Better debug/error information

[konstantinzolotarev]

For now there is no good way to handle internal error messages + debugging this errors.

For example:
We have CloudFlare -> Nginx -> Node.js (engine.io ws server) cluster
Pretty often I see such errors:
*3712847 upstream prematurely closed connection while reading response header from upstream, client: 172.31.54.181, server: , request:

But I couldn't debug this issue because If I'll enable debug for ws. It will flash me with tones of useless information.

As well on Socket close event I have only forced close message and have no idea why and where. error event is also not fired.

socket closed and transport closed are also not very good info for searching an issue.

[darrachequesne]

Which version of engine.io are you using? Could this be related to #283 (fixed in 1.8.2 by #458)?

Regarding the debug message, you should be able to see the engine.io logs with DEBUG=engine node index.js, does it help? Else, do you know what we could improve here?

[konstantinzolotarev]

@darrachequesne I'll check version thank you.
Yep I know that I'm able to enable debug mode. but it gives totally useless messages.
Another issue with it that when I'm enabling debug messages socket.io starts to print all messages it receive/send. It would be nice if there would be several log levels.
Example:

• level one - received/sent messages
• level two - transport close details (something more than transport closed)

Some more examples:
https://github.com/socketio/engine.io/blob/master/lib/socket.js#L102 - here if socket receive pack with error - it might contain some useful information in packet. But message will be parse error. And developers will need to handle packet event, and recheck type == 'error' in handler.

https://github.com/socketio/engine.io/blob/master/lib/socket.js#L190
https://github.com/socketio/engine.io/blob/master/lib/socket.js#L217 - this 2 lines wouldn't provide any information about why transport closed. it means developer have to clone repo and patch it.

Same with forced close message. It sends from several different places. And you have to guess where system closed connection.

[darrachequesne]

@konstantinzolotarev could you please open a pull request with the change you're suggesting?

[konstantinzolotarev]

@darrachequesne I'll try. but not sure about available free time )

[konstantinzolotarev]

@darrachequesne I created an sample PR with idea. #496

Pls take a look if you are ok with this approach I'll finish with other parts of the system

[darrachequesne]

Closed due to inactivity, please reopen if needed.