I have a Web App built in Flask where tweets are captured (using Tweepy library) and displayed on the front-end. I used Socket IO to display the tweets live on the front-end.
My code works fine when I run this locally. The tweets appear instantly.
However, when i Dockerized the web app, the front-end doesn’t update immediately. It takes some time to show the changes (sometimes I think tweets are lost due to the slowness)
Below are code extracts from my website:
fortsocket.js
$(document).ready(function () {
/************************************/
/*********** My Functions ***********/
/************************************/
function stream_active_setup() {
$("#favicon").attr("href", "/static/icons/fortnite-active.png");
$("#stream-status-ic").attr("src", "/static/icons/stream-active.png");
$("#stream-status-text").text("Live stream active");
}
function stream_inactive_setup() {
$("#favicon").attr("href", "/static/icons/fortnite-inactive.png");
$("#stream-status-ic").attr("src", "/static/icons/stream-inactive.png");
$("#stream-status-text").text("Live stream inactive");
}
/*********************************/
/*********** My Events ***********/
/*********************************/
// Socket connection to server
// Prometheus
//var socket = io.connect('http://104.131.173.145:8083');
// Local
var socket = io.connect(window.location.protocol + '//' + document.domain + ':' + location.port);
// Heroku
//var socket = io.connect('https://fortweet.herokuapp.com/');
// Send a hello to know
// if a stream is already active
socket.on('connect', () => {
socket.emit('hello-stream', 'hello-stream');
});
// Listene for reply from hello
socket.on('hello-reply', function (bool) {
if (bool == true) {
stream_active_setup()
} else {
stream_inactive_setup()
}
});
// Listens for tweets
socket.on('stream-results', function (results) {
// Insert tweets in divs
$('#live-tweet-container').prepend(`
<div class="row justify-content-md-center mt-3">
<div class="col-md-2">
<img width="56px" height="56px" src="${results.profile_pic !== "" ? results.profile_pic : "/static/icons/profile-pic.png"}" class="mx-auto d-block rounded" alt="">
</div>
<div class="col-md-8 my-auto">
<div><b>${results.author}</b></div>
<div>${results.message}</div>
</div>
</div>
`);
});
// Listener for when a stream of tweets starts
socket.on('stream-started', function (bool) {
if (bool == true) {
stream_active_setup()
}
});
// Listener for when a stream of tweets ends
socket.on('stream-ended', function (bool) {
if (bool == true) {
stream_inactive_setup()
}
});
});
init.py
# Create the app
app = create_app()
# JWT Configurations
jwt = JWTManager(app)
# Socket IO
socketio = SocketIO(app, cors_allowed_origins="*")
# CORS
CORS(app)
app.config["CORS_HEADERS"] = "Content-Type"
# Creates default admins and insert in db
create_default_admin()
# Main error handlers
@app.errorhandler(404) # Handling HTTP 404 NOT FOUND
def page_not_found(e):
return Err.ERROR_NOT_FOUND
# Listen for hello emit data
# from client
@socketio.on("hello-stream")
def is_stream_active(hello_stream):
emit("hello-reply", streamer.StreamerInit.is_stream_active(), broadcast=True)
streamer.py
import time
import tweepy
import threading as Coroutine
import app.messages.constants as Const
import app.setup.settings as settings_mod
import app.models.tweet as tweet_mod
import app.services.logger as logger
import app
class FStreamListener(tweepy.StreamListener):
def __init__(self):
self.start_time = time.time()
self.limit = settings_mod.TwitterSettings.get_instance().stream_time
logger.get_logger().debug("Live capture has started")
# Notify client that a live capture will start
app.socketio.emit(
"stream-started", True, broadcast=True,
)
super(FStreamListener, self).__init__()
def on_status(self, status):
if (time.time() - self.start_time) < self.limit:
# Create tweet object
forttweet = tweet_mod.TweetModel(
status.source,
status.user.name,
status.user.profile_background_image_url_https,
status.text,
status.created_at,
status.user.location,
)
# Emit to socket
app.socketio.emit(
"stream-results",
{
"profile_pic": forttweet.profile_pic,
"author": forttweet.author,
"message": forttweet.message,
},
broadcast=True,
)
# Add to database
forttweet.insert()
return True
else:
logger.get_logger().debug("Live capture has ended")
# Notify client that a live capture has ended
app.socketio.emit(
"stream-ended", True, broadcast=True,
)
# Stop the loop of streaming
return False
def on_error(self, status):
logger.get_logger().debug(f"An error occurred while fetching tweets: {status}")
raise Exception(f"An error occurred while fetching tweets: {status}")
class StreamerInit:
# [Private] Twitter configurations
def __twitterInstantiation(self):
# Get settings instance
settings = settings_mod.TwitterSettings.get_instance()
# Auths
auth = tweepy.OAuthHandler(settings.consumer_key, settings.consumer_secret,)
auth.set_access_token(
settings.access_token, settings.access_token_secret,
)
# Get API
api = tweepy.API(auth)
# Live Tweets Streaming
myStreamListener = FStreamListener()
myStream = tweepy.Stream(auth=api.auth, listener=myStreamListener)
myStream.filter(track=settings.filters)
def start(self):
for coro in Coroutine.enumerate():
if coro.name == Const.FLAG_TWEETS_LIVE_CAPTURE:
return False
stream = Coroutine.Thread(target=self.__twitterInstantiation)
stream.setName(Const.FLAG_TWEETS_LIVE_CAPTURE)
stream.start()
return True
@staticmethod
def is_stream_active():
for coro in Coroutine.enumerate():
if coro.name == Const.FLAG_TWEETS_LIVE_CAPTURE:
return True
return False
The streamer.py is called on a button click
Dockerfile
# Using python 3.7 in Alpine
FROM python:3.6.5-stretch
# Set the working directory to /app
WORKDIR /app
# Copy the current directory contents into the container at /app
ADD . /app
RUN apt-get update -y && apt-get upgrade -y && pip install -r requirements.txt
# Run the command
ENTRYPOINT ["uwsgi", "app.ini"]
#ENTRYPOINT ["./entry.sh"]
docker-compose.yml
version: "3.8"
services:
fortweet:
container_name: fortweet
image: mervin16/fortweet:dev
build: ./
env_file:
- secret.env
networks:
plutusnet:
ipv4_address: 172.16.0.10
expose:
- 8083
restart: always
nginx_fortweet:
image: nginx
container_name: nginx_fortweet
ports:
- "8083:80"
networks:
plutusnet:
ipv4_address: 172.16.0.100
volumes:
- ./nginx/nginx.conf:/etc/nginx/conf.d/default.conf
depends_on:
- fortweet
restart: always
networks:
plutusnet:
name: plutus_network
driver: bridge
ipam:
driver: default
config:
- subnet: 172.16.0.0/24
gateway: 172.16.0.1
app.ini
[uwsgi]
module = run:app
master = true
processes = 5
# Local & Prometheus
http-socket = 0.0.0.0:8083
http-websockets = true
chmod-socket = 660
vacuum = true
die-on-term = true
For a full, updated code, you can find it here under the branch dev/mervin
Any help is appreciated.
2
Answers
Unfortunately I can’t reproduce the issue without the configuration, so I can’t verify my answer.
I was able to find a similar issue on a JP’s blog: Performance problems with Flask and Docker
In short, it might be that having both IPv6 and IPv4 configs on the container are causing the issue.
In order to verify the issue:
If the app runs smoothly then you’ve identified your issue.
The solution would be to tweak the uwsgi parameters.
What the author did in the blog post:
in order to see if ipv6 is responsible i would suggest you shutdown everything
open
/etc/sysctl.conf
and add the following lines to disable ipv6run
sudo sysctl -p
so changes can take effectstart nginx and the docker again
if you dont see any difference then you can just change the settings to 0 and rerun
sysctl -p
and let me know