Railway•2y ago

SSE connections timeout each 5 minutes

I have deployed a flask sse based app into railway using a dockerfile and gevent. When I check the Networking tab on the inspection window in my browser I see the connection restarting each 5 minutes which is not the case when I was developping my app locally. This issue leads after some days of redeploying the app to have a stream timeout error and stop giving any sse connection until snapshot restarted.

32 Replies

Percy•2y ago

Project ID: 87705bfd-1f41-4d43-8e4d-ed1380fbc20e

0us5amaOP•2y ago

87705bfd-1f41-4d43-8e4d-ed1380fbc20e

Brody•2y ago

is this a post request?

0us5amaOP•2y ago

it's an event stream

Brody•2y ago

tell me the request method please

0us5amaOP•2y ago

it's like a websocket

Brody•2y ago

tell me the request method please

0us5amaOP•2y ago

okey sorry it's a get request to the sse endpoint which makes the connection with the server and keeps it alive until the client aborts

Brody•2y ago

it's a get request

thank you

0us5amaOP•2y ago

I was just confused if you were familiar with the topic. This is my fault sorry I didn't answer you first straight forwardly

Brody•2y ago

i am familiar

0us5amaOP•2y ago

in any case I should have answered directly

Brody•2y ago

dont worry about it so far, i have been able to hold a sse connection open done with a get request, time is sitting at 6 minutes you can try it for yourself https://utilities.up.railway.app/sse

0us5amaOP•2y ago

locally? okey

Brody•2y ago

it sends a timestamp every second it may not follow EventStream spec, but it is still sse

0us5amaOP•2y ago

this is the part of my code responsible for sse. Is there anything here that maybe causing the connection restarting when hosted in railway?

@app.get("/sse")
def sse():
    if "text/event-stream" not in request.accept_mimetypes:
        abort(400)
    def send_events():
        nonlocal variable
        while True:
            event_binary = b''
            if condition:
              data = ...
              _event = ...
              event = ServerSentEvent(data, _event)
              event_binary = event.encode()
               yield event_binary
            time.sleep(0.1)

    response = Response(
        send_events(),
        mimetype="text/event-stream",
    )
    response.timeout = None
    return response

@app.get("/sse")
def sse():
    if "text/event-stream" not in request.accept_mimetypes:
        abort(400)
    def send_events():
        nonlocal variable
        while True:
            event_binary = b''
            if condition:
              data = ...
              _event = ...
              event = ServerSentEvent(data, _event)
              event_binary = event.encode()
               yield event_binary
            time.sleep(0.1)

    response = Response(
        send_events(),
        mimetype="text/event-stream",
    )
    response.timeout = None
    return response

maybe this if "text/event-stream" not in request.accept_mimetypes: abort(400)?

Brody•2y ago

id have to guess it would more so be with your gunicorn and gevent setup

0us5amaOP•2y ago

yeah that's highly probably since I didn't use it in the dev process. "gunicorn -b 0.0.0.0:8000 main:app --worker-class gevent" this is my startup command

Brody•2y ago

can you show me the headers tab of this?

0us5amaOP•2y ago

Brody•2y ago

is that all of the response headers?

0us5amaOP•2y ago

yes

Brody•2y ago

show me the same screenshot but to the server running locally

0us5amaOP•2y ago

ok one minute

0us5amaOP•2y ago

Brody•2y ago

connection: close send Connection: Keep-Alive instead, the demo app sends keep alive dont know if thats your issue but worth a shot

0us5amaOP•2y ago

hahahaha

Brody•2y ago

interesting, fix that and then try it out on railway

0us5amaOP•2y ago

I added it to my github repo and redeployed the app but the connection keep-alive was not added

Brody•2y ago

was the connection still closed after 5 minutes

0us5amaOP•2y ago

Yes the same issue persists

Brody•2y ago

well keep playing around, im sure youll get it

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SSE connections timeout each 5 minutes