OpenTelemetry SDK

The OpenTelemetry PHP SDK implements the API, and should be used in conjunction with contributed exporter(s) to generate and export telemetry.

Documentation

https://opentelemetry.io/docs/instrumentation/php/sdk/

Getting started

Manual setup

See https://github.com/open-telemetry/opentelemetry-php/tree/main/examples

SDK Builder

See https://github.com/open-telemetry/opentelemetry-php/blob/main/examples/sdk_builder.php

Autoloading

SDK autoloading works with configuration values provided via the environment (or php.ini).

The SDK can be automatically created and registered, if the following conditions are met:

• OTEL_PHP_AUTOLOAD_ENABLED=true
• all required SDK configuration is provided

SDK autoloading will be attempted as part of composer's autoloader:

require 'vendor/autoload.php';

$tracer = \OpenTelemetry\API\Globals::tracerProvider()->getTracer('example');
$meter = \OpenTelemetry\API\Globals::meterProvider()->getMeter('example');

If autoloading was not successful (or partially successful), no-op implementations of the above may be returned.

See https://github.com/open-telemetry/opentelemetry-php/blob/main/examples/autoload_sdk.php for a more detailed example.

Consistent probability samplers (experimental)

OpenTelemetry\SDK\Trace\Sampler\Consistent contains the composable samplers of the SDK specification, which implement TraceState probability sampling: the sampling threshold is propagated in the ot entry of the W3C tracestate, so that services sampling with different probabilities still make consistent decisions about a trace and the adjusted count of sampled spans is known.

A CompositeSampler wraps a composable sampler and makes the final decision. The composable samplers are ComposableAlwaysOn, ComposableAlwaysOff, ComposableProbability, ComposableParentThreshold, ComposableRuleBased (with PredicatedSampler and Predicate) and ComposableAnnotating. Custom samplers implement ComposableSamplerInterface.

use OpenTelemetry\SDK\Trace\Sampler\Consistent\ComposableParentThreshold;
use OpenTelemetry\SDK\Trace\Sampler\Consistent\ComposableProbability;
use OpenTelemetry\SDK\Trace\Sampler\Consistent\CompositeSampler;

// 10% of the root spans, children follow the parent
$sampler = new CompositeSampler(new ComposableParentThreshold(new ComposableProbability(0.1)));

The same samplers are available in declarative configuration (probability/development and composite/development with always_on, always_off, probability, parent_threshold and rule_based, in open-telemetry/sdk-configuration). They are not available through OTEL_TRACES_SAMPLER.

Limitations:

• The thresholds are 56-bit values held in native integers, so 64-bit PHP is required.
• The specification recommends a compatibility warning when the randomness of a span with a parent is taken from the trace ID but the Random trace flag is not set. This is not implemented yet.
• Everything here is experimental and may change.

Contributing

This repository is a read-only git subtree split. To contribute, please see the main OpenTelemetry PHP monorepo.