在node.js中使用UnhandledPromiseRejectionWarning: Error: Upload failed时得到@google-cloud/storage。
这些错误在处理数千个请求时出现。造成错误的比例很小，但是由于缺乏处理错误的能力以及错误消息中缺少适当的上下文，很难确定WHICH文件是否失败。
我知道一般而言，promise必须具有.catch或被try / catch块包围。但是在这种情况下，我使用的是写流。关于被拒绝的承诺的实际位置以及如何截取它，我有些困惑。堆栈跟踪没有帮助，因为它仅包含库代码：
UnhandledPromiseRejectionWarning: Error: Upload failed
at Request.requestStream.on.resp (.../node_modules/gcs-resumable-upload/build/src/index.js:163:34)
at emitTwo (events.js:131:20)
at Request.emit (events.js:214:7)
at Request.<anonymous> (.../node_modules/request/request.js:1161:10)
at emitOne (events.js:121:20)
at Request.emit (events.js:211:7)
at IncomingMessage.<anonymous> (.../node_modules/request/request.js:1083:12)
at Object.onceWrapper (events.js:313:30)
at emitNone (events.js:111:20)
at IncomingMessage.emit (events.js:208:7)
创建writeStream的代码如下：
const {join} = require('path')
const {Storage} = require('@google-cloud/storage')
module.exports = (config) => {
const storage = new Storage({
projectId: config.gcloud.project,
keyFilename: config.gcloud.auth_file
})
return {
getBucketWS(path, contentType) {
const {bucket, path_prefix} = config.gcloud
// add path_prefix if we have one
if (path_prefix) {
path = join(path_prefix, path)
}
let setup = storage.bucket(bucket).file(path)
let opts = {}
if (contentType) {
opts = {
contentType,
metadata: {contentType}
}
}
const stream = setup.createWriteStream(opts)
stream._bucket = bucket
stream._path = path
return stream
}
}
}
使用的代码如下：
const gcs = require('./gcs-helper.js')
module.exports = ({writePath, contentType, item}, done) => {
let ws = gcs.getBucketWS(writePath, contentType)
ws.on('error', (err) => {
err.message = `Could not open gs://${ws._bucket}/${ws._path}: ${err.message}`
done(err)
})
ws.on('finish', () => {
done(null, {
path: writePath,
item
})
})
ws.write(item)
ws.end()
}
鉴于我已经在监听流中的error事件，因此看不到我还能做什么。在我正在使用的@google-cloud/storage级别上没有达成承诺。
堆栈跟踪的第一行将我们带到gcs-resumable-upload节点模块中的代码块，如下所示：
requestStream.on('complete', resp => {
if (resp.statusCode < 200 || resp.statusCode > 299) {
this.destroy(new Error('Upload failed'));
return;
}
this.emit('metadata', resp.body);
this.deleteConfig();
this.uncork();
});
这会将错误传递给流上的destroy方法。 @google-cloud/common project's utility module正在创建流，并且正在使用duplexify node module创建流。 destroy方法在双工化流上定义，可以在README文档中找到。
在阅读the duplexify code时，我看到它先发出this._ondrain的信息，然后才发出错误。也许我可以提供一个回调来避免未解决此错误？
我尝试了ws.write(item, null, cb)，但仍然得到了相同的UnhandledPromiseRejectionWarning。我尝试了ws.end(item, null, cb)，甚至将.end调用包装在一个try catch中，最终收到此错误，使该过程完全崩溃：
events.js:183
throw er; // Unhandled 'error' event
^
Error: The uploaded data did not match the data from the server. As a precaution, the file has been deleted. To be sure the content is the same, you should try uploading the file again.
at delete (.../node_modules/@google-cloud/storage/build/src/file.js:1295:35)
at Util.handleResp (.../node_modules/@google-cloud/common/build/src/util.js:123:9)
at retryRequest (.../node_modules/@google-cloud/common/build/src/util.js:404:22)
at onResponse (.../node_modules/retry-request/index.js:200:7)
at .../node_modules/teeny-request/build/src/index.js:208:17
at <anonymous>
at process._tickCallback (internal/process/next_tick.js:189:7)
我的最终代码如下：
let ws = gcs.getBucketWS(writePath, contentType)
const handleErr = (err) => {
if (err) err.message = `Could not open gs://${ws._bucket}/${ws._path}: ${err.message}`
done(err)
}
ws.on('error', handleErr)
// trying to do everything we can to handle these errors
// for some reason we still get UnhandledPromiseRejectionWarning
try {
ws.write(item, null, err => {
handleErr(err)
})
ws.end()
} catch (e) {
handleErr(e)
}
对于我来说，@google-cloud/storage库（或duplexify）的用户应该如何执行正确的错误处理仍然是一个谜。来自任何一个项目的图书馆维护者的评论将不胜感激。谢谢！