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Nested transactions are stuck #925
Description
I have a test like this:
test("Finagle StdClient is stuck on nested transaction") {
val finagleClient: Client with Transactions = getUnderlyingFinagleClient
val future = finagleClient.transaction { tx1 =>
for {
_ <- tx1.execute[Unit](sql"select * from nodes limit 1")
_ <- finagleClient.transaction { tx2 =>
tx2.execute(sql"select * from nodes limit 1")
}
} yield ()
}
intercept[TimeoutException] {
Await.result(future, Duration.fromSeconds(42)) // always throws timeout exception
}
}This is minimal example, but it reflects what I actually've faced. I knows that I'm shouldn't do that in general. But in large code base with a bunch of Dao and Repositories is really hard to catch this case.
Is this usage of client valid?Is it a bug?
Activity
joybestourous commentedon Feb 23, 2022
Nested transactions aren't permitted in mysql: https://dev.mysql.com/doc/refman/5.7/en/implicit-commit.html
c-solo commentedon Feb 24, 2022
The question is about API of finagle-mysql that allows to make stuff like that.
I'm figured out why it's stuck. The reason is session pool with max size 1. If increase max size of session poll up to N then N number of nested transaction are allowed. In fact all transactions are just parallel and don't share any state.
The second problem is deadlocks. If you update row in parent transaction and then try to update the same row in child transaction they will be wait each other.
I understand that it's difficult to ban expression like above in compile time. But maybe better if nested transactions will be raise some exception in runtime?
joybestourous commentedon Feb 24, 2022
gotcha, yeah we can make more clear that we don't support nested transactions via the api. to clarify, when you made those changes, you were able to get nested transactions working?