Struct ConnectionPool 

pub struct ConnectionPool { /* private fields */ }

A read-write connection pool for SQLite.

Architecture:

• 1 writer connection protected by a Mutex (exclusive access)
• N reader connections in a lock-free queue (concurrent access)
• All connections share the same database file in WAL mode

For in-memory databases, or when WAL mode is disabled/unavailable, the pool degrades to single-connection mode and routes all operations through the writer connection.

Implementations

impl ConnectionPool

pub fn new(config: PoolConfig) -> Result<Self, SqliteError>

Create a new connection pool.

Opens 1 writer + N reader connections to the same database when pooling is enabled. All connections are configured consistently (busy timeout, foreign keys, cache, mmap, temp store). For in-memory databases, or when WAL is disabled or unavailable, the pool falls back to single-connection mode.

pub fn reader(&self) -> Result<ReaderGuard<'_>, SqliteError>

Check out a reader connection.

Tries to pop from the lock-free queue. If empty, spins briefly then waits with exponential backoff up to checkout_timeout.

Deadlock Warning

In degraded mode (WAL unavailable, max_readers == 0), this method locks the writer mutex. If the calling thread already holds a WriterGuard, this will deadlock (parking_lot Mutex is not reentrant). Never call reader() while holding a WriterGuard on the same pool.

pub fn writer(&self) -> Result<WriterGuard<'_>, SqliteError>

Check out the writer connection.

Waits up to checkout_timeout for the writer Mutex and returns Err(SqliteError::InvalidData) if the timeout is exceeded.

pub fn try_writer(&self) -> Result<WriterGuard<'_>, SqliteError>

Non-panicking writer checkout.

Returns Err on timeout instead of panicking. Use this in request handlers where a 500 is preferable to crashing the process.

pub fn available_readers(&self) -> usize

Get the current number of available reader connections.

pub fn max_readers(&self) -> usize

Get the total number of reader connections in the pool.

pub fn config(&self) -> &PoolConfig

Return the pool configuration.

pub fn legacy_conn(&self) -> Arc<Mutex<Connection>>

Compatibility method: returns the writer connection wrapped in Arc.

WARNING: This exists only for backward compatibility with code that calls store.conn(). New code should use reader() and writer().