Sequelize中的事务操作及异常处理

近日，遇到一事务问题，在执行create时报以下错误：

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Unhandled rejection SequelizeUniqueConstraintError: Validation error
    at Query.formatError (/Users/fuyun/.../node_modules/sequelize/lib/dialects/mysql/query.js:223:16)
    at Execute.handler [as onResult] (/Users/fuyun/.../node_modules/sequelize/lib/dialects/mysql/query.js:51:23)
    at Execute.execute (/Users/fuyun/.../node_modules/mysql2/lib/commands/command.js:30:14)
    at Connection.handlePacket (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:417:32)
    at PacketParser.onPacket (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:75:12)
    at PacketParser.executeStart (/Users/fuyun/.../node_modules/mysql2/lib/packet_parser.js:75:16)
    at Socket.<anonymous> (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:82:25)
    at Socket.emit (events.js:223:5)
    at Socket.EventEmitter.emit (domain.js:498:23)
    at addChunk (_stream_readable.js:309:12)
    at readableAddChunk (_stream_readable.js:290:11)
    at Socket.Readable.push (_stream_readable.js:224:10)
    at TCP.onStreamRead (internal/stream_base_commons.js:181:23)Unhandled rejection SequelizeUniqueConstraintError: Validation error
    at Query.formatError (/Users/fuyun/.../node_modules/sequelize/lib/dialects/mysql/query.js:223:16)
    at Execute.handler [as onResult] (/Users/fuyun/.../node_modules/sequelize/lib/dialects/mysql/query.js:51:23)
    at Execute.execute (/Users/fuyun/.../node_modules/mysql2/lib/commands/command.js:30:14)
    at Connection.handlePacket (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:417:32)
    at PacketParser.onPacket (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:75:12)
    at PacketParser.executeStart (/Users/fuyun/.../node_modules/mysql2/lib/packet_parser.js:75:16)
    at Socket. (/Users/fuyun/.../node_modules/mysql2/lib/connection.js:82:25)
    at Socket.emit (events.js:223:5)
    at Socket.EventEmitter.emit (domain.js:498:23)
    at addChunk (_stream_readable.js:309:12)
    at readableAddChunk (_stream_readable.js:290:11)
    at Socket.Readable.push (_stream_readable.js:224:10)
    at TCP.onStreamRead (internal/stream_base_commons.js:181:23)

查看日志后发现问题出在主键重复了，便引入异常处理，将error抛出，再通过reject返回给上层进行统一处理。但，此时又报另一个异常：

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Unhandled rejection Error: rollback has been called on this transaction(639ce933-3246-484d-9183-699093ee4cbd), you can no longer use it. (The rejected query is attached as the 'sql' property of this error)
    at checkTransaction (/Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:623:25)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:636:9
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Function.Promise.attempt.Promise.try (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/method.js:39:29)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:631:53
    at /Users/fuyun/.../node_modules/retry-as-promised/index.js:70:21
    at new Promise (<anonymous>)
    at retryAsPromised (/Users/fuyun/.../node_modules/retry-as-promised/index.js:60:10)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:631:30
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Function.Promise.attempt.Promise.try (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/method.js:39:29)
    at Sequelize.query (/Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:580:23)
    at QueryInterface.insert (/Users/fuyun/.../node_modules/sequelize/lib/query-interface.js:885:27)
    at /Users/fuyun/.../node_modules/sequelize/lib/model.js:3987:52
    at bound (domain.js:419:14)
    at runBound (domain.js:432:12)
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:547:31)
    at Promise._settlePromise (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:604:18)
    at Promise._settlePromise0 (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:649:10)
    at Promise._settlePromises (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:729:18)
    at _drainQueueStep (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:93:12)
    at _drainQueue (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:86:9)
    at Async._drainQueues (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:102:5)
    at Immediate.Async.drainQueues [as _onImmediate] (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:15:14)
    at processImmediate (internal/timers.js:439:21)
    at process.topLevelDomainCallback (domain.js:130:23)Unhandled rejection Error: rollback has been called on this transaction(639ce933-3246-484d-9183-699093ee4cbd), you can no longer use it. (The rejected query is attached as the 'sql' property of this error)
    at checkTransaction (/Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:623:25)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:636:9
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Function.Promise.attempt.Promise.try (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/method.js:39:29)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:631:53
    at /Users/fuyun/.../node_modules/retry-as-promised/index.js:70:21
    at new Promise ()
    at retryAsPromised (/Users/fuyun/.../node_modules/retry-as-promised/index.js:60:10)
    at /Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:631:30
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Function.Promise.attempt.Promise.try (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/method.js:39:29)
    at Sequelize.query (/Users/fuyun/.../node_modules/sequelize/lib/sequelize.js:580:23)
    at QueryInterface.insert (/Users/fuyun/.../node_modules/sequelize/lib/query-interface.js:885:27)
    at /Users/fuyun/.../node_modules/sequelize/lib/model.js:3987:52
    at bound (domain.js:419:14)
    at runBound (domain.js:432:12)
    at tryCatcher (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/util.js:16:23)
    at Promise._settlePromiseFromHandler (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:547:31)
    at Promise._settlePromise (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:604:18)
    at Promise._settlePromise0 (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:649:10)
    at Promise._settlePromises (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/promise.js:729:18)
    at _drainQueueStep (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:93:12)
    at _drainQueue (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:86:9)
    at Async._drainQueues (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:102:5)
    at Immediate.Async.drainQueues [as _onImmediate] (/Users/fuyun/.../node_modules/sequelize/node_modules/bluebird/js/release/async.js:15:14)
    at processImmediate (internal/timers.js:439:21)
    at process.topLevelDomainCallback (domain.js:130:23)

同时，还有一个warning：

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(node:48615) [DEP0097] DeprecationWarning: Using a domain property in MakeCallback is deprecated. Use the async_context variant of MakeCallback or the AsyncResource class instead.(node:48615) [DEP0097] DeprecationWarning: Using a domain property in MakeCallback is deprecated. Use the async_context variant of MakeCallback or the AsyncResource class instead.

网上搜了一圈，并没有找到解决方案，只找到一些关于Promise的异常处理的文章，于是试着加上try {...} catch {...}，问题依旧。

而后将models.sequelize.transaction()层的.then(onFulfill, onReject)改为.then(onFulfill).catch(onError)，依然无法解决。

甚至，因为关于domain的那个warning ，而琢磨是否domain的问题？于是又对照了一番node.js的官方API，发现除去deprecated的警告外，用法并没有错误。看来，问题还是出在Promise上。

又琢磨了半天，偶然发现model.create()的结果处理中遗漏了reject和catch部分，于是分别在事务的几个子查询中都加上了异常处理逻辑。结果完美验证了所想。只是，虽然解决了error问题，但上面那个醒目的warning依然存在……

毫无头绪，既然都已经捕获了，也不再bubble了，结果也返回到页面了，为何还会出现warning？必然是在某个环节触发了domain机制。无解ing……

此问题也说明了，异步操作中的异常处理是何等复杂，如幽灵一般，难以捉摸……

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