"toString()" failed Page.printToPDF

[AmarildoK]

Component	Version
Operating system	Ubuntu 16.04 LTS
Node.js	6.10.0
Chrome/Chromium/...	63.0.3239.108
chrome-remote-interface	0.24.5

Is Chrome running in a container? NO

Hi,
First of all let me thank you for your great work. This package has been a lot of help, but
recently I got this error ' "toString()" failed'.

Here is the full error stack trace.

buffer.js:509
    throw new Error('"toString()" failed');
    ^

Error: "toString()" failed
    at Buffer.toString (buffer.js:509:11)
    at Receiver.dataMessage (/home/amarildo/Documents/projects/generate-pdf/node_modules/ws/lib/Receiver.js:385:28)
    at extension.decompress (/home/amarildo/Documents/projects/generate-pdf/node_modules/ws/lib/Receiver.js:354:40)
    at _inflate.flush (/home/amarildo/Documents/projects/generate-pdf/node_modules/ws/lib/PerMessageDeflate.js:279:12)
    at afterWrite (_stream_writable.js:383:3)
    at onwrite (_stream_writable.js:374:7)
    at afterTransform (_stream_transform.js:79:3)
    at TransformState.afterTransform (_stream_transform.js:54:12)
    at Zlib.callback (zlib.js:625:5)

This Error happens when I try to generate a pdf from a huge html file(a lot of high res pic in it) with Page.printToPDF(someOptions).

The code itself is straightforward, go to page, and generatePdf then save it to s3.
A link to the code the error starts

I can only think of the limit of max buffer size being hit and that being the reason the code throws an error.
Have you ever encounter this error before?

[cyrus-and]

Thanks! :)

What version of ws are you using?

[AmarildoK]

@cyrus-and
The version currently installed is 2.0.3

[cyrus-and]

I can only think of the limit of max buffer size being hit and that being the reason the code throws an error.

Well yes, it looks like it (see nodejs/node#3175). Tl;dr:

$ node -p 'new Buffer((1 << 28) - 16 + 1).toString().length'
buffer.js:571
    return this.utf8Slice(0, this.length);
                ^

Error: "toString()" failed
    at Buffer.toString (buffer.js:571:17)
    at [eval]:1:32
    at ContextifyScript.Script.runInThisContext (vm.js:44:33)
    at Object.runInThisContext (vm.js:116:38)
    at Object.<anonymous> ([eval]-wrapper:6:22)
    at Module._compile (module.js:569:30)
    at evalScript (bootstrap_node.js:432:27)
    at startup (bootstrap_node.js:139:9)
    at bootstrap_node.js:575:3

My suggestion is to send out the buffer in chunks.

[AmarildoK]

Hmmm,
But the error happens in the Page.printToPdf(), how can I change the inner code?

[cyrus-and]

Sorry, my bad, I was thinking about something else; ignore that phrase.

Let me look into this.

[cyrus-and]

OK, so this is ultimately a Node.js/V8 limitation of the String object, the latest Node.js version (9.3.0) seems to work fine.

I suspect though that a different implementation of ws could make it work even with LTS Node.js, but that would require to switch to Buffer instead of String to manage big text messages; probably not worth it, but you could try to file an issue for that project anyway.

Here's a minimal way to reproduce this using python-websocket-server and wscat:

from websocket_server import WebsocketServer

s = 'x' * ((1 << 28) - 16 + 1)

def new_client(client, server):
    server.send_message(client, s)

server = WebsocketServer(1234)
server.set_fn_new_client(new_client)
server.run_forever()

Start the above then wscat -c localhost:1234.