DOCSP-17837 logging page update (#224)

* updated logging page

Author: kyuan-mongodb

source/fundamentals/logging.txt

@@ -10,216 +10,21 @@ Logging
    :depth: 1
    :class: singlecols
 
-Overview
---------
+.. important::
 
-This guide shows you how to configure the driver logger which is responsible
-for reporting events that occur while your application is running. You can
-set the logger level, specify logging settings for individual classes, and
-provide a custom logger implementation.
+  The driver doesn't use the logger in this version. Attempting to use
+  prior settings in this version won't print anything. Instead, see our
+  :doc:`command monitoring guide <monitoring/command-monitoring>`. 
 
-You should read this guide if you need to customize the default behavior of the
-driver logger or want to explore the information provided by the logger.
+Temporary Alternative
+---------------------
 
-Log Levels
-----------
+The Node.js team is currently working on rewriting the logger. In the
+meantime, you can output monitor events using the following snippet:
 
-You can configure the driver to report logger messages at three different
-levels as shown in the following table.
+.. code-block:: javascript
 
-.. list-table::
-   :widths: 25 75
-   :header-rows: 1
-
-   * - Logger Level
-     - Description
-
-   * - ``debug``
-     - The most verbose logger level which shows all logger messages reported
-       by the driver including those reported in the ``info`` and ``error``
-       levels.
-
-   * - ``info``
-     - Include informational messages reported by the driver including those
-       reported in the ``error`` level.
-
-   * - ``error``
-     - Only include error messages reported by the driver. This is the default
-       setting.
-
-The following example demonstrates how to set the logger to the ``debug``
-level:
-
-.. literalinclude:: /code-snippets/logging/levels.js
-   :language: javascript
-   :start-after: begin-ex
-   :end-before: end-ex
-
-This snippet should output a few lines of logging information that
-resemble the following:
-
-.. code-block:: none
-
-   [DEBUG-Db:63846] 1585699200000 executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}] {
-     type: 'debug',
-     message: 'executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}]',
-     className: 'Db',
-     ...,
-   }
-   [DEBUG-Server:63846] 1585699200000 executing command [{"ns":"sample_mflix.$cmd","cmd":{"isMaster":true},"options":{}}] against myClusterHostname:27017:27017 {
-     ...
-   }
-   [DEBUG-Server:63846] 11585699200000 executing command
-   [{"ns":"admin.$cmd","cmd":{"endSessions":[{"id":"DQLUQ1/LRKOYMy2CD13iLQ=="}]},"options":{}}] against myClusterHostname:27017 {
-     ...
-   }
-
-
-Filter on a Specific Class
---------------------------
-
-You can set the Logger to only produce log messages generated by specific
-classes by defining a filter on it. The following example demonstrates how to
-apply a filter to log messages from the ``Db`` class only.
-
-.. code-block:: js
-
-     // Set debug level
-     Logger.setLevel("debug");
-
-     // Only log statements on "Db" class
-     Logger.filter("class", ["Db"]);
-
-     const db = client.db("sample_mflix");
-
-     // Execute command { isMaster: true } against db
-     await db.command({ isMaster: true });
-   }
-
-The logger output of the code above is similar to the prior example, but
-excludes logging from classes other than ``Db`` such as ``Server`` and
-resembles the following:
-
-.. code-block:: none
-
-   [DEBUG-Db:63846] 1585699200000 executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}] {
-     type: 'debug',
-     message: 'executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}]',
-     className: 'Db',
-     ...
-
-You can specify any number of the following driver classes in the logging
-filter array to control what information is passed to the Logger:
-
-.. list-table::
-   :widths: 25 75
-   :header-rows: 1
-
-   * - Class name
-     - Description
-
-   * - ``Db``
-     - Information related to calls on a db instance
-
-   * - ``Server``
-     - Information related to a server instance (standalone instance,
-       ``mongos`` instance, or replica set member).
-
-   * - ``ReplSet``
-     - Information related to a replica set.
-
-   * - ``Mongos``
-     - Information related to a ``mongos`` instance.
-
-   * - ``Cursor``
-     - Information related to a cursor.
-
-   * - ``Pool``
-     - Information related to a connection pool.
-
-   * - ``Connection``
-     - Information related to a single-instance connection.
-
-   * - ``Ping``
-     - Information related to a replica set ping operation.
-
-You can add your own classes to the logger by creating your own logger
-instances as shown in the following sample code.
-
-.. code-block:: js
-
-   const { Logger } = require("mongodb");
-
-   class A {
-     constructor() {
-       this.logger = new Logger("A");
-     }
-
-     doSomething() {
-       if (this.logger.isInfo()) {
-         this.logger.info("logging A", {});
-       }
-     }
-   }
-
-   // Execute A to produce logging messages
-   const a = new A();
-   a.doSomething();
-
-The logging message is triggered when ``doSomething()`` is called and is
-presented in the following format:
-
-.. code-block:: none
-
-   [INFO-A:65156] 1585699200000 logging A {
-     type: 'info',
-     message: 'logging A',
-     className: 'A',
-     ...
-   }
-
-
-Custom Logger
--------------
-
-You can configure the behavior and format of the messages reported by the
-logger by passing in a **logger callback function** which allows you
-to access and modify the message and metadata of the logger message.
-
-The following example demonstrates how to define a logger callback
-function and add custom logic to it.
-
-.. code-block:: js
-
-   // Set debug level
-   Logger.setLevel("debug");
-
-   // Set our own logger
-   Logger.setCurrentLogger((msg, context) => {
-     // Add your custom logic here
-     context['foo'] = 'bar';
-     msg = "Hello, World! " + msg;
-
-     console.log(msg, context);
-   });
-
-   const db = client.db("sample_mflix");
-
-   // Run a command to produce logger messages
-   await db.command({ isMaster: true });
-
-The code example above adds additional information in the callback function.
-The output of the example resembles the following:
-
-.. code-block:: none
-
-   Hello, World! [DEBUG-Db:65873] 1585699200000 executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}] {
-     type: 'debug',
-     message: 'executing command {"isMaster":true} against sample_mflix.$cmd with options [{"readPreference":{"mode":"primary"}}]',
-     className: 'Db',
-     foo: 'bar',
-     ...
-   }
-
-For more information on the methods available on the ``Logger``, see the
-:node-api-4.0:`Logger API documentation </classes/logger.html>`.
+  const client = new MongoClient(CONNECTION_STRING, { monitorCommands:true });
+  client.on('commandStarted', (event) => console.debug(event));
+  client.on('commandSucceeded', (event) => console.debug(event));
+  client.on('commandFailed', (event) => console.debug(event));