Display the contents of a log file as it is updated

by

Use a Flask view to continuously read from the file forever and stream the response. Use JavaScript to read from the stream and update the page. This example sends the entire file, you may want to truncate that at some point to save bandwidth and memory. This example sleeps between reads to reduce cpu load from the endless loop and allow other threads more active time.

from time import sleep
from flask import Flask, render_template

app = Flask(__name__)

@app.route("https://stackoverflow.com/")
def index():
    return render_template('index.html')

@app.route('/stream')
def stream():
    def generate():
        with open('job.log') as f:
            while True:
                yield f.read()
                sleep(1)

    return app.response_class(generate(), mimetype="text/plain")

app.run()

<pre id="output"></pre>
<script>
    var output = document.getElementById('output');

    var xhr = new XMLHttpRequest();
    xhr.open('GET', '{{ url_for('stream') }}');
    xhr.send();

    setInterval(function() {
        output.textContent = xhr.responseText;
    }, 1000);
</script>

This is almost the same as this answer, which describes how to stream and parse messages, although reading from an external file forever was novel enough to be it’s own answer. The code here is simpler because we don’t care about parsing messages or ending the stream, just tailing the file forever.

More Related Contents:

  1. Display data streamed from a Flask view as it updates
  2. JavaScript raises SyntaxError with data rendered in Jinja template
  3. How can I pass data from Flask to JavaScript in a template?
  4. Flask – Calling python function on button OnClick event
  5. Pass parameter with Python Flask in external Javascript
  6. Rendering to JS with Jinja produces invalid number rather than string
  7. Pass JavaScript variable to Flask url_for
  8. Update and render a value from Flask periodically
  9. Javascript – No ‘Access-Control-Allow-Origin’ header is present on the requested resource
  10. Solve Cross Origin Resource Sharing with Flask
  11. How can I pass parameter through serialization and then parse them using external JavaScript?
  12. Unable to pass jinja2 variables into javascript snippet
  13. Flask Dynamic data update without reload page
  14. Passing variables from Flask to JavaScript
  15. Get data from html and and pass the data back to the front end using ajax or js
  16. Python Flask Cors Issue
  17. Running python on client side
  18. Web-scraping JavaScript page with Python
  19. WebDriver click() vs JavaScript click()
  20. Getting the return value of Javascript code in Selenium
  21. Find the longest common starting substring in a set of strings [closed]
  22. Scrolling to top of the page in Python using Selenium
  23. Mechanize and Javascript
  24. Returning JSON array from a Django view to a template
  25. How to download an image with Python 3/Selenium if the URL begins with “blob:”?
  26. How can I have a host and container read/write the same files with Docker?
  27. Return data from html/js to python
  28. How to use the variables from “views.py” in JavasScript, “” in Django Template?
  29. sending data as JSON object from Python to Javascript with Jinja [duplicate]
  30. Process a continuous stream of JSON

Leave a Comment