A ReplicaSet’s purpose is to maintain a stable set of replica Pods running at any given time . As such, it is often used to guarantee the availability of a specified number of identical Pods.
What are replica sets?
A replica set is a group of mongod instances that maintain the same data set . A replica set contains several data bearing nodes and optionally one arbiter node. Of the data bearing nodes, one and only one member is deemed the primary node, while the other nodes are deemed secondary nodes.
What are the possible states of a pod replica?
There are three possible container states: Waiting , Running , and Terminated . To check the state of a Pod’s containers, you can use kubectl
How are replica set often created?
When you deploy a pod within a Kubernetes cluster , you will often create replicas of the pod to scale an application or service. The best way to control these replicas is via a ReplicaSet, which makes sure specified replica pods are always running at the desired state.
Why do pods restart?
OOM(Out of Memory) Kill
This is one of the common reason of restarting container which happens the resource usage is not configured or application itself behaves unpredictable. If we have allocated 600Mi of memory for a container and it tries to allocate more than this limit, the pod will be killed with OOM.
How do you destroy a pod in Kubectl?
Destroy Pod
The action of deleting the pod is simple. To delete the pod you have created, just run kubectl delete pod nginx . Be sure to confirm the name of the pod you want to delete before pressing Enter. If you have completed the task of deleting the pod successfully, pod nginx deleted will appear in the terminal.
What is difference between POD and container?
“A container runs logically in a pod (though it also uses a container runtime); A group of pods, related or unrelated , run on a cluster. A pod is a unit of replication on a cluster; A cluster can contain many pods, related or unrelated [and] grouped under the tight logical borders called namespaces.”
What are primary and secondary replica sets?
In a replica, one node is primary node that receives all write operations. All other instances, such as secondaries, apply operations from the primary so that they have the same data set. ... In a replica set, one node is primary node and remaining nodes are secondary . All data replicates from primary to secondary node.
Is MongoDB single master?
MongoDB can be set up in a way that there is no single point of failure (at least none specific to MongoDB). When you set up replication as suggested (which includes primary, secondary and an arbiter on a 3rd server), the secondary will take the role of the primary when it goes down.
What is the difference between a replica set and replication controller?
The replica set are also known as next generation replication controller. The only difference between replica set and replication controller is the selector types . The replication controller supports equality based selectors whereas the replica set supports equality based as well as set based selectors.
Can you rescale a replica set?
You can easily change the number of pods a particular ReplicaSet manages in one of two ways: Edit the controllers configuration by using kubectl edit rs ReplicaSet_name and change the replicas count up or down as you desire. Use kubectl directly. For example, kubectl scale –replicas=2 rs/web .
How do I remove replica set?
- Shut down the mongod instance for the member you wish to remove. To shut down the instance, connect using mongosh and use the db. ...
- Connect to the replica set’s current primary. To determine the current primary, use db. ...
- Use rs.remove() in either of the following forms to remove the member:
What is the difference between StatefulSet and Deployment?
A StatefulSet is another Kubernetes controller that manages pods just like Deployments. But it differs from a Deployment in that it is more suited for stateful apps . A stateful application requires pods with a unique identity (for example, hostname). One pod should be able to reach other pods with well-defined names.
How do I check the reason for pod restart?
You can also write a final message to /dev/termination-log, and this will show up as described in the docs. kubectl get pods will actually list any restarts of the container also the describe command can be of help cause it lists any events associated with the pod.
How do I get all pods in namespaces?
- Fetch all Pods in all namespaces using kubectl get pods –all-namespaces.
- Format the output to include only the list of Container image names using -o jsonpath={. items[*]. spec. ...
- Format the output using standard tools: tr , sort , uniq. Use tr to replace spaces with newlines.
What is the reason for pod eviction?
If a system daemon (such as kubelet , docker , and journald ) is consuming more resources than were reserved via system-reserved or kube-reserved allocations, and the node only has Guaranteed or Burstable pods using less resources than requests left on it, then the kubelet must choose to evict one of these pods to ...
