Examples

Telemetry

Description

Pass trace context across service boundaries.
Propagators extract context from incoming requests and inject it into outgoing requests, enabling distributed traces that span multiple services.

Documentation

Telemetry Library
OTLP Bridge - Export telemetry data to OpenTelemetry Protocol backends
PSR-18 Telemetry Bridge - HTTP client instrumentation for telemetry
PSR-7 Telemetry Bridge - HTTP message telemetry formatting
Monolog Telemetry Bridge - Integrate telemetry with Monolog logging
Symfony HttpFoundation Telemetry - Telemetry events for Symfony HTTP requests
Symfony Telemetry Bundle - Symfony bundle for telemetry integration

Code

<?php

declare(strict_types=1);

use Flow\Telemetry\Tracer\SpanKind;
use Flow\Telemetry\Tracer\SpanStatus;
use function Flow\Telemetry\DSL\{
    array_carrier,
    composite_propagator,
    console_exporter,
    memory_context_storage,
    memory_span_processor,
    resource_detector,
    telemetry,
    tracer_provider,
    w3c_baggage,
    w3c_trace_context
};
use function Flow\ETL\DSL\clock;

require __DIR__ . '/vendor/autoload.php';

$telemetry = telemetry(
    resource_detector()->detect(),
    tracer_provider(
        memory_span_processor(console_exporter(colors: false)),
        clock(),
        memory_context_storage(),
    ),
)->registerShutdownFunction();

// Create composite propagator (W3C Trace Context + Baggage)
$propagator = composite_propagator(
    w3c_trace_context(),
    w3c_baggage(),
);

// Simulate incoming request headers from upstream service
$incomingHeaders = [
    'traceparent' => '00-0af7651916cd43dd8448eb211c80319c-00f067aa0ba902b7-01',
    'baggage' => 'userId=alice,requestId=req-123',
];

// Extract context from incoming request
$carrier = array_carrier($incomingHeaders);
$extractedContext = $propagator->extract($carrier);

// Access extracted data
if ($extractedContext->spanContext !== null) {
    echo "Trace ID: " . $extractedContext->spanContext->traceId->toHex() . "\n";
    echo "Parent Span ID: " . $extractedContext->spanContext->spanId->toHex() . "\n";
    echo "Is Sampled: " . ($extractedContext->spanContext->traceFlags->isSampled() ? 'yes' : 'no') . "\n";
}

if ($extractedContext->baggage !== null) {
    echo "User ID: " . $extractedContext->baggage->get('userId') . "\n";
    echo "Request ID: " . $extractedContext->baggage->get('requestId') . "\n";
}

// Create a span as child of the extracted context
$tracer = $telemetry->tracer('order-service');

// Use extracted span context as explicit parent
$span = $tracer->span('handle-request', SpanKind::SERVER, parentContext: $extractedContext->spanContext);
$span->setAttribute('http.method', 'POST');
$span->setAttribute('http.route', '/api/orders');

// Process request...

$span->setStatus(SpanStatus::ok());
$tracer->complete($span);

// Inject context into outgoing response headers
$outgoingCarrier = array_carrier();
$propagator->inject($extractedContext, $outgoingCarrier);
$outgoingHeaders = $outgoingCarrier->unwrap();

echo "\nOutgoing headers:\n";
foreach ($outgoingHeaders as $name => $value) {
    echo "  {$name}: {$value}\n";
}

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