Setting redshift data source

Hi I tried to make datasource with Redshift.
FYI, SSL setting of Redshift is true.
But I have no idea what I should set in SSL MODE.

and when I clicked test connection button
I got the following message.
Connection Test Failed:
could not send SSL negotiation packet: Resource temporarily unavailable
please let me know how to solve it.

That error message usually means that a firewall is blocking access between Redash and your Redshift instance.

ssl_mode=prefer should suffice.