README

This is a read-only subtree split of https://github.com/open-telemetry/opentelemetry-php-contrib.

OpenTelemetry Monolog handler

A monolog handler for OpenTelemetry. See https://opentelemetry.io/docs/instrumentation/php/manual/#logs for further documentation.

Requirements

API + SDK

This package depends on the OpenTelemetry API, but a configured OpenTelemetry SDK should also be provided.

Exporter

Usually logs are exported to a receiver via the otlp protocol in the protobuf format, via http or gRPC.

This requires:

a protobuf implementation; either the protobuf extension or the google/protobuf package
the open-telemetry/exporter-otlp package
the open-telemetry/transport-grpc package, if using gRPC transport
a PSR-7 and PSR-18 implementation, if using HTTP transport

Receiver

Logs must be emitted to a receiver/system that understands the OpenTelemetry protocol, such as the OpenTelemetry collector.

Installation

composer require open-telemetry/opentelemetry-logger-monolog

Usage

The OpenTelemetry handler, configured with an OpenTelemetry LoggerProvider, is used to send Monolog LogRecords to OpenTelemetry.

The LoggerProvider can be configured in a number of ways: manually, via an SDK Builder, or automatically (using environment/php.ini variables).

Manual configuration

Set up an SDK LoggerProvider and pass it to the handler:

$loggerProvider = new \OpenTelemetry\SDK\Logs\LoggerProvider(/* params */);
$handler = new \OpenTelemetry\Contrib\Logs\Monolog\Handler(
    $loggerProvider,
    'info',
    true,
);

Automatic configuration

If you use OpenTelemetry SDK autoloading, you can retrieve the global logger provider. That may be a no-op implementation if there was any misconfiguration.

See autoload-sdk example for how to use autoloading with the OpenTelemetry SDK.

Create a Logger

Finally, add the handler to a Monolog logger:

$logger = new \Monolog\Logger(
    'name',
    [$handler],
);
$logger->info('hello world');

Attributes Mode

This OpenTelemetry handler will convert any context array or extra array in the Monolog\LogRecord to OpenTelemetry\API\Logs\LogRecord attributes. There are two options for handling conflicts between the classes.

Note 1: Exceptions have special handling in both the PSR-3 spec and the OpenTelemetry spec. If a PHP Throwable is included in the context array with a key of exception, it will be added as exception. attributes to the OpenTelemetry Log Record.

Note 2: Both Monolog and the OpenTelemetry Protocol employ serialization algorithms when encoding attributes. This combination can lead to obtuse JSON blobs in the OTLP log records; this can be avoided by using only scalar values for attributes.

By default, the attribute keys will be context and extra, along with context. and extra. prefixed keys with the individual array entries. Example:

$host = new stdClass();
$host->name = 'example.com';
$host->tcp = 80;
new Monolog\LogRecord(
    ...,
    context: [
        'foo' => 'bar',
        'baz' => 'bat',
    ],
    extra: [
        'host' => $host,
    ]
);

/**
 * becomes:
 *
 * OpenTelemetry\API\Logs\LogRecord (
 *     ...,
 *     attributes => array (
 *         context => array (
 *             foo => 'bar',
 *             baz => 'bat',
 *         )
 *         context.foo => 'bar'
 *         context.baz => 'bat'
 *         extra => array (
 *             host => array (
 *                 stdClass => array (
 *                     name => 'example.com'
 *                     tcp => 80
 *                 )
 *             )
 *         )
 *         extra.host => stdClass (
 *             name => 'example.com'
 *             tcp => 80
 *         )
 *     )
 * )
 */

Alternatively, if your context and extra keys do not conflict with OpenTelemetry Semantic Conventions for Attribute keys, you can set OTEL_PHP_MONOLOG_ATTRIB_MODE=otel and they will be sent directly as Attributes. Example:

new Monolog\LogRecord(
    ...,
    context: [
        'myapp.data.foo' => 'bar',
        'myapp.data.baz' => 'bat',
    ],
    extra: [
        'server.address' => 'example.com',
        'server.port' => 80,
    ]
);

/**
 * becomes:
 *
 * OpenTelemetry\API\Logs\LogRecord (
 *     ...,
 *     attributes => array (
 *         myapp.data.foo => 'bar'
 *         myapp.data.baz => 'bat'
 *         server.address => 'example.com'
 *         server.port => 80
 *      )
 * )
 */

open-telemetry / opentelemetry-logger-monolog

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