[doc] Add instructions about how to use SSL/TLS for redis connection.

[fishbone]

Why are these changes needed?

This PR adds the instruction about how to use SSL/TLS for redis connection.

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• I've made sure the tests are passing.
• Testing Strategy
  • Unit tests
  • Manual tests
  • This PR is not tested :(

[kevin85421]

Thank @iycheng for this contribution!

I am not familiar with Redis, SSL, and TLS. How can I check whether the configuration is set properly and what is the expected behavior (For example, I need to log in to the head pod. Next, execute a command in the pod, and the output will show whether the functionality works successfully or not.)? Thank you!

[fishbone]

Thank @iycheng for this contribution!

I am not familiar with Redis, SSL, and TLS. How can I check whether the configuration is set properly and what is the expected behavior (For example, I need to log in to the head pod. Next, execute a command in the pod, and the output will show whether the functionality works successfully or not.)? Thank you!

If the ray cluster runs health, it's working then. I think you need a redis cluster enabled TLS/SSL first. (https://github.com/allen-munsch/docker-redis-ssl-example)
(remember to add rediss:// as the prefix)

[kevin85421]

Thank @iycheng for this contribution!
I am not familiar with Redis, SSL, and TLS. How can I check whether the configuration is set properly and what is the expected behavior (For example, I need to log in to the head pod. Next, execute a command in the pod, and the output will show whether the functionality works successfully or not.)? Thank you!

If the ray cluster runs health, it's working then. I think you need a redis cluster enabled TLS/SSL first. (https://github.com/allen-munsch/docker-redis-ssl-example) (remember to add rediss:// as the prefix)

Thank you for your reply!

[kevin85421]

Can I merge this PR? @iycheng @simon-mo