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| author | version | line-number | content |
|---|---|---|---|
| 1 | get命令本质是调用了lookupKeyRead这个底层方法， | ||
| 2 | lookupKeyRead方法如下： | ||
| 3 | |||
| 4 | {{plantuml}} | ||
| 5 | @startuml | ||
| 6 | start | ||
| 7 | |||
| 8 | |||
| 9 | : lookupKeyReadWithFlags; | ||
| 10 | |||
| 11 | |||
| 12 | end | ||
| 13 | @enduml | ||
| 14 | {{/plantuml}} | ||
| 15 | |||
| 16 | |||
| 17 | lookupKeyReadWithFlags方法如下： | ||
| 18 | |||
| 19 | {{plantuml}} | ||
| 20 | @startuml | ||
| 21 | start | ||
| 22 | |||
| 23 | if(调用expireIfNeeded方法判断key是否过期)then(1:代表过期) | ||
| 24 | if(当前环境为主节点)then(yes) | ||
| 25 | :返回null; | ||
| 26 | stop | ||
| 27 | endif | ||
| 28 | |||
| 29 | if(当前环境为从节点，并且命令为读的时候，那说明key过期是安全的)then(yes) | ||
| 30 | :返回null; | ||
| 31 | stop | ||
| 32 | endif | ||
| 33 | endif | ||
| 34 | |||
| 35 | :调用lookupKey方法，查询value的值; | ||
| 36 | if(返回值为空)then(yes) | ||
| 37 | :缓存命中+1; | ||
| 38 | else(no) | ||
| 39 | :缓存非命中+1; | ||
| 40 | endif | ||
| 41 | |||
| 42 | :返回查询的结果; | ||
| 43 | |||
| 44 | end | ||
| 45 | @enduml | ||
| 46 | {{/plantuml}} | ||
| 47 | |||
| 48 | |||
| 49 | expireIfNeeded方法用来判断一个key是否过期 | ||
| 50 | 返回1，说明已经过期 | ||
| 51 | 返回0，说明数据没有过期 | ||
| 52 | |||
| 53 | {{plantuml}} | ||
| 54 | @startuml | ||
| 55 | start | ||
| 56 | |||
| 57 | |||
| 58 | :查询key的过期时间戳; | ||
| 59 | :获取当前时刻的时间戳; | ||
| 60 | if(过期时间<0)then(yes) | ||
| 61 | :说明该key不存在过期设置，返回0; | ||
| 62 | stop | ||
| 63 | endif | ||
| 64 | |||
| 65 | if(服务器正在启动中)then(yes) | ||
| 66 | :过期时间表可能没加载完全，这时直接返回0; | ||
| 67 | stop | ||
| 68 | endif | ||
| 69 | |||
| 70 | if(当前环境是从服务器)then(yes) | ||
| 71 | :对于从服务器无需删除过期key, 直接计算过期时间和当前时间的关系并返回; | ||
| 72 | note left | ||
| 73 | 过期时间 <= 当前时间 : 已经过期 | ||
| 74 | 过期时间 > 当前时间 : 没有过期 | ||
| 75 | stop | ||
| 76 | endif | ||
| 77 | |||
| 78 | :写aof删除过期key; | ||
| 79 | :创建消息通知，用来回调那些监控key过期的钩子; | ||
| 80 | if(判断服务器是否打开惰性删除)then(yes) | ||
| 81 | :调用dbAsyncDelete方法异步删除; | ||
| 82 | else(no) | ||
| 83 | :调用dbSyncDelete方法同步删除; | ||
| 84 | endif | ||
| 85 | |||
| 86 | |||
| 87 | end | ||
| 88 | @enduml | ||
| 89 | {{/plantuml}} |