Enabling vSAN File Service Active Directory integration fails with "Exception caught when running preflight check"

Products

• VMware vSAN

Issue/Introduction

• When attempting to configure Active Directory integration during vSAN File Service enablement, the process fails at the "Edit Domain" wizard.

• The vSphere Client UI displays the following error message:

  Failed to check domain configuration: Exception caught when running preflight check on file server.

• Reviewing the vsanmgmt.log (/var/log/vsanmgmt.log) on the ESXi hosts reveals a thread collision error referencing a specific Domain Controller hostname:

  Er(11) vsand[9257274]: [opID=agw...] Exception caught when running preflight check on file server. In(14) vsand[9257274]: [opID=agw...] PRECHECK: Caught unexpected error: Thread name dc01.example.com-A already exists In(14) vsand[9257274]: [opID=agw...] PRECHECK: PRECHECKOUTPUT: {"error": "Thread name dc01.example.com-A already exists"}

• Querying the Active Directory domain for LDAP SRV records (_ldap._tcp.<domain>) returns multiple, duplicate entries for the exact same Domain Controller hostname. Example:

   

  $ dig SRV _ldap._tcp.example.com
  _ldap._tcp.example.com. 600 IN SRV 0 75 389 dc01.example.com.
  _ldap._tcp.example.com. 600 IN SRV 0 100 389 dc01.example.com.

Environment

VMware vSAN 8.x
VMware vSAN File Services

Cause

This issue occurs due to a code limitation in the vSAN File Service validation script (precheck.py) regarding how it handles duplicate DNS SRV records.

During the Active Directory configuration, the preflight check queries DNS for _ldap._tcp.<domain> SRV records to discover Domain Controllers. If the DNS environment returns multiple records for the exact same Domain Controller (e.g., duplicated records with different weights/priorities), the Python script fails to deduplicate the array of target hostnames.

The script iterates through the list and attempts to spawn a background validation thread for each record. When it encounters the duplicate entry, it attempts to spawn a second, concurrent thread using the exact same name (e.g., dc01.example.com-A). Python rejects this and throws the Thread name ... already exists exception, immediately crashing the preflight check and failing the wizard.

Resolution

Broadcom Engineering has identified a fix for this issue, which will be available in a future release.

If you encounter this issue, please contact Broadcom Support for assistance and reference this KB article. For instructions on how to open a support case, please review the following guide: How to create and manage support cases with Broadcom Support