Problem:
you got the following error when you try to run puppetca command or puppet on the agent
err: Could not call list: header too long
Solution
1. Check if /var is full
2. after clear space in /var, check for zero byte file under puppet/ssl such as /var/lib/puppet/ssl/ca/requests, /var/lib/puppet/ssl/ca/signed, /var/puppet/ssl/ca/requests, or /var/puppet/ssl/ca/signed depending on where you specify the ssl directory for puppet.