BitLogger/docs/api/async-logger-last-error.md

name, group, category, update-time, description, key-word

name	group	category	update-time	description	key-word
async-logger-last-error	api	async	20260614	Read the last error string recorded by the async logger worker after run() resets and runtime failure capture.	async logger failure public

Async-logger-last-error

Read the last error string recorded by the async logger worker. This helper gives the textual detail behind has_failed().

Interface

pub fn[S] AsyncLogger::last_error(self : AsyncLogger[S]) -> String {}

input

• self : AsyncLogger[S] - Async logger whose last worker error should be inspected.

output

• String - Last recorded worker error message, or an empty string if no error was recorded.

Explanation

Detailed rules explaining key parameters and behaviors

• run() resets the stored error string when the worker starts.
• If the worker loop fails, the error text is captured from the raised exception.
• An empty string normally means no failure has been recorded.
• Once a failure string is recorded, it stays in place until a later run() invocation actually starts and clears it.
• This helper reports worker execution errors, not ordinary overflow or backpressure conditions.
• A new successful run() attempt clears any previously stored error text before drain work begins again.

How to Use

Here are some specific examples provided.

When Need Failure Detail In Diagnostics

When a compact error message should be surfaced to operators:

if logger.has_failed() {
  println(logger.last_error())
}

In this example, the error string is only read when failure is present.

When Export Full Async State

When custom diagnostics want to include the last error field directly:

let err = logger.last_error()

In this example, the helper provides the textual failure detail without building a full snapshot.

Error Case

e.g.:

• If no runtime failure has occurred, the method returns an empty string.

• An empty string does not prove the queue is empty or the worker is idle; it only means no failure string is currently recorded.

• If callers need broader context than just the error text, they should use state().

• close() or shutdown() do not clear a previously recorded error string by themselves; the reset happens when a later run() has already started.

Notes

1. Read this helper together with has_failed() when interpreting worker health.

2. The stored value is a diagnostic string, not a typed error object.

3. Pair it with is_running() or pending_count() when you need to know whether failure left the logger with unfinished backlog.