Knowledge Base

Troubleshooting Composer for VMware Horizon View

***UPDATE: We just published a great troubleshooting KB article for Composer that covers a lot of the common issues customers encounter here.

At some point, every View administrator who uses a linked clone pool is going to need to do some troubleshooting. Most linked clone troubleshooting involves a component called Composer.
What is composer, and what does it do?
Composer is an add-on for VMware Horizon View and is used to build linked clone desktops. Details about linked clones and Composer operations can be found in my previous posts, What is a linked clone? and part II of that topic.

Today we will focus on troubleshooting Composer when it breaks.

We are in the process of compiling a KB which will serve as the go-to article for Composer. This will contain links to important KBs, common issues, and procedures for repair. In the meantime, I thought this tactic would be good to share.


Compatibility is more important than many admins realize. VMware builds, tests, certifies and supports components that are built to work together.

The Connection Server talks to:

  • Composer
  • View Agent
  • vCenter
  • Security Server
  • and the clients

Composer in turn, talks to:

  • vCenter,
  • Connection Server
  • The hosts
  • Active Directory
  • The guest OS

As you can imagine, it’s easy for problems to balloon out of control if a component doesn’t talk properly to another. So, you need to ensure that every component is compatible and is designed to work with every other.

Here’s how-

Identifying where a problem exists is the first step to solving it. Composer can be nonfunctional because of factors that are entirely outside of Composer itself. For example, View doesn’t build desktops, that step is done by vCenter through API calls. If you are trying to build desktops and nothing is happening, it doesn’t mean View or Composer are at fault. vCenter needs to be fully functioning properly for View to be able to provision desktops. Along the same lines, Composer needs to be able to talk to all of the hosts in a cluster plus your Active Directory to be able to customize VMs, so if you have a dead host, Composer will fail.

Is Composer at fault then if it doesn’t work? Well, what about the guest VM? Does it get an IP address? Does it boot? If the answer to any of these is no, then Composer can’t do its job.

One of the tactics I take when Composer fails is to manually step though all of the processes involved.

  • Can I clone the base image?
  • Can I change customize it?
  • Can I activate it?
  • Is it network accessible?

If the answer to any of these questions is no, the problem is outside of Composer. Understanding where the linked clone process fails is the key to resolving problems.


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