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Railway•14mo ago

Server-Sent Events on NodeJS+Express not working

Project ID: 81fdcea2-2cc1-4581-a362-97564aa3a6d7 So, I have this NodeJS+Express REST API which has an endpoint that performs a time-consuming task. For this reason I'm using Server-Sent Events to send a progress update to the client. Locally, it all worked fine but was closing the connection after a few seconds once I deployed it on Railway. Looking through the KB I noticed the WebSockets issue with wildcard domains (I was using one), so I bought a domain and setup a custom domain for this API. It's still failing 😦 I'm not sure if there's a configuration to be made for streaming events that I'm missing or something of that sort. I'm running my application with npm start

  "scripts": {
    "start": "node index.js"
  },

  "scripts": {
    "start": "node index.js"
  },

These are my dependencies:

  "dependencies": {
    "axios": "^1.4.0",
    "bcryptjs": "^2.4.3",
    "cookie-parser": "^1.4.6",
    "cors": "^2.8.5",
    "dotenv": "^16.3.1",
    "express": "^4.18.2",
    "jsonwebtoken": "^9.0.1",
    "pg": "^8.11.3",
    "qs": "^6.11.2",
    "redis": "^4.6.7",
    "sequelize": "^6.32.1",
    "xml-js": "^1.6.11"
  },

  "dependencies": {
    "axios": "^1.4.0",
    "bcryptjs": "^2.4.3",
    "cookie-parser": "^1.4.6",
    "cors": "^2.8.5",
    "dotenv": "^16.3.1",
    "express": "^4.18.2",
    "jsonwebtoken": "^9.0.1",
    "pg": "^8.11.3",
    "qs": "^6.11.2",
    "redis": "^4.6.7",
    "sequelize": "^6.32.1",
    "xml-js": "^1.6.11"
  },

I attached what my Network tab looks like from the browser. The API is supposed to be sending messages every couple of seconds, so it's not a default HTTP timeout that could be easily solved with keep-alive messages. Any ideas of what might be going on? Any further information needed, I'll provide. Thanks in advance.

No description

35 Replies

Percy•14mo ago

Project ID: 81fdcea2-2cc1-4581-a362-97564aa3a6d7

Brody•14mo ago

server sent events and websockets are nothing alike and there is no timeouts for server sent events, you can watch this until the cows come home https://utilities.up.railway.app/sse this would be a problem with your code how are you doing sse?

Gabo BermudezOP•14mo ago

I know there are differences between the two, but thought that holding the connection up was the culprit. Seems like it's not. So, for SSE I don't need a custom domain?

Brody•14mo ago

well for websockets you dont even need a custom domain, that article is very old and no longer an issue

Gabo BermudezOP•14mo ago

This is how I'm responding on the server

res.setHeader('Content-Type', 'text/event-stream')
  res.setHeader('Cache-Control', 'no-cache')
  res.setHeader('Connection', 'keep-alive')
  res.flushHeaders()

  let isConnectionOpen = true

  req.on('close', () => {
    res.end()
    isConnectionOpen = false
  })

res.setHeader('Content-Type', 'text/event-stream')
  res.setHeader('Cache-Control', 'no-cache')
  res.setHeader('Connection', 'keep-alive')
  res.flushHeaders()

  let isConnectionOpen = true

  req.on('close', () => {
    res.end()
    isConnectionOpen = false
  })

I send the message using

res.write(`data: {"progress": ${progressRoundUp > 100 ? 100 : progressRoundUp}}\n\n`)

res.write(`data: {"progress": ${progressRoundUp > 100 ? 100 : progressRoundUp}}\n\n`)

And close it at the end of it (it it didn't close on the client first) using

res.end()

res.end()

Brody•14mo ago

can you share a link to where i could test your sse endpoint? similar to my sse link

Gabo BermudezOP•14mo ago

Sure. https://www.selina-panama-lavu.app/facturarCierreDeDia

Brody•14mo ago

does this work locally?

Gabo BermudezOP•14mo ago

When I put it directly on the browser it does send more messages –it sent about 25 messages, instead of 9. Yes, let me double check

Brody•14mo ago

im only getting a single message when using that link you just sent

Gabo BermudezOP•14mo ago

Could you try again? It's a time-sensitive task so probably it's up-to-date and doesn't need to perform anything yet. I just updated the timeframe so that it sends about 60 messages. Locally works like a charm

Brody•14mo ago

okay its counting coming up on a minute and still connected

Gabo BermudezOP•14mo ago

That's more than I got

Brody•14mo ago

stuck at 27 but still connected

Gabo BermudezOP•14mo ago

I can see the logs stuck It looks like it just stopped logging

Brody•14mo ago

looks like you have some debugging to do coming up on 3 minutes and still connected conncetion closed after 3 minutes and 6 seconds

Gabo BermudezOP•14mo ago

Probably closed because it was idle? Meaning... it's expected and not an infrastructure issue. And if so, probably I need to check my code?

Brody•14mo ago

railway would not close idle connections that fast yeah this would be a code issue

Gabo BermudezOP•14mo ago

huh, so definitely a code issue

Brody•14mo ago

definitely

Gabo BermudezOP•14mo ago

Ok, sounds good. Thanks very much for you help. I'll do some debugging and post here the solution for future reference.

Brody•14mo ago

i look forward to seeing what was wrong 🙂

Gabo BermudezOP•14mo ago

Me too. I look forward to being embarrassed by –probably– a very obvious issue 🙃

Brody•14mo ago

thats coding for you 🤣

Gabo BermudezOP•14mo ago

I've noticed something! It's always getting stuck before it makes an API call to a third party REST API. The third party API does not have any query per minute restrictions, I made sure of it. Does Railway might be limiting in some way the requests that go out to an external API?

Brody•14mo ago

railway does not have any such restrictions what 3rd party api are you trying to call?

Gabo BermudezOP•14mo ago

Then, I've found myself in a really odd situation. It's a POS system called LAVU.

Brody•14mo ago

very odd situation indeed

Gabo BermudezOP•14mo ago

So, funny thing... I tried a different platform (not sure if I can say their name) and it worked with no issues. The exact same code

Brody•14mo ago

say name

Gabo BermudezOP•14mo ago

Heroku

Brody•14mo ago

they are monkey patching your code railway runs your code as is

Gabo BermudezOP•14mo ago

oh, really? Well, dang... I'm still on the hunt, then

Brody•14mo ago

as you can see, absoletely nothing wrong with sse on railway wish i knew what was wrong with your code though, sorry

Gabo BermudezOP•14mo ago

Yeah, no worries. Thanks for the help

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