Global variables getting ignored after some duration

[AlcoholicCoder]

I have a global variable isRunning and a loop myLoop in globals.dart which starts when /test route is hit. When there are no requests to /test route for few minutes (Don't know the specific duration) and /test route gets a hit then isRunning gets ignored and loop starts twice.

To start the server server.dart:

import 'dart:io';
import 'dart:isolate';
import 'package:shelf/shelf.dart';
import 'package:shelf/shelf_io.dart';
import 'router.dart';

void main() {
  int numberOfCores = Platform.numberOfProcessors;
  final handler = const Pipeline()
      .addMiddleware(
        logRequests(),
      )
      .addHandler(router);
  for (int i = 1; i < numberOfCores; i++) {
    Isolate.spawn(startServer, handler);
  }
  startServer(handler);
}

startServer(Handler handler) async {
  HttpServer myserver = await serve(
    handler,
    '0.0.0.0',
    8000,
    shared: true,
  );
  print('Serving at http://${myserver.address.host}:${myserver.port}');
}

Handle routes router.dart:

import 'package:shelf/shelf.dart';
import 'package:shelf_router/shelf_router.dart';
import 'test_controller.dart';

Handler get router {
  final router = Router();

  router.get('/test', (Request request) async {
    return await testController(request);
  });

  return router;
}

Testing controller test_controller.dart:

import 'package:shelf/shelf.dart';
import 'globals.dart';

Future<Response> testController(Request request) async {
  return await myFunction("JUSTFORTESTING");
}

Global functions and variables globals.dart:

import 'package:shelf/shelf.dart';

bool isRunning = false;

Future<Response> myFunction(String param) async {
  if (!isRunning) {
    print("🔁 Starting loop...");
    isRunning = true;
    myLoop();
  }
  return Response.ok('Test route');
}

Future myLoop() async {
  int i = 0;
  while (true) {
    i++;
    print("✅ Done $i");
    await Future.delayed(Duration(seconds: 5));
  }
}

Output:

Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
Serving at http://0.0.0.0:8000
🔁 Starting loop...
✅ Done 1
2024-07-07T19:38:16.517826  0:00:00.006100 GET     [200] /test
✅ Done 2
✅ Done 3
✅ Done 4
✅ Done 5
✅ Done 6
✅ Done 7
✅ Done 8
✅ Done 9
✅ Done 10
✅ Done 11
2024-07-07T19:39:08.385526  0:00:00.000280 GET     [200] /test
✅ Done 12
✅ Done 13
✅ Done 14
✅ Done 15
✅ Done 16
✅ Done 17
✅ Done 18
✅ Done 19
✅ Done 20
✅ Done 21
🔁 Starting loop...
✅ Done 1 // Loop started again while previous loop is already running
2024-07-07T19:40:00.279199  0:00:00.000169 GET     [200] /test
✅ Done 22
✅ Done 2
✅ Done 23
✅ Done 3
✅ Done 24

[AlcoholicCoder]

Upon further investigation it looks like it is happening because of isolates. Is there any way to share the global variable and sync between them?

[ykmnkmi]

You can look at aqueduct/conduit MessageHub & Threading.