feat!: zero-downtime restarts and bind to all IPs

The server can now restart with zero downtime. The server also now binds
to all IPv4 and IPv6 addresses, so the ADDR config value is removed.

README.md

@@ -9,3 +9,7 @@ cd burgercat
 python init_db
 python main
 ```
+
+### zero downtime restarts:
+- launch new burgercat server
+- close previous server

config.ini

@@ -1,5 +1,4 @@
 [config]
-HOST = 0.0.0.0
 PORT = 8080
 SECRET_KEY = placeholder
 UPLOAD_FOLDER = uploads

main

@@ -6,6 +6,7 @@ import time
 import json
 import secrets
 import datetime
+import socket
 from itertools import groupby
 from waitress import serve
 from werkzeug.utils import secure_filename
@@ -19,7 +20,6 @@ from flask_limiter.util import get_remote_address
 config = configparser.ConfigParser()
 config.read("config.ini")
 
-HOST = config["config"]["HOST"]
 PORT = config["config"]["PORT"]
 SECRET_KEY = config["config"]["SECRET_KEY"]
 UPLOAD_FOLDER = config["config"]["UPLOAD_FOLDER"]
@@ -644,6 +644,12 @@ def page_not_found(e):
 
 if __name__ == "__main__":
     print("[INFO] Server started")
-    serve(app, host=HOST, port=PORT)
-    #app.run(host=HOST, port=PORT, debug=True)
+
+    with socket.socket(socket.AF_INET6, socket.SOCK_STREAM) as sock:
+        sock.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_V6ONLY, 0)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEPORT, 1)
+        sock.bind(('', int(PORT)))
+        serve(app, sockets=[sock])
+
     print("[INFO] Server stopped")