MongoDBClient-addSubscriber.txt

================================
MongoDB\\Client::addSubscriber()
================================

.. versionadded:: 1.18


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Definition
----------

.. phpmethod:: MongoDB\Client::addSubscriber()

   Registers a monitoring event subscriber with this Client. The subscriber
   will be notified of all events for this Client.

   .. code-block:: php

      function addSubscriber(MongoDB\Driver\Monitoring\Subscriber $subscriber): void

Parameters
----------

``$subscriber`` : :php:`MongoDB\Driver\Monitoring\Subscriber <class.mongodb-driver-monitoring-subscriber>`
  A monitoring event subscriber to register with this Client.

Errors/Exceptions
-----------------

.. include:: /includes/extracts/error-invalidargumentexception.rst

:php:`MongoDB\Driver\Exception\InvalidArgumentException <mongodb-driver-exception-invalidargumentexception>`
if subscriber is a :php:`MongoDB\Driver\Monitoring\LogSubscriber <class.mongodb-driver-monitoring-logsubscriber>`,
since loggers can only be registered globally with
:php:`MongoDB\Driver\Monitoring\addSubscriber <function.mongodb.driver.monitoring.addsubscriber>`.

Behavior
--------

If ``$subscriber`` is already registered with this Client, this function is a
no-op. If ``$subscriber`` is also registered globally, it will still only be
notified once of each event for this Client.

Example
-------

Create a :php:`MongoDB\Driver\Monitoring\CommandSubscriber <manual/en/class.mongodb-driver-monitoring-commandsubscriber>`
that logs all events:

.. code-block:: php

    <?php

    use MongoDB\Driver\Monitoring\CommandSubscriber;
    use MongoDB\Driver\Monitoring\CommandStartedEvent;
    use MongoDB\Driver\Monitoring\CommandSucceededEvent;
    use MongoDB\Driver\Monitoring\CommandFailedEvent;

    class LogCommandSubscriber implements CommandSubscriber
    {
        private $stream;
        public function __construct($stream)
        {
            $this->stream = $stream;
        }

        public function commandStarted(CommandStartedEvent $event): void
        {
            fwrite($this->stream, sprintf(
                'Started command #%d "%s": %s%s',
                $event->getRequestId(),
                $event->getCommandName(),
                Document::fromPHP($event->getCommand())->toCanonicalExtendedJSON(),
                PHP_EOL,
            ));
        }

        public function commandSucceeded(CommandSucceededEvent $event): void
        {
            fwrite($this->stream, sprintf(
                'Succeeded command #%d "%s" in %d microseconds: %s%s',
                $event->getRequestId(),
                $event->getCommandName(),
                $event->getDurationMicros(),
                json_encode($event->getReply()),
                PHP_EOL,
            ));
        }

        public function commandFailed(CommandFailedEvent $event): void
        {
            fwrite($this->stream, sprintf(
                'Failed command #%d "%s" in %d microseconds: %s%s',
                $event->getRequestId(),
                $event->getCommandName(),
                $event->getDurationMicros(),
                $event->getError()->getMessage(),
                PHP_EOL,
            ));
        }
    }

The subscriber can then be registered with a Client:

.. code-block:: php

    <?php

    $client = new MongoDB\Client();
    $subscriber = new LogCommandSubscriber(STDERR);

    $client->addSubscriber($subscriber);

    $client->test->users->insertOne(['username' => 'alice']);

The above code will write the following to stderr output:

.. code-block:: text

    Started command #1 "insert": { "insert" : "users", "ordered" : true, "$db" : "test", "lsid" : { "id" : { "$binary" : { "base64" : "dKTBhZD7Qvi0vUhvR58mCA==", "subType" : "04" } } }, "documents" : [ { "username" : "alice", "_id" : { "$oid" : "655d1fca12e81018340a4fc2" } } ] }
    Succeeded command #1 "insert" in 876 microseconds: {"n":1,"ok":1}

See Also
--------

- :phpmethod:`MongoDB\Client::removeSubscriber()`
- :php:`Application Performance Monitoring (APM) <manual/en/mongodb.tutorial.apm>`
- :php:`MongoDB\Driver\Manager::addSubscriber() <manual/en/mongodb-driver-manager.addsubscriber>`
- :php:`MongoDB\Driver\Monitoring\CommandSubscriber <manual/en/class.mongodb-driver-monitoring-commandsubscriber>`