Module observability 

Tracing/observability instrumentation guards.

When the tracing feature is disabled, all guards are zero-sized types with no-op constructors — eliminated entirely by the compiler.

Usage

Providers and connections create guards at the start of instrumented operations. The guard emits a tracing event on Drop:

• QueryGuard — wraps a single query/execute call; emits DEBUG on completion, WARN if the elapsed time exceeds the slow-query threshold.
• PoolAcquireGuard — wraps a connection-pool acquisition; emits INFO with the acquire duration.
• SaveChangesGuard — wraps a save_changes call; emits INFO with the total elapsed time.

Structs

PoolAcquireGuard

QueryGuard

No-op stub when tracing is disabled — zero-sized, eliminated by compiler.

SaveChangesGuard