I'm piping a CCTV stream using request, and serve it using Express.
Sometimes there is problem with network connection in the middle of streaming, that cause in the client picture freeze on the last chunked data.
I need to catch this event so I can manipulate on the client by serve some-error image file. I tried exit, close, finish, stop events but none success.
So far I didn't found similar problem on request's Issues or on other SO questions.
Sorry for being late,
I figure out that passing timeout option can catch network disconnection and trigger error event. It printed as Error: ESOCKETTIMEDOUT.
This is quite enough for my needs.
Related
I use net.connect to make socket connection, I wonder how to detect it when a connection has failed?
It seems this doesn't work
//this will return a net.Socket and automatically connect
var client = net.connect({port:22000, host:'10.123.9.163'});
//doesn't trigger a error event even if connection fails
client.on('error', (err)=>{console.log('something wrong')});
//now an error event is emitted reasonably
client.write('hello');
when I run this piece of code, the connection should fail, and it indeed fails because when I write some data, an error occurs. But, I can not detect the connection failure. How can I do that?
=====Ready to close======
God damn it, I think I have just make a mistake. In fact the connection succeeded but due to some security strategy the server close the connection, I find out by doing a telnet. After trying other port which should definitely fail, the error event is emitted, everything go normal as expected. So, I am gonna close this question in case of misleading other people, and also thank you guys for helping me :)
The easiest and most portable way is to simply implement a 'ping-pong' check where both sides send some kind of 'ping' request every so often. If n outstanding ping requests go unanswered after some period of time, then consider the connection dead. This kind of algorithm is basically what OpenSSH uses for example (although it's not enabled by default).
I'm struggling with a technical issue, and because of I'm pretty new on NodeJS world I think I don't have the proper good practise and tools to help me solve this.
Using the well known request module, I'm making a stream proxy from a remote server to the client. Almost everything is fine and working properly until a certain point, if there is too much requests at the same time the server does no longer respond. Actualy it does get the client request but is unable to go through the stream process and serve the content.
What I'm currently doing:
Creating a server with http module with http.createServer
Getting remote url from a php script using exec
Instanciate the stream
How I did it:
http://pastebin.com/a2ZX5nRr
I tried to investigate on the pooling stuff and did not understand everything, same thing the pool maxSocket was recently added, but did not helped me. I was also seting before the http.globalAgent to infinity, but I read that this was no longer limited in nodeJS from a while, so it does not help.
See here: https://nodejs.org/api/http.html#http_http_globalagent
I also read this: Nodejs Max Socket Pooling Settings but I'm wondering what is the difference between a custom agent and the global one.
I believed that it could come from the server but I tested it on a very small one and a bigger one and it was not coming from there. I think it definitely coming from my app that has to be better designed. Indeed each time I'm restarting the app instance it works again. Also if I'm starting a fork of the server meanwhile the other is not serving anything on another port it will work. So it might not be about ressources.
Do you have any clue, tools or something that may help me to understand and debug what is going on?
NPM Module that can help handle stream properly:
https://www.npmjs.com/package/pump
I made few tests, and I think I've found what I was looking for. The unpipe things more info here:
https://nodejs.org/api/stream.html#stream_readable_unpipe_destination
Can see and read this too, it leads me to understand few things about pipe remaining open when target failed or something:
http://www.bennadel.com/blog/2679-how-error-events-affect-piped-streams-in-node-js.htm
So what I've done, i'm currently unpiping pipes when stream's end event is fired. However I guess you can make this in different ways, it depends on how you want to handle the thing but you may unpipe also on error from source/target.
Edit: I still have issues, it seams that the stream is now unpiping when it does not have too. I'll have to doubile check this.
Situation:
User has sent image, after image, he will send message. While the second user does not receive a picture, the message will not be sended.
How to send messages normally, like in normal chat?
I have found, that there are "async" module for node.js, but how to use it with Socket IO?
You could simply pass every messages in a queue. So each messages must wait for the first one to be send before passing to the next.
Although, here in your case. I don't think waiting for an image to be sent is wise - this will make your chat unresponsive.
Rather, use simple text image message. Once you receive this, put a placeholder in the chat where you'll load the image when you received it (displaying a loader meanwhile). This will allow you to continue the chat without being blocked by a long IO process to finish.
Socket.IO uses a single WebSocket connection which only allows for sending one item at a time. You should consider sending that image out-of-band on a separate WebSocket, or via another method.
I have a similar situation where I must stream continuous binary data and signaling messages. For this, I use BinaryJS to set up logical streams which are mirrored on both ends. One stream is used for binary streaming, and the other is used for RPC. Unfortunately, Socket.IO cannot use arbitrary streams. The only RPC library that seems to work is rpc-stream. The RPC functionality isn't nearly as powerful as Socket.IO (in particular when dealing with callbacks), but it does work well.
In the Node.JS docs for HTTP (v0.8.20), under ServerRequest, I see events for data and end. I do not see an event for error.
Normally, if there was an interruption while receiving data, I could detect it by looking at error. But will that work for postdata?
How can I be sure whether have received the entire postdata, and that it was not truncated due to network failure?
I have not confirmed this with actual running code, but just looking at the manual, http.ServerRequest is a Readable Stream and that has Event: 'error' documented.
there's been a recent issue on this: https://github.com/joyent/node/pull/4775
in general, you should always listen for and handle errors from any streams and eventemitters
I have an application which writes to a datastore, so I attempt to send an HTTP request out to the datastore (hbase + stargate). ETIMEDOUT exception, which kills the process.
I have .on('error') on every socket connection present or at least seemingly present, including requests and responses. I even took an extreme step and make a change to the source code, which is supposed to "ignore" those errors in the third post:
http://comments.gmane.org/gmane.comp.lang.javascript.nodejs/25283
I even have a
process.on('uncaughtException', function(){})
All of this still to no avail, and my processes keep dying. Potentially losing everything that built up in the ZMQ stream queue.
The weirdest part yet is that one server out of the 4 server cluster, behaves just fine.
I had a like-issue with our datastore that relied on HTTP requests.
How are you sending the "HTTP request out"? Is it with a library? Have you tried putting a timeout limit on the HTTP request to avoid the ETIMEDOUT exception? Although this does not address the main issue, it will give you the ability to catch the timeout by throwing your own controlled exception.