Module error 

Client error types.

All fallible operations return Error. Beyond matching specific variants, the key question for resilience is whether an error is worth retrying.

Transient vs terminal

Error::is_transient reports whether an error is likely to succeed on retry (timeouts, connection drops, transient server conditions); Error::is_terminal reports the opposite (syntax errors, constraint violations, authentication failures). Retry only transient errors — retrying a terminal one just repeats the failure.

fn should_retry(err: &Error) -> bool {
    err.is_transient()
}

Transient SQL Server conditions include deadlock victim (1205), Azure throttling (10928/10929) and service errors (40197/40501/40613), and failover (4060). Terminal server errors include syntax (102), invalid object/column (208/207), and constraint/unique violations (547/2627/2601). For server errors, Error::class exposes the TDS severity (classes 11-16 are user errors; 17+ indicate resource or system problems).

Retrying

Retry transient errors with capped exponential backoff plus jitter and a small attempt limit (3-5). The pool and the configured RetryPolicy handle common connection-level cases automatically; apply application-level retries around whole logical operations, and only when the work is idempotent or transaction-wrapped.

Structs

SharedIoError

A cloneable wrapper around std::io::Error that preserves the error source chain.

Enums

Error

Errors that can occur during client operations.

Type Aliases

Result

Result type for client operations.