Closing Tabs after printToPdf

[gnat42]

Apologies, I've nearly got this working but can't seem to figure out how to close a tab that was opened.

Component	Version
Operating system	CentOS7
Node.js	8.2.1
Chrome	60.0.3112.66
chrome-remote-interface	0.24.2

Everything seems to work except for one part which is closing the tabs I've opened. I expose this code via https get/post requests. For each request I open a new tab and either fetch the html or load the html directly. Once loaded, output a pdf and return the filename they can request to get the printed pdf (or directly return it). This works pretty good. Using ab I can do many concurrent requests and everything seems to work. There is one small issue is that it doesn't seem to close the tab. Since I'm running headless I'm seeing a new process for each request open. For example, when I first start Chrome, I have a total of 5 processes. For every request I make, I get another chrome process. It doesn't seem to go away. I'm fairly certain its because I'm calling client.close(); but not closing the tab first. You can see in the function getPdf included below that I've commented where I think I should be closing the tab but have so far been unable to do so. Full project source is here

async function load(html) {
    console.log('Load(html) called');

    const tab = await CDP.New({port: options.port});
    const client = await CDP({tab});
    const {Network, Page} = client;
    await Promise.all([Network.enable(), Page.enable()]);

    return new Promise((resolve, reject) => {
        let failed = false;

        Network.loadingFailed(() => {
            failed = true;
            console.log('Load(html) Network.loadingFailed');
            reject(new Error('Load(html) unable to load remote URL: ' + html));
        });

        const url = /^(https?|file|data):/i.test(html) ? html : `data:text/html,${html}`;
        Page.navigate({url});
        Page.loadEventFired(() => {
            if (!failed) {
                console.log('Load(html) resolved');
                resolve({client: client, tab: tab});
            }
        });
    });
}

async function getPdf(html) {
    const {client, tab} = await load(html);
    const {Page} = client;

    console.log("tabID: "+tab.id);
    // https://chromedevtools.github.io/debugger-protocol-viewer/tot/Page/#method-printToPDF
    const pdf = await Page.printToPDF(options.printOptions);

    // how do I close the tab here???
    client.close();

    return pdf;
}

[hbakhtiyor]

you can use CDP.Close method

e.g.

async function getPdf(html) {
    const {client, tab} = await load(html);
    const {Page} = client;

    console.log("tabID: "+tab.id);
    // https://chromedevtools.github.io/debugger-protocol-viewer/tot/Page/#method-printToPDF
    const pdf = await Page.printToPDF(options.printOptions);

    await CDP.Close({port: options.port, id: tab.id}); // here's you need to pass tab id

    return pdf;
}

[cyrus-and]

@gnat42 yes you can do as @hbakhtiyor says (thanks!); as you can see there should be no need to also close the client.

Just make sure to proper handle errors in your code so you don't leave dangling tabs around.

[gnat42]

Ah, that's how it works, I had tried CDP.Close({tab.id}); client.target.closeTarget() and a variety of others. This works perfectly. @hbakhtiyor Much appreciated!

One question @cyrus-and being quite new to Node/JS and this api. I don't really know all the places/errors I could experience. I'm thinking that I need to close the tab in

Page.loadEventFired(() => {
            if (!failed) {
                console.log('Load(html) resolved');
                resolve({client: client, tab: tab});
                return;
            }
            CDP.Close({port: options.port,id: tab.id});
        });

Are there other places in that code that you see have potential for errors I'm not catching? If so are there docs someplace that detail what exceptions/errors a function can throw?

[cyrus-and]

@gnat42 every method that returns a Promise could in principle fail, if you use the async/await pattern this means that each await f(); could throw an exception. Make sure to properly use try/catch/finally to handle your errors and perform cleanup code. For example:

try {
    await f();
} catch (err) {
    // notify the user
} finally {
    // cleanup code
}