Self-sharding with only one viking Service instance is not an error.

Only issue a log warning in this case. Verified with an e2e test.

Closes #44

pkg/controller/varnishconfig.go

@@ -417,7 +417,7 @@ func (worker *NamespaceWorker) configSharding(spec *vcl.Spec,
 		}
 	}
 	if len(spec.ShardCluster.Nodes) <= 1 {
-		return update.MakeFatal(
+		worker.log.Warnf(
 			"Sharding requested, but %d endpoint addresses found "+
 				"for service %s/%s",
 			len(spec.ShardCluster.Nodes), svc.Namespace, svc.Name)

test/e2e.sh

@@ -86,6 +86,15 @@ make EXAMPLE=primary-only-by-clientid deploy verify undeploy
 echo Self-sharding under conditions example
 make EXAMPLE=shard-conditions deploy verify undeploy
 
+echo Self-sharding with 1 replica
+make EXAMPLE=self-sharding deploy verify
+kubectl scale --replicas=1 --timeout=2m deploy/varnish-ingress
+wait_for_replica_count app=varnish-ingress 1
+make EXAMPLE=self-sharding verify
+kubectl scale --replicas=2 --timeout=2m deploy/varnish-ingress
+wait_for_replica_count app=varnish-ingress 2
+make EXAMPLE=self-sharding verify undeploy
+
 echo Basic Authentication example
 cd ${MYPATH}/../examples/authentication/
 make EXAMPLE=basic-auth deploy verify undeploy

test/utils.sh

@@ -88,3 +88,29 @@ function wait_until_not_configured {
 
     wait_for_config_status ${label} ${ns} ${timeout} ${port} '503'
 }
+
+# kubectl scale --timeout is evidently buggy in some versions, so we
+# wait until kubectl get pods outputs the expected number of replicas.
+function wait_for_replica_count {
+    local label="$1"
+    local replicas="$2"
+    local ns=${3-default}
+    local timeout=${4-120}
+
+    local N=0
+    while true; do
+        local npods=$(kubectl get pods -n ${ns} -l ${label} --no-headers | wc -l)
+        if [ $? -ne 0 ]; then
+            exit 1
+        fi
+        if [ ${npods} -eq ${replicas} ]; then
+            break
+        fi
+        if [ $N -ge ${timeout} ]; then
+            echo "Timed out waiting for $replicas replicas"
+            exit 1
+        fi
+        N=$(( N + 1 ))
+        sleep 1
+    done
+}