Improve CockroachDB example

* Use an init container to eliminate potential edge case where losing
  the first pet's could cause it to start a second logical cluster
* Exec the cockroach binary so that it runs as PID 1 in the container
* Make some small improvements to the README

examples/cockroachdb/README.md

@@ -12,10 +12,11 @@ a PetSet. CockroachDB is a distributed, scalable NewSQL database. Please see
 Standard PetSet limitations apply: There is currently no possibility to use
 node-local storage (outside of single-node tests), and so there is likely
 a performance hit associated with running CockroachDB on some external storage.
-Note that CockroachDB already does replication and thus should not be deployed on
-a persistent volume which already replicates internally.
-High-performance use cases on a private Kubernetes cluster should consider
-a DaemonSet deployment.
+Note that CockroachDB already does replication and thus it is unnecessary to
+deploy it onto persistent volumes which already replicate internally.
+For this reason, high-performance use cases on a private Kubernetes cluster
+may want to consider a DaemonSet deployment until PetSets support node-local
+storage (see #7562).
 
 ### Recovery after persistent storage failure
 
@@ -27,17 +28,25 @@ first node is special in that the administrator must manually prepopulate the
 parameter. If this is not done, the first node will bootstrap a new cluster,
 which will lead to a lot of trouble.
 
-### Dynamic provisioning
+### Dynamic volume provisioning
 
-The deployment is written for a use case in which dynamic provisioning is
+The deployment is written for a use case in which dynamic volume provisioning is
 available. When that is not the case, the persistent volume claims need
 to be created manually. See [minikube.sh](minikube.sh) for the necessary
-steps.
+steps. If you're on GCE or AWS, where dynamic provisioning is supported, no
+manual work is needed to create the persistent volumes.
 
 ## Testing locally on minikube
 
 Follow the steps in [minikube.sh](minikube.sh) (or simply run that file).
 
+## Testing in the cloud on GCE or AWS
+
+Once you have a Kubernetes cluster running, just run
+`kubectl create -f cockroachdb-petset.yaml` to create your cockroachdb cluster.
+This works because GCE and AWS support dynamic volume provisioning by default,
+so persistent volumes will be created for the CockroachDB pods as needed.
+
 ## Accessing the database
 
 Along with our PetSet configuration, we expose a standard Kubernetes service
@@ -48,8 +57,7 @@ Start up a client pod and open up an interactive, (mostly) Postgres-flavor
 SQL shell using:
 
 ```console
-$ kubectl run -it cockroach-client --image=cockroachdb/cockroach --restart=Never --command -- bash
-root@cockroach-client # ./cockroach sql --host cockroachdb-public
+$ kubectl run -it --rm cockroach-client --image=cockroachdb/cockroach --restart=Never --command -- ./cockroach sql --host cockroachdb-public
 ```
 
 You can see example SQL statements for inserting and querying data in the
@@ -57,6 +65,19 @@ included [demo script](demo.sh), but can use almost any Postgres-style SQL
 commands. Some more basic examples can be found within
 [CockroachDB's documentation](https://www.cockroachlabs.com/docs/learn-cockroachdb-sql.html).
 
+## Accessing the admin UI
+
+If you want to see information about how the cluster is doing, you can try
+pulling up the CockroachDB admin UI by port-forwarding from your local machine
+to one of the pods:
+
+```shell
+kubectl port-forward cockroachdb-0 8080
+```
+
+Once you’ve done that, you should be able to access the admin UI by visiting
+http://localhost:8080/ in your web browser.
+
 ## Simulating failures
 
 When all (or enough) nodes are up, simulate a failure like this:
@@ -77,10 +98,17 @@ database and ensuring the other replicas have all data that was written.
 
 ## Scaling up or down
 
-Simply edit the PetSet (but note that you may need to create a new persistent
-volume claim first). If you ran `minikube.sh`, there's a spare volume so you
-can immediately scale up by one. Convince yourself that the new node
-immediately serves reads and writes.
+Simply patch the PetSet by running
+
+```shell
+kubectl patch petset cockroachdb -p '{"spec":{"replicas":4}}'
+```
+
+Note that you may need to create a new persistent volume claim first. If you
+ran `minikube.sh`, there's a spare volume so you can immediately scale up by
+one. If you're running on GCE or AWS, you can scale up by as many as you want
+because new volumes will automatically be created for you. Convince yourself
+that the new node immediately serves reads and writes.
 
 ## Cleaning up when you're done