> For the complete documentation index, see [llms.txt](https://documentation.dnanexus.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://documentation.dnanexus.com/user/spark/apollo-apps.md).

# Apollo Apps

## Spark Applications

{% hint style="info" %}
A license is required to access Spark functionality on the DNAnexus Platform. [Contact DNAnexus Sales](mailto:sales@dnanexus.com) for more information.
{% endhint %}

The Spark application is an extension of the current app(let) framework. App(let)s have a [specification](/developer/apps/io-and-run-specifications.md) for their VM (instance type, OS, packages). This has been extended to allow for an additional optional [cluster specification](/developer/apps/developing-spark-apps.md#cluster-specifications) with `type=dxspark`.

* Calling `/app-xxxx/run` or `/applet-xxxx/run` for Spark apps creates a Spark cluster (+ master VM).
* The master VM (where the app shell code runs) acts as the driver node for Spark.
* Code in the master VM uses the Spark infrastructure.
* Job mechanisms (monitoring, termination, and management) are the same for Spark apps as for any other regular app(let)s on the Platform.
* Spark apps use the same platform `dx` communication between the master VM and DNAnexus API servers.
* You can use the log collection [mechanism](/developer/apps/developing-spark-apps.md#collecting-cluster-logs) to collect logs from all nodes.
* You can use the [Spark UI](/developer/apps/developing-spark-apps.md#monitoring-the-spark-ui) to monitor a running job using ssh tunneling.

Spark apps can be launched over a distributed Spark cluster.


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