如何从Google Cloud Function(Cheerio，Node.js)发出多个http请求 [英] How to make multiple http requests from a Google Cloud Function (Cheerio, Node.js)
问题描述
我的问题:
我正在使用Cheerio，Node.js和Google Cloud Functions构建一个网络爬虫.
I'm building a web-scraper with Cheerio, Node.js, and Google Cloud Functions.
问题是我需要发出多个请求，然后将每个请求中的数据写入Firestore数据库，然后再调用response.send()从而终止该函数.
The problem is I need to make multiple requests, then write data from each request to a Firestore database before calling response.send() and thereby terminating the function.
我的代码需要两个循环:第一个循环是数据库中的URL，每个循环都发出一个单独的请求.第二个循环是Cheerio使用.each从DOM抓取表数据的多行并为每行进行单独写入的循环.
My code requires two loops: the first loop is with urls from my db, with each one making a separate request. The second loop is with Cheerio using .each to scrape multiple rows of table data from the DOM and make a separate write for each row.
我尝试过的事情:
我已经尝试将每个请求推送到一个Promise数组，然后在调用res.send()之前等待所有Promise用Promise.all()解决，但是我对Promise还是有些不确定确保这是正确的方法. (我已经以这种方式获得了适用于较小数据集的代码，但是仍然不一致.)
I've tried pushing each request to an array of promises and then waiting for all the promises to resolve with promises.all() before calling res.send(), but I'm still a little shaky on promises and not sure that is the right approach. (I have gotten the code to work for smaller datasets that way, but still inconsistently.)
我还尝试将每个请求创建为新的Promise，并使用async/await等待来自forEach循环的每个函数调用，以便为每个请求留出时间，并完全完成写入操作，因此我可以在之后调用res.send()，我发现forEach不支持Async/await.
I also tried creating each request as a new promise and using async/await to await each function call from the forEach loop to allow time for each request and write to fully finish so I could call res.send() afterward, but I found out that forEach doesn't support Async/await.
我试图通过p-iteration模块解决这个问题，但是因为它实际上不是forEach而是查询的一种方法(doc.forEach())，所以我认为它不是那样工作的.
I tried to get around that with the p-iteration module but because its not actually forEach but rather a method on the query (doc.forEach()) I don't think it works like that.
这是我的代码.
注意:
如上所述，这不是我尝试过的所有事情(我删除了我的诺言尝试)，但这应该表明我正在努力实现的目标.
As mentioned, this is not everything I tried (I removed my promise attempts), but this should show what I am trying to accomplish.
export const getCurrentLogs = functions.https.onRequest((req, response) => {
//First, I make a query from my db to get the urls
// that I want the webscrapper to loop through.
const ref = scheduleRef.get()
.then((snapshot) => {
snapshot.docs.forEach((doc) => {
const scheduleGame = doc.data()
const boxScoreUrl = scheduleGame.boxScoreURL
//Inside the forEach I call the request
// as a function with the url passed in
updatePlayerLogs("https://" + boxScoreUrl + "/");
});
})
.catch(err => {
console.log('Error getting schedule', err);
});
function updatePlayerLogs (url){
//Here I'm not sure on how to set these options
// to make sure the request stays open but I have tried
// lots of different things.
const options = {
uri: url,
Connection: 'keep-alive',
transform: function (body) {
return cheerio.load(body);
}
};
request(options)
.then(($) => {
//Below I loop through some table data
// on the dom with cheerio. Every loop
// in here needs to be written to firebase individually.
$('.stats-rows').find('tbody').children('tr').each(function(i, element){
const playerPage = $(element).children('td').eq(0).find('a').attr('href');
const pts = replaceDash($(element).children('td').eq(1).text());
const reb = replaceDash($(element).children('td').eq(2).text());
const ast = replaceDash($(element).children('td').eq(3).text());
const fg = replaceDash($(element).children('td').eq(4).text());
const _3pt = replaceDash($(element).children('td').eq(5).text());
const stl = replaceDash($(element).children('td').eq(9).text());
const blk = replaceDash($(element).children('td').eq(10).text());
const to = replaceDash($(element).children('td').eq(11).text());
const currentLog = {
'pts': + pts,
'reb': + reb,
'ast': + ast,
'fg': fgPer,
'3pt': + _3ptMade,
'stl': + stl,
'blk': + blk,
'to': + to
}
//here is the write
playersRef.doc(playerPage).update({
'currentLog': currentLog
})
.catch(error =>
console.error("Error adding document: ", error + " : " + url)
);
});
})
.catch((err) => {
console.log(err);
});
};
//Here I call response.send() to finish the function.
// I have tried doing this lots of different ways but
// whatever I try the response is being sent before all
// docs are written.
response.send("finished writing logs")
});
我尝试过的所有结果均会导致最后期限超出错误(可能是由于我调查了配额限制，但我认为我不应该超过此限制)或某些无法解释的错误，其中代码未完成执行但显示我在日志中什么也没有.
Everything I have tried either results in a deadline exceeded error (possibly because of quota limits which I have looked into but I don't think I should be exceeding) Or some unexplained error where the code doesn't finish executing but shows me nothing in the logs.
请帮助，在我不了解的这种情况下，有没有办法使用异步/等待?有没有一种使用诺言使之优雅的方法?
Please help, is there a way to use async/await in this scenario that I am not understanding? Is there a way to use promises to make this elegant?
非常感谢，
推荐答案
也许看看这样的东西.它使用蓝鸟承诺和
Maybe have a look at something like this. It uses Bluebird promises and the request-promise library
const Promise = require('bluebird');
var rp = require('request-promise');
const urlList = ['http://www.google.com', 'http://example.com']
async function getList() {
await Promise.map(urlList, (url, index, length) => {
return rp(url)
.then((response) => {
console.log(`${'\n\n\n'}${url}:${'\n'}${response}`);
return;
}).catch(async (err) => {
console.log(err);
return;
})
}, {
concurrency: 10
}); //end Promise.map
}
getList();
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