Add hybrid workflow documentation for Azure (#5361) [ci skip]

Signed-off-by: adamrtalbot <[email protected]>
Signed-off-by: Adam Talbot <[email protected]>
Signed-off-by: Paolo Di Tommaso <[email protected]>
Co-authored-by: Christopher Hakkaart <[email protected]>
Co-authored-by: Paolo Di Tommaso <[email protected]>

docs/azure.md

@@ -405,6 +405,50 @@ The value of the setting must be the identifier of a subnet available in the vir
 Batch Authentication with Shared Keys does not allow to link external resources (like Virtual Networks) to the pool. Therefore, Active Directory Authentication must be used in conjunction with the `virtualNetwork` setting.
 :::
 
+### Hybrid workloads
+
+Nextflow allows the use of multiple executors in the same workflow application. This feature lets you deploy hybrid workloads, where some jobs run on the local computer or local computing cluster, while others are offloaded to Azure Batch.
+
+To enable this feature, configure one or more {ref}`config-process-selectors` in your Nextflow configuration to apply the Azure Batch settings to the processes you want to offload. For example:
+
+```groovy
+process {
+    withLabel: bigTask {
+        executor = 'azurebatch'
+        queue = 'my-batch-pool'
+        container = 'my/image:tag'
+    }
+}
+
+azure {
+    storage {
+        accountName = '<YOUR STORAGE ACCOUNT NAME>'
+        accountKey = '<YOUR STORAGE ACCOUNT KEY>'
+    }
+    batch {
+        location = '<YOUR LOCATION>'
+        accountName = '<YOUR BATCH ACCOUNT NAME>'
+        accountKey = '<YOUR BATCH ACCOUNT KEY>'
+    }
+}
+```
+
+With the above configuration, processes with the bigTask {ref}`process-label` run on Azure Batch, while the remaining processes run on the local computer.
+
+Next, launch the pipeline with the `-bucket-dir` option to specify an Azure Blob Storage path for the jobs running on Azure Batch, and optionally, use the `-work-dir` option to specify local storage for the jobs running locally:
+
+```bash
+nextflow run <script or project name> -bucket-dir az://my-container/some/path
+```
+
+:::{warning}
+The Azure Blob Storage path needs to contain at least one sub-directory (e.g. `az://my-container/work` rather than `az://my-container`).
+:::
+
+:::{tip}
+When using [Fusion](./fusion.md), the `-bucket-dir` option is not required. Fusion implements a distributed virtual file system that allows seamless access to Azure Blob Storage using a standard POSIX interface, enabling direct mounting of remote blob storage as if it were a local file system. This simplifies and speeds up most operations, bridging the gap between cloud-native storage and data analysis workflows.
+:::
+
 ## Microsoft Entra
 
 Using Microsoft Entra for role-based access control is more secure than using access keys and should be used wherever possible. You can authenticate to Azure Entra using a Managed Identity when running on resources within the Azure environment, or by authenticating as an Azure Service Principal when running on external resources.