Enum Error 

#[non_exhaustive]
pub enum Error<E> {
    Backend(E),
    Timeout,
    Closed,
    InvalidConfig(&'static str),
}

Available on crate feature std only.

An error returned by a Pool operation.

The type parameter E is the manager’s own error type (Manager::Error). A failure that originates inside the manager — a connection that could not be opened, a transaction that could not be rolled back — is carried unchanged in Error::Backend, so the caller can inspect or match on the underlying cause rather than a stringified copy of it.

The enum is #[non_exhaustive]: future versions may add variants, so a match on it must include a wildcard arm.

Examples

Distinguish a saturated pool from a backend failure:

use pool_mod::Error;
use std::convert::Infallible;

fn describe(err: &Error<Infallible>) -> &'static str {
    match err {
        Error::Timeout => "pool is busy, try again",
        Error::Closed => "pool is shut down",
        _ => "other",
    }
}

assert_eq!(describe(&Error::Timeout), "pool is busy, try again");

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

Backend(E)

The manager failed to create or recycle a resource. Carries the manager’s own error.

Inspect the inner error to decide whether the failure is transient (worth retrying) or permanent.

Timeout

The configured wait elapsed before a resource became available.

The pool is healthy but saturated. Retry later, raise max_size, or hold borrowed resources for less time.

Closed

The pool has been shut down with Pool::close.

No further resources will be handed out; this is terminal for the pool.

InvalidConfig(&'static str)

The pool could not be built because its configuration is invalid.

The message names the constraint that was violated (for example, a max_size of zero).

Trait Implementations

impl<E: Debug> Debug for Error<E>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<E: Display> Display for Error<E>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<E> Error for Error<E>

where E: Error + 'static,

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.