Add resource version parameter for kubernetes strategy

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+- Add `kubernetes_use_cached_resources` option to Kubernetes strategy
+
+## 3.4.1
+
 - Use new cypher names
 - Allow Epmd strategy to reconnect after connection failures
 - Detect Self Signed Certificate Authority for Kubernetes Strategy

lib/strategy/kubernetes.ex

@@ -25,6 +25,7 @@ defmodule Cluster.Strategy.Kubernetes do
      - `:kubernetes_selector`
      - `:kubernetes_service_name`
      - `:kubernetes_ip_lookup_mode`
+     - `:kubernetes_use_cached_resources`
      - `:mode`
 
   ## Getting `<basename>`
@@ -70,6 +71,11 @@ defmodule Cluster.Strategy.Kubernetes do
 
   Then, this strategy will fetch the IP of all pods with that label and attempt to connect.
 
+  ### `kubernetes_use_cached_resources` option
+
+  When setting this value, this strategy will use cached resource version value to fetch k8s resources.
+  In k8s resources are incremented by 1 on every change, this version will set requested resourceVersion
+  to 0, that will use cached versions of resources, take in mind that this may be outdated or unavailable.
 
   ### `:mode` option
 
@@ -362,6 +368,9 @@ defmodule Cluster.Strategy.Kubernetes do
     selector = Keyword.fetch!(config, :kubernetes_selector)
     ip_lookup_mode = Keyword.get(config, :kubernetes_ip_lookup_mode, :endpoints)
 
+    use_cache = Keyword.get(config, :kubernetes_use_cached_resources, false)
+    resource_version = if use_cache, do: 0, else: nil
+
     master_name = Keyword.get(config, :kubernetes_master, @kubernetes_master)
     cluster_domain = System.get_env("CLUSTER_DOMAIN", "#{cluster_name}.local")
 
@@ -380,12 +389,19 @@ defmodule Cluster.Strategy.Kubernetes do
 
     cond do
       app_name != nil and selector != nil ->
-        selector = URI.encode(selector)
+        query_params =
+          []
+          |> apply_param(:labelSelector, selector)
+          |> apply_param(:resourceVersion, resource_version)
+          |> URI.encode_query(:rfc3986)
 
         path =
           case ip_lookup_mode do
-            :endpoints -> "api/v1/namespaces/#{namespace}/endpoints?labelSelector=#{selector}"
-            :pods -> "api/v1/namespaces/#{namespace}/pods?labelSelector=#{selector}"
+            :endpoints ->
+              "api/v1/namespaces/#{namespace}/endpoints?#{query_params}"
+
+            :pods ->
+              "api/v1/namespaces/#{namespace}/pods?#{query_params}"
           end
 
         headers = [{~c"authorization", ~c"Bearer #{token}"}]
@@ -440,6 +456,12 @@ defmodule Cluster.Strategy.Kubernetes do
     end
   end
 
+  defp apply_param(params, key, value) when value != nil do
+    [{key, value} | params]
+  end
+
+  defp apply_param(params, _key, _value), do: params
+
   defp parse_response(:endpoints, resp) do
     case resp do
       %{"items" => items} when is_list(items) ->

test/fixtures/vcr_cassettes/kubernetes.json

@@ -31,6 +31,38 @@
       "type": "ok"
     }
   },
+  {
+    "request": {
+      "body": "",
+      "headers": {
+        "authorization": "***"
+      },
+      "method": "get",
+      "options": {
+        "httpc_options": [],
+        "http_options": {
+          "ssl": "[verify: :verify_none]"
+        }
+      },
+      "request_body": "",
+      "url": "https://cluster.localhost./api/v1/namespaces/__libcluster_test/endpoints?labelSelector=app=test_selector&resourceVersion=0"
+    },
+    "response": {
+      "binary": false,
+      "body": "{\"kind\":\"EndpointsList\",\"apiVersion\":\"v1\",\"metadata\":{\"selfLink\":\"SELFLINK_PLACEHOLDER\",\"resourceVersion\":\"17042410\"},\"items\":[{\"metadata\":{\"name\":\"development-development\",\"namespace\":\"airatel-service-localization\",\"selfLink\":\"SELFLINK_PLACEHOLDER\",\"uid\":\"7e3faf1e-0294-11e8-bcad-42010a9c01cc\",\"resourceVersion\":\"17037787\",\"creationTimestamp\":\"2018-01-26T12:29:03Z\",\"labels\":{\"app\":\"development\",\"chart\":\"CHART_PLACEHOLDER\"}},\"subsets\":[{\"addresses\":[{\"hostname\":\"my-hostname-0\",\"ip\":\"10.48.33.136\",\"nodeName\":\"gke-jshmrtn-cluster-default-pool-a61da41f-db9x\",\"targetRef\":{\"kind\":\"Pod\",\"namespace\":\"airatel-service-localization\",\"name\":\"development-4292695165-mgq9f\",\"uid\":\"eb0f3e80-0295-11e8-bcad-42010a9c01cc\",\"resourceVersion\":\"17037783\"}}],\"ports\":[{\"name\":\"web\",\"port\":8443,\"protocol\":\"TCP\"}]}]}]}\n",
+      "headers": {
+        "date": "Fri, 26 Jan 2018 13:18:46 GMT",
+        "content-length": "877",
+        "content-type": "application/json"
+      },
+      "status_code": [
+        "HTTP/1.1",
+        200,
+        "OK"
+      ],
+      "type": "ok"
+    }
+  },
   {
     "request": {
       "body": "",

test/fixtures/vcr_cassettes/kubernetes_pods.json

@@ -30,5 +30,37 @@
       ],
       "type": "ok"
     }
+  },
+  {
+    "request": {
+      "body": "",
+      "headers": {
+        "authorization": "***"
+      },
+      "method": "get",
+      "options": {
+        "httpc_options": [],
+        "http_options": {
+          "ssl": "[verify: :verify_none]"
+        }
+      },
+      "request_body": "",
+      "url": "https://cluster.localhost./api/v1/namespaces/__libcluster_test/pods?labelSelector=app=test_selector&resourceVersion=0"
+    },
+    "response": {
+      "binary": false,
+      "body": "{\"kind\":\"PodList\",\"apiVersion\":\"v1\",\"metadata\":{\"selfLink\":\"SELFLINK_PLACEHOLDER\",\"resourceVersion\":\"17042410\"},\"items\":[{\"metadata\":{\"name\":\"development-development\",\"namespace\":\"airatel-service-localization\",\"selfLink\":\"SELFLINK_PLACEHOLDER\",\"uid\":\"7e3faf1e-0294-11e8-bcad-42010a9c01cc\",\"resourceVersion\":\"17037787\",\"creationTimestamp\":\"2018-01-26T12:29:03Z\",\"labels\":{\"app\":\"development\",\"chart\":\"CHART_PLACEHOLDER\"}},\"spec\": { \"hostname\": \"my-hostname-0\" },\"status\":{\"podIP\": \"10.48.33.136\"}}]}\n",
+      "headers": {
+        "date": "Fri, 26 Jan 2018 13:18:46 GMT",
+        "content-length": "877",
+        "content-type": "application/json"
+      },
+      "status_code": [
+        "HTTP/1.1",
+        200,
+        "OK"
+      ],
+      "type": "ok"
+    }
   }
 ]

test/kubernetes_test.exs

@@ -81,6 +81,60 @@ defmodule Cluster.Strategy.KubernetesTest do
       end
     end
 
+    test "works with cached resources" do
+      use_cassette "kubernetes", custom: true do
+        capture_log(fn ->
+          start_supervised!({Kubernetes,
+           [
+             %Cluster.Strategy.State{
+               topology: :name,
+               config: [
+                 kubernetes_node_basename: "test_basename",
+                 kubernetes_selector: "app=test_selector",
+                 kubernetes_use_cached_resources: true,
+                 # If you want to run the test freshly, you'll need to create a DNS Entry
+                 kubernetes_master: "cluster.localhost.",
+                 kubernetes_service_account_path:
+                   Path.join([__DIR__, "fixtures", "kubernetes", "service_account"])
+               ],
+               connect: {Nodes, :connect, [self()]},
+               disconnect: {Nodes, :disconnect, [self()]},
+               list_nodes: {Nodes, :list_nodes, [[]]}
+             }
+           ]})
+
+          assert_receive {:connect, _}, 5_000
+        end)
+      end
+    end
+
+    test "works with no cached resources" do
+      use_cassette "kubernetes", custom: true do
+        capture_log(fn ->
+          start_supervised!({Kubernetes,
+           [
+             %Cluster.Strategy.State{
+               topology: :name,
+               config: [
+                 kubernetes_node_basename: "test_basename",
+                 kubernetes_selector: "app=test_selector",
+                 kubernetes_use_cached_resources: false,
+                 # If you want to run the test freshly, you'll need to create a DNS Entry
+                 kubernetes_master: "cluster.localhost.",
+                 kubernetes_service_account_path:
+                   Path.join([__DIR__, "fixtures", "kubernetes", "service_account"])
+               ],
+               connect: {Nodes, :connect, [self()]},
+               disconnect: {Nodes, :disconnect, [self()]},
+               list_nodes: {Nodes, :list_nodes, [[]]}
+             }
+           ]})
+
+          assert_receive {:connect, _}, 5_000
+        end)
+      end
+    end
+
     test "works with dns and cluster_name" do
       use_cassette "kubernetes", custom: true do
         capture_log(fn ->
@@ -201,6 +255,34 @@ defmodule Cluster.Strategy.KubernetesTest do
       end
     end
 
+    test "works with pods and cached resources" do
+      use_cassette "kubernetes_pods", custom: true do
+        capture_log(fn ->
+          start_supervised!({Kubernetes,
+           [
+             %Cluster.Strategy.State{
+               topology: :name,
+               config: [
+                 kubernetes_node_basename: "test_basename",
+                 kubernetes_selector: "app=test_selector",
+                 # If you want to run the test freshly, you'll need to create a DNS Entry
+                 kubernetes_master: "cluster.localhost.",
+                 kubernetes_ip_lookup_mode: :pods,
+                 kubernetes_use_cached_resources: true,
+                 kubernetes_service_account_path:
+                   Path.join([__DIR__, "fixtures", "kubernetes", "service_account"])
+               ],
+               connect: {Nodes, :connect, [self()]},
+               disconnect: {Nodes, :disconnect, [self()]},
+               list_nodes: {Nodes, :list_nodes, [[]]}
+             }
+           ]})
+
+          assert_receive {:connect, :"test_basename@10.48.33.136"}, 5_000
+        end)
+      end
+    end
+
     test "works with pods and dns" do
       use_cassette "kubernetes_pods", custom: true do
         capture_log(fn ->