Why is my node.js server chopping off the response body? - node.js

Question

My node server has a strange behaviour when it comes to a GET endpoint that resplies with a big JSON (30-35MB).
I am not using any npm package. Just the core API.
The unexpected behaviour only happens when querying the server from the Internet and it behaves fine if it is queried from the local network.
The problem is that the server stops writing to the response after it writes the first 1260 bytes of the content body. It does not close the connection nor throw an error. Insomnia (the REST client I use for testing) just states that it received a 1260B chunk. If I query the same endpoint from a local machine it says that it received more and bigger chunks (a few KB each).
I don't even think the problem is caused by node but since I am on a clean raspberry pi (installed raspbian and then just node v13.0.1) and the only process I use is node.js I don't know how to find the source of the problem, there is no load balancer or web server to blame. Also the public IP seems OK, every other endpoint is working fine (they reply with less than 1260B per request)
The code for that endpoint looks like this
const text = url.parse(req.url, true).query.text;
if (text.length > 4) {
let results = await models.fullTextSearch(text);
results = await results.map(async result=>{
result.Data = await models.FindData(result.ProductID, 30);
return result;
});
results = await Promise.all(results);
results = JSON.stringify(results);
res.writeHead(200, {'Content-Type': 'application/json', 'Transfer-Encoding': 'chunked', 'Access-Control-Allow-Origin': '*', 'Cache-Control': 'max-age=600'});
res.write(results);
res.end();
break;
}
res.writeHead(403, {'Content-Type': 'text/plain', 'Access-Control-Allow-Origin': '*'});
res.write("You made an invalid request!");
break;

Answer 1

Here are a number of things to do in order to debug this:
Add console.log(results.length) to make sure the length of the data is what you expect it to be.
Add a callback to res.end(function() { console.log('finished sending response')}) to see if the http library thinks it is done sending the response.
Check the return value from res.write(). If it is false (indicating that not all data has yet been sent), add a handler for the drain event and see if it gets called.
Try increasing the sending timeout with res.setTimeout() in case it's just taking too long to send all the data.