Configure dns replicas

cluster.example.yml

@@ -11,6 +11,7 @@ hosts:
     private_address: 10.10.1.3
     role: worker
 network:
+  dns_replicas: 3
   service_cidr: 10.96.0.0/12
   pod_network_cidr: 10.32.0.0/12
   trusted_subnets:
@@ -31,4 +32,4 @@ addons:
     enabled: true
     interval: 7d
   kured:
-    enabled: true
+    enabled: true

lib/kupo/config.rb

@@ -5,8 +5,21 @@
 
 module Kupo
   class Config < Dry::Struct
+    HOSTS_PER_DNS_REPLICA = 10
+
     attribute :hosts, Types::Coercible::Array.of(Kupo::Configuration::Host)
     attribute :network, Kupo::Configuration::Network
     attribute :addons, Kupo::Types::Hash
+
+    # @return [Integer]
+    def dns_replicas
+      if network.dns_replicas
+        return network.dns_replicas
+      elsif hosts.length == 1
+        return 1
+      else
+        return 1 + (hosts.length / HOSTS_PER_DNS_REPLICA.to_f).ceil
+      end
+    end
   end
-end
+end

lib/kupo/config_schema.rb

@@ -8,6 +8,13 @@ class ConfigSchema
     # @return [Dry::Validation::Schema]
     def self.build
       Dry::Validation.Form do
+        configure do
+          def self.messages
+            super.merge(
+              en: { errors: {network_dns_replicas: "network.dns_replicas cannot be larger than the number of hosts"}}
+            )
+          end
+        end
         required(:hosts).each do
           schema do
             required(:address).filled
@@ -18,12 +25,17 @@ def self.build
           end
         end
         optional(:network).schema do
+          optional(:dns_replicas).filled(:int?, gt?: 0)
           optional(:service_cidr).filled(:str?)
           optional(:pod_network_cidr).filled(:str?)
           optional(:trusted_subnets).each(type?: String)
         end
         optional(:addons).filled
+
+        validate(network_dns_replicas: [:network, :hosts]) do |network, hosts|
+          !network[:dns_replicas] || network[:dns_replicas] <= hosts.length
+        end
       end
     end
   end
-end
+end

lib/kupo/configuration/network.rb

@@ -2,8 +2,9 @@ module Kupo::Configuration
   class Network < Dry::Struct
     constructor_type :schema
 
+    attribute :dns_replicas, Kupo::Types::Int
     attribute :service_cidr, Kupo::Types::String.default('10.96.0.0/12')
     attribute :pod_network_cidr, Kupo::Types::String.default('10.32.0.0/12')
     attribute :trusted_subnets, Kupo::Types::Array.member(Kupo::Types::String)
   end
-end
+end

lib/kupo/kube.rb

@@ -10,10 +10,38 @@ def entities
       @entities
     end
 
+    def entity_for_resource(resource)
+      name = Kubeclient::ClientMixin.underscore_entity(resource.kind.to_s)
+      definition = entities[name]
+
+      fail "Unknown entity for resource #{resource.kind} => #{name}" unless definition
+
+      definition
+    end
+
     def apis(options= {})
       response = rest_client.get(@headers)
       format_response(options[:as] || @as, response.body)
     end
+
+    # @param resource [Kubeclient::Resource]
+    # @return [Kubeclient::Resource]
+    def update_resource(resource)
+      definition = entity_for_resource(resource)
+
+      old_resource = get_entity(definition.resource_name, resource.metadata.name, resource.metadata.namespace)
+      resource.metadata.resourceVersion = old_resource.metadata.resourceVersion
+      merged_resource = Kubeclient::Resource.new(old_resource.to_h.deep_merge!(resource.to_h, {overwrite_arrays: true}))
+      update_entity(definition.resource_name, merged_resource)
+    end
+
+    # @param resource [Kubeclient::Resource]
+    # @return [Kubeclient::Resource]
+    def create_resource(resource)
+      definition = entity_for_resource(resource)
+
+      create_entity(resource.kind, definition.resource_name, resource)
+    end
   end
 
   RESOURCE_LABEL = 'kupo.kontena.io/stack'.freeze
@@ -100,17 +128,22 @@ def self.prune_stack(host, stack, checksum)
   # @return [Kubeclient::Resource]
   def self.apply_resource(host, resource)
     resource_client = self.client(host, resource.apiVersion)
+
     begin
-      definition = resource_client.entities[underscore_entity(resource.kind.to_s)]
-      old_resource = resource_client.get_entity(definition.resource_name, resource.metadata.name, resource.metadata.namespace)
-      resource.metadata.resourceVersion = old_resource.metadata.resourceVersion
-      merged_resource = Kubeclient::Resource.new(old_resource.to_h.deep_merge!(resource.to_h, {overwrite_arrays: true}))
-      resource_client.update_entity(definition.resource_name, merged_resource)
+      resource_client.update_resource(resource)
     rescue Kubeclient::ResourceNotFoundError
-      resource_client.create_entity(resource.kind, definition.resource_name, resource)
+      resource_client.create_resource(resource)
     end
   end
 
+  # @param host [String]
+  # @param resource [Kubeclient::Resource]
+  # @return [Kubeclient::Resource]
+  def self.update_resource(host, resource)
+    resource_client = self.client(host, resource.apiVersion)
+    resource_client.update_resource(resource)
+  end
+
   # @param host [String]
   # @param resource [Kubeclient::Resource]
   # @return [Kubeclient::Resource]
@@ -149,4 +182,4 @@ def self.parse_resource_file(path, vars = {})
   def self.underscore_entity(kind)
     Kubeclient::ClientMixin.underscore_entity(kind.to_s)
   end
-end
+end

lib/kupo/phases/configure_client.rb

@@ -3,6 +3,7 @@
 module Kupo::Phases
   class ConfigureClient < Base
 
+    # @param master [Kupo::Configuration::Host]
     def initialize(master)
       @master = master
     end
@@ -26,4 +27,4 @@ def config_dir
       File.join(Dir.home, '.kupo')
     end
   end
-end
+end

lib/kupo/phases/configure_dns.rb

@@ -0,0 +1,99 @@
+require_relative 'base'
+
+module Kupo::Phases
+  class ConfigureDNS < Base
+    # @param master [Kupo::Configuration::Node]
+    # @param config [Kupo::Config]
+    def initialize(master, config)
+      @master = master
+      @config = config
+    end
+
+    def call
+      patch_kubedns(
+        replicas: @config.dns_replicas,
+        max_surge: self.max_surge,
+        max_unavailable: self.max_unavailable,
+      )
+    end
+
+    # @return [Integer]
+    def max_surge
+      replicas = @config.dns_replicas
+      nodes = @config.hosts.length
+
+      if replicas == nodes
+        # cannot create any extra replicas
+        0
+      elsif nodes <= replicas * 1.5
+        # at most one per extra node
+        nodes - replicas
+      else
+        # half
+        (replicas * 0.5).floor
+      end
+    end
+
+    # @return [Integer]
+    def max_unavailable
+      replicas = @config.dns_replicas
+
+      if replicas == 1
+        # must allow taking down all replicas
+        1
+      else
+        # half
+        (replicas * 0.5).floor
+      end
+    end
+
+    # @param replicas [Integer]
+    # @param nodes [Integer]
+    def patch_kubedns(replicas: , max_surge: , max_unavailable: )
+      logger.info(@master.address) { "Patching kube-dns addon with #{replicas} replicas (max-surge #{max_surge}, max-unavailable #{max_unavailable})..." }
+
+      kube_client = Kupo::Kube.update_resource(@master.address, Kubeclient::Resource.new({
+        apiVersion: 'extensions/v1beta1',
+        kind: 'Deployment',
+        metadata: {
+          namespace: 'kube-system',
+          name: 'kube-dns',
+        },
+        spec: {
+          replicas: replicas,
+          strategy: {
+            type: "RollingUpdate",
+            rollingUpdate: {
+              maxSurge: max_surge, # must be zero for a two-node cluster
+              maxUnavailable: max_unavailable, # must be at least one, even for a single-node cluster
+            },
+          },
+          template: {
+            spec: {
+              affinity: {
+                podAntiAffinity: {
+                  requiredDuringSchedulingIgnoredDuringExecution: [
+                    {
+                      labelSelector: {
+                        matchExpressions: [
+                          {
+                            key: "k8s-app",
+                            operator: "In",
+                            values: [
+                              "kube-dns",
+                            ],
+                          },
+                        ],
+                      },
+                      topologyKey: "kubernetes.io/hostname",
+                    },
+                  ],
+                },
+              },
+            },
+          },
+        },
+      }))
+    end
+  end
+end

lib/kupo/phases/configure_host.rb

@@ -10,6 +10,7 @@ class ConfigureHost < Base
       name: 'kubernetes', version: '1.9.3', license: 'Apache License 2.0'
     ))
 
+    # @param host [Kupo::Configuration::Host]
     def initialize(host)
       @host = host
       @ssh = Kupo::SSH::Client.for_host(@host)
@@ -41,4 +42,4 @@ def exec_script(script)
       end
     end
   end
-end
+end

lib/kupo/phases/configure_kubelet.rb

@@ -5,7 +5,7 @@ class ConfigureKubelet < Base
 
     DROPIN_PATH = "/etc/systemd/system/kubelet.service.d/5-kupo.conf".freeze
 
-    # @param master [Kupo::Configuration::Host]
+    # @param host [Kupo::Configuration::Host]
     def initialize(host)
       @host = host
       @ssh = Kupo::SSH::Client.for_host(@host)
@@ -37,4 +37,4 @@ def build_systemd_dropin
       config + args.join(' ') + "'"
     end
   end
-end
+end

lib/kupo/phases/configure_master.rb

@@ -3,6 +3,8 @@
 module Kupo::Phases
   class ConfigureMaster < Base
 
+    # @param master [Kupo::Configuration::Host]
+    # @param config [Kupo::Configuration::Network]
     def initialize(master, config)
       @master = master
       @config = config
@@ -68,4 +70,4 @@ def upgrade
       end
     end
   end
-end
+end

lib/kupo/phases/configure_metrics.rb

@@ -11,6 +11,7 @@ class ConfigureMetrics < Base
       name: 'heapster', version: '1.5.1', license: 'Apache License 2.0'
     ))
 
+    # @param master [Kupo::Configuration::Host]
     def initialize(master)
       @master = master
     end
@@ -22,4 +23,4 @@ def call
       Kupo::Kube.apply_stack(@master.address, 'heapster', {version: '1.5.1'})
     end
   end
-end
+end

lib/kupo/phases/configure_network.rb

@@ -7,6 +7,8 @@ class ConfigureNetwork < Base
       name: 'weave', version: '2.2.0', license: 'Apache License 2.0'
     ))
 
+    # @param master [Kupo::Configuration::Host]
+    # @param config [Kupo::Configuration::Network]
     def initialize(master, config)
       @master = master
       @config = config
@@ -49,4 +51,4 @@ def generate_password
       SecureRandom.hex(24)
     end
   end
-end
+end

lib/kupo/phases/join_node.rb

@@ -3,6 +3,8 @@
 module Kupo::Phases
   class JoinNode < Base
 
+    # @param host [Kupo::Configuration::Host]
+    # @param master [Kupo::Configuration::Host]
     def initialize(host, master)
       @host = host
       @master = master
@@ -33,4 +35,4 @@ def call
       end
     end
   end
-end
+end

lib/kupo/phases/validate_host.rb

@@ -4,6 +4,7 @@ module Kupo::Phases
   class ValidateHost
     include Kupo::Phases::Logging
 
+    # @param host [Kupo::Configuration::Host]
     def initialize(host)
       @host = host
     end
@@ -18,4 +19,4 @@ def call
       end
     end
   end
-end
+end

lib/kupo/up_command.rb

@@ -115,6 +115,7 @@ def handle_masters(master, config)
       Phases::ConfigureKubelet.new(master).call
       Phases::ConfigureMaster.new(master, config.network).call
       Phases::ConfigureClient.new(master).call
+      Phases::ConfigureDNS.new(master, config).call
       Phases::ConfigureNetwork.new(master, config.network).call
       Phases::ConfigureMetrics.new(master).call
     end