Introduction¶

Altair SLC Hub and Altair Analytics Workbench™ can make various parts of the filesystem of the Altair SLC Hub server node and the Altair SLC Hub worker nodes available to users of the Altair Analytics Workbench™. There are a number of related concepts and configuration to understand to make effective use of these facilities.

Shared Filesystem¶

Altair SLC Hub allows workloads to be run on a pool of worker machines. Typically a workload will need to access some file based resources such as data files, or program source files. Since the workload can be run on any of the workers in the pool those file resources need to be accessed in a consistent way regardless of the worker that the workload is run on. This means that those file resources need to be on a shared filesystem that was mounted into each worker node in the same way.

In the case of Altair Analytics Workbench™ Workflows, different nodes of a workflow might be executed on different Altair SLC Hub worker nodes. In order to be able to share intermediate result files between nodes in the Workflow, those intermediate result files need to be stored on a location in the shared network filesystem so that they can be accessed by subsequent Workflow nodes, regardless of which Altair SLC Hub worker node those workflow nodes are run on.

WebDAV Servers¶

Altair SLC Hub has a built-in WebDAV server running on the server node. The intent of this WebDAV server is to make one or more shared filesystem locations to users of Altair Analytics Workbench. For example, typically the "/home" directory would be made available, along with any shared file systems that might be mounted into the worker machines.

Note

This functionality is available when the Altair SLC Hub server is running on a Linux platforms.

Normal filesystem access control is used to govern access to the file system locations that are made available. Files are accessed as the user configured in the UNIX User Name field of the Hub user.

In addition, each link session also has a WebDAV server. This will give access to the complete filesystem of the worker on which the link session is running. Access to the filesystem is performed by the link session executable, and access is governed by standard filesystem access control based on the user account under which that link session is running. This functionality is available on all platforms, not just Linux.

Directory Shortcuts¶

On top of the underlying WebDAV servers, there is a configurable set of Directory Shortcuts defining a view of those file systems that are then made available to the users of Altair Analytics Workbench. That is, the directory shortcuts are a set of named locations within the locations made available by the WebDAV server. Configuring a directory shortcut on its own will not make the directory available via WebDAV, the directory shortcuts can only link to locations that are already available via the WebDAV servers.

For example, the Altair SLC Hub WebDAV server may make the /home directory available over WebDAV, but Altair Analytics Workbench may be configured to only make /home/{username} visible to the user so that each user can see their own home directory.

Typically some of those directory shortcuts will make use of certain substitution variables, for example ${userId} or ${homeDirectory}.

Configuration¶

Altair SLC Hub WebDAV Server¶

The list of filesystem locations that are made available is configured using the webdav.rootPaths configuration setting in Altair SLC Hub. Only the paths listed in the webdav.rootPaths configuration setting are available over WebDAV, no other parts of the filesystem are available.

Altair Analytics Workbench Directory Shortcuts¶

The list of directory shortcuts that Altair Analytics Workbench provides is configured by the workbench.directoryShortcuts configuration setting.

The list of directory shortcuts that an individual link session provides is governed by configuration on the execution profile used to launch the link session. Different link sessions might be launched with different execution profiles, so different views of the worker filesystem might be available from different link sessions. In addition, since each link session might be running on a different worker machine, the filesystem exposed via each link session might be different.

Typically the directory shortcuts for an individual link session would be configured to include the complete root filesystem, plus shortcuts for commonly used locations such as /home. Since the programs run by SLC have access to the complete filesystem, a program could read from or write to files in any location, subject to normal filesystem access control restrictions. It is therefore convenient to be able to access any filesystem location through Altair Analytics Workbench so that any files that are written or read by the programs can be easily viewed or edited through Altair Analytics Workbench. However, individual installation circumstances would govern which shortcuts are appropriate to provide.

Altair Analytics Workbench Workflow Intermediate Files Location¶

As mentioned above, Altair Analytics Workbench Workflow requires that there be a shared filesystem available to all workers that might be used for running Altair Analytics Workbench Workflows so that intermediate result files can be shared between nodes of a workflow, with those nodes potentially being run by SLC engines running on different worker nodes. The location of that intermediate files location is part of the configuration of an execution profile.

Path Substitutions¶

There are a few variable substitutions that can be used in the configuration of the directory shortcuts.

Variable	Value	Example
`${userId}`	The Hub user name	FinanceUser
`${homeDirectory}`	The UNIX home directory property for the Hub user	/home/finance
`${homeDirectorySuffix}`	The last part of the Hub user UNIX home directory property	finance

Example¶

In an example configuration there might be a number of shared file systems. There might be one containing the users home directories, and there might be one containing shared resources such as program source files. Assume that these are mounted equally into the Altair SLC Hub worker nodes and the Altair SLC Hub server node, using paths of /home and /sources respectively.

The Altair SLC Hub webdav.rootPaths configuration option would be set to include both /home and and /sources:

    webdav:
      rootPaths:
        - /home
        - /sources

In order that these filesystem locations are available to users of the Altair Analytics Workbench the Altair SLC Hub workbench.directoryShortcuts configuration option might be set as follows:

workbench:
  directoryShortcuts:
    - name: Home
      path: /home/${userId}
    - name: Sources
      path: /sources

Here, note that the directory shortcuts have a name, and also that the directory shortcut for "Home" includes a path substitution variable so that the shortcut is to the relevant home directory. If a path of / is used as a location, then all WebDAV root paths are shown under that directory shortcut, it does not show the complete filesystem of the Altair SLC Hub server node.

An execution profile would then be created and configured such that the Intermediate files directory was set to, for example, /home/${userId}/workflowIntermediateFiles/. Also within the execution profile, directory shortcuts might be created for /home/${userId} and /.

Recap¶

To recap:

Altair SLC Hub exposes certain filesystem locations over WebDAV from the main server node. The list of locations exposed is configured by the webdav.rootPaths configuration setting. Typically, the locations exposed would be shared file systems that are mounted into both the Altair SLC Hub server node and all of the Altair SLC Hub worker nodes.
Altair Analytics Workbench gives access to a subset of those filesystem locations in the file explorer view in the form of a set of directory shortcuts. The list of directory shortcuts is governed by the workbench.directoryShortcuts configuration setting.
Each link session exposes all of the filesystem of the worker on which it is running, subject to standard operating system access control.
Altair Analytics Workbench gives access to a subset of those filesystem locations in the file explorer view in the form of a set of directory shortcuts. The list of directory shortcuts is governed by the "Directory Shortcuts" in the execution profile used to launch the link session.