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chore: document PoolBuilder::fair()

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Austin Bonander 2020-07-01 14:20:17 -07:00 committed by Ryan Leckey
parent 17e88ac1a4
commit 15e0a5553a
1 changed files with 15 additions and 1 deletions
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16
sqlx-core/src/pool/options.rs
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@ -34,7 +34,8 @@ impl<DB: Database> Builder<DB> {
idle_timeout: None,
// If true, test the health of a connection on acquire
test_on_acquire: true,
fair: false,
// If true, calls to `acquire()` must always wait in line.
fair: true,
},
}
}
@ -107,6 +108,19 @@ impl<DB: Database> Builder<DB> {
self
}
/// If set to `true`, calls to `acquire()` are fair and connections are issued
/// in first-come-first-serve order. If `false`, "drive-by" tasks may steal idle connections
/// ahead of tasks that have been waiting.
///
/// According to `sqlx-bench/benches/pg_pool` this may slightly increase time
/// to `acquire()` at low pool contention but at very high contention it helps
/// avoid tasks at the head of the waiter queue getting repeatedly preempted by
/// these "drive-by" tasks and tasks further back in the queue timing out because
/// the queue isn't moving.
///
/// Currently only exposed for benchmarking; `fair = true` seems to be the superior option
/// in most cases.
#[doc(hidden)]
pub fn fair(mut self, fair: bool) -> Self {
self.options.fair = fair;
self