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//! Busy handler (when the database is locked)
use std::convert::TryInto;
use std::mem;
use std::os::raw::{c_int, c_void};
use std::panic::catch_unwind;
use std::ptr;
use std::time::Duration;
use crate::ffi;
use crate::{Connection, InnerConnection, Result};
impl Connection {
/// Set a busy handler that sleeps for a specified amount of time when a
/// table is locked. The handler will sleep multiple times until at
/// least "ms" milliseconds of sleeping have accumulated.
///
/// Calling this routine with an argument equal to zero turns off all busy
/// handlers.
///
/// There can only be a single busy handler for a particular database
/// connection at any given moment. If another busy handler was defined
/// (using [`busy_handler`](Connection::busy_handler)) prior to calling this
/// routine, that other busy handler is cleared.
///
/// Newly created connections currently have a default busy timeout of
/// 5000ms, but this may be subject to change.
pub fn busy_timeout(&self, timeout: Duration) -> Result<()> {
let ms: i32 = timeout
.as_secs()
.checked_mul(1000)
.and_then(|t| t.checked_add(timeout.subsec_millis().into()))
.and_then(|t| t.try_into().ok())
.expect("too big");
self.db.borrow_mut().busy_timeout(ms)
}
/// Register a callback to handle `SQLITE_BUSY` errors.
///
/// If the busy callback is `None`, then `SQLITE_BUSY` is returned
/// immediately upon encountering the lock. The argument to the busy
/// handler callback is the number of times that the
/// busy handler has been invoked previously for the
/// same locking event. If the busy callback returns `false`, then no
/// additional attempts are made to access the
/// database and `SQLITE_BUSY` is returned to the
/// application. If the callback returns `true`, then another attempt
/// is made to access the database and the cycle repeats.
///
/// There can only be a single busy handler defined for each database
/// connection. Setting a new busy handler clears any previously set
/// handler. Note that calling [`busy_timeout()`](Connection::busy_timeout)
/// or evaluating `PRAGMA busy_timeout=N` will change the busy handler
/// and thus clear any previously set busy handler.
///
/// Newly created connections default to a
/// [`busy_timeout()`](Connection::busy_timeout) handler with a timeout
/// of 5000ms, although this is subject to change.
pub fn busy_handler(&self, callback: Option<fn(i32) -> bool>) -> Result<()> {
unsafe extern "C" fn busy_handler_callback(p_arg: *mut c_void, count: c_int) -> c_int {
let handler_fn: fn(i32) -> bool = mem::transmute(p_arg);
c_int::from(catch_unwind(|| handler_fn(count)).unwrap_or_default())
}
let c = self.db.borrow_mut();
let r = match callback {
Some(f) => unsafe {
ffi::sqlite3_busy_handler(c.db(), Some(busy_handler_callback), f as *mut c_void)
},
None => unsafe { ffi::sqlite3_busy_handler(c.db(), None, ptr::null_mut()) },
};
c.decode_result(r)
}
}
impl InnerConnection {
#[inline]
fn busy_timeout(&mut self, timeout: c_int) -> Result<()> {
let r = unsafe { ffi::sqlite3_busy_timeout(self.db, timeout) };
self.decode_result(r)
}
}
#[cfg(test)]
mod test {
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::mpsc::sync_channel;
use std::thread;
use std::time::Duration;
use crate::{Connection, ErrorCode, Result, TransactionBehavior};
#[test]
fn test_default_busy() -> Result<()> {
let temp_dir = tempfile::tempdir().unwrap();
let path = temp_dir.path().join("test.db3");
let mut db1 = Connection::open(&path)?;
let tx1 = db1.transaction_with_behavior(TransactionBehavior::Exclusive)?;
let db2 = Connection::open(&path)?;
let r: Result<()> = db2.query_row("PRAGMA schema_version", [], |_| unreachable!());
assert_eq!(
r.unwrap_err().sqlite_error_code(),
Some(ErrorCode::DatabaseBusy)
);
tx1.rollback()
}
#[test]
#[ignore] // FIXME: unstable
fn test_busy_timeout() {
let temp_dir = tempfile::tempdir().unwrap();
let path = temp_dir.path().join("test.db3");
let db2 = Connection::open(&path).unwrap();
db2.busy_timeout(Duration::from_secs(1)).unwrap();
let (rx, tx) = sync_channel(0);
let child = thread::spawn(move || {
let mut db1 = Connection::open(&path).unwrap();
let tx1 = db1
.transaction_with_behavior(TransactionBehavior::Exclusive)
.unwrap();
rx.send(1).unwrap();
thread::sleep(Duration::from_millis(100));
tx1.rollback().unwrap();
});
assert_eq!(tx.recv().unwrap(), 1);
let _ = db2
.query_row("PRAGMA schema_version", [], |row| row.get::<_, i32>(0))
.expect("unexpected error");
child.join().unwrap();
}
#[test]
#[ignore] // FIXME: unstable
fn test_busy_handler() {
static CALLED: AtomicBool = AtomicBool::new(false);
fn busy_handler(_: i32) -> bool {
CALLED.store(true, Ordering::Relaxed);
thread::sleep(Duration::from_millis(100));
true
}
let temp_dir = tempfile::tempdir().unwrap();
let path = temp_dir.path().join("test.db3");
let db2 = Connection::open(&path).unwrap();
db2.busy_handler(Some(busy_handler)).unwrap();
let (rx, tx) = sync_channel(0);
let child = thread::spawn(move || {
let mut db1 = Connection::open(&path).unwrap();
let tx1 = db1
.transaction_with_behavior(TransactionBehavior::Exclusive)
.unwrap();
rx.send(1).unwrap();
thread::sleep(Duration::from_millis(100));
tx1.rollback().unwrap();
});
assert_eq!(tx.recv().unwrap(), 1);
let _ = db2
.query_row("PRAGMA schema_version", [], |row| row.get::<_, i32>(0))
.expect("unexpected error");
assert!(CALLED.load(Ordering::Relaxed));
child.join().unwrap();
}
}