docs: Describe dead node replace procedure (#48)

scylladb · Nov 17, 2020 · f01f491 · f01f491
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diff --git a/docs/source/index.rst b/docs/source/index.rst
@@ -36,6 +36,7 @@ Currently it supports:
 * :doc:`Deploying Scylla on EKS <eks>`
 * :doc:`Deploying Scylla on GKE <gke>`
 * :doc:`Deploying Scylla Manager on a Kubernetes Cluster <manager>`
+* :doc:`Node operations <node_operations>`
 * :doc:`Scylla Cluster Custom Resource Definition (CRD) <scylla_cluster_crd>`
 * :doc:`Contributing to the Scylla Operator Project <contributing>`
 

diff --git a/docs/source/node_operations.md b/docs/source/node_operations.md
@@ -0,0 +1,73 @@
+# Node operations using Scylla Operator
+
+### Replacing a Scylla node
+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**
+
+1. Verify the status of the node using `nodetool status` command, the node with status DN is down and need to be replaced
+    ```bash
+    $ 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
+    ```
+1. Identify service which is bound to down node by checking IP address
+    ```bash
+    $ 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
+    ```
+1. Drain node which we would like to replace using
+    ```bash
+    $ kubectl drain gke-scylla-demo-default-pool-b4b390a1-6j12 --ignore-daemonsets --delete-local-data 
+    ```
+
+    Pod which will be replaced should enter the `Pending` state
+    ```bash
+    $ 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
+    ```
+1. To being node replacing, add `scylla/replace=""` label to service bound to pod we are replacing. 
+    ```bash
+    $ kubectl -n scylla label svc simple-cluster-us-east-1-us-east-1a-2 scylla/replace=""
+    ```
+    Your failed pod should be recreated on available node
+    ```bash
+    $ 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`
+   ```bash
+   $ 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
+   ```
+1. 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.