rusqlite/
busy.rs

1///! Busy handler (when the database is locked)
2use std::convert::TryInto;
3use std::mem;
4use std::os::raw::{c_int, c_void};
5use std::panic::catch_unwind;
6use std::ptr;
7use std::time::Duration;
8
9use crate::ffi;
10use crate::{Connection, InnerConnection, Result};
11
12impl Connection {
13    /// Set a busy handler that sleeps for a specified amount of time when a
14    /// table is locked. The handler will sleep multiple times until at
15    /// least "ms" milliseconds of sleeping have accumulated.
16    ///
17    /// Calling this routine with an argument equal to zero turns off all busy
18    /// handlers.
19    ///
20    /// There can only be a single busy handler for a particular database
21    /// connection at any given moment. If another busy handler was defined
22    /// (using [`busy_handler`](Connection::busy_handler)) prior to calling this
23    /// routine, that other busy handler is cleared.
24    ///
25    /// Newly created connections currently have a default busy timeout of
26    /// 5000ms, but this may be subject to change.
27    pub fn busy_timeout(&self, timeout: Duration) -> Result<()> {
28        let ms: i32 = timeout
29            .as_secs()
30            .checked_mul(1000)
31            .and_then(|t| t.checked_add(timeout.subsec_millis().into()))
32            .and_then(|t| t.try_into().ok())
33            .expect("too big");
34        self.db.borrow_mut().busy_timeout(ms)
35    }
36
37    /// Register a callback to handle `SQLITE_BUSY` errors.
38    ///
39    /// If the busy callback is `None`, then `SQLITE_BUSY` is returned
40    /// immediately upon encountering the lock. The argument to the busy
41    /// handler callback is the number of times that the
42    /// busy handler has been invoked previously for the
43    /// same locking event. If the busy callback returns `false`, then no
44    /// additional attempts are made to access the
45    /// database and `SQLITE_BUSY` is returned to the
46    /// application. If the callback returns `true`, then another attempt
47    /// is made to access the database and the cycle repeats.
48    ///
49    /// There can only be a single busy handler defined for each database
50    /// connection. Setting a new busy handler clears any previously set
51    /// handler. Note that calling [`busy_timeout()`](Connection::busy_timeout)
52    /// or evaluating `PRAGMA busy_timeout=N` will change the busy handler
53    /// and thus clear any previously set busy handler.
54    ///
55    /// Newly created connections default to a
56    /// [`busy_timeout()`](Connection::busy_timeout) handler with a timeout
57    /// of 5000ms, although this is subject to change.
58    pub fn busy_handler(&self, callback: Option<fn(i32) -> bool>) -> Result<()> {
59        unsafe extern "C" fn busy_handler_callback(p_arg: *mut c_void, count: c_int) -> c_int {
60            let handler_fn: fn(i32) -> bool = mem::transmute(p_arg);
61            if let Ok(true) = catch_unwind(|| handler_fn(count)) {
62                1
63            } else {
64                0
65            }
66        }
67        let c = self.db.borrow_mut();
68        let r = match callback {
69            Some(f) => unsafe {
70                ffi::sqlite3_busy_handler(c.db(), Some(busy_handler_callback), f as *mut c_void)
71            },
72            None => unsafe { ffi::sqlite3_busy_handler(c.db(), None, ptr::null_mut()) },
73        };
74        c.decode_result(r)
75    }
76}
77
78impl InnerConnection {
79    #[inline]
80    fn busy_timeout(&mut self, timeout: c_int) -> Result<()> {
81        let r = unsafe { ffi::sqlite3_busy_timeout(self.db, timeout) };
82        self.decode_result(r)
83    }
84}
85
86#[cfg(test)]
87mod test {
88    use std::sync::atomic::{AtomicBool, Ordering};
89    use std::sync::mpsc::sync_channel;
90    use std::thread;
91    use std::time::Duration;
92
93    use crate::{Connection, ErrorCode, Result, TransactionBehavior};
94
95    #[test]
96    fn test_default_busy() -> Result<()> {
97        let temp_dir = tempfile::tempdir().unwrap();
98        let path = temp_dir.path().join("test.db3");
99
100        let mut db1 = Connection::open(&path)?;
101        let tx1 = db1.transaction_with_behavior(TransactionBehavior::Exclusive)?;
102        let db2 = Connection::open(&path)?;
103        let r: Result<()> = db2.query_row("PRAGMA schema_version", [], |_| unreachable!());
104        assert_eq!(
105            r.unwrap_err().sqlite_error_code(),
106            Some(ErrorCode::DatabaseBusy)
107        );
108        tx1.rollback()
109    }
110
111    #[test]
112    #[ignore] // FIXME: unstable
113    fn test_busy_timeout() {
114        let temp_dir = tempfile::tempdir().unwrap();
115        let path = temp_dir.path().join("test.db3");
116
117        let db2 = Connection::open(&path).unwrap();
118        db2.busy_timeout(Duration::from_secs(1)).unwrap();
119
120        let (rx, tx) = sync_channel(0);
121        let child = thread::spawn(move || {
122            let mut db1 = Connection::open(&path).unwrap();
123            let tx1 = db1
124                .transaction_with_behavior(TransactionBehavior::Exclusive)
125                .unwrap();
126            rx.send(1).unwrap();
127            thread::sleep(Duration::from_millis(100));
128            tx1.rollback().unwrap();
129        });
130
131        assert_eq!(tx.recv().unwrap(), 1);
132        let _ = db2
133            .query_row("PRAGMA schema_version", [], |row| row.get::<_, i32>(0))
134            .expect("unexpected error");
135
136        child.join().unwrap();
137    }
138
139    #[test]
140    #[ignore] // FIXME: unstable
141    fn test_busy_handler() {
142        static CALLED: AtomicBool = AtomicBool::new(false);
143        fn busy_handler(_: i32) -> bool {
144            CALLED.store(true, Ordering::Relaxed);
145            thread::sleep(Duration::from_millis(100));
146            true
147        }
148
149        let temp_dir = tempfile::tempdir().unwrap();
150        let path = temp_dir.path().join("test.db3");
151
152        let db2 = Connection::open(&path).unwrap();
153        db2.busy_handler(Some(busy_handler)).unwrap();
154
155        let (rx, tx) = sync_channel(0);
156        let child = thread::spawn(move || {
157            let mut db1 = Connection::open(&path).unwrap();
158            let tx1 = db1
159                .transaction_with_behavior(TransactionBehavior::Exclusive)
160                .unwrap();
161            rx.send(1).unwrap();
162            thread::sleep(Duration::from_millis(100));
163            tx1.rollback().unwrap();
164        });
165
166        assert_eq!(tx.recv().unwrap(), 1);
167        let _ = db2
168            .query_row("PRAGMA schema_version", [], |row| row.get::<_, i32>(0))
169            .expect("unexpected error");
170        assert!(CALLED.load(Ordering::Relaxed));
171
172        child.join().unwrap();
173    }
174}
rusqlite/busy.rs

rusqlite/
busy.rs
