Threading in Jeamlit - Jeamlit Docs

Multithreading in Jeamlit

Jeamlit uses threads within its architecture, which can make it difficult for app developers to include their own multithreaded processes.

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Note

Jeamlit Threading experience is a work in progress. Reach out on the forum for any question.

Here is the current state:

❌ Jt. commands in Threads are not supported ❌

// DON'T - will throw an exception
new Thread(
  () -> {Jt.text("Hello").use();}
).start();

❌ non-daemon threads can outlive the app run and leak ... ❌

// DON'T - the scheduler will run forever - one new scheduler will be recreated at every app run
ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);
scheduler.scheduleAtFixedRate(() -> {...}, 10, 10, TimeUnit.SECONDS)

✅ ... but in some cases it's ok ✅

// DANGEROUS but ok-ish - will complete eventually - using Threads for logging/tracing/metrics purpose is ok    
new Thread(() -> {System.out.println("Log some traces")}).start();

✅ Compute/IO in threads is supported, but make sure to complete all threads and shutdown the scheduler ✅

// OK - background computation, render results on main thread
ExecutorService executor = Executors.newFixedThreadPool(4);
try {
    List<Future<String>> futures = new ArrayList<>();
    for (int i = 0; i < 5; i++) {
        final int taskId = i;
        futures.add(executor.submit(() -> {
            // ✅ Can do computation/IO here
            Thread.sleep(1000);
            return "Task " + taskId + " completed";
        }));
    }

    // Collect results and display on main thread
    for (Future<String> future : futures) {
        String result = future.get(); // Wait for result
        Jt.text(result).use(); // ✅ Safe - on main thread
    }
} catch (ExecutionException e) {
          throw new RuntimeException(e);
} finally {
    executor.shutdown(); // Always clean up
}

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