traceStart() function

Starts a named span for tracing a block of code that no decorator can wrap, to be closed later by traceEnd() with the same name.

Signature:

export declare function traceStart(name: string, tags?: TraceAttributes, tracerName?: string): void;

Parameters

Parameter	Type	Description
name	string	span name, and the key traceEnd() will close it by
tags	TraceAttributes	(Optional) attributes to set on the span at creation; values must be strings
tracerName	string	(Optional) tracer to create the span with, `'basic'` by default

Returns:

void

Exceptions

TypeError if a span under this name is already open

Remarks

Spans started here are held in a module-level registry keyed by name, which is what lets traceEnd() find one from an unrelated call site. Two consequences follow, and both matter:

A name may have only ONE span open at a time. Starting a second under a live name throws rather than silently replacing it, since replacing would leak the first span forever. - A span left unclosed is never exported. Prefer traced(), or a try/finally around the traceEnd() call, wherever the block can throw.

The span is created standalone, NOT as a child of whatever span is currently active, and it is not made active for the code in between. Use it to time a region, not to parent the spans that region creates.

Example

import {
    traceStart,
    traceEnd,
} from '@imqueue/opentelemetry';

traceStart('import-batch', { 'batch.size': String(rows.length) });

try {
    await importRows(rows);
} finally {
    traceEnd('import-batch');
}

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