panic in sqlx_core::pool::connection::Floating<DB,sqlx_core::pool::connection::Idle<DB>>::metadata

[lovasoa]

When using PoolOptions::before_acquire, I got a panic crashing my entire server with the following error:

thread 'main' panicked at 'supplied instant is later than self', library/std/src/time.rs:313:48
stack backtrace:
   0: rust_begin_unwind
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
   1: core::panicking::panic_fmt
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
   2: core::panicking::panic_display
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:72:5
   3: core::panicking::panic_str
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:56:5
   4: core::option::expect_failed
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/option.rs:1817:5
   5: core::option::Option<T>::expect
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/option.rs:692:21
   6: std::time::Instant::duration_since
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/time.rs:313:9
   7: sqlx_core::pool::connection::Floating<DB,sqlx_core::pool::connection::Idle<DB>>::metadata
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/connection.rs:328:18
   8: sqlx_core::pool::inner::check_idle_conn::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/inner.rs:374:20
   9: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  10: sqlx_core::pool::inner::PoolInner<DB>::acquire::{{closure}}::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/inner.rs:197:79
  11: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  12: <tokio::time::timeout::Timeout<T> as core::future::future::Future>::poll
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/time/timeout.rs:176:33
  13: sqlx_core::pool::inner::PoolInner<DB>::acquire::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/inner.rs:219:10
  14: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  15: sqlx_core::pool::Pool<DB>::acquire::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/mod.rs:343:38
  16: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  17: sqlx_core::pool::executor::<impl sqlx_core::executor::Executor for &sqlx_core::pool::Pool<DB>>::prepare_with::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/sqlx-core-0.6.0/src/pool/executor.rs:58:45
  18: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  19: <core::pin::Pin<P> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/future.rs:123:9
  20: opcua_server::database::Database::init::{{closure}}
             at ./src/database.rs:76:18
  21: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  22: opcua_server::Main::create::{{closure}}
             at ./src/main.rs:38:91
  23: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  24: opcua_server::main::{{closure}}
             at ./src/main.rs:88:66
  25: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/future/mod.rs:84:19
  26: tokio::park::thread::CachedParkThread::block_on::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/park/thread.rs:263:54
  27: tokio::coop::with_budget::{{closure}}
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/coop.rs:102:9
  28: std::thread::local::LocalKey<T>::try_with
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:412:16
  29: std::thread::local::LocalKey<T>::with
             at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/thread/local.rs:388:9
  30: tokio::coop::with_budget
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/coop.rs:95:5
  31: tokio::coop::budget
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/coop.rs:72:5
  32: tokio::park::thread::CachedParkThread::block_on
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/park/thread.rs:263:31
  33: tokio::runtime::enter::Enter::block_on
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/runtime/enter.rs:151:13
  34: tokio::runtime::thread_pool::ThreadPool::block_on
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/runtime/thread_pool/mod.rs:90:9
  35: tokio::runtime::Runtime::block_on
             at /home/olojkine/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-1.19.2/src/runtime/mod.rs:482:43
  36: opcua_server::main
             at ./src/main.rs:101:5

[lovasoa]

sqlx should probably use saturating_duration_since instead of duration_since in Floating::metadata.

See: https://doc.rust-lang.org/std/time/struct.Instant.html#monotonicity

[abonander]

No, I'm dumb. These need to be reversed: https://github.com/launchbadge/sqlx/blob/main/sqlx-core/src/pool/connection.rs#L328-L329

So

        PoolConnectionMetadata {
            age: now.duration_since(self.created_at),
            idle_for: now.duration_since(self.idle_since),
        }

The receiver of the method is supposed to be the later Instant and the argument is the earlier one. Kinda easy to confuse tbh, I probably should have just used the - operator as getting that wrong would be easier to spot.

[lovasoa]

Well, actually, looking at the code: it looks like the subtraction is done in the wrong order !

[lovasoa]

You beat me to it :)

[lovasoa]

The receiver of the method is supposed to be the later Instant and the argument is the earlier one. Kinda easy to confuse tbh, I probably should have just used the - operator as getting that wrong would be easier to spot.

I think the main takeaway is rather: there should have been a test catching that 😉

[lovasoa]

This code was obviously not executed a single time before being published on crates.io...

[abonander]

Yeah, I meant to add a test but forgot.