feat: restore previous current context (#63)

When API Server stops will restore the previous context to be active.

Author: csviri

core/src/main/java/io/javaoperatorsdk/jenvtest/KubeAPIServer.java

@@ -55,7 +55,7 @@ public void stop() {
     log.debug("Stopping");
     kubeApiServerProcess.stopApiServer();
     etcdProcess.stopEtcd();
-    kubeConfig.cleanupFromKubeConfig();
+    kubeConfig.restoreKubeConfig();
     etcdProcess.cleanEtcdData();
     log.debug("Stopped");
   }

core/src/main/java/io/javaoperatorsdk/jenvtest/kubeconfig/KubeConfig.java

@@ -2,6 +2,7 @@
 
 import java.io.IOException;
 import java.io.InputStream;
+import java.nio.charset.Charset;
 import java.nio.charset.StandardCharsets;
 import java.text.MessageFormat;
 import java.util.ArrayList;
@@ -22,6 +23,7 @@ public class KubeConfig {
 
   private final CertManager certManager;
   private final BinaryManager binaryManager;
+  private String previousCurrentContext;
 
   public KubeConfig(CertManager certManager, BinaryManager binaryManager) {
     this.certManager = certManager;
@@ -30,6 +32,7 @@ public KubeConfig(CertManager certManager, BinaryManager binaryManager) {
 
   public void updateKubeConfig(int apiServerPort) {
     log.debug("Updating kubeconfig");
+    previousCurrentContext = execWithKubectlConfigAndWait("current-context").trim();
     execWithKubectlConfigAndWait("set-cluster", JENVTEST,
         "--server=https://127.0.0.1:" + apiServerPort,
         "--certificate-authority=" + certManager.getAPIServerCertPath());
@@ -41,12 +44,15 @@ public void updateKubeConfig(int apiServerPort) {
     execWithKubectlConfigAndWait("use-context", JENVTEST);
   }
 
-  public void cleanupFromKubeConfig() {
+  public void restoreKubeConfig() {
     log.debug("Cleanig up kubeconfig");
     unset("contexts." + JENVTEST);
     unset("clusters." + JENVTEST);
     unset("users." + JENVTEST);
     unset("current-context");
+    if (previousCurrentContext != null && !previousCurrentContext.isEmpty()) {
+      execWithKubectlConfigAndWait("use-context", previousCurrentContext);
+    }
   }
 
   private void unset(String target) {
@@ -65,14 +71,19 @@ public String generateKubeConfigYaml(int apiServerPort) {
     }
   }
 
-  private void execWithKubectlConfigAndWait(String... arguments) {
+  private String execWithKubectlConfigAndWait(String... arguments) {
     try {
       List<String> args = new ArrayList<>(arguments.length + 2);
       args.add(binaryManager.binaries().getKubectl().getPath());
       args.add("config");
       args.addAll(List.of(arguments));
       var process = new ProcessBuilder(args).start();
+      String stdout;
+      try (InputStream is = process.getInputStream()) {
+        stdout = IOUtils.toString(is, Charset.defaultCharset());
+      }
       process.waitFor();
+      return stdout;
     } catch (IOException e) {
       throw new JenvtestException(e);
     } catch (InterruptedException e) {

core/src/test/java/io/javaoperatorsdk/jenvtest/kubeconfig/KubeConfigTest.java

@@ -14,6 +14,7 @@ class KubeConfigTest {
   public static final String CLIENT_KEY_PATH = "~/.jenvtest/clientcertkey";
   public static final String CLIENT_CERT_PATH = "~/.jenvtest/clientcertpath";
   public static final int API_SERVER_PORT = 32101;
+
   CertManager certManagerMock = mock(CertManager.class);
   KubeConfig kubeConfig = new KubeConfig(certManagerMock, null);