Unable to Sync Updates on the vCenter due to error "At least one online depot is not accessible"

Products

• VMware vCenter Server

Issue/Introduction

 

• Error on the UI suggests failure in connecting to the online repo hosted on dl.broadcom.com through https .
• Checking the logs on the /var/log/vmware/vmware-updatemgr/vum-server/vmware-vum-server.log  highlights error "At least one online depot is not accessible"
• Connectivity through the proxy can be verified with the below commands that bypass the environment variable for the proxy configuration.
  
  1. curl -vk https://dl.broadcom.com/token/path/.... -x http://proxy.com:port/   # -------->  Shows successful connection
  2. curl -vk https://dl.broadcom.com/token/path/.... -x https://proxy.com:port/ # --------> Shows failed connection. 

Environment

VMware vCenter Server configured with Proxy

Cause

This occurs because vCenter sends HTTPS requests to the proxy server using the HTTPS protocol.
However, although the proxy can forward HTTPS traffic, it expects clients to connect  to it using HTTP and then perform the HTTPS tunnel through it (via the CONNECT method).

This is as per functioning of proxy servers.
Refer article : CONNECT request method - HTTP | MDN

Resolution

1. Start an SSH session to the vCenter Server
2. Run vi /etc/sysconfig/proxy
3. Change the line for https_proxy from https://proxy.com:port/ to http://proxy.com:port/
4. Update the environment variable with command export https_proxy=http://proxy.com:port/