simple webapp example 

2 web apps app a call app-b , in Python port 5000 und 5001

app-a.py

from flask import Flask, render_template_string, request

import requests

import time

import threading

app = Flask(__name__)

app.config['REQUEST_COUNT'] = 0

lock = threading.Lock()

@app.route('/')

def index():

    return render_template_string("""

        <h1>Welcome to App A</h1>

        <form action="/call-b" method="post">

            <button type="submit">Call App B</button>

        </form>

    """)

@app.route('/call-b', methods=['POST'])

def call_b():

    with lock:

        app.config['REQUEST_COUNT'] += 1

        current = app.config['REQUEST_COUNT']

    try:

        if current % 10 == 0:

            print(f"⌛ Simulating 5-second delay on request {current}")

            time.sleep(5)

        response = requests.get("http://linux:5001/ping")

        return f"<h2>Response from App B:</h2><p>{response.text}</p><p>Request #{current}</p>"

    except Exception as e:

        return f"<h2>Error contacting App B:</h2><pre>{e}</pre><p>Request #{current}</p>"

if __name__ == '__main__':

    app.run(host='0.0.0.0', port=5000)

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app-b

# app_b.py

from flask import Flask

import instana

app = Flask(__name__)

@app.route('/ping')

def ping():

    return "✅ App B reached!"

if __name__ == '__main__':

    app.run(host='0.0.0.0', port=5001)

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