the tracer default span's id may equal it parent id

[riccccck]

in tracer.php

$span = new Span(
    TracerInfo::getTraceSpanId(),
    $this->name,
    new AnnotationBlock(
        $this->endpoint,
        $this->startTimestamp,
        zipkin_timestamp(),
        AnnotationBlock::SERVER
    )
);

in span.php

$this->setIdentifier('parentId', $parentId, [TracerInfo::class, 'getTraceSpanId']);

when tracer type is backend, the tracer default span's id equal parentId.
Is it right ?

[chrisleavoy]

I've confirmed this is likely a bug/design issue. As you pointed out, the root Span created in tracer.php:126 does not have a concept of which span is the parent span. line 135 should allow reporting Metadata and a parent trace id. My work around is kind of gross because a proper fix would introduce breaking changes.

@whitemerry can you confirm? Can you offer a cleaner solution that I'm not seeing?

class FixedTracer extends Tracer
{
    /** @var SpanContext $context */
    private $context;

    /**
     * @param SpanContext $context
     * @return $this
     */
    public function setSpanContext(SpanContext $context)
    {
        $this->context = $context;
        return $this;
    }

    /**
     * Save trace
     * @override
     */
    public function trace()
    {
        $this->traceRoot(null);
    }

    public function traceRoot(Metadata $metadata = null)
    {
        if (!TracerInfo::isSampled()) {
            return;
        }

        $rootSpan = new Span(
            new SpanIdentifier($this->context->getSpanId()),
            $this->name,
            new AnnotationBlock(
                $this->endpoint,
                $this->startTimestamp,
                zipkin_timestamp(),
                AnnotationBlock::SERVER
            ),
            $metadata,
            new TraceIdentifier($this->context->getTraceId()),
            new SpanIdentifier($this->context->getParentSpanId())
        );

        $this->addSpan($rootSpan);

        $this->logger->trace($this->spans);
    }
}

[riccccck]

I fix this problem in this way.

public function trace()
{
    if (!TracerInfo::isSampled()) {
        return;
    }

    $unsetParentId = true;
    if ($this->profile === static::BACKEND && !$this->unsetParentIdForBackend) {
        $unsetParentId = false;
    }

    if ($this->profile == Tracer::FRONTEND) {
        $this->addTraceSpan($unsetParentId);
    }

    $this->logger->trace($this->spans);
}

when profile is FRONTEND, I do not add a root Span .