In the latest release, the spinnaker front50 service can write to redis. If enable redis true in config, doesn't spinnaker need cassandra? Is there any spinnaker service need cassandra? Spinnaker could just write to redis, not write to cassandra? Cassandra is just an option, Spinnaker could use redis to replace it?
There are currently two services that used to depend on Cassandra, Front50 and echo.
Front50 can use either s3 or redis as well. There are guides in the spinnaker.io page - http://www.spinnaker.io/docs/front50-cassandra-to-s3 and http://www.spinnaker.io/docs/front50-cassandra-to-redis
Echo also has a dependency on Cassandra, but this can be replaced by the in-memory version. You can set it by adding the property spinnaker.inMemory.enabled to true and setting spinnaker.cassandra.enabled to false. ( See this pr - https://github.com/spinnaker/echo/commit/2361cbceb91e423a3d3d0b97225e088cde55463d )