In the case of a host failure, it may not be possible to bring back the node to life.
Replace dead node operation will cause the other nodes in the cluster to stream data to the node that was replaced. This operation can take some time (depending on the data size and network bandwidth).
This procedure is for replacing one dead node. To replace more than one dead node, run the full procedure to completion one node at a time
Procedure
Verify the status of the node using nodetool status command, the node with status DN is down and need to be replaced
kubectl -n scylla exec -ti simple-cluster-us-east-1-us-east-1a-0 -c scylla -- nodetool status
Datacenter: us-east-1
=====================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 10.43.125.110 74.63 KB 256 ? 8ebd6114-969c-44af-a978-87a4a6c65c3e us-east-1a
UN 10.43.231.189 91.03 KB 256 ? 35d0cb19-35ef-482b-92a4-b63eee4527e5 us-east-1a
DN 10.43.43.51 74.77 KB 256 ? 1ffa7a82-c41c-4706-8f5f-4d45a39c7003 us-east-1a
Identify service which is bound to down node by checking IP address
kubectl -n scylla get svc
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
simple-cluster-client ClusterIP None <none> 9180/TCP 3h12m
simple-cluster-us-east-1-us-east-1a-0 ClusterIP 10.43.231.189 <none> 7000/TCP,7001/TCP,7199/TCP,10001/TCP,9042/TCP,9142/TCP,9160/TCP 3h12m
simple-cluster-us-east-1-us-east-1a-1 ClusterIP 10.43.125.110 <none> 7000/TCP,7001/TCP,7199/TCP,10001/TCP,9042/TCP,9142/TCP,9160/TCP 3h11m
simple-cluster-us-east-1-us-east-1a-2 ClusterIP 10.43.43.51 <none> 7000/TCP,7001/TCP,7199/TCP,10001/TCP,9042/TCP,9142/TCP,9160/TCP 3h5m
Drain node which we would like to replace using. This command may delete your data from local disks attached to given node!
kubectl drain gke-scylla-demo-default-pool-b4b390a1-6j12 --ignore-daemonsets --delete-local-data
Pod which will be replaced should enter the Pending state
kubectl -n scylla get pods
NAME READY STATUS RESTARTS AGE
simple-cluster-us-east-1-us-east-1a-0 2/2 Running 0 3h21m
simple-cluster-us-east-1-us-east-1a-1 2/2 Running 0 3h19m
simple-cluster-us-east-1-us-east-1a-2 0/2 Pending 0 8m14s
To being node replacing, add scylla/replace="" label to service bound to pod we are replacing.
kubectl -n scylla label svc simple-cluster-us-east-1-us-east-1a-2 scylla/replace=""
Your failed Pod should be recreated on available k8s node
kubectl -n scylla get pods
NAME READY STATUS RESTARTS AGE
simple-cluster-us-east-1-us-east-1a-0 2/2 Running 0 3h27m
simple-cluster-us-east-1-us-east-1a-1 2/2 Running 0 3h25m
simple-cluster-us-east-1-us-east-1a-2 1/2 Running 0 9s
Because other nodes in cluster must stream data to new node this operation might take some time depending on how much data your cluster stores.
After bootstraping is over, your new Pod should be ready to go.
Old one shouldn’t be no longer visible in nodetool status
kubectl -n scylla exec -ti simple-cluster-us-east-1-us-east-1a-0 -c scylla -- nodetool status
Datacenter: us-east-1
=====================
Status=Up/Down
|/ State=Normal/Leaving/Joining/Moving
-- Address Load Tokens Owns Host ID Rack
UN 10.43.125.110 74.62 KB 256 ? 8ebd6114-969c-44af-a978-87a4a6c65c3e us-east-1a
UN 10.43.231.189 91.03 KB 256 ? 35d0cb19-35ef-482b-92a4-b63eee4527e5 us-east-1a
UN 10.43.191.172 74.77 KB 256 ? 1ffa7a82-c41c-4706-8f5f-4d45a39c7003 us-east-1a
Run the repair on the cluster to make sure that the data is synced with the other nodes in the cluster. You can use Scylla Manager to run the repair.