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【MongoDB】4.0版本事务上手测试

事务上手测试

基础：

原来3版本的只能叫单文档事务，即针对行的事务。所以没必要显式提供调用，多文档事务由于有损耗，照顾到性能的需求，提供了事务开启关闭的接口。
多行，多集合，多库之间读肯定会牵扯到一致性读，所以多文档事务肯定是有必要的。
4.2版本可能会支持分片系统多文档事务，4.0的多文档事务最多只面向复制集

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准备

集合：

use dba;
[10.240.129.36:30001_primary@dba]> db.coll_2.find()
[10.240.129.36:30001_primary@dba]> db.coll_1.find()
{ "_id" : ObjectId("5b371e120d6160b73a9fcee6"), "test" : true }
{ "_id" : ObjectId("5b371e6d0d6160b73a9fcee7"), "test" : true }

精简命令：

// 显式开启一个会话（难道通过shell链接来本身不就是会话吗？）
session=db.getMongo().startSession()
// 显式开启事务
session.startTransaction()
// 获取表对象
coll_1=session.getDatabase('dba').coll_1
coll_2=session.getDatabase('dba').coll_2;
// 使用表对象的插入函数进行插入
coll_1.insertOne({'not_test':false})
coll_2.insertOne({'not_test':false})
// 提交事务
session.commitTransaction()
// 回滚事务
session.abortTransaction()
// 检查事务准确性
db.coll_1.find()
db.coll_2.find()

超时参数怎么设置？

默认事务生命周期为60秒，超出后会被自动清理

// The minimum value for transactionLifetimeLimitSeconds is 1 second.
db.adminCommand( { setParameter: 1, transactionLifetimeLimitSeconds: 30 } )
// You can also set parameter transactionLifetimeLimitSeconds at startup time.
// 可以考虑写在配置文件中
mongod --setParameter "transactionLifetimeLimitSeconds=30"

第一次尝试

因为忘记设置后向兼容性，执行失败，在同一个shell中进行设置后，再次插入，提示事务不存在

[10.240.129.36:30001_primary@dba]> Session.startTransactions()
2018-06-30T14:17:10.670+0800 E QUERY    [js] ReferenceError: Session is not defined :
@(shell):1:1
[10.240.129.36:30001_primary@dba]> db.getMongo()
connection to 127.0.0.1:30001
[10.240.129.36:30001_primary@dba]> db.getMongo().startSession()
session { "id" : UUID("887f4564-4f8a-4783-886d-a55a536f41aa") }
[10.240.129.36:30001_primary@dba]> session=db.getMongo().startSession()
session { "id" : UUID("9b3e10b9-93cd-4010-b1a3-0e7b49796db3") }
[10.240.129.36:30001_primary@dba]> session.startTransaction()
[10.240.129.36:30001_primary@dba]> coll_1=session.getDatabase('dba').coll_1;
dba.coll_1
[10.240.129.36:30001_primary@dba]> coll_2=session.getDatabase('dba').coll_2;
dba.coll_2
[10.240.129.36:30001_primary@dba]> coll_1.insertOne({'not_test':false})
// 后向兼容性要求为4，也就是说想开启事务必须是mongod4以上的版本
2018-06-30T14:28:55.708+0800 E QUERY    [js] WriteCommandError: Transactions are only supported in featureCompatibilityVersion 4.0. See http://dochub.MongoDB.org/core/4.0-feature-compatibility for more information. :
WriteCommandError({
    "ok" : 0,
    "errmsg" : "Transactions are only supported in featureCompatibilityVersion 4.0. See http://dochub.mongodb.org/core/4.0-feature-compatibility for more information.",
    "code" : 50773,
    "codeName" : "Location50773"
})
WriteCommandError@src/mongo/shell/bulk_api.js:420:48
Bulk/executeBatch@src/mongo/shell/bulk_api.js:902:1
Bulk/this.execute@src/mongo/shell/bulk_api.js:1150:21
DBCollection.prototype.insertOne@src/mongo/shell/crud_api.js:252:9
@(shell):1:1
[10.240.129.36:30001_primary@dba]> db.adminCommand({setFeatureCompatibilityVersion:'4.0'})
{ "ok" : 1 }

// 可以看到，报错，重新设置版本兼容性后，原先的事务出现了问题
[10.240.129.36:30001_primary@dba]> coll_1.insertOne({'not_test':false})
2018-06-30T14:31:16.706+0800 E QUERY    [js] WriteCommandError: Given transaction number 0 does not match any in-progress transactions. :
WriteCommandError({
    "errorLabels" : [
        "TransientTransactionError"
    ],
    "ok" : 0,
    "errmsg" : "Given transaction number 0 does not match any in-progress transactions.",
    "code" : 251,
    "codeName" : "NoSuchTransaction"
})
WriteCommandError@src/mongo/shell/bulk_api.js:420:48
Bulk/executeBatch@src/mongo/shell/bulk_api.js:902:1
Bulk/this.execute@src/mongo/shell/bulk_api.js:1150:21
DBCollection.prototype.insertOne@src/mongo/shell/crud_api.js:252:9
@(shell):1:1

// 事务怎么也调不好了

[10.240.129.36:30001_primary@dba]> session.startTransaction()
2018-06-30T14:33:53.293+0800 E QUERY    [js] Error: Transaction already in progress on this session. :
startTransaction@src/mongo/shell/session.js:732:1
startTransaction@src/mongo/shell/session.js:925:17
@(shell):1:1
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]>
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> db.getMongo().abortTransaction
[10.240.129.36:30001_primary@dba]> exit
// 直接退出当前连接

第二次尝试：

[10.240.129.36:30001_primary@admin]> session=db.getMongo().startSession()
session { "id" : UUID("b82d71b0-b698-4909-b5b8-a7845dba98b2") }
[10.240.129.36:30001_primary@admin]>  session.startTransaction()
[10.240.129.36:30001_primary@admin]> coll_1=session.getDatabase('dba').coll_1
dba.coll_1
[10.240.129.36:30001_primary@admin]> coll_2=session.getDatabase('dba').coll_2;
dba.coll_2
[10.240.129.36:30001_primary@admin]> coll_1.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b37270429c5c0c486b4b17b")
}
[10.240.129.36:30001_primary@admin]> coll_2.insertOne({'not_test':false})

// 这里的事务回滚可能是因为超时引起的，默认事务生命周期最大值为1分钟

2018-06-30T15:00:50.629+0800 E QUERY    [js] WriteCommandError: Transaction 0 has been aborted. :
WriteCommandError({
    "errorLabels" : [
        "TransientTransactionError"
    ],
    "ok" : 0,
    "errmsg" : "Transaction 0 has been aborted.",
    "code" : 251,
    "codeName" : "NoSuchTransaction"
})
WriteCommandError@src/mongo/shell/bulk_api.js:420:48
Bulk/executeBatch@src/mongo/shell/bulk_api.js:902:1
Bulk/this.execute@src/mongo/shell/bulk_api.js:1150:21
DBCollection.prototype.insertOne@src/mongo/shell/crud_api.js:252:9
@(shell):1:1
[10.240.129.36:30001_primary@admin]> coll_2.insertOne({'not_test':false})
2018-06-30T15:00:59.308+0800 E QUERY    [js] WriteCommandError: Transaction 0 has been aborted. :
WriteCommandError({
    "errorLabels" : [
        "TransientTransactionError"
    ],
    "ok" : 0,
    "errmsg" : "Transaction 0 has been aborted.",
    "code" : 251,
    "codeName" : "NoSuchTransaction"
})
WriteCommandError@src/mongo/shell/bulk_api.js:420:48
Bulk/executeBatch@src/mongo/shell/bulk_api.js:902:1
Bulk/this.execute@src/mongo/shell/bulk_api.js:1150:21
DBCollection.prototype.insertOne@src/mongo/shell/crud_api.js:252:9
@(shell):1:1

// 事务超时回滚之后，应该还可以重开新的事务才对，这里老是报错

[10.240.129.36:30001_primary@admin]> session.startTransaction()
2018-06-30T15:01:04.932+0800 E QUERY    [js] Error: Transaction already in progress on this session. :
startTransaction@src/mongo/shell/session.js:732:1
startTransaction@src/mongo/shell/session.js:925:17
@(shell):1:1

// 内部已经回滚掉了，结果竟然需要我手动回滚才行，晕

[10.240.129.36:30001_primary@admin]> session.abortTransaction()
[10.240.129.36:30001_primary@admin]> session.startTransaction()
[10.240.129.36:30001_primary@admin]> coll_1.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b372ac229c5c0c486b4b17e")
}
[10.240.129.36:30001_primary@admin]> coll_2.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b372ac529c5c0c486b4b17f")
}

// 试试能不能进行explain操作

[10.240.129.36:30001_primary@admin]> coll_1.explain().find({'test_explain':1})
2018-06-30T15:03:09.375+0800 E QUERY    [js] Error: explain failed: {
    "ok" : 0,
    "errmsg" : "Cannot run 'explain' in a multi-document transaction.",
    "code" : 50767,
    "codeName" : "Location50767"
} :  // 果然是报错了呢，在事务中不能进行explain操作
_getErrorWithCode@src/mongo/shell/utils.js:25:13
throwOrReturn@src/mongo/shell/explainable.js:31:1
constructor/this.finish@src/mongo/shell/explain_query.js:171:24
constructor/this.shellPrint@src/mongo/shell/explain_query.js:210:26
shellPrintHelper@src/mongo/shell/utils.js:594:1
@(shell2):1:1

// 尝试提交时报错
[10.240.129.36:30001_primary@admin]> session.commitTransaction()
2018-06-30T15:04:21.985+0800 E QUERY    [js] Error: command failed: {
    "errorLabels" : [
        "TransientTransactionError"
    ],
    "ok" : 0,
    "errmsg" : "Transaction 1 has been aborted.",
    "code" : 251,
    "codeName" : "NoSuchTransaction"
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:534:17
assert.commandWorked@src/mongo/shell/assert.js:618:16
commitTransaction@src/mongo/shell/session.js:929:17
@(shell):1:1

[10.240.129.36:30001_primary@dba]> db.coll_1.find()
{ "_id" : ObjectId("5b371e120d6160b73a9fcee6"), "test" : true }
{ "_id" : ObjectId("5b371e6d0d6160b73a9fcee7"), "test" : true }
[10.240.129.36:30001_primary@dba]> db.coll_2.find()
// 这边可以看到，插入语句并没有真正被执行

[10.240.129.36:30001_primary@dba]> session.commitTransaction()
2018-06-30T15:05:46.288+0800 E QUERY    [js] Error: command failed: {
    "errorLabels" : [
        "TransientTransactionError"
    ],
    "ok" : 0,
    "errmsg" : "Transaction 1 has been aborted.",
    "code" : 251,
    "codeName" : "NoSuchTransaction"
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
doassert@src/mongo/shell/assert.js:18:14
_assertCommandWorked@src/mongo/shell/assert.js:534:17
assert.commandWorked@src/mongo/shell/assert.js:618:16
commitTransaction@src/mongo/shell/session.js:929:17
@(shell):1:1

// 这儿又抽风了，内部回滚之后禁止提交操作，尝试进行回滚，结果说已经提交了，不能回滚，真是晕死

[10.240.129.36:30001_primary@dba]> session.abortTransaction()
2018-06-30T15:06:04.162+0800 E QUERY    [js] Error: Cannot call abortTransaction after calling commitTransaction. :
abortTransaction@src/mongo/shell/session.js:764:1
abortTransaction@src/mongo/shell/session.js:934:17
@(shell):1:1

第三次尝试（成功提交）：

[10.240.129.36:30001_primary@admin]> session=db.getMongo().startSession()
session { "id" : UUID("e7935985-160d-4969-adfe-3bae401e155f") }
[10.240.129.36:30001_primary@admin]> session.startTransaction()
[10.240.129.36:30001_primary@admin]> coll_1=session.getDatabase('dba').coll_1
dba.coll_1
[10.240.129.36:30001_primary@admin]> coll_2=session.getDatabase('dba').coll_2;
dba.coll_2
[10.240.129.36:30001_primary@admin]> coll_1.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b373202d0b208b7386e9c20")
}
[10.240.129.36:30001_primary@admin]> coll_2.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b373202d0b208b7386e9c21")
}
[10.240.129.36:30001_primary@admin]> session.commitTransaction()
[10.240.129.36:30001_primary@admin]> use dba
switched to db dba
[10.240.129.36:30001_primary@dba]> db.coll_1.find()
{ "_id" : ObjectId("5b371e120d6160b73a9fcee6"), "test" : true }
{ "_id" : ObjectId("5b371e6d0d6160b73a9fcee7"), "test" : true }
{ "_id" : ObjectId("5b373202d0b208b7386e9c20"), "not_test" : false }
[10.240.129.36:30001_primary@dba]> db.coll_2.find()
{ "_id" : ObjectId("5b373202d0b208b7386e9c21"), "not_test" : false }

第四次尝试（测试回滚）：

[10.240.129.36:30001_primary@admin]> session=db.getMongo().startSession()
session { "id" : UUID("e7935985-160d-4969-adfe-3bae401e155f") }
[10.240.129.36:30001_primary@admin]> session.startTransaction()
[10.240.129.36:30001_primary@admin]> coll_1=session.getDatabase('dba').coll_1
dba.coll_1
[10.240.129.36:30001_primary@admin]> coll_2=session.getDatabase('dba').coll_2;
dba.coll_2
[10.240.129.36:30001_primary@admin]> coll_1.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b373202d0b208b7386e9c20")
}
[10.240.129.36:30001_primary@admin]> coll_2.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b373202d0b208b7386e9c21")
}
[10.240.129.36:30001_primary@admin]> session.commitTransaction()
[10.240.129.36:30001_primary@admin]> use dba
switched to db dba
[10.240.129.36:30001_primary@dba]> db.coll_1.find()
{ "_id" : ObjectId("5b371e120d6160b73a9fcee6"), "test" : true }
{ "_id" : ObjectId("5b371e6d0d6160b73a9fcee7"), "test" : true }
{ "_id" : ObjectId("5b373202d0b208b7386e9c20"), "not_test" : false }
[10.240.129.36:30001_primary@dba]> db.coll_2.find()
{ "_id" : ObjectId("5b373202d0b208b7386e9c21"), "not_test" : false }
[10.240.129.36:30001_primary@dba]> session=db.getMongo().startSession()
session { "id" : UUID("cc0e2d23-1766-4ea5-87a5-957efcae28ad") }
[10.240.129.36:30001_primary@dba]> session.startTransaction()
[10.240.129.36:30001_primary@dba]> coll_1=session.getDatabase('dba').coll_1
dba.coll_1
[10.240.129.36:30001_primary@dba]> coll_2=session.getDatabase('dba').coll_2;
dba.coll_2
[10.240.129.36:30001_primary@dba]> coll_1.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b3732f0d0b208b7386e9c22")
}
[10.240.129.36:30001_primary@dba]> coll_2.insertOne({'not_test':false})
{
    "acknowledged" : true,
    "insertedId" : ObjectId("5b3732f1d0b208b7386e9c23")
}
[10.240.129.36:30001_primary@dba]> session.abortTransaction()
[10.240.129.36:30001_primary@dba]> db.coll_2.find()
{ "_id" : ObjectId("5b373202d0b208b7386e9c21"), "not_test" : false }
[10.240.129.36:30001_primary@dba]> db.coll_1.find()
{ "_id" : ObjectId("5b371e120d6160b73a9fcee6"), "test" : true }
{ "_id" : ObjectId("5b371e6d0d6160b73a9fcee7"), "test" : true }
{ "_id" : ObjectId("5b373202d0b208b7386e9c20"), "not_test" : false }

注意

默认事务超时时间有点短，1分钟
默认锁等待时间短，5毫秒
事务的操作有些繁琐，不如RDS的 begin commit rollback方便（指SHELL操作）
一个事务的对应的oplog不能超过16M（指BSON格式的文件大小)
显式事务功能的开启对WT缓存提出了新的要求。类似于IBP事务不按时提交，类似undo用于存放快照或者旧版本的东西肯定会占用大量WT的空间。


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