recently experienced vCloud Director webpage HTTP error 503, which caused brief outage and engaged with VMware GSS support to get this resolved and sharing this as below.
Issue: vCloud Director webpage shows HTTP 503 error briefly
Solution:
Increase the number of connections each vCloud Director Cell can make to the database.
1. SSH into each vCloud Director Cell.
2. Run this command to backup the global.properties:
cp /opt/vmware/vcloud-director/etc/global.properties /opt/vmware/vcloud-director/etc/global.properties.bak
3. Then edit the global.properties, using vi or the editor of your choice:
vi /opt/vmware/vcloud-director/etc/global.properties
4. edit the entry for database.pool.maxActive
database.pool.maxActive = -1
(Note: Inputting a negative number, such as -1, will allow unlimited connections to the database)
5. Restart the cell or restart the services:
service vmware-vcd restart
( Note: taken from VMware KB 57013 )