gcloud Nodejs http 500 error cannot find server.js in workspace [more detailed repost] - node.js

Question

I am new to google cloud and so I deployed a Nodejs app using the tutorial. Everything worked just fine, here is my file structure (I didn't make the my-nodejs-service folder):
app.yaml
server.js
package.json
I deployed it, everything was fine. So then I tried to make it look like this:
mySite/
server.js
package.json
app.yaml
public/
site contents
I just forked a github repo, deployed it, and it didn't work. By that I mean the site didn't load! I checked the logs, and here was what appeared:
Error: Cannot find module '/workspace/server.js'
at Function.Module._resolveFilename (loader.js:880)
at Function.Module._load (loader.js:725)
at Function.executeUserEntryPoint (internal/modules/run_main.js:72)
"GET / HTTP/1.1" 500
listening on port 3000
It said it couldn't find the server.js file. Was it because I moved the code into the folder? I deployed it on the current working directory being the folder mySite.
package.json (Im only including the scripts part, it other stuff such as the dependencies):
{
"scripts": {
"test": "echo \"Error: no test specified\" && exit 1",
"start": "node server.js"
}
}
Other things I tried:
deploying with app.yaml at the end of the deployment command
Using path.join()
Deploying multiple times
Other info:
I checked the logs and I got this:
"GET / HTTP/1.1" 500 - - "Web browser agent info in here"
Another showed:
i This request caused a new process to be started for your application, and thus caused your application code to be loaded for the first time. This request may thus take longer and use more CPU than a typical request for your application.
And another log said:
!! Process was terminated because the request deadline was exceeded. Please ensure that your HTTP server is listening for requests on 0.0.0.0 and on the PORT environment variable. (Error code 123)

Answer 1

App Engine uses a set of conventions in order to be able to deploy and run code successfully. As you've seen, you can't necessarily take an arbitrary web server solution and deploy it successfully.
Please include more details about specific steps you take. For example, you say "I .. deployed it". It would be useful for you to include the command that you used and any immediate errors that were thrown to provide readers with more context when helping answer your question. It's unclear to me from which directory you attempted to deploy the mySite example but I assume from within mySite.
The first error Cannot find module '/workspace/server.js' results because App Engine builds your code using Cloud Build and Cloud Build (by default) puts your code into a /workspace directory on the build VM. It's not very user-friendly, but it was unable to find server.js and, because your package.json specifies node server.js, it needs it.
Another statement that gives me pause is listening on port 3000. I'm not very familiar with the Node.JS runtime but generally App Engine expects web server's to either listen on port :8080 or provide an environment variable that specifies the port, In your tutorial, this is explained: "process.env.PORT is not set, port 8080". That's probably (!?) another issue.
Lastly, you may (I think you probably don't) need to explicitly reference the public subdirectory (unsure) in order to ensure that it's available at runtime.