How to catch node TimeoutError and log the request? - node.js

Question

I'm writing an application in node in which I do many websocket requests to a remote service (using the ws library). So the remote service is the server, and my node application is the client. It works quite well, but occasionally I suddenly get a long list of the following TimeoutError:
Unhandled rejection TimeoutError: ResourceRequest timed out
at ResourceRequest._fireTimeout (/Users/kramer65/repos/mmj/node_modules/generic-pool/lib/ResourceRequest.js:58:17)
at Timeout.bound (/Users/kramer65/repos/mmj/node_modules/generic-pool/lib/ResourceRequest.js:8:15)
at ontimeout (timers.js:386:11)
at tryOnTimeout (timers.js:250:5)
at Timer.listOnTimeout (timers.js:214:5)
Since I do many different websocket calls I now wonder for which call this error occurs. I tried wrapping the ws.send() in a try/catch as I pasted below, but that doesn't seem to do anything.
try {
ws.send(request_json);
} catch(e) {
console.log('WEBSOCKET ERROR', e);
console.log('WEBSOCKET JSON', request_json);
}
Does anybody know how I can catch the TimeoutError and log the request contents? All tips are welcome!
[EDIT]
As suggested by #Mark_M I added a callback to the ws.send() method as follows:
ws.send(JSON.stringify(request_obj)), (error)=>{
console.log('WEBSOCKET ERROR', request_obj.action, error);
});
Unfortunately I still get the same errors as I posted on the top of this question.
[EDIT2]
I also tried the suggestion made by #wrangler:
ws.send(JSON.stringify(request_obj));
ws.onerror = function(event) {
console.log('WEBSOCKET ONERROR', request_obj.action, event);
};
ws.onclose = function (event){
console.log('WEBSOCKET ONCLOSE', request_obj.action, event);
};
but unfortunately this also doesn't seem to work. I still get the same errors as I posted on the top of this question.
Any other ideas?

Answer 1

The ws.library send() method takes an optional callback that will be called when it encounters an error. You can catch those errors with:
ws.send('something', function ack(error) {
if(error) //handle error
}
Try/catch will catch immediate errors, but, as you noticed, it doesn't help with async errors.
Alternatively, it looks like you are calling send() within some other async code (because you aren't just getting an error, you're getting an unhandled promise rejection). You could add a .catch() onto that promise if it's in your own code.

Answer 2

You can use onerror callback of websocket object for receiving any error.
Example:
var exampleSocket = new WebSocket("ws://echo.websocket.org");
exampleSocket.onopen = function (event) {
console.log("open");
exampleSocket.send("hellow world");
};
exampleSocket.onmessage = function (event) {
console.log(event.data);
}
exampleSocket.onerror=function(event){
console.log("Error");
}
Link:http://jsfiddle.net/g28yuymv/1/
Link2:http://jsfiddle.net/g28yuymv/10/

Answer 3

Ok, stupid me. After looking at the initial error a bit better I found that it was an error in the generic-pool package. On its npm page it says it's
a Promise based API, which can be used to reuse or throttle usage of
expensive resources such as database connections
The problem turned out to be my database connection (which is used extensively). I solved it using this tip on github, which suggests to set the sequelize init pool settings as follows:
pool: {max: 5, min: 0, idle: 20000, acquire: 20000}
That solved it for me.
Thanks to the answers, I now have proper websocket error reporting though.. :-)