README

Census for PHP. Census provides a framework to measure a server's resource usage and collect performance stats. This repository contains PHP related utilities and supporting software needed by Census.

Installation & basic usage

Install the opencensus/opencensus package using composer:
```
$ composer require opencensus/opencensus:~0.2
```
IMPORTANT: Please ensure your version is >= 0.2.0. There is a potential security vulnerability in < 0.2.0.
[Optional]: Install the opencensus extension from PECL:
```
$ pecl install opencensus-alpha
```
Enable the extension in your php.ini:
```
extension=opencensus.so
```

Initialize a tracer for your application:

use OpenCensus\Trace\Tracer;
use OpenCensus\Trace\Exporter\EchoExporter;

Tracer::start(new EchoExporter());

Usage

To add tracing to a block of code, you can use the closure/callable form or explicitly open and close spans yourself.

Closure/Callable (preferred)

$pi = Tracer::inSpan(['name' => 'expensive-operation'], function() {
    // some expensive operation
    return calculatePi(1000);
});

$pi = Tracer::inSpan(['name' => 'expensive-operation'], 'calculatePi', [1000]);

Explicit Span Management

// Creates a detached span
$span = Tracer::startSpan(['name' => 'expensive-operation']);

// Opens a scope that attaches the span to the current context
$scope = Tracer::withSpan($span);
try {
    $pi = calculatePi(1000);
} finally {
    // Closes the scope (ends the span)
    $scope->close();
}

Customization

Samplers

You can specify different samplers when initializing a tracer. The default sampler is the AlwaysSampleSampler which will attempt to trace all requests.

The provided samplers are:

Class	Description
NeverSampleSampler	Never trace any requests
AlwaysSampleSampler	Trace all requests
MultiSampler	Check multiple samplers
QpsSampler	Trace X requests per second. Requires a PSR-6 cache implementation
ProbabilitySampler	Trace X percent of requests.

If you would like to provide your own sampler, create a class that implements SamplerInterface.

Exporters

You can choose different exporters to send the collected traces to.

The provided exporters are:

Class	Description	Dependency
EchoExporter	Output the collected spans to stdout
FileExporter	Output JSON encoded spans to a file
JaegerExporter	Report traces to Jaeger server via Thrift over UDP	opencensus/opencensus-exporter-jaeger
LoggerExporter	Exporter JSON encoded spans to a PSR-3 logger
NullExporter	No-op
OneLineEchoExporter	Output the collected spans to stdout with one-line
StackdriverExporter	Report traces to Google Cloud Stackdriver Trace	opencensus/opencensus-exporter-stackdriver
ZipkinExporter	Report collected spans to a Zipkin server	opencensus/opencensus-exporter-zipkin

If you would like to provide your own reporter, create a class that implements ExporterInterface.

Versioning

This library follows Semantic Versioning.

Please note it is currently under active development. Any release versioned 0.x.y is subject to backwards incompatible changes at any time.

GA: Libraries defined at a GA quality level are stable, and will not introduce backwards-incompatible changes in any minor or patch releases. We will address issues and requests with the highest priority.

Beta: Libraries defined at a Beta quality level are expected to be mostly stable and we're working towards their release candidate. We will address issues and requests with a higher priority.

Alpha: Libraries defined at an Alpha quality level are still a work-in-progress and are more likely to get backwards-incompatible updates.

Current Status: Alpha

Contributing

Contributions to this library are always welcome and highly encouraged.

See CONTRIBUTING for more information on how to get started.

Releasing

See RELEASING for more information on releasing new versions.

License

Apache 2.0 - See LICENSE for more information.

Disclaimer

This is not an official Google product.

a1comms / opencensus

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