503: Too Many Connections For Client-Username

Hi @Yogi. Well, that's interesting. What have you configured your "max clients per username" setting to? You can find this in the Client Profile for your particular Client Username.

That definitely sounds like you hit the value configured for your client profile. Getting the exact same error with a JMS client if I have maxed out the # of connections for a particular username:

Initialization error: client creation failed.
javax.naming.NamingException: JNDI lookup failed - 503: Too Many Connections For Client-Username

This is different if the Message VPN has hit its max limit:

Initialization error: client creation failed.
javax.naming.NamingException: JNDI lookup failed - 503: Too Many Connections For VPN

Or if the broker has reached its maximum system limit:

Initialization error: client creation failed.
javax.naming.NamingException: JNDI lookup failed - 503: Too Many Clients

If you look through the event.log on the broker, you will see entries that should correspond to your connection limit being breached. From CLI:

solace1040> show log event find VPN_CLIENT_USERNAME_CONNECTIONS
2023-05-15T15:13:21.255+00:00 <local3.warning> solace1040 event: VPN: VPN_CLIENT_USERNAME_CONNECTIONS_HIGH: default - Message VPN (0) default client-username aaron connections threshold 4(80%) reached: 4 Service (Combined)
2023-05-15T15:13:24.581+00:00 <local3.warning> solace1040 event: VPN: VPN_CLIENT_USERNAME_CONNECTIONS_EXCEEDED: default - Message VPN (0) default client-username aaron Maximum connections exceeded : 5 Service (Combined)

Do you monitor the active number of connections on the broker? Like, polling SEMP and storing in a time-series database? Is there a connection spike around the time of your error?