Make jenkins agent more flexible (#1602)

README.md

@@ -185,7 +185,12 @@ spec:
 Multiple containers can be defined for the agent pod, with shared resources, like mounts. Ports in each container can
 be accessed as in any Kubernetes pod, by using `localhost`.
 
-The `container` step allows executing commands into each container.
+One container must run the Jenkins agent. If unspecified, a container named `jnlp` will be created with the inbound-agent image.
+The Jenkins agent requires a JRE to run, so you can avoid the extra container by providing a name using the `agentContainer`.
+To get the Jenkins agent injected, you will also need to set `agentInjection` to `true`, and leave the command and argument fields empty for this container.
+The container specified by `agentContainer` will be the one where shell steps (or any other step running remote commands on the agent) will run on.
+
+To execute commands in another container part of the pod (different from the one running the Jenkins agent), you can use the `container` step.
 
 **Note**
 ---
@@ -194,8 +199,11 @@ It is recommended to use the same uid across the different containers part of th
 ---
 
 ```groovy
-podTemplate(containers: [
-    containerTemplate(name: 'maven', image: 'maven:3.8.1-jdk-8', command: 'sleep', args: '99d'),
+podTemplate(
+  agentContainer: 'maven',
+  agentInjection: true,
+  containers: [
+    containerTemplate(name: 'maven', image: 'maven:3.9.9-eclipse-temurin-17'),
     containerTemplate(name: 'golang', image: 'golang:1.16.5', command: 'sleep', args: '99d')
   ]) {
 
@@ -229,17 +237,16 @@ podTemplate(containers: [
 or
 
 ```groovy
-podTemplate(yaml: '''
+podTemplate(
+  agentContainer: 'maven',
+  agentInjection: true,
+  yaml: '''
     apiVersion: v1
     kind: Pod
     spec:
       containers:
       - name: maven
-        image: maven:3.8.1-jdk-8
-        command:
-        - sleep
-        args:
-        - 99d
+        image: maven:3.9.9-eclipse-temurin-17
       - name: golang
         image: golang:1.16.5
         command:
@@ -269,7 +276,6 @@ podTemplate(yaml: '''
         }
       }
     }
-
   }
 }
 ```

examples/maven-with-cache.groovy

@@ -7,18 +7,14 @@
  * two concurrent jobs with this pipeline. Or change readOnly: true after the first run
  */
 
-podTemplate(containers: [
-  containerTemplate(name: 'maven', image: 'maven:3.8.1-jdk-8', command: 'sleep', args: '99d')
-  ], volumes: [
-  persistentVolumeClaim(mountPath: '/root/.m2/repository', claimName: 'maven-repo', readOnly: false)
-  ]) {
+podTemplate(agentContainer: 'maven', agentInjection: true, containers: [
+  containerTemplate(name: 'maven', image: 'maven:3.9.9-eclipse-temurin-17')
+  ], volumes: [genericEphemeralVolume(accessModes: 'ReadWriteOnce', mountPath: '/root/.m2/repository', requestsSize: '1Gi')]) {
 
   node(POD_LABEL) {
     stage('Build a Maven project') {
       git 'https://github.com/jenkinsci/kubernetes-plugin.git'
-      container('maven') {
-        sh 'mvn -B -ntp clean package -DskipTests'
-      }
+      sh 'mvn -B -ntp clean package -DskipTests'
     }
   }
 }

examples/multi-container.groovy

@@ -2,32 +2,27 @@
  * This pipeline describes a multi container job, running Maven and Golang builds
  */
 
-podTemplate(yaml: '''
-              apiVersion: v1
-              kind: Pod
-              spec:
-                containers:
-                - name: maven
-                  image: maven:3.8.1-jdk-8
-                  command:
-                  - sleep
-                  args:
-                  - 99d
-                - name: golang
-                  image: golang:1.16.5
-                  command:
-                  - sleep
-                  args:
-                  - 99d
+podTemplate(agentContainer: 'maven',
+            agentInjection: true,
+            yaml: '''
+apiVersion: v1
+kind: Pod
+spec:
+  containers:
+  - name: maven
+    image: maven:3.9.9-eclipse-temurin-17
+  - name: golang
+    image: golang:1.23.1-bookworm
+    command:
+    - sleep
+    args:
+    - 99d
 '''
   ) {
-
   node(POD_LABEL) {
     stage('Build a Maven project') {
       git 'https://github.com/jenkinsci/kubernetes-plugin.git'
-      container('maven') {
-        sh 'mvn -B -ntp clean package -DskipTests'
-      }
+      sh 'mvn -B -ntp clean package -DskipTests'
     }
     stage('Build a Golang project') {
       git url: 'https://github.com/hashicorp/terraform.git', branch: 'main'

src/main/java/org/csanchez/jenkins/plugins/kubernetes/PodTemplate.java

@@ -188,6 +188,10 @@ protected static MessageDigest getLabelDigestFunction() {
 
     private Long terminationGracePeriodSeconds;
 
+    private String agentContainer;
+
+    private boolean agentInjection;
+
     /**
      * Persisted yaml fragment
      */
@@ -638,6 +642,25 @@ public boolean isCapOnlyOnAlivePods() {
         return capOnlyOnAlivePods;
     }
 
+    @CheckForNull
+    public String getAgentContainer() {
+        return agentContainer;
+    }
+
+    @DataBoundSetter
+    public void setAgentContainer(@CheckForNull String agentContainer) {
+        this.agentContainer = Util.fixEmpty(agentContainer);
+    }
+
+    public boolean isAgentInjection() {
+        return agentInjection;
+    }
+
+    @DataBoundSetter
+    public void setAgentInjection(boolean agentInjection) {
+        this.agentInjection = agentInjection;
+    }
+
     public List<TemplateEnvVar> getEnvVars() {
         if (envVars == null) {
             return Collections.emptyList();
@@ -1173,6 +1196,8 @@ public String toString() {
                 + (nodeProperties == null || nodeProperties.isEmpty() ? "" : ", nodeProperties=" + nodeProperties)
                 + (yamls == null || yamls.isEmpty() ? "" : ", yamls=" + yamls)
                 + (!unwrapped ? "" : ", unwrapped=" + unwrapped)
+                + (agentContainer == null ? "" : ", agentContainer='" + agentContainer + '\'')
+                + (!agentInjection ? "" : ", agentInjection=" + agentInjection)
                 + '}';
     }
 }

src/main/java/org/csanchez/jenkins/plugins/kubernetes/PodTemplateBuilder.java

@@ -24,6 +24,7 @@
 
 package org.csanchez.jenkins.plugins.kubernetes;
 
+import static org.csanchez.jenkins.plugins.kubernetes.ContainerTemplate.DEFAULT_WORKING_DIR;
 import static org.csanchez.jenkins.plugins.kubernetes.KubernetesCloud.JNLP_NAME;
 import static org.csanchez.jenkins.plugins.kubernetes.PodTemplateUtils.combine;
 import static org.csanchez.jenkins.plugins.kubernetes.PodTemplateUtils.isNullOrEmpty;
@@ -41,6 +42,7 @@
 import io.fabric8.kubernetes.api.model.ContainerBuilder;
 import io.fabric8.kubernetes.api.model.ContainerPort;
 import io.fabric8.kubernetes.api.model.EnvVar;
+import io.fabric8.kubernetes.api.model.EnvVarBuilder;
 import io.fabric8.kubernetes.api.model.ExecAction;
 import io.fabric8.kubernetes.api.model.LocalObjectReference;
 import io.fabric8.kubernetes.api.model.Pod;
@@ -51,6 +53,7 @@
 import io.fabric8.kubernetes.api.model.ResourceRequirements;
 import io.fabric8.kubernetes.api.model.ResourceRequirementsBuilder;
 import io.fabric8.kubernetes.api.model.Volume;
+import io.fabric8.kubernetes.api.model.VolumeBuilder;
 import io.fabric8.kubernetes.api.model.VolumeMount;
 import io.fabric8.kubernetes.api.model.VolumeMountBuilder;
 import io.fabric8.kubernetes.client.utils.Serialization;
@@ -101,6 +104,9 @@ public class PodTemplateBuilder {
     public static final String LABEL_KUBERNETES_CONTROLLER = "kubernetes.jenkins.io/controller";
     static final String NO_RECONNECT_AFTER_TIMEOUT =
             SystemProperties.getString(PodTemplateBuilder.class.getName() + ".noReconnectAfter", "1d");
+    private static final String JENKINS_AGENT_FILE_ENVVAR = "JENKINS_AGENT_FILE";
+    private static final String JENKINS_AGENT_AGENT_JAR = "/jenkins-agent/agent.jar";
+    private static final String JENKINS_AGENT_LAUNCHER_SCRIPT_LOCATION = "/jenkins-agent/jenkins-agent";
 
     @SuppressFBWarnings(value = "MS_SHOULD_BE_FINAL", justification = "tests")
     @Restricted(NoExternalUse.class)
@@ -124,7 +130,7 @@ public class PodTemplateBuilder {
     }
 
     @Restricted(NoExternalUse.class)
-    static final String DEFAULT_JNLP_IMAGE =
+    static final String DEFAULT_AGENT_IMAGE =
             System.getProperty(PodTemplateStepExecution.class.getName() + ".defaultImage", defaultImageName);
 
     static final String DEFAULT_JNLP_CONTAINER_MEMORY_REQUEST = System.getProperty(
@@ -309,39 +315,92 @@ public Pod build() {
             }
         }
 
-        // default jnlp container
-        Optional<Container> jnlpOpt = pod.getSpec().getContainers().stream()
-                .filter(c -> JNLP_NAME.equals(c.getName()))
+        // default agent container
+        String agentContainerName = StringUtils.defaultString(template.getAgentContainer(), JNLP_NAME);
+        Optional<Container> agentOpt = pod.getSpec().getContainers().stream()
+                .filter(c -> agentContainerName.equals(c.getName()))
                 .findFirst();
-        Container jnlp = jnlpOpt.orElse(new ContainerBuilder()
-                .withName(JNLP_NAME)
-                .withVolumeMounts(volumeMounts
-                        .values()
-                        .toArray(new VolumeMount[volumeMounts.values().size()]))
+        Container agentContainer = agentOpt.orElse(new ContainerBuilder()
+                .withName(agentContainerName)
+                .withVolumeMounts(volumeMounts.values().toArray(VolumeMount[]::new))
                 .build());
-        if (!jnlpOpt.isPresent()) {
-            pod.getSpec().getContainers().add(jnlp);
+        if (agentOpt.isEmpty()) {
+            pod.getSpec().getContainers().add(agentContainer);
         }
+        var workingDir = agentContainer.getWorkingDir();
         pod.getSpec().getContainers().stream()
                 .filter(c -> c.getWorkingDir() == null)
-                .forEach(c -> c.setWorkingDir(jnlp.getWorkingDir()));
-        if (StringUtils.isBlank(jnlp.getImage())) {
-            String jnlpImage = DEFAULT_JNLP_IMAGE;
+                .forEach(c -> c.setWorkingDir(workingDir));
+        if (StringUtils.isBlank(agentContainer.getImage())) {
+            String agentImage = DEFAULT_AGENT_IMAGE;
             if (cloud != null && StringUtils.isNotEmpty(cloud.getJnlpregistry())) {
-                jnlpImage = Util.ensureEndsWith(cloud.getJnlpregistry(), "/") + jnlpImage;
+                agentImage = Util.ensureEndsWith(cloud.getJnlpregistry(), "/") + agentImage;
             } else if (StringUtils.isNotEmpty(DEFAULT_JNLP_DOCKER_REGISTRY_PREFIX)) {
-                jnlpImage = Util.ensureEndsWith(DEFAULT_JNLP_DOCKER_REGISTRY_PREFIX, "/") + jnlpImage;
+                agentImage = Util.ensureEndsWith(DEFAULT_JNLP_DOCKER_REGISTRY_PREFIX, "/") + agentImage;
             }
-            jnlp.setImage(jnlpImage);
+            agentContainer.setImage(agentImage);
         }
         Map<String, EnvVar> envVars = new HashMap<>();
-        envVars.putAll(jnlpEnvVars(jnlp.getWorkingDir()));
+        envVars.putAll(agentEnvVars(workingDir));
         envVars.putAll(defaultEnvVars(template.getEnvVars()));
-        Optional.ofNullable(jnlp.getEnv()).ifPresent(jnlpEnv -> {
-            jnlpEnv.forEach(var -> envVars.put(var.getName(), var));
+        Optional.ofNullable(agentContainer.getEnv()).ifPresent(agentEnv -> {
+            agentEnv.forEach(var -> envVars.put(var.getName(), var));
         });
-        jnlp.setEnv(new ArrayList<>(envVars.values()));
-        if (jnlp.getResources() == null) {
+        if (template.isAgentInjection()) {
+            var agentVolumeMountBuilder =
+                    new VolumeMountBuilder().withName("jenkins-agent").withMountPath("/jenkins-agent");
+            var oldInitContainers = pod.getSpec().getInitContainers();
+            var jenkinsAgentInitContainer = new ContainerBuilder()
+                    .withName("set-up-jenkins-agent")
+                    .withImage(DEFAULT_AGENT_IMAGE)
+                    .withCommand(
+                            "/bin/sh",
+                            "-c",
+                            "cp $(command -v jenkins-agent) " + JENKINS_AGENT_LAUNCHER_SCRIPT_LOCATION + ";"
+                                    + "cp /usr/share/jenkins/agent.jar " + JENKINS_AGENT_AGENT_JAR)
+                    .withVolumeMounts(agentVolumeMountBuilder.build())
+                    .build();
+            if (oldInitContainers != null) {
+                var newInitContainers = new ArrayList<>(oldInitContainers);
+                newInitContainers.add(jenkinsAgentInitContainer);
+                pod.getSpec().setInitContainers(newInitContainers);
+            } else {
+                pod.getSpec().setInitContainers(List.of(jenkinsAgentInitContainer));
+            }
+            var oldVolumes = pod.getSpec().getVolumes();
+            var jenkinsAgentSharedVolume = new VolumeBuilder()
+                    .withName("jenkins-agent")
+                    .withNewEmptyDir()
+                    .and()
+                    .build();
+            if (oldVolumes != null) {
+                var newVolumes = new ArrayList<>(oldVolumes);
+                newVolumes.add(jenkinsAgentSharedVolume);
+                pod.getSpec().setVolumes(newVolumes);
+            } else {
+                pod.getSpec().setVolumes(List.of(jenkinsAgentSharedVolume));
+            }
+            var existingVolumeMounts = agentContainer.getVolumeMounts();
+            if (existingVolumeMounts != null) {
+                var newVolumeMounts = new ArrayList<>(existingVolumeMounts);
+                newVolumeMounts.add(agentVolumeMountBuilder.withReadOnly().build());
+                agentContainer.setVolumeMounts(newVolumeMounts);
+            } else {
+                agentContainer.setVolumeMounts(
+                        List.of(agentVolumeMountBuilder.withReadOnly().build()));
+            }
+            agentContainer.setWorkingDir(DEFAULT_WORKING_DIR);
+            agentContainer.setCommand(List.of(JENKINS_AGENT_LAUNCHER_SCRIPT_LOCATION));
+            agentContainer.setArgs(List.of());
+            envVars.put(
+                    JENKINS_AGENT_FILE_ENVVAR,
+                    new EnvVarBuilder()
+                            .withName(JENKINS_AGENT_FILE_ENVVAR)
+                            .withValue(JENKINS_AGENT_AGENT_JAR)
+                            .build());
+        }
+        agentContainer.setEnv(new ArrayList<>(envVars.values()));
+        if (agentContainer.getResources() == null) {
 
             Map<String, Quantity> reqMap = new HashMap<>();
             Map<String, Quantity> limMap = new HashMap<>();
@@ -361,7 +420,7 @@ public Pod build() {
                     .withLimits(limMap)
                     .build();
 
-            jnlp.setResources(reqs);
+            agentContainer.setResources(reqs);
         }
         if (cloud != null) {
             pod = PodDecorator.decorateAll(cloud, pod);
@@ -406,9 +465,9 @@ private Map<String, EnvVar> defaultEnvVars(Collection<TemplateEnvVar> globalEnvV
         return envVarsMap;
     }
 
-    private Map<String, EnvVar> jnlpEnvVars(String workingDir) {
+    private Map<String, EnvVar> agentEnvVars(String workingDir) {
         if (workingDir == null) {
-            workingDir = ContainerTemplate.DEFAULT_WORKING_DIR;
+            workingDir = DEFAULT_WORKING_DIR;
         }
         // Last-write wins map of environment variable names to values
         HashMap<String, String> env = new HashMap<>();
@@ -462,7 +521,7 @@ private Container createContainer(
         Map<String, EnvVar> envVarsMap = new HashMap<>();
         String workingDir = substituteEnv(containerTemplate.getWorkingDir());
         if (JNLP_NAME.equals(containerTemplate.getName())) {
-            envVarsMap.putAll(jnlpEnvVars(workingDir));
+            envVarsMap.putAll(agentEnvVars(workingDir));
         }
         envVarsMap.putAll(defaultEnvVars(globalEnvVars));
 
@@ -541,7 +600,7 @@ private Container createContainer(
     private VolumeMount getDefaultVolumeMount(@CheckForNull String workingDir) {
         String wd = workingDir;
         if (wd == null) {
-            wd = ContainerTemplate.DEFAULT_WORKING_DIR;
+            wd = DEFAULT_WORKING_DIR;
             LOGGER.log(Level.FINE, "Container workingDir is null, defaulting to {0}", wd);
         }
         return new VolumeMountBuilder()