Beyond the UI: Mastering vSphere’s Managed Object Browser

If you are writing scripts for VMware vSphere, simply using the GUI is not an option. To automate properly, you must know the underlying api. The managed object browser (MOB) is a powerful tool for devs and admins. It's effectively a live and interactive map of the vSphere API that allows you to navigate your code structure around the bits and pieces in your virtual environment.

In this guide, we’ll give a brief introduction to the MOB and how you can get to it and use it to make your API development faster.

What is the Managed Object Browser (MOB)?

The Managed Object Browser is an out-of-the-box web server application included in both vCenter Server and ESXi servers. It is really intended to open up the vSphere object model in a browserable, tree-like structure.

In the world of vSphere, everything from a gigantic datacenter all the way down to an individual network interface on a VM is considered a "managed object." The MOB permits you to view these objects in the same way the API does. It’s not only a read-only viewer, but it is also capable of invoking methods and performing actions directly against the server, which can be really handy for testing and validation before writing any PowerCLI or Python!

Accessing the MOB

The browser is easy to access; it's a little different whether you're connecting to vCenter or an individual host. You must be logged in to an account with admin rights.

For vCenter Server

Open your web browser and navigate to:

https://<your_vcenter_ip_or_fqdn>/mob

For ESXi Hosts

Navigate to:

https://<your_esxi_ip_or_fqdn>/mob

Note: Starting with vSphere 6.0, the MOB is disabled by default on ESXi hosts for security reasons. To use it, you must manually enable it in the host's Advanced Settings under Config.HostAgent.plugins.solo.enableMob.

Navigating the MOB

Once logged in, the interface may look sparse, but it is dense with information. The entry point is usually the ServiceInstance, which leads you to the root folder of your environment.

Understanding Managed Objects

Every item you click on is a Managed Object, identified by a unique Managed Object Reference (MoRef) ID (e.g., vm-725). When writing scripts, this ID is how you tell the API exactly which component to act upon.

Methods and Tasks

The MOB separates Properties (information about the object, like a VM’s name) and Methods (things you can do with it).

Methods represent tasks. For instance, a Virtual Machine object has methods like PowerOnVM_Task or CreateSnapshot_Task. When calling these methods in the MOB, you actually make things happen out there.

There are times when debugging API calls is a little abstract. In other ecosystems, developers are concerned about Platform Event Trap, a problem with Salesforce platform events that simply fail or results to an unexpected issue on production. Similarly, in vSphere, you can make API calls, and there's nothing that says, "Hey, this just failed silently." To prevent this ambiguity, you can use the MOB, which will allow you to manually test methods and see their return values on the fly.

Use Cases for vSphere API Development

The MOB is most valuable when bridging the gap between a concept and a working script.

1. Accessing Detailed Information

Standard GUIs often hide advanced configuration details. The MOB exposes raw property values, such as specific hardware device keys or VMX file paths, which are essential for advanced automation scripts.

2. Invoking Methods (Powering Off a VM)

You can test specific operations. To power off a VM:

1. Navigate to the specific VM's page in the MOB.
2. Locate the PowerOffVM_Task method.
3. Click the link and select "Invoke Method."
4. The browser returns a Task object, allowing you to track the success or failure of the command.

3. Asynchronous Task Verification

Developers need to know what can be launched asynchronously if they are optimizing for speed. The MOB allows you to use the available *_Task methods that return a Task object and not block for testing if they match or not.

Below is a table that summarizes the release of certain async methods in the vSphere Web Services API, which may help you correlate compatibility with your environment.

Method Name

Associated Managed Object

Version Introduced

ConfigureVFlashResourceEx_Task

HostVFlashManager

vSphere 5.5

AttachScsiLunEx_Task

HostStorageSystem

vSphere 6.0

CreateSecondaryVMEx_Task

VirtualMachine

vSphere 6.0

MarkPerenniallyReservedEx_Task

HostStorageSystem

vSphere 6.7.2

DeleteVStorageObjectEx_Task

VcenterVStorageObjectManager

vSphere 7.0.2.0

Next Steps for Developers

The MOB is much more than a troubleshooting tool; it's an essential learning aid. As a visual representation of the API structure itself, there is that duck/tedious trial-and-error from scripting.

The next time you cannot figure out what property path to use in a PowerCLI script or need to figure out why that one API call fails, just open the MOB. It gives you the visibility to create better and more efficient automation for your infrastructure.