Vault returns "context deadline exceeded" when logging in via LDAP Auth method.

Problem

When attempting to log into vault via the UI, you may observe an infinite hang on the User interface. 

While attempting to log into vault via the CLI, you may observe a "context deadline exceeded" error after waiting around 60 seconds.

Example:

$ vault login -method=ldap username=aubry
Password (will be hidden):
Error authenticating: context deadline exceeded

Prerequisites:

• Vault versions v1.14.10 and below
• Vault versions v.1.15.6 and below

Cause

• This issue may be caused by a deadlock when User Lockout feature is enabled. 
• To confirm the issue is caused by a deadlock, review the active nodes operational log for the following error:

[ERROR] core: failed to persist failed login user entry: error="context canceled"

• If the error is present, and you are on vault versions v1.14.10. and v.1.15.6 and below, the login failures may be caused by a deadlock on the active Vault node. 

Solutions:

• To workaround the issue, restart the vault service on the active node, and disable user lockout.
• To resolve the issue, upgrade vault to v1.14.11 or v.1.15.7 or v1.16.0 and above. 

Additional Information

• https://github.com/hashicorp/vault/pull/25697

• User Lockout