feat(Kubernetes Client): add version / namespace calls.

This adds the possibility to fetch the version
of the actual kubernetes cluster via the client.

This adds the possiblity to fetch the used namespace
via downwardAPI, file, or default from kubernetes.

Author: Christoph Bühler

src/KubeOps.Testing/MockKubernetesClient.cs

@@ -24,6 +24,11 @@ public class MockKubernetesClient : IKubernetesClient
 
         public object? UpdateResult { get; set; }
 
+        public Task<string> GetCurrentNamespace(string downwardApiEnvName = "POD_NAMESPACE") =>
+            Task.FromResult("default");
+
+        public Task<VersionInfo> GetServerVersion() => Task.FromResult(new VersionInfo());
+
         public Task<TResource?> Get<TResource>(string name, string? @namespace = null)
             where TResource : class, IKubernetesObject<V1ObjectMeta>
             => Task.FromResult(GetResult as TResource);

src/KubeOps/Operator/Builder/OperatorBuilder.cs

@@ -118,26 +118,24 @@ internal IOperatorBuilder AddOperatorBase(OperatorSettings settings)
             Services.AddTransient<EntitySerializer>();
 
             Services.AddTransient<IKubernetesClient, KubernetesClient>();
+            Services.AddSingleton(KubernetesClientConfiguration.BuildDefaultConfig());
             Services.AddSingleton<IKubernetes>(
-                _ =>
+                services => new Kubernetes(
+                    services.GetRequiredService<KubernetesClientConfiguration>(),
+                    new ClientUrlFixer())
                 {
-                    var config = KubernetesClientConfiguration.BuildDefaultConfig();
-
-                    return new Kubernetes(config, new ClientUrlFixer())
+                    SerializationSettings =
+                    {
+                        ContractResolver = new NamingConvention(),
+                        Converters = new List<JsonConverter>
+                            { new StringEnumConverter { NamingStrategy = new CamelCaseNamingStrategy() } },
+                    },
+                    DeserializationSettings =
                     {
-                        SerializationSettings =
-                        {
-                            ContractResolver = new NamingConvention(),
-                            Converters = new List<JsonConverter>
-                                { new StringEnumConverter { NamingStrategy = new CamelCaseNamingStrategy() } },
-                        },
-                        DeserializationSettings =
-                        {
-                            ContractResolver = new NamingConvention(),
-                            Converters = new List<JsonConverter>
-                                { new StringEnumConverter { NamingStrategy = new CamelCaseNamingStrategy() } },
-                        },
-                    };
+                        ContractResolver = new NamingConvention(),
+                        Converters = new List<JsonConverter>
+                            { new StringEnumConverter { NamingStrategy = new CamelCaseNamingStrategy() } },
+                    },
                 });
 
             Services.AddTransient(typeof(IResourceCache<>), typeof(ResourceCache<>));

src/KubeOps/Operator/Client/IKubernetesClient.cs

@@ -12,6 +12,36 @@ public interface IKubernetesClient
     {
         IKubernetes ApiClient { get; }
 
+        /// <summary>
+        /// Returns the name of the current namespace.
+        /// To determine the current namespace the following places (in the given order) are checked:
+        /// <list type="number">
+        /// <item>
+        /// <description>The created kubernetes configuration (from file / incluster)</description>
+        /// </item>
+        /// <item>
+        /// <description>
+        ///     The env variable given as the param to the function (default "POD_NAMESPACE")
+        ///     which can be provided by the <a href="https://kubernetes.io/docs/tasks/inject-data-application/downward-api-volume-expose-pod-information/#capabilities-of-the-downward-api">kubernetes downward API</a>
+        /// </description>
+        /// </item>
+        /// <item>
+        /// <description>
+        ///     The fallback secret file if running on the cluster
+        ///     (/var/run/secrets/kubernetes.io/serviceaccount/namespace)
+        /// </description>
+        /// </item>
+        /// <item>
+        /// <description>"default"</description>
+        /// </item>
+        /// </list>
+        /// </summary>
+        /// <param name="downwardApiEnvName">Customizable name of the env var to check for the namespace.</param>
+        /// <returns>A string containing the current namespace (or a fallback of it).</returns>
+        Task<string> GetCurrentNamespace(string downwardApiEnvName = "POD_NAMESPACE");
+
+        Task<VersionInfo> GetServerVersion();
+
         Task<TResource?> Get<TResource>(string name, string? @namespace = null)
             where TResource : class, IKubernetesObject<V1ObjectMeta>;
 

src/KubeOps/Operator/Client/KubernetesClient.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Net;
 using System.Threading;
@@ -16,13 +17,42 @@ namespace KubeOps.Operator.Client
 {
     internal class KubernetesClient : IKubernetesClient
     {
-        public KubernetesClient(IKubernetes apiClient)
+        private const string DownwardApiNamespaceFile = "/var/run/secrets/kubernetes.io/serviceaccount/namespace";
+        private const string DefaultNamespace = "default";
+
+        private readonly KubernetesClientConfiguration _clientConfig;
+
+        public KubernetesClient(IKubernetes apiClient, KubernetesClientConfiguration clientConfig)
         {
+            _clientConfig = clientConfig;
             ApiClient = apiClient;
         }
 
         public IKubernetes ApiClient { get; }
 
+        public async Task<string> GetCurrentNamespace(string downwardApiEnvName = "POD_NAMESPACE")
+        {
+            if (_clientConfig.Namespace != null)
+            {
+                return _clientConfig.Namespace;
+            }
+
+            if (Environment.GetEnvironmentVariable(downwardApiEnvName) != null)
+            {
+                return Environment.GetEnvironmentVariable(downwardApiEnvName) ?? string.Empty;
+            }
+
+            if (File.Exists(DownwardApiNamespaceFile))
+            {
+                var ns = await File.ReadAllTextAsync(DownwardApiNamespaceFile) ?? string.Empty;
+                return ns.Trim();
+            }
+
+            return DefaultNamespace;
+        }
+
+        public Task<VersionInfo> GetServerVersion() => ApiClient.GetCodeAsync();
+
         public async Task<TResource?> Get<TResource>(
             string name,
             string? @namespace = null)

src/KubeOps/Operator/Commands/RunOperator.cs

@@ -1,6 +1,7 @@
 using System.Threading.Tasks;
 using KubeOps.Operator.Commands.Generators;
 using KubeOps.Operator.Commands.Management;
+using KubeOps.Operator.Commands.Utilities;
 using McMaster.Extensions.CommandLineUtils;
 using Microsoft.Extensions.Hosting;
 
@@ -10,6 +11,7 @@ namespace KubeOps.Operator.Commands
     [Subcommand(typeof(Generator))]
     [Subcommand(typeof(Install))]
     [Subcommand(typeof(Uninstall))]
+    [Subcommand(typeof(Version))]
     internal class RunOperator
     {
         private readonly IHost _host;

src/KubeOps/Operator/Commands/Utilities/Version.cs

@@ -0,0 +1,33 @@
+using System.Threading.Tasks;
+using KubeOps.Operator.Client;
+using McMaster.Extensions.CommandLineUtils;
+
+namespace KubeOps.Operator.Commands.Utilities
+{
+    [Command(
+        "version",
+        "v",
+        Description = "Prints the actual server version of the connected kubernetes cluster.")]
+    internal class Version
+    {
+        private readonly IKubernetesClient _client;
+
+        public Version(IKubernetesClient client)
+        {
+            _client = client;
+        }
+
+        public async Task<int> OnExecuteAsync(CommandLineApplication app)
+        {
+            var version = await _client.GetServerVersion();
+            await app.Out.WriteLineAsync(
+                $@"The kubernetes api reported the following version:
+Git-Version: {version.GitVersion}
+Major:       {version.Major}
+Minor:       {version.Minor}
+Platform:    {version.Platform}");
+
+            return ExitCodes.Success;
+        }
+    }
+}