111 lines
3.0 KiB
PHP
111 lines
3.0 KiB
PHP
<?php
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namespace Wikimedia\Telemetry;
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use Wikimedia\Assert\Assert;
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/**
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* @since 1.43
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* @internal
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*/
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class Tracer implements TracerInterface {
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/**
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* The length of a trace ID in bytes, as specified by the OTEL specification.
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*/
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private const TRACE_ID_BYTES_LENGTH = 16;
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/**
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* The length of a span ID in bytes, as specified by the OTEL specification.
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*/
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private const SPAN_ID_BYTES_LENGTH = 8;
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private Clock $clock;
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private SamplerInterface $sampler;
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private ExporterInterface $exporter;
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private TracerState $tracerState;
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/**
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* Whether tracing has been explicitly ended by calling shutdown() on this instance.
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* @var bool
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*/
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private bool $wasShutdown = false;
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public function __construct(
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Clock $clock,
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SamplerInterface $sampler,
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ExporterInterface $exporter,
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TracerState $tracerState
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) {
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$this->clock = $clock;
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$this->sampler = $sampler;
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$this->exporter = $exporter;
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$this->tracerState = $tracerState;
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}
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/** @inheritDoc */
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public function createSpan( string $spanName ): SpanInterface {
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$activeSpanContext = $this->tracerState->getActiveSpanContext();
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// Gracefully handle attempts to instrument code after shutdown() was called.
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if ( !$this->wasShutdown ) {
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Assert::precondition(
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$activeSpanContext !== null,
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'Attempted to create a span with the currently active span as the implicit parent, ' .
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'but no span was active. Use createRootSpan() to create a span with no parent (i.e. a root span).'
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);
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}
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return $this->newSpan( $spanName, $activeSpanContext );
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}
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/** @inheritDoc */
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public function createRootSpan( string $spanName ): SpanInterface {
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return $this->newSpan( $spanName, null );
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}
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/** @inheritDoc */
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public function createSpanWithParent( string $spanName, SpanContext $parentSpanContext ): SpanInterface {
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return $this->newSpan( $spanName, $parentSpanContext );
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}
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private function newSpan( string $spanName, ?SpanContext $parentSpanContext ): SpanInterface {
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$traceId = $parentSpanContext !== null ?
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$parentSpanContext->getTraceId() : $this->generateId( self::TRACE_ID_BYTES_LENGTH );
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$spanId = $this->generateId( self::SPAN_ID_BYTES_LENGTH );
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$sampled = $this->sampler->shouldSample( $parentSpanContext );
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$spanContext = new SpanContext(
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$traceId,
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$spanId,
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$parentSpanContext !== null ? $parentSpanContext->getSpanId() : null,
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$spanName,
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$sampled
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);
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if ( $this->wasShutdown || !$sampled ) {
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return new NoopSpan( $spanContext );
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}
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return new Span(
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$this->clock,
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$this->tracerState,
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$spanContext
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);
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}
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/** @inheritDoc */
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public function shutdown(): void {
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$this->wasShutdown = true;
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$this->exporter->export( $this->tracerState );
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}
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/**
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* Generate a valid hexadecimal string for use as a trace or span ID, with the given length in bytes.
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*
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* @param int $bytesLength The byte length of the ID
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* @return string The ID as a hexadecimal string
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*/
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private function generateId( int $bytesLength ): string {
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return bin2hex( random_bytes( $bytesLength ) );
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}
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}
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