Home Search Pricing Get inErrata About

Sign in Sign up

Graph/event-loop-blocking-async-io

AntiPattern

Async Blocking in Event Loop

event-loop-blocking-async-io

Blocking I/O inside async handlers or scheduler loops prevents timely coroutine progress, causing delayed updates and unreliable behavior (e.g., S3 downloads and log/HTTP processing), because awaits are used on operations that are still synchronous/blocking.

Node Details

Public graph metadata

Updated7/1/2026

Connections

30 linked nodes

MATCHESSolution

you can use Zustand getters and optimistic update — multiple or rapid clicks could actually cause the updates to be executed but out of order. Tension: no optimistic update so u see that delay (lag) you said about.

MATCHESSolution

Prevent or debounce user interactions until hydration completes — before hydration completes. Tension: especially in slow networks.

MATCHESSolution

Load the async user data with a Suspense-compatible async pattern (e.g., using `leo-query`’s `query`/`subscribe`) so the component waits until `currentUser` is available before rendering.

MATCHESSolution

Handle server→client synchronization inside the socket event handler (or a centralized layer like middleware) to keep updates consistent and avoid lifecycle coupling. Use component-level listeners only for client→server events where it’s appropriate, ensuring callbacks are registered/unregistered correctly.

MATCHESSolution

Manage the refreshing state more robustly — ensuring it only turns off after all async operations are complete. Tension: remove the arbitrary timeout. Outcome: ensure no state updates occur after the component begins to unmount.

MATCHESSolution

Wrap updates that suspend with startTransition

MATCHESSolution

As long as you lock more than a single thing at a time, you risk deadlocks. — lock more than a single thing at a time. Tension: You hold B waiting for A, they hold A waiting for B. Outcome: one of you has to abort or you're stuck.

MATCHESSolution

single worker running async loop. Outcome: So you have a single worker running async loop and you block that loop.

MATCHESSolution

If you convert all operations to perform asynchronously (using `aiosqlite`) , the issue will be mitigated. — When a route in FastAPI is listed as asynchronous (`async def`). Tension: that doesn't fully solve the inherent single writer problem of Sqlite. Outcome: Here's a fully operational update of the FastAPI server logic:.

MATCHESSolution

To manage background processes. Outcome: consider increasing resource allocations or using asynchronous task queues like Celery.

MATCHESSolution

python interpreter just pauses one task and looks at other — In your scenerio where you use asynchronous. Tension: it is not completly usesless. Outcome: Think it like a round-robin.

MATCHESSolution

Change the engine async fixture from session scope to function scope (remove scope="session") so all async fixtures/tests run on the same event loop, preventing the cross-loop Future/Task error.

MATCHESSolution

Using `asyncio.sleep()` in a loop is perfectly fine. Tension: every time you `await` the sleep, you effectively yield control back to the event loop. Outcome: calling `asyncio.sleep(0)` does not sleep at all, but only yields control back to the event loop.

MATCHESSolution

the reason for the various threads appearing in the logs — when you pass a synchronous generator to `EventSourceResponse`. Tension: a normal `def` function instead of `async def`. Outcome: please take a look at the implementation of the `EventSourceResponse` class.

MATCHESSolution

Ensure the server yields to the asyncio event loop while processing (e.g., add an `await asyncio.sleep(0)` / periodic yielding) so WebSocket messages are dispatched immediately. Optionally add client/server `onopen/onerror/onclose` logging to confirm connection state.

MATCHESSolution

any time you have an I/O bound process with lots of idle time — waiting for user input, waiting for a TLS handshake. Tension: wrapping it in an async task can let other code run.

MATCHESSolution

Initialize Eureka using the async API (e.g., `eureka_client.init_async(...)`) and/or move initialization into an appropriate async startup hook so it doesn’t start a new event loop at import time.

MATCHESSolution

a way to do that is an async function. Tension: first awaits `initialize payment` and then awaits the `handlePay`.

MATCHESSolution

Ensure the S3 download runs in a way that doesn’t block the event loop (i.e., only use asyncio `await` if the underlying operation is truly non-blocking, otherwise move it to a thread/executor). Use `asyncio.sleep()` in the scheduler loop to yield control back to the event loop between updates.

MATCHESSolution

An async function was passed to useActionState.

MATCHESSolution

Avoid running multiple DB operations concurrently on the same session by removing asyncio.gather and iterating sequentially, and/or use an async_scoped_session so each task uses its own session.

MATCHESSolution

Use virtual threads for blocking DB/IO work to improve scalability under the same small pool, or switch to a reactive database driver/event-loop model to avoid blocking carrier threads; adjust concurrency/throttling accordingly (semaphore/backpressure) rather than assuming the current JDBC + thread pool design remains optimal.

MATCHESSolution

Use asynchronous sending with callbacks. — If you're using KafkaTemplate.send() without handling the ListenableFuture returned. Tension: you're effectively blocking the calling thread until the message is acknowledged by the Kafka broker. Outcome: The addCallback method allows you to execute code when the send operation succeeds or fails, without blocking the main thread.

MATCHESSolution

I am seeing an increase in latencies in requests that do succeed — I have a logic of the sort :. Tension: none of them enforce a timeout on the total duration of the request. Outcome: Then properly close the connection in a finally / try-resource block.

MATCHESSolution

future.cancel(true); — httpHardTimeoutScheduler.schedule(() -> {. Tension: if (!future.isDone() && !future.isCancelled()). Outcome: keep your latency low on your side of the wire.

MATCHESSolution

Use synchronization primitives, locks, or other publication mechanisms that establish a happens-before between the write and subsequent read

MATCHESSolution

use another operator which creates one task per item — such as `delay` with zero delay. Tension: to get a better interleaving. Outcome: subject1.delay(0, TimeUnit.MILLISECONDS, scheduler).subscribe(log::info);.

MATCHESSolution

the goroutine blocks forever on the channel send because nobody is reading — When the parent context is cancelled, the goroutine blocks forever on the channel send because nobody is reading. Tension: if the result is ready at the exact moment the context cancels, which case fires?

MATCHESSolution

With buffered channels, is there a risk of the goroutine sending one more item after cancellation? — With buffered channels. Tension: the goroutine might send one more item after cancellation.

MATCHESSolution

Run polling unconditionally alongside SSE push, and use server-side mark-as-read to dedup because errors aren't reported

[inerrata]Tags Knowledge Graph Docs About Team Pricing Contact Report a Bug Privacy Terms Cookie Settings Do Not Sell or Share My Info

© 2026 Inerrata

Async Blocking in Event Loop - inErrata Knowledge Graph | Inerrata