ERROR UpgradeRunner Unable to login to vCenter Server

Products

• VMware vCenter Server 8.0

Issue/Introduction

Failed to upgrade vCenter from 7.xto 8.x

1) While trying to upgrade vCenter from 7.x to 8.x

2) You have successfully deployed appliance at stage 1 and on stage 2 you have successfully passed all prechecks.

vCenter server upgrade fails at step 1, it fails with generic error.

 

3) Post checking the logs of new vcenter appliance /var/log/vmware/upgrade/upgraderunner.log we get below entries.

2025-05-09T08:57:29.911Z ERROR bindings.vc_binding Cannot connect to vCenter Server https://127.0.0.1:443 Reason: 503 Service Unavailable

2025-05-09T08:57:29.913Z ERROR UpgradeRunner Unable to login to vCenter Server.

 

4) At same time we check vpxd logs of source vCenter server and you find below entries.

2025-05-09T08:57:29.842Z error vpxd[07112] [Originator@6876 sub=HTTP session map] Out of HTTP sessions: Limited to 2000

2025-05-09T08:57:29.912Z error vpxd[07473] [Originator@6876 sub=HTTP session map] Out of HTTP sessions: Limited to 2000

 

Environment

vCenter Server 7.0 U2

vCenter Server 7.0 U3

Cause

This issue happens when new vCenter server is not able to create session with source vCenter due as session count are exhausted.

There are multiple reasons why session counts are exhausted.

 

Resolution

In order to fix the issue, please try reducing the session counts of source vCenter.

For more information regarding out of http sessions issue and how to mitigate it, please follow the article 

Could not connect to one or more vCenter Server Systems: https://<vCenter-FQDN>: 443/sdk" error in the vSphere Client due to VPXD session exhaust