May not be possible to run Dockerfile on Google Cloud Run

[danoc]

Hi! Thanks for this great resource.

I'm trying to run the Dockerfile on Google Cloud Run. One of the requirements of Cloud Run is:

The service must listen for requests on the port defined by the PORT environment variable.

The Browserless site suggests using docker run -p 8080:3000, but Cloud Run doesn't provide a way to do this kind of port mapping.

Is there another way to do this? Or would this require a change to Browserless?

Thanks!

[knksmith57]

The batteries-included browserless/chrome image actually does respect $PORT; however, because the container process is configured to run as a non-privileged user, only ports > 1024 are going to bind successfully.

Unfortunately, Cloud Run doesn't make any guarantees about the port range it'll request, and, after trying myself, I can confirm that Cloud Run can set $PORT < 1024.

Given you're likely already re-tagging + publishing the browserless image to your own GCR registry, there's a quick fix: extend the browserless/chrome image you're currently targeting and change the user to one with privileges to bind to all ports (eg: back to root):

FROM browserless/chrome:1-chrome-stable
USER root

note: running as root isn't a particularly good idea, and Joel definitely opted to run the browserless server this way for a reason (see his blog post where he talks about sandboxing). that said, unlike browserless.io, you're probably not going to be operating a multi-tenant environment (I'm guessing?). so maybe this is an acceptable amount of risk for your particular use case. YMMV!

[joelgriffith]

Pretty much what @knksmith57 said: you'll likely need to run as a privileged user if the port assignments are less than 1024. Otherwise it'd be nice if they could specify a range?

[joelgriffith]

https://github.com/browserless/chrome/blob/master/src/config.ts#L120

[danoc]

Thanks, @joelgriffith and @knksmith57! I'll try this out tonight and report back. I'll share my Dockerfile if it works well. 😄

[joelgriffith]

Looks like websockets aren't really supported on Cloud Run https://github.com/ahmetb/cloud-run-faq#are-websockets-supported-on-cloud-run. I had success using the REST API, but I had to disable the ENTRYPOINT in my dockerfile to do so

[danoc]

Ah, right!

They list the lack of support as a "Known Issue" which, I imagine, means that they plan to add support in the future.

I'll close this for now and then circle back once they have support for it! Thanks again for digging into this.

[joelgriffith]

Yup, no worries. I did a test and their service took roughly 2-3 seconds to screenshot example.com with Chrome pre-started. Our usage-based cluster does it in roughly 600ms, and wo Chrome pre-started.

I know others have complained about slow start times in GCP, so use caution if speed is necessary.

[danoc]

I know others have complained about slow start times in GCP, so use caution if speed is necessary.

Yeah, the Chrome built into Cloud Functions is sadly very slow.