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#PSR-18 Telemetry Bridge

Flow PSR-18 Telemetry Bridge provides a traceable HTTP client wrapper for PSR-18 compliant HTTP clients, enabling automatic span creation and telemetry context propagation for outgoing HTTP requests.

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#Installation

For detailed installation instructions, see the installation page.

#Overview

This bridge connects Flow PHP's Telemetry library with PSR-18 compliant HTTP clients, providing automatic tracing for outgoing HTTP requests. It wraps any PSR-18 ClientInterface implementation to create spans with HTTP request/response metadata.

This is particularly useful for:

• Automatic tracing of outgoing HTTP requests
• Recording HTTP method, URL, status code, and other attributes
• Error tracking for failed requests (4xx/5xx responses)
• Exception recording when HTTP clients throw errors
• Integration with OpenTelemetry-based observability stacks
• Framework-agnostic HTTP client instrumentation

Note: This bridge works with any PSR-18 compliant HTTP client implementation (Guzzle, Symfony HttpClient with PSR-18 adapter, Buzz, etc.).

#Requirements

• PHP 8.3+
• flow-php/telemetry
• psr/http-client ^1.0
• psr/http-message ^1.0 || ^2.0

#Usage

#Wrapping a PSR-18 HTTP Client

use Flow\Bridge\Psr18\Telemetry\PSR18TraceableClient;
use Flow\Telemetry\Telemetry;
use Symfony\Component\HttpClient\Psr18Client;

// Create your telemetry instance
$telemetry = /* ... your Telemetry setup ... */;

// Wrap any PSR-18 client
$httpClient = new Psr18Client();
$traceableClient = new PSR18TraceableClient($httpClient, $telemetry);

// Use it like any other PSR-18 client
$request = new Request('GET', 'https://api.example.com/users');
$response = $traceableClient->sendRequest($request);

// A span is automatically created with:
// - Name: "GET api.example.com"
// - Kind: CLIENT
// - Attributes: http.method, http.url, http.scheme, http.host, http.status_code
// - Status: OK for 2xx/3xx, ERROR for 4xx/5xx

#Span Attributes

The traceable client automatically records the following span attributes:

#Error Handling

The client handles errors in two ways:

1. HTTP Error Responses (4xx/5xx): The span status is set to ERROR with the message "HTTP {status_code}"
2. Exceptions: If the underlying client throws an exception, it is recorded on the span and re-thrown

try {
    $response = $traceableClient->sendRequest($request);
} catch (\Throwable $e) {
    // Exception is recorded on the span with:
    // - exception.type
    // - exception.message
    // - exception.stacktrace
    // The span status is set to ERROR
    throw $e;
}

#DSL Functions

The bridge provides a convenient DSL function:

use function Flow\Bridge\Psr18\Telemetry\DSL\psr18_traceable_client;

$traceableClient = psr18_traceable_client($httpClient, $telemetry);