store: Do not use a fdw connection to check active_copies #5938
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Copying checks the active_copies table through the primary_public.active_copies foreign table to determine whether the copy has been cancelled and it should stop. With a large number of copies running, that causes a large number of postgres_fdw connections into the primary, which can overwhelm the primary. Instead, we now pass the connection pool for the primary into the copy code so that it can do this check without involving postgres_fdw.
zorancv
approved these changes
Apr 10, 2025
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| fn unlock(&mut self, dst: &Site) -> Result<(), StoreError> { | ||
| if !self.has_lock { |
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I guess here and in the two previous ifs if would be nice to get an error logged. Also in the else branch in switch().
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I think only the ifs in lock and unlock need logging; the else in switch is not an issue; we basically just want to make sure we put the right connection back into other, not just any. Changing those two ifs
store/postgres/src/copy.rs
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| /// Put `self` into `other` if `self` has the lock. | ||
| fn switch(self, other: &mut Option<Self>) { |
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Isn't extract more suitable name?
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I was definitely struggling with the name. But I like extract better.
Otherwise, the lock will linger and can block an attempt to restart a copy that failed for transient reasons
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Copying checks the active_copies table through the primary_public.active_copies foreign table to determine whether the copy has been cancelled and it should stop.
With a large number of copies running, that causes a large number of postgres_fdw connections into the primary, which can overwhelm the primary.
Instead, we now pass the connection pool for the primary into the copy code so that it can do this check without involving postgres_fdw.