HDFS-13309. Ozone: Improve error message in case of missing nodes. Contributed by Elek, Marton.

hadoop-hdsl/server-scm/src/main/java/org/apache/hadoop/ozone/scm/container/ContainerStateManager.java

@@ -291,6 +291,11 @@ public ContainerInfo allocateContainer(PipelineSelector selector, HdslProtos
 
     Pipeline pipeline = selector.getReplicationPipeline(type,
         replicationFactor, containerName);
+
+    Preconditions.checkNotNull(pipeline, "Pipeline type=%s/"
+        + "replication=%s couldn't be found for the new container. "
+        + "Do you have enough nodes?", type, replicationFactor);
+
     ContainerInfo containerInfo = new ContainerInfo.Builder()
         .setContainerName(containerName)
         .setState(HdslProtos.LifeCycleState.ALLOCATED)