Andrushika opened a new pull request, #70078:
URL: https://github.com/apache/airflow/pull/70078
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Register asset events before taking the task_instance row lock
---
## Why
When a task succeeds, `ti_update_state` currently takes the `task_instance`
row lock and then registers asset events while holding the lock.
Asset registration can be slow because it performs asset lookups, event
inserts, and Dag-run queueing. When many tasks finish at the same time,
concurrent requests can wait for the row lock while each request continues to
use an API-server thread. In the case reported in #66853, this caused the API
server to run out of memory and get OOMKilled.
## What
This change registers the asset events before taking the `task_instance` row
lock:
<img width="1688" height="882" alt="image"
src="https://github.com/user-attachments/assets/0420c4fa-7a7d-4f5e-9835-731812f70906";
/>
The asset events and the task state are still written in the same database
transaction.
In this PR, we first read the state without the row lock, then perform the
asset registration. This can hit a TOCTOU problem: the state may change in
between, for example, when the worker retries. So before we actually change the
state, we take the row lock and read the state one more time. The lock makes
sure no one else can change it after this point. Then we decide what to do.
There are three cases:
1. The state is still `RUNNING`: the normal path. We change the state to
`SUCCESS` and commit. The state and the events are saved together in one
transaction.
2. The state is already `SUCCESS`: another request won the race and already
saved its own events. We roll back so the events are not saved twice, and
return 200.
3. The state is something else, such as `FAILED`: the task is no longer
running, so the update is rejected with 409 and the transaction is rolled back.
No events from this request are saved.
This locked re-check keeps the task state and asset events atomic: the
events are committed only together with the `SUCCESS` state.
This is an alternative to #66854.
related: #66853
---
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