Login to vCenter fails with "[500] An error occurred while fetching identity providers" due to OutofMemoryError of lookupservice

Products

• VMware vCenter Server 7.0

Issue/Introduction

• Unable to login to vCenter Server UI with error "[500] An error occurred while fetching identity providers"
• All services on vCenter Server appear to be in running state when checking with "service-control --status --all"
• In /var/log/vmware/vsphere-ui/vsphere_client_virgo.log there may be similar messages:
  
  [ERROR] http-nio-5090-exec-37        70000906 100098 ###### com.vmware.vsphere.client.security.oauth2.LoginRequestHandler     An error occurred while fetching providers java.lang.IllegalArgumentException: The validated object is null
  
  
• In /var/log/vmware/lookupsvc/lookupserver-default.log there may be similar messages:

  Task com.vmware.vim.vmomi.server.impl.InvocationTask@527b0e15 rejected from java.util.concurrent.ThreadPoolExecutor@17798a3e[Running, pool size = 100, active threads = 100, queued tasks = 0, completed tasks = 92181]
java.util.concurrent.RejectedExecutionException: Task com.vmware.vim.vmomi.server.impl.InvocationTask@527b0e15 rejected from java.util.concurrent.ThreadPoolExecutor@17798a3e[Running, pool size = 100, active threads = 100, queued tasks = 0, completed tasks = 92181]

  Java heap space
java.lang.OutOfMemoryError: Java heap space

Environment

VMware vCenter Server 7.0

Cause

Lookupservice ran into Out Of Memory (OOM) state and as a result vCenter vsphere-ui service is unable to connect to lookupservice. This causes failure to login vCenter Server UI.

Resolution

The issue has been fixed in vCenter Server 8.0.1 and later versions. 
To fix the issue upgrade to the latest vCenter version.