Warn about kubernetes minimum version (#237)

*Warning if attempting to deploy to a cluster with kubectl version less than 1.6

lib/kubernetes-deploy.rb

@@ -21,5 +21,6 @@
 require 'kubernetes-deploy/duration_parser'
 
 module KubernetesDeploy
+  MIN_KUBE_VERSION = '1.6.0'
   KubernetesDeploy::StatsD.build
 end

lib/kubernetes-deploy/deploy_task.rb

@@ -441,6 +441,9 @@ def confirm_cluster_reachable
         end
       end
       raise FatalDeploymentError, "Failed to reach server for #{@context}" unless success
+      if kubectl.server_version < Gem::Version.new(MIN_KUBE_VERSION)
+        @logger.warn(KubernetesDeploy::Errors.server_version_warning(server_version))
+      end
     end
 
     def confirm_namespace_exists

lib/kubernetes-deploy/errors.rb

@@ -8,4 +8,11 @@ def initialize(name, context)
       super("Namespace `#{name}` not found in context `#{context}`")
     end
   end
+  module Errors
+    extend self
+    def server_version_warning(server_version)
+      "Minimum cluster version requirement of #{MIN_KUBE_VERSION} not met. "\
+      "Using #{server_version} could result in unexpected behavior as it is no longer tested against"
+    end
+  end
 end

lib/kubernetes-deploy/restart_task.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 require 'kubernetes-deploy/kubeclient_builder'
 require 'kubernetes-deploy/resource_watcher'
+require 'kubernetes-deploy/kubectl'
 
 module KubernetesDeploy
   class RestartTask
@@ -32,7 +33,9 @@ def perform(deployments_names = nil)
       @logger.phase_heading("Initializing restart")
       verify_namespace
       deployments = identify_target_deployments(deployments_names)
-
+      if kubectl.server_version < Gem::Version.new(MIN_KUBE_VERSION)
+        @logger.warn(KubernetesDeploy::Errors.server_version_warning(kubectl.server_version))
+      end
       @logger.phase_heading("Triggering restart by touching ENV[RESTARTED_AT]")
       patch_kubeclient_deployments(deployments)
 
@@ -153,6 +156,10 @@ def kubeclient
       @kubeclient ||= build_v1_kubeclient(@context)
     end
 
+    def kubectl
+      @kubectl ||= Kubectl.new(namespace: @namespace, context: @context, logger: @logger, log_failure_by_default: true)
+    end
+
     def v1beta1_kubeclient
       @v1beta1_kubeclient ||= build_v1beta1_kubeclient(@context)
     end

lib/kubernetes-deploy/runner_task.rb

@@ -34,7 +34,9 @@ def run!(task_template:, entrypoint:, args:, env_vars: [])
       @logger.reset
       @logger.phase_heading("Validating configuration")
       validate_configuration(task_template, args)
-
+      if kubectl.server_version < Gem::Version.new(MIN_KUBE_VERSION)
+        @logger.warn(KubernetesDeploy::Errors.server_version_warning(kubectl.server_version))
+      end
       @logger.phase_heading("Fetching task template")
       raw_template = get_template(task_template)
 
@@ -127,14 +129,17 @@ def validate_pod_spec(pod)
       f.write recursive_to_h(pod).to_json
       f.close
 
-      kubectl = Kubectl.new(namespace: @namespace, context: @context, logger: @logger, log_failure_by_default: true)
       _out, err, status = kubectl.run("apply", "--dry-run", "-f", f.path)
 
       unless status.success?
         raise FatalTaskRunError, "Invalid pod spec: #{err}"
       end
     end
 
+    def kubectl
+      @kubectl ||= Kubectl.new(namespace: @namespace, context: @context, logger: @logger, log_failure_by_default: true)
+    end
+
     def recursive_to_h(struct)
       if struct.is_a?(Array)
         return struct.map { |v| v.is_a?(OpenStruct) || v.is_a?(Array) || v.is_a?(Hash) ? recursive_to_h(v) : v }