A small library that uses a PSR-3 compliant logger to send HTTP/Application telemetry metrics to a given log service/system

v1.1.0 2022-04-06 18:30 UTC

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Last update: 2024-05-07 02:18:09 UTC


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slick/telemetry is a small library that uses a PSR-3 compliant logger to send HTTP/Application telemetry metrics to a given log service/system. It abstracts the concepts of a metric, dependency, exception, PSR-14 slick implementation of an event and HTTP requests. It also implements PSR-3LoggerInterface allowing its usage as a regular logger.

This package is compliant with PSR-12 code standards and PSR-4 autoload standards. It also applies the semantic version 2.0.0 specification.


Via Composer

$ composer require slick/telemetry

If you need to use slick/telemetry with version 7.4.x of PHP please do de following

$ composer require slick/telemetry:^1.0


To start using the telemetry logger you will need a PSR-3 implementation that will deliver the information to your preferred log system.
We recommend monolog\monolog package, developed by Jordi Boggiano with one of its handlers. Please visit Monolog project site on GitHub for more information.

To add monolog\monolog to you project run the following:

$ composer require monolog\monolog

Create a telemetry client

With a PSR-3 logger we are now ready to create our client:


namespace App;

use Monolog\Handler\StreamHandler;
use Monolog\Logger;
use Slick\Telemetry\TelemetryClient;

$logger = new Logger('my-app');
    new StreamHandler('path/to/your.log', Logger::INFO)

$telemetryClient = new TelemetryClient($logger);

Register a metric

There are 2 types of metric telemetry: single measurement and pre-aggregated metric. Single measurement is just a name and value. Pre-aggregated metric specifies minimum and maximum value of the metric in the aggregation interval and standard deviation of it.


$telemetryClient->trackMetric("Open processes", 345); // measurement
$telemetryClient->tracMetric("Memory", 89.43, 8, 60.3, 94.323, 5) // Pre-aggregated metric

// adding more context to the measurement
$telemetryClient->trackMetric("Open processes", 345, context: ["region" => "north"]);

Register a dependency

Dependency represents an interaction of the application with a remote component such as SQL or an HTTP endpoint.


// A SQL example of a dependency entry
    "Query user tasks list",
    "select * from tasks where user_id = :uid",
        "database" => "Local MySQL DB",
        "rows" => 23,
        "uid" => 212

Register an exception

Exception represents a handled or unhandled exception that occurred during execution of the monitored application.

// Handled exception
try {
    // faulty code
} catch (\Exception $e) {

// Unhandled exception
function exception_handler($exception) {

throw new Exception('Uncaught Exception');

Register an event

Event telemetry represent an event that occurred in your application. Typically it is a user interaction such as button click or order checkout. It can also be an application life cycle event like initialization or configuration update.

Semantically, events may or may not be correlated to requests. However, if used properly, event telemetry is more important than requests. Events represent business telemetry.

In order to use this telemetry item, you need to create events with slick/event, witch is a required dependency for this library. slick/event is a simple PSR-14 event handling implementation library. We also recommend that event objects should implement the JsonSerializable interface so that the data can be passed as context to the log service.


namespace App;
use Slick\Event\Domain\AbstractEvent;
use Slick\Event\Event as SlickEvent;

 * Event class example
class TaskWasFinished extends AbstractEvent implements SlickEvent, \JsonSerializable
    public function __construct(private int $taskId)
    public function jsonSerializa()
        return ['taskId' => $this->taskId];

// track the event
$telemetryClient->trackEvent(new TaskWasFinished(34));

Register a HTTP request

An HTTP request can be used to register information of a request: path, duration, post data or headers can be registered here.

Single call

    'create user',
Request factory methods

With these methods we can let the telemetry client calculate time and duration for us. This is done by registering the difference between beginRequest() and endRequest() method calls.

Let's see an example:

// front-controller script
$trackableRequest = $telemetryClient->beginRequest('create user', '/users', $_REQUEST);

// front-controller execution code

$telemetryClient->endRequest($trackableRequest, 201);

This code as the same effect as the one make with a single call to TelemetryClient::trackRquest() method

Other features

Message interpolation

In all calls to TelemetryClient::track() or TelemetryClient::log() methods you set placeholders in the message parameter so that they can be replaced by values from the context array. You need to follow these rules:

  • Placeholder names MUST correspond to keys in the context array;
  • Placeholder names MUST be delimited with a single opening brace { and a single closing brace };
  • There MUST NOT be any whitespace between the delimiters and the placeholder name.

    "User {name}, was suspended because {reason}.",
    ["name" => "John Doe", "he had too many login attempts"]

// Resulting message will be:
// User John Doe, was suspended because he had too many login attempts.
Log level override

All methods have a logLevel assign by default. For all the default is LogLevel::INFO except for TrackableException where the default is LogLevel::ERROR.

In addition Dependency and Request can have LogLevel::WARNING if its isSuccessfull property is false.

You can change this log level if you pass the level key to the context parameter:


// Override LogLevel::INFO with LogLevel::WARNING in a metric register
$telemeteryClient->trackMetric('free space', 20, context: ['level' => LogLevel::WARNING]);


We use PHPSpec for unit testing.

# unit tests with phpspec
$ composer test


Please see CONTRIBUTING for details.


If you discover any security related issues, please email instead of using the issue tracker.



The MIT License (MIT). Please see License File for more information.