README1.md

2pc 优化

数据存储

数据链

//类似于单链表 data_key1_entry --> data_key1_begin_ts1 --> data_key1_begin_ts --> data_key1_begin_ts_old
//data_key1_ver3 --> {state:deleted, value:value22}
data_key1_entry --> {state:update, value:value3, next:begin_ts1, cur_version:begin_ts2}
data_key1_begin_ts1 --> {state:update, value:value3, next:begin_ts}
data_key1_begin_ts --> {state:update, value:value2, next:begin_ts_old}
data_key1_begin_ts_old --> {state:insert, value:value1, next:null}

data_key2_entry --> {state:update, value:value3, next:begin_ts1, cur_version:begin_ts3}
data_key2_begin_ts1 --> {state:update, value:value3, next:begin_ts}
data_key2_begin_ts --> {state:update, value:value2, next:begin_ts_old}
data_key2_begin_ts_old --> {state:insert, value:value1, next:null}

锁

lock_key1 --> {trans:begin_ts2}
lock_key2 --> {trans:begin_ts3}

事务链

//
trans_begin_ts3 --> {state:begin, commitTrans:null,  startTrans:null,   transList:[id0, id1/*参与者列表*/]}
trans_begin_ts2 --> {state:prepared, commitTrans:commit_ts2,  startTrans:start_ts2,   transList:[id0, id1/*参与者列表*/]}
trans_begin_ts1 --> {state:commited, commitTrans:commit_ts1, startTrans:start_ts1,   transList:[id0, id1/*参与者列表*/]}
trans_begin_ts --> {state:commited, commitTrans:commit_ts, startTrans:start_ts,   transList:[id0, id1/*参与者列表*/]}

流程

begin_ts = getTS()
begin(begin_ts)   //  trans_begin_ts --> {state:begin, }
value = get(key, begin_ts) 
value2 += value
update(key, value2, begin_ts)   // data_key_begin_ts --> {state:update, value:value}
                                // trans_begin_ts --> {state:begin, keys:[key, ] }
start_ts = getTS()
prepare(start_ts)      // trans_begin_ts --> {state:prepared, startTrans:start_ts,   transList:[id0, id1/*参与者列表*/]}
//所有的参与者都prepare成功
commit_ts = getTS()
commit(commit_ts)   // trans_begin_ts --> {state:commited, startTrans:start_ts,   transList:[id0, id1/*参与者列表*/]}
                    // 清除锁
// else 
rollback(commit_ts)

访问

begin(start_ts)

增加记录 trans_begin_ts --> {state:begin, }

get(key, begin_ts)

读取data_key1_entry --> {state:update, value:value3, next:begin_ts1},
loop 取next --> state:update, value:value3, next:begin_ts1
    1, 如果next是begin_ts, 返回value, 这是自己修改的记录
    2, 通过next:begin_ts1查找事务的trans_begin_ts1, 如果trans_start_ts小于输入参数begin_ts: 事务状态是commited, 返回value; 事务状态为prepared则等待(prepared说明事务提交中)
        返回最大的commited的commit_ts的数据
    3, 返回not found

update(key, value2, begin_ts)

加锁key, 增加lock_key --> {trans:begin_ts}
读取data_key_entry-->{state:update, value:value3, next:begin_ts2, cur_version:begin_ts1}
更新记录data_key_begin_ts1 --> {state:update, value:value3, next:begin_ts2}
更新data_key_entry-->{state:update, value:value2, next:begin_ts1, cur_version:begin_ts}
trans_begin_ts --> {state:begin, keys:[key, ] }中keys增加key

prepared(start_ts, transList)

参与者:写redolog, 更新trans_begin_ts --> {state:prepared, commitTrans:null, startTrans:start_ts, next:null,  transList:[id0, id1/*参与者列表*/]}, 返回
协调者:如果所有节点prepare返回成功, 则返回client成功, 异步通知transList:id0成功commit(commit_ts)
todo:这里client先知道提交成功, 如果client又马上begin(begin_ts), 而参与者还没有commit(commit_ts), 这里begin_ts有可能大于commit_ts, 会读不到数据
-->参与者返回前commit_ts = getTs(),这个commit_ts各个参与者相互比较,最大的是最终的commit_ts.

commit(commit_ts) #可选

参与者:更新trans_begin_ts --> {state:commited, commitTrans:commit_ts, startTrans:start_ts, next:null,  transList:[id0, id1/*参与者列表*/]}
清除锁
参与者:transList:id0异步收集其他参与者状态, 都prepared后, 或者收到协调者通知prepared, 通知其他参与者commited

rollback(commit_ts)

参与者: 更新trans_begin_ts --> {state:aborted, commitTrans:commit_ts, startTrans:null, next:null,  transList:[id0, id1/*参与者列表*/]}
清除锁

清理数据

死锁检测

启动检查及处理异常事务