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"503 Service Unavailable" error on the vSphere Web Client when logging in or accessing the vCenter Server

  Symptoms

  • Logging in to the vCenter Server or vCenter Server appliance (VCSA) using the vSphere Web Client fails.
  • Accessing the vCenter Server or vCenter Server appliance using the vSphere Web Client fails.
  • You see these errors similar to:

    503 Service Unavailable.
    503 Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http20NamedPipeServiceSpecE:0x00007fb7d00200a0] _serverNamespace = / action = Allow _pipeName =/var/run/vmware/vpxd-webserver-pipe)
Note: vCenter STS Certificate may expire soon in certain configuration and you will observe the symptoms mentioned in this KB if STS certificate is expired, please refer following KBs to verify the validity of STS / Signing Certificate and replace it if already expired:
Purpose
This article provides insights and troubleshooting steps when you encountered this error while logging in and accessing the vCenter Server using your vSphere Web Client.
Cause
This issue may occur due to a number of reasons such as:
  • The vCenter Server currently down because of maintenance.
  • The reverse Proxy service on vCenter Server is down.
  • The vSphere web client service is down.
  • Mis-configured Firewall settings.

    Notes:
    This mis-configuration can only occur on a Windows installation of vCenter Server.
    A VCSA installation can only have this problem if deliberate changes were made to firewall settings.
Impact / Risks
Managing the vCenter Server or vCenter Server appliance fails.
Resolution
Before troubleshooting, it is critical to understand what a "503 Service Unavailable" error is.
For more insights, see
 
List of HTTP Status Codes
503 Service Unavailable Flow Chart

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A 503 Service Unavailable error is an HTTP response status code that indicates that the server is temporarily unable to handle your request. This can be due to a number of reasons already mentioned in the cause section.

There are also different looking 503 pages on other websites:

For example:
  • 503 Service Unavailable (Failed to connect to endpoint: [N7Vmacore4Http20NamedPipeServiceSpecE:0x00007fb7d00200a0] _serverNamespace = / action = Allow _pipeName =/var/run/vmware/vpxd-webserver-pipe)
  • 503 Error
  • Service Unavailable – DNS Failure
  • HTTP Error 503
  • HTTP 503
  • 503 Service Temporarily Available
An important thing to remember is that a 503 error is a server-side error. This means that the problem exists within the vCenter Server or website (server) you are trying to access, and not your computer (client).

Troubleshooting HTTP response status code "503" on the vSphere Web Client when connecting to the vCenter Server. 

  1. Try again in a few minutes.

    Note: it is most likely that the vCenter Server is just busy acknowledging your request. The vCenter server was able to process your request and was able to respond back with the "503 Service Unavailable" error. It is just not able to acknowledge your request either because it is busy with other tasks at the moment or it currently down with very limited services due to maintenance.
  2. Try again in a few minutes on a different client. Confirm if you are still get the same error.
  3. Confirm the status of the VMware vCenter Services. Ensure all required vCenter Server and vCenter Server appliance services are up, running and functional. For more insights, see:
  1. Check if there are an disk space issues on the vCenter Server or the vCenter Server Appliance. 

    Notes: 

    Disk space issues can cause more than one service to shutdown which can result in the HTTP 503 Error Response Code.
    Disk space issues do not directly cause a 503 Error Response Code, but the services being down due to a failure causes the error. For relevant articles, see:
  1. From the vCenter Server, investigate the vsphere_client_virgo.log file located at:
    • Windows vCenter Server - C:\ProgamData\VMware\vCenterServer\logs\vsphere-client\logs\
    • vCenter Server Appliance - /var/log/vmware/vsphere-client/logs/

      Also, look at the vpxd.log file located at:
      • Windows vCenter Server: C:\ProgramData\VMware\vCenterServer\logs\vmware-vpx
      • vCenter Server Appliance: /var/log/vmware/vpxd
  1. VMware strongly recommends on following Performance Best Practices on VMware vSphere 6.x/7.x
  1. For more insights on Troubleshooting VMware vCenter Server, the vSphere Web Client, Storage and Networking, see the VMware vSphere Troubleshooting Guide.

For Troubleshooting Work Flow , see:

Process to troubleshoot
Additional Resources

Related Products:

  • VMware vCenter Server
  • VMware vCenter Server Appliance

Related Versions:

  • VMware vCenter Server 7.0.x
  • VMware vCenter Server Appliance 6.5.x
  • VMware vCenter Server 6.7.x
  • VMware vCenter Server Appliance 6.7.x
  • VMware vCenter Server Appliance 5.5.x
  • VMware vCenter Server Appliance 6.0.x
  • VMware vCenter Server 5.5.x
  • VMware vCenter Server 6.0.x

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Last Updated: Jun 11 2020


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