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From what I can tell in the documentation, a ReplicaSet is created when running a Deployment. It seems to support some of the same features of a ReplicationController - scale up/down and auto restart, but it's not clear if it supports rolling upgrades or autoscale.
The v1.1.8 user guide shows how to create a deployment in Deploying Applications (which automatically creates a ReplicaSet), yet the kubectl get replicasets command is not available until v1.2.0. I cannot find any other information about ReplicaSet in the documentation.
Will ReplicaSet eventually replace ReplicationController? Why would I want to use Deployment and ReplicaSet instead of ReplicationController?
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The replica set and the replication controller's key difference is that the replication controller only supports equality-based selectors whereas the replica set supports set-based selectors.
A ReplicaSet ensures that a specified number of pod replicas are running at any given time. However, a Deployment is a higher-level concept that manages ReplicaSets and provides declarative updates to Pods along with a lot of other useful features.
Note: A Deployment that configures a ReplicaSet is now the recommended way to set up replication. A ReplicationController ensures that a specified number of pod replicas are running at any one time. In other words, a ReplicationController makes sure that a pod or a homogeneous set of pods is always up and available.
Generally, the replica set name is the cluster name plus -shard-0 . i.e. cluster name test , replica set name is test-shard-0 .
Replica Set is the next generation of Replication Controller. Replication controller is kinda imperative, but replica sets try to be as declarative as possible.
1.The main difference between a Replica Set and a Replication Controller right now is the selector support.
+--------------------------------------------------+-----------------------------------------------------+ | Replica Set | Replication Controller | +--------------------------------------------------+-----------------------------------------------------+ | Replica Set supports the new set-based selector. | Replication Controller only supports equality-based | | This gives more flexibility. for eg: | selector. for eg: | | environment in (production, qa) | environment = production | | This selects all resources with key equal to | This selects all resources with key equal to | | environment and value equal to production or qa | environment and value equal to production | +--------------------------------------------------+-----------------------------------------------------+ 2.The second thing is the updating the pods.
+-------------------------------------------------------+-----------------------------------------------+ | Replica Set | Replication Controller | +-------------------------------------------------------+-----------------------------------------------+ | rollout command is used for updating the replica set. | rolling-update command is used for updating | | Even though replica set can be used independently, | the replication controller. This replaces the | | it is best used along with deployments which | specified replication controller with a new | | makes them declarative. | replication controller by updating one pod | | | at a time to use the new PodTemplate. | +-------------------------------------------------------+-----------------------------------------------+ These are the two things that differentiates RS and RC. Deployments with RS is widely used as it is more declarative.
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