Don't mistakenly take a lock on DagRun via ti.refresh_from_fb #25312
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/cc @potiuk Even if this doesn't fix the deadlock it's probably worth doing |
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@RNHTTR Can you see if this change does anything for the deadlock you are able to reproduce? |
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In 2.2.0 we made TI.dag_run be automatically join-loaded, which is fine for most cases, but for `refresh_from_db` we don't need that (we don't access anything under ti.dag_run) and it's possible that when `lock_for_update=True` is passed we are locking more than we want to and _might_ cause deadlocks. Even if it doesn't, selecting more than we need is wasteful.
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Co-authored-by: Jed Cunningham <66968678+jedcunningham@users.noreply.github.com>
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In 2.2.0 we made TI.dag_run be automatically join-loaded, which is fine for most cases, but for `refresh_from_db` we don't need that (we don't access anything under ti.dag_run) and it's possible that when `lock_for_update=True` is passed we are locking more than we want to and _might_ cause deadlocks. Even if it doesn't, selecting more than we need is wasteful. (cherry picked from commit be2b53e)
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Fundamentally what's going on here is we need a TaskInstance object instead of a Row object when sending over the wire in RPC call. But the full story on this one is actually somewhat complicated. It was back in 2.2.0 in apache#25312 when we converted to query with the column attrs instead of the TI object (apache#28900 only refactored this logic into a function). The reason was to avoid locking the dag_run table since TI newly had a dag_run relationship attr. Now, this causes a problem with AIP-44 because the RPC api does not know how to serialize a Row object. This PR switches back to querying a TaskInstance object, but avoids locking dag_run by using lazy_load option. Meanwhile, since try_number is a horrible attribute (which gives you a different answer depending on the state), we have to switch it back to look at the underlying private attr instead of the public accesor.
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Fundamentally what's going on here is we need a TaskInstance object instead of a Row object when sending over the wire in RPC call. But the full story on this one is actually somewhat complicated. It was back in 2.2.0 in #25312 when we converted to query with the column attrs instead of the TI object (#28900 only refactored this logic into a function). The reason was to avoid locking the dag_run table since TI newly had a dag_run relationship attr. Now, this causes a problem with AIP-44 because the RPC api does not know how to serialize a Row object. This PR switches back to querying a TaskInstance object, but avoids locking dag_run by using lazy_load option. Meanwhile, since try_number is a horrible attribute (which gives you a different answer depending on the state), we have to switch it back to look at the underlying private attr instead of the public accesor.
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In 2.2.0 we made TI.dag_run be automatically join-loaded, which is fine
for most cases, but for
refresh_from_dbwe don't need that (we don'taccess anything under ti.dag_run) and it's possible that when
lock_for_update=Trueis passed we are locking more than we want to andmight cause deadlocks.
Even if it doesn't, selecting more than we need is wasteful.
Idea inspired by @dstaple, except rather than not locking it changed to not even select against the DagRun table in the first place.
Might fix #23361