Add docs for the Fabric WandbLogger hosted in the wandb SDK (#19451)

Co-authored-by: awaelchli <aedu.waelchli@gmail.com>

docs/source-fabric/api/loggers.rst

@@ -18,3 +18,14 @@ Loggers
     Logger
     CSVLogger
     TensorBoardLogger
+
+
+Third-party Loggers
+^^^^^^^^^^^^^^^^^^^
+
+.. list-table::
+   :widths: 50 50
+   :header-rows: 0
+
+   * - :doc:`WandbLogger <../guide/loggers/wandb>`
+     - Log to `Weights & Biases <https://www.wandb.ai/>`_.

docs/source-fabric/glossary/index.rst

@@ -7,6 +7,7 @@ Glossary
    :hidden:
 
    Checkpoint <../guide/checkpoint/index>
+   Weights and Biases <../guide/loggers/wandb>
 
 
 .. raw:: html
@@ -204,6 +205,11 @@ Glossary
     :button_link: ../guide/trainer_template.html
     :col_css: col-md-4
 
+.. displayitem::
+    :header: Weights and Biases
+    :button_link: ../guide/loggers/wandb.html
+    :col_css: col-md-4
+
 .. displayitem::
     :header: 16-bit, 8-bit, 4-bit
     :button_link: ../fundamentals/precision.html

docs/source-fabric/guide/loggers/wandb.rst

@@ -0,0 +1,120 @@
+##################
+Weights and Biases
+##################
+
+`Weights & Biases (W&B) <https://wandb.ai>`_  allows machine learning practitioners to track experiments, visualize data, and share insights with a few lines of code.
+
+It integrates seamlessly with your Lightning ML workflows to log metrics, output visualizations, and manage artifacts.
+This integration provides a simple way to log metrics and artifacts from your Fabric training loop to W&B via the ``WandbLogger``.
+The ``WandbLogger`` also supports all features of the Weights and Biases library, such as logging rich media (image, audio, video), artifacts, hyperparameters, tables, custom visualizations, and more.
+`Check the official documentation here <https://docs.wandb.ai>`_.
+
+
+----
+
+
+*************************
+Set Up Weights and Biases
+*************************
+
+First, you need to install the ``wandb`` package:
+
+.. code-block:: bash
+
+    pip install wandb
+
+Then log in with your API key found in your W&B account settings:
+
+.. code-block:: bash
+
+    wandb login <your-api-key>
+
+
+You are all set and can start logging your metrics to Weights and Biases.
+
+
+----
+
+
+*************
+Track metrics
+*************
+
+To start tracking metrics in your training loop, import the WandbLogger and configure it with your settings:
+
+.. code-block:: python
+
+    from lightning.fabric import Fabric
+
+    # 1. Import the WandbLogger
+    from wandb.integration.lightning.fabric import WandbLogger
+
+    # 2. Configure the logger
+    logger = WandbLogger(project="my-project")
+
+    # 3. Pass it to Fabric
+    fabric = Fabric(loggers=logger)
+
+
+Next, add :meth:`~lightning.fabric.fabric.Fabric.log` calls in your code.
+
+.. code-block:: python
+
+    value = ...  # Python scalar or tensor scalar
+    fabric.log("some_value", value)
+
+
+To log multiple metrics at once, use :meth:`~lightning.fabric.fabric.Fabric.log_dict`:
+
+.. code-block:: python
+
+    values = {"loss": loss, "acc": acc, "other": other}
+    fabric.log_dict(values)
+
+
+----
+
+
+**************************************************
+Logging media, artifacts, hyperparameters and more
+**************************************************
+
+With ``WandbLogger`` you can also log images, text, tables, checkpoints, hyperparameters and more.
+For a description of all features, check out the official Weights and Biases documentation and examples.
+
+
+.. raw:: html
+
+    <div class="display-card-container">
+        <div class="row">
+
+.. displayitem::
+    :header: Official WandbLogger Lightning and Fabric Documentation
+    :description: Learn about all features from Weights and Biases
+    :button_link: https://docs.wandb.ai/guides/integrations/lightning
+    :col_css: col-md-4
+    :height: 150
+
+.. displayitem::
+    :header: Fabric WandbLogger Example
+    :description: Official example of how to use the WandbLogger with Fabric
+    :button_link: https://colab.research.google.com/github/wandb/examples/blob/master/colabs/pytorch-lightning/Track_PyTorch_Lightning_with_Fabric_and_Wandb.ipynb
+    :col_css: col-md-4
+    :height: 150
+
+.. displayitem::
+    :header: Lightning WandbLogger Example
+    :description: Official example of how to use the WandbLogger with Lightning
+    :button_link: wandb.me/lightning
+    :col_css: col-md-4
+    :height: 150
+
+
+.. raw:: html
+
+        </div>
+    </div>
+
+
+|
+|

docs/source-fabric/guide/logging.rst

@@ -32,10 +32,11 @@ To track a metric, add the following:
     fabric = Fabric(loggers=logger)
 
 
-Built-in loggers you can choose from:
+Loggers you can choose from:
 
 - :class:`~lightning.fabric.loggers.TensorBoardLogger`
 - :class:`~lightning.fabric.loggers.CSVLogger`
+- :doc:`WandbLogger <loggers/wandb>`
 
 |