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从Firebase Cloud Function在Google Cloud Bucket中创建文件
我有一个监视实时数据库中节点的函数，一旦有新的子节点写入该节点，该函数只需要在Google Cloud存储桶中创建一个html文档。 HTML文档将具有唯一的名称，并将包含来自该节点的一些数据。一切都很简单，但是我实际上无法创建和写入文档。到目前为止，我已经尝试了3种方法（在下面的代码中概述），这些方法都不起作用。
const {Storage} = require('@google-cloud/storage');
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();
const fs = require('fs');
const {StringStream} = require('@rauschma/stringio')
const instanceId = 'my-project-12345';
const bucketName = 'my-bucket';
exports.processCertification = functions.database.instance(instanceId).ref('/t/{userId}/{testId}')
.onCreate((snapshot, context) => {
const dataJ = snapshot.toJSON();
var testResult = "Invalid";
if(dataJ.r == 1) {testResult = "Positive";}
else if(dataJ.r == 2) {testResult = "Negative";}
console.log('Processing certificate:', context.params.testId, testResult);
var storage = new Storage({projectId: instanceId});
const fileName = context.params.testId + '.html';
const fileContents = "<html><head></head><body>Result: " + testResult + "</body></html>"
const options = {resumable:false, metadata:{contentType:'text/html'}};
const bucket = storage.bucket(bucketName);
const file = bucket.file(fileName);
console.log('Saving to:' + bucketName + '/' + fileName);
if(false) {
// Test 1. the file.save method
// Errors with:
// (node:2) MetadataLookupWarning: received unexpected error = URL is not defined code = UNKNOWN
file.save(fileContents, options, function(err) {
if (!err) {console.log("Save created object at " + bucketName + "/" + fileName);}
else {console.log("Save Failed " + err);}
});
} else if(true) {
// Test 2. the readStream.pipe method
// No errors, doesn't output error message, doesn't output finish message, no file created
fs.createReadStream(fileContents)
.pipe(file.createWriteStream(options))
.on('error', function(err) {console.log('WriteStream Error');})
.on('finish', function() {console.log('WriteStream Written');});
} else {
// Test 3. the StringStream with readStream.pipe method
// Errors with:
// (node:2) MetadataLookupWarning: received unexpected error = URL is not defined code = UNKNOWN
const writeStream = storage.bucket(bucketName).file(fileName).createWriteStream(options);
writeStream.on('finish', function(){console.log('WriteStream Written');}).on('error', function(err){console.log('WriteStream Error');});
const readStream = new StringStream(fileContents);
readStream.pipe(writeStream);
}
console.log('Function Finished');
return 0;
});
在所有情况下，都会出现“正在处理证书”和“保存到”输出，每次我也收到“功能已完成”消息。错误（或者在某种情况下没有响应）针对代码中的每个测试编写。
我的下一步是在本地创建文件，然后使用upload（）方法，但是这些方法中的每一种似乎都应该起作用，再加上我仅有的错误消息是关于URL错误的信息，所以我怀疑尝试使用上载（）方法也会遇到相同的问题。
我正在使用Node.JS v8.17.0和以下软件包
"dependencies": {
"@google-cloud/storage": "^5.0.0",
"@rauschma/stringio": "^1.4.0",
"firebase-admin": "^8.10.0",
"firebase-functions": "^3.6.1"
}
欢迎任何意见
回答如下：在每种情况下，您都无法正确使用诺言。对于数据库触发器（和所有其他背景触发器），必须在函数中return a promise that resolves when all of the asynchronous work is complete。现在，您没有对诺言做任何事情，而您正在调用的每个API都是异步的。您的函数只是立即返回0，而无需等待上传完成，而Cloud Functions只是在发生任何事情之前终止并清理掉。]
我建议选择一种返回上载承诺的方法完成（可能是file.save()），然后从函数中返回该承诺。
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从Firebase Cloud Function在Google Cloud Bucket中创建文件
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