为什么操纵up的人报告“ UnhandledPromiseRejectionWarning：错误：导航失败，因为浏览器已断开连接！”？

Question

我有一个简单的node.js脚本来捕获一些网页的屏幕截图。看来我在使用async / await的过程中被绊倒了，但我不知道在哪里。我目前正在使用puppeteer v1.11.0。

const puppeteer = require('puppeteer');

//a list of sites to screenshot
const papers =
{
     nytimes: "https://www.nytimes.com/",
     wapo: "https://www.washingtonpost.com/"
};

//launch puppeteer, do everything in .then() handler
puppeteer.launch({devtools:false}).then(function(browser){

//create a load_page function that returns a promise which resolves when screenshot is taken
async function load_page(paper){

    const url = papers[paper];

    return new Promise(async function(resolve, reject){

        const page = await browser.newPage();
        await page.setViewport({width:1024, height: 768});

        //screenshot on first console message
        page.once("console", async console_msg => {        
            await page.pdf({path: paper + '.pdf',
                            printBackground:true,
                            width:'1024px',
                            height:'768px',
                            margin: {top:"0px", right:"0px", bottom:"0px", left:"0px"}
                        });

            //close page
            await page.close();

            //resolve promise
            resolve();
        });

        //go to page
        await page.goto(url, {"waitUntil":["load", "networkidle0"]});

    })     
}

//step through the list of papers, calling the above load_page()
async function stepThru(){
    for(var p in papers){
        if(papers.hasOwnProperty(p)){
            //wait to load page and screenshot before loading next page
            await load_page(p);
        }
    }

    //close browser after loop has finished (and all promises resolved)
    await browser.close();  
}

//kick it off
stepThru();

//getting this error message:
//UnhandledPromiseRejectionWarning: Error: Navigation failed because browser has disconnected!

});

Answer 1

该Navigation failed because browser has disconnected错误通常意味着启动Puppeteer的节点脚本结束而无需等待Puppeteer操作完成。因此，正如您所说的，这是一个等待的问题。

关于您的脚本，我进行了一些更改以使其起作用：

1-首先，您不等待功能的（异步）结束，stepThru因此请进行更改

stepThru();

至

await stepThru();

和

puppeteer.launch({devtools:false}).then(function(browser){

至

puppeteer.launch({devtools:false}).then(async function(browser){

（我加了async）

2-我更改了您管理goto和pagce.once承诺的方式

PDF许诺现在

new Promise(async function(resolve, reject){
    //screenshot on first console message
    page.once("console", async () => {
      await page.pdf({path: paper + '.pdf', printBackground:true, width:'1024px', height:'768px', margin: {top:"0px", right:"0px", bottom:"0px", left:"0px"} });
      resolve();
    });
})

它只负责PDF的创建。

3-然后我page.goto通过Promise.all

await Promise.all([
    page.goto(url, {"waitUntil":["load", "networkidle2"]}),
    new Promise(async function(resolve, reject){
        // ... pdf creation as above        
    })
]);

4-我搬了page.close之后Promise.all

await Promise.all([
    // page.goto
    // PDF creation
]);

await page.close();
resolve();

现在它可以工作了，这里是完整的工作脚本

const puppeteer = require('puppeteer');

//a list of sites to screenshot
const papers =
{
  nytimes: "https://www.nytimes.com/",
  wapo: "https://www.washingtonpost.com/"
};
//launch puppeteer, do everything in .then() handler
puppeteer.launch({devtools:false}).then(async function(browser){

  //create a load_page function that returns a promise which resolves when screenshot is taken
  async function load_page(paper){
    const url = papers[paper];
    return new Promise(async function(resolve, reject){
      const page = await browser.newPage();
      await page.setViewport({width:1024, height: 768});

      await Promise.all([
        page.goto(url, {"waitUntil":["load", "networkidle2"]}),
        new Promise(async function(resolve, reject){

          //screenshot on first console message
          page.once("console", async () => {
            await page.pdf({path: paper + '.pdf', printBackground:true, width:'1024px', height:'768px', margin: {top:"0px", right:"0px", bottom:"0px", left:"0px"} });
            resolve();
          });
        })
      ]);

      await page.close();
      resolve();
    })
  }

  //step through the list of papers, calling the above load_page()
  async function stepThru(){
    for(var p in papers){
      if(papers.hasOwnProperty(p)){
        //wait to load page and screenshot before loading next page
        await load_page(p);
      }
    }

    await browser.close();
  }

  await stepThru();
});

请注意：-我更改networkidle0为，networkidle2因为nytimes.com网站花费很长时间才能获得0网络请求状态（由于AD等）。您networkidle0显然可以等待，但这取决于您，这超出了您的问题范围（page.goto在这种情况下，增加了超时时间）- www.washingtonpost.com网站出现TOO_MANY_REDIRECTS错误，因此我更改为，washingtonpost.com但我认为您应该对此进行更多调查。为了测试脚本，我在nytimes网站和其他网站上使用了更多次。再说一次：这超出了您的问题范围

让我知道您是否需要更多帮助

Answer 2

当系统磁盘已满时，我遇到了同样的错误。