过期或者被删除时,可设置回调函数，参数是(key、val,reason)默认是nil不设置 OnRemoveWithReason func(key string, entry []byte, reason RemoveReason) onRemoveFilter int // Logger is a logging interface and used in combination with `Verbose` // Defaults to `DefaultLogger()` Logger Logger} |
BigCache的实现是 一种索引和数据分离的多阶hash。
主索引（多阶hash数组）的value保存的是在数据段的位置，通过二次定位拿到某个key对应的真实的value。
以上就是go内存缓存如何new一个bigcache对象示例详解的详细内容，更多关于go new bigcache对象的资料请关注脚本之家其它相关文章！
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