DevOps

kpack - A guide to build optimized app-image

kpack extends Kubernetes and utilizes it’s capabilities for building OCI images as a platform implementation of Cloud Native Buildpacks (CNB)

May 1, 2021 16 min read

#Kubernetes #Kpack

kpack extends Kubernetes and utilizes kubernetes capabilities to provide builds of OCI images as a platform implementation of Cloud Native Buildpacks (CNB). It provides a declarative image type that builds an image ( with app source and configurations) and then schedules image rebuilds for any source or underlying buildpack changes.

Some history about kpack

Buildpacks were first conceived by Heroku in 2011. Later, Pivotal and Heroku teamed up to create Cloud Native Buildpacks for Kubernetes. Then, Pivotal open-sourced kpack, which started as an experimental build service Kubernetes resource controllers but soon going to be the key to app build and modernisation process.

Prerequisites for image build

A Kubernetes cluster version 1.15 or later
kubectl CLI
User with cluster-admin permission
Accessible Docker V2 Registry

Configure kpack

kpack services provide a kubernetes build type to execute a single Cloud Native Buildpack image build. The process generates an image resource which actively keeps watch on any buildpack or source change for rebuild. For supporting the App image creation process, there would be a cache maintained as persistent-storage for each image resource with all the underlying app dependencies & supporting resources during image build process.

Install kpack

We can download the resources for kpack from here We can apply resources to install kpack to a kubernetes cluster.

kubectl apply -f release-0.0.9.yaml

Result shows various resource created in k8s cluster.

$ kubectl apply -f release-0.2.2.yamlnamespace/kpack createdcustomresourcedefinition.apiextensions.k8s.io/builds.kpack.io createdcustomresourcedefinition.apiextensions.k8s.io/builders.kpack.io createdcustomresourcedefinition.apiextensions.k8s.io/clusterbuilders.kpack.io createdcustomresourcedefinition.apiextensions.k8s.io/clusterstores.kpack.io createdconfigmap/build-init-image createdconfigmap/build-init-windows-image createdconfigmap/rebase-image createdconfigmap/lifecycle-image createdconfigmap/completion-image createdconfigmap/completion-windows-image createddeployment.apps/kpack-controller createdserviceaccount/controller createdclusterrole.rbac.authorization.k8s.io/kpack-controller-admin createdclusterrolebinding.rbac.authorization.k8s.io/kpack-controller-admin-binding createdrole.rbac.authorization.k8s.io/kpack-controller-local-config createdrolebinding.rbac.authorization.k8s.io/kpack-controller-local-config-binding createdcustomresourcedefinition.apiextensions.k8s.io/images.kpack.io createdservice/kpack-webhook createdcustomresourcedefinition.apiextensions.k8s.io/sourceresolvers.kpack.io createdcustomresourcedefinition.apiextensions.k8s.io/clusterstacks.kpack.io createdWarning: admissionregistration.k8s.io/v1beta1 MutatingWebhookConfiguration is deprecated in v1.16+, unavailable in v1.22+; use admissionregistration.k8s.io/v1 MutatingWebhookConfigurationmutatingwebhookconfiguration.admissionregistration.k8s.io/defaults.webhook.kpack.io createdWarning: admissionregistration.k8s.io/v1beta1 ValidatingWebhookConfiguration is deprecated in v1.16+, unavailable in v1.22+; use admissionregistration.k8s.io/v1 ValidatingWebhookConfigurationvalidatingwebhookconfiguration.admissionregistration.k8s.io/validation.webhook.kpack.io createdsecret/webhook-certs createddeployment.apps/kpack-webhook createdserviceaccount/webhook createdrole.rbac.authorization.k8s.io/kpack-webhook-certs-admin createdrolebinding.rbac.authorization.k8s.io/kpack-webhook-certs-admin-binding createdclusterrole.rbac.authorization.k8s.io/kpack-webhook-mutatingwebhookconfiguration-admin createdclusterrolebinding.rbac.authorization.k8s.io/kpack-webhook-certs-mutatingwebhookconfiguration-admin-binding created

We can observe the controller and webhook resources created for kpack.

$ kubectl get all -n kpackNAME                                    READY   STATUS    RESTARTS   AGEpod/kpack-controller-6d7b8f49ff-fcc8d   1/1     Running   0          17spod/kpack-webhook-597484b97-pzbtp       1/1     Running   0          17sNAME                    TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)   AGEservice/kpack-webhook   ClusterIP   100.71.36.244   <none>        443/TCP   18sNAME                               READY   UP-TO-DATE   AVAILABLE   AGEdeployment.apps/kpack-controller   1/1     1            1           18sdeployment.apps/kpack-webhook      1/1     1            1           18sNAME                                          DESIRED   CURRENT   READY   AGEreplicaset.apps/kpack-controller-6d7b8f49ff   1         1         1       18sreplicaset.apps/kpack-webhook-597484b97       1         1         1       18s

Once we install kpack, the following kubernetes custom resources get installed in to the cluster.

$ kubectl api-resources | grep kpack -ibuilders                          bldr,bldrs                    kpack.io/v1alpha1                                    true         Builderbuilds                            cnbbuild,cnbbuilds,bld,blds   kpack.io/v1alpha1                                    true         Buildclusterbuilders                   clstbldr,clstbldrs            kpack.io/v1alpha1                                    false        ClusterBuilderclusterstacks                                                   kpack.io/v1alpha1                                    false        ClusterStackclusterstores                                                   kpack.io/v1alpha1                                    false        ClusterStoreimages                            cnbimage,cnbimages,img,imgs   kpack.io/v1alpha1                                    true         Imagesourceresolvers                                                 kpack.io/v1alpha1                                    true         SourceResolver

Add custom certs to kpack

In case we are using a registry that has a self-signed certificate, need to update kpack controller to trust that certificate. It can be done by using SSL_CERT_FILE and SSL_CERT_DIR environment variables, so registry can be trusted by mounting the certificates into the controller’s deployment and setting the environment variable.

To perform, we need to create a kubernetes secret of tls type with the cert and key for the registry’s CA. Then, mount the secret into kpack controller and pass the path as an environment variable.

$ kubectl create secret tls  custom-ca --cert=ca.crt --key=ca.key -n kpacksecret/custom-ca created$ kubectl edit deploy kpack-controller -n kpackapiVersion: apps/v1kind: Deploymentmetadata:  name: kpack-controller  namespace: kpackspec:  replicas: 1  selector:    matchLabels:      app: kpack-controller  template:    metadata:      labels:        app: kpack-controller        version: 0.2.2-rc.1    spec:      serviceAccountName: controller      nodeSelector:        kubernetes.io/os: linux      volumes:        - name: custom-certs          secret:            secretName: custom-ca      containers:        - name: controller          image: gcr.io/cf-build-service-public/kpack/controller@sha256:ec256da7e29eeecdd0821f499e754080672db8f0bc521b2fa1f13f6a75a04835          volumeMounts:            - name: custom-certs              mountPath: /certs          env:            - name: SSL_CERT_DIR              value: /certs

Install logs utility

We would also install the kpack log utility. It would be used later to access and monitor build logs for image creation process. The utility resource to install can be found here.

$ logs -hUsage of logs:  -build string    	The build number to tail logs  -image string    	The image name to tail logs  -kubeconfig string    	Path to a kubeconfig.  -master string    	The address of the Kubernetes API server. Overrides any value in kubeconfig.  -namespace string    	The namespace of the image (default "default")

Prepare cluster for image builds

The entire cloud native buildpack stack consists of some key components. We would prepare the cluster with those components.

Configure ClusterStack

A ClusterStore resource is a repository of buildpacks packaged in buildpackages that can be used by kpack to build images.

apiVersion: kpack.io/v1alpha1kind: ClusterStoremetadata:  name: defaultspec:  sources:  - image: gcr.io/paketo-buildpacks/java  - image: gcr.io/paketo-buildpacks/nodejs

Configure ClusterStore

A ClusterStack resource is the specification for a cloud native buildpacks stack used during build and in the resulting app image. A stack is composed of two images that are intended to work together:

The build image of a stack provides the base image from which the build environment is constructed. The build environment is the containerized environment in which the lifecycle (and thereby buildpacks) are executed.
The run image of a stack provides the base image from which application images are built.

apiVersion: kpack.io/v1alpha1kind: ClusterStackmetadata:  name: basespec:  id: "io.buildpacks.stacks.bionic"  buildImage:    image: "paketobuildpacks/build:base-cnb"  runImage:    image: "paketobuildpacks/run:base-cnb"

Configure ClusterBuilder

A Builder is the kpack configuration for a builder image that includes the stack and buildpacks needed to build an image from your app source code. This builder object uses a ClusterStore, a ClusterStack, and an order definition to construct a builder image.

clusterbuilder.yml

$ cat clusterbuilder.ymlapiVersion: kpack.io/v1alpha1kind: ClusterBuildermetadata:  name: defaultspec:  tag: pvtregistry.txvlab.com/kpack/builder  stack:    name: base    kind: ClusterStack  store:    name: default    kind: ClusterStore  serviceAccountRef:    name: build-sa    namespace: kpack  order:  - group:    - id: paketo-buildpacks/java  - group:    - id: paketo-buildpacks/nodejs

I have also created a kubernetes secret of registry type to pass the credentials for the private registry. We assign the secret to act as the imagePullSecret during builder creation, by assigning secret to service account “build-sa”

$ cat build-sa.ymlapiVersion: v1kind: ServiceAccountmetadata:  name: build-sasecrets:  - name: regcredhbrimagePullSecrets:  - name: regcredhbr

Install clusterBuilder :

$ kubectl apply -f clusterbuilder.ymlclusterbuilder.kpack.io/default created

Result:

$ kubectl get clusterbuilders.kpack.io defaultNAME      LATESTIMAGE                                                                                                    READYdefault   pvtregistry.txvlab.com/kpack/builder@sha256:f819bc21837c2faf9858934c810bfc3ee9739455a18aa835a578bbcc0bf0866e   True

Details about the supported buildpacks in the builder can be found with kubectl describe command.

Builder Metadata:    Homepage:  https://github.com/paketo-buildpacks/bellsoft-liberica    Id:        paketo-buildpacks/bellsoft-liberica    Version:   8.0.0    Homepage:  https://github.com/paketo-buildpacks/spring-boot    Id:        paketo-buildpacks/spring-boot    Version:   4.2.0    Homepage:  https://github.com/paketo-buildpacks/google-stackdriver    Id:        paketo-buildpacks/google-stackdriver    Version:   3.10.0    Homepage:  https://github.com/paketo-buildpacks/apache-tomcat    Id:        paketo-buildpacks/apache-tomcat    Version:   5.3.0    Homepage:  https://github.com/paketo-buildpacks/azure-application-insights    Id:        paketo-buildpacks/azure-application-insights    Version:   4.3.0    Homepage:  https://github.com/paketo-buildpacks/ca-certificates    Id:        paketo-buildpacks/ca-certificates    Version:   2.2.0    Homepage:  https://github.com/paketo-buildpacks/ca-certificates    Id:        paketo-buildpacks/ca-certificates    Version:   2.1.0    Homepage:  https://github.com/paketo-buildpacks/procfile    Id:        paketo-buildpacks/procfile    Version:   4.1.0    Homepage:  https://github.com/paketo-buildpacks/node-engine    Id:        paketo-buildpacks/node-engine    Version:   0.3.0    Homepage:  https://github.com/paketo-buildpacks/yarn-install    Id:        paketo-buildpacks/yarn-install    Version:   0.3.0    Homepage:  https://github.com/paketo-buildpacks/yarn    Id:        paketo-buildpacks/yarn    Version:   0.2.0    Homepage:  https://github.com/paketo-buildpacks/encrypt-at-rest    Id:        paketo-buildpacks/encrypt-at-rest    Version:   3.0.0    Homepage:  https://github.com/paketo-buildpacks/debug    Id:        paketo-buildpacks/debug    Version:   3.0.0    Homepage:  https://github.com/paketo-buildpacks/maven    Id:        paketo-buildpacks/maven    Version:   5.1.0    Homepage:  https://github.com/paketo-buildpacks/sbt    Id:        paketo-buildpacks/sbt    Version:   5.2.0    Homepage:  https://github.com/paketo-buildpacks/gradle    Id:        paketo-buildpacks/gradle    Version:   5.2.0    Homepage:  https://github.com/paketo-buildpacks/leiningen    Id:        paketo-buildpacks/leiningen    Version:   3.1.0    Homepage:  https://github.com/paketo-buildpacks/jmx    Id:        paketo-buildpacks/jmx    Version:   3.0.0    Homepage:  https://github.com/paketo-buildpacks/npm-install    Id:        paketo-buildpacks/npm-install    Version:   0.3.0    Homepage:  https://github.com/paketo-buildpacks/npm-start    Id:        paketo-buildpacks/npm-start    Version:   0.2.0    Homepage:  https://github.com/paketo-buildpacks/yarn-start    Id:        paketo-buildpacks/yarn-start    Version:   0.1.0    Homepage:  https://github.com/paketo-buildpacks/node-start    Id:        paketo-buildpacks/node-start    Version:   0.2.0    Homepage:  https://github.com/paketo-buildpacks/executable-jar    Id:        paketo-buildpacks/executable-jar    Version:   5.0.0    Homepage:  https://github.com/paketo-buildpacks/environment-variables    Id:        paketo-buildpacks/environment-variables    Version:   3.0.0    Homepage:  https://github.com/paketo-buildpacks/image-labels    Id:        paketo-buildpacks/image-labels    Version:   3.0.0    Homepage:  https://github.com/paketo-buildpacks/dist-zip    Id:        paketo-buildpacks/dist-zip    Version:   4.0.0    Homepage:  https://github.com/paketo-buildpacks/java    Id:        paketo-buildpacks/java    Version:   5.7.0    Homepage:  https://github.com/paketo-buildpacks/nodejs    Id:        paketo-buildpacks/nodejs    Version:   0.3.0

Image Build Process

Lets create a namespace to use for the app image build process

$ kubectl create ns helloapp-projectnamespace/helloapp-project created

As part of preparation to build app image, need to configure the kubernetes secret of registry type for the private registry and any other registry to be used for storing app images (i.e docker registry in current case).

Also need to configure secret for git repo credentials. We assume the source code is maintained in a github repo.

kubectl create secret docker-registry regcreddoc \    --docker-username=USERNAME \    --docker-password=PASSWORD \    --docker-server=https://index.docker.io/v1/ \    --namespace helloapp-projectkubectl create secret docker-registry regcredhbr \    --docker-username=USERNAME \    --docker-password=PASSWORD \    --docker-server=https://pvtregistry.txvlab.com \    --namespace helloapp-project$ cat git-cred.ymlapiVersion: v1kind: Secretmetadata:  name: git-cred  annotations:    build.pivotal.io/git: https://github.comtype: kubernetes.io/basic-authstringData:  username: <username>  password: <password>$ cat app-sa.ymlapiVersion: v1kind: ServiceAccountmetadata:  name: app-sasecrets:  - name: regcreddoc  - name: regcredhbr  - name: git-credimagePullSecrets:  - name: regcreddoc  - name: regcredhbr

Apply the kubernetes resource to create docker-registry and git-cred secret and the “app-sa” service account. Let’s prepare the app image resource specifying the configured ClusterBuilder, service-account and source path.

appimage.yml

$ cat appimage.ymlapiVersion: kpack.io/v1alpha1kind: Imagemetadata:  name: helloapp  namespace: helloapp-projectspec:  tag: txconsole/helloapp  serviceAccount: app-sa  builder:    name: default    kind: ClusterBuilder  source:    git:      url: https://github.com/txconsole/helloapp.git      revision: master

Now, apply the image resource to the kubernetes cluster.

Once the image resources is applied, it would create resources for image, build and a pod to perform the build action.

$ kubectl get pod,builds,image -n helloapp-projectNAME                                   READY   STATUS     RESTARTS   AGEpod/helloapp-build-1-jtsdc-build-pod   0/1     Init:0/6   0          6sNAME                                    IMAGE   SUCCEEDEDbuild.kpack.io/helloapp-build-1-jtsdc           UnknownNAME                      LATESTIMAGE   READYimage.kpack.io/helloapp                 Unknown

We can use the logs executable(installed in local-workstation) to monitor the image build logs and status.

logs utility tool uses the kubernetes context from configured kubeconfig in local-workspation to detect & connect to the current “in-use” kubernetes cluster context.

The builder image represented by the ClusterBuilder resources provisions the lifecycle scripts which would facilitate the image build.

During the build process, the lifecycle orchestrates the buildpack execution, then assembles resulting artifacts into final app image. At high level, lifecycle stages can be defined as below :

Detection – Finds an ordered group of buildpacks to use during the build phase.
Analysis – Restores files that buildpacks may use to optimize the build and export phases.
Build – Transforms app source code into runnable artifacts to be packaged as a container.
Export – Creates the final OCI image.

$ logs -image helloapp -namespace helloapp-project===> PREPAREBuild reason(s): CONFIGCONFIG:	resources: {}	- source: {}	+ source:	+   git:	+     revision: 76e91560cce2abe386af0d133d3ede96599277e2	+     url: https://github.com/txconsole/helloapp.gitLoading secret for "https://index.docker.io/v1/" from secret "regcreddoc" at location "/var/build-secrets/regcreddoc"Loading secret for "https://pvtregistry.txvlab.com" from secret "regcredhbr" at location "/var/build-secrets/regcredhbr"Cloning "https://github.com/txconsole/helloapp.git" @ "76e91560cce2abe386af0d133d3ede96599277e2"...Successfully cloned "https://github.com/txconsole/helloapp.git" @ "76e91560cce2abe386af0d133d3ede96599277e2" in path "/workspace"===> DETECT7 of 18 buildpacks participatingpaketo-buildpacks/ca-certificates   2.2.0paketo-buildpacks/bellsoft-liberica 8.0.0paketo-buildpacks/maven             5.1.0paketo-buildpacks/executable-jar    5.0.0paketo-buildpacks/apache-tomcat     5.3.0paketo-buildpacks/dist-zip          4.0.0paketo-buildpacks/spring-boot       4.2.0===> ANALYZEPrevious image with name "txconsole/helloapp" not found===> RESTORE===> BUILDPaketo CA Certificates Buildpack 2.2.0  https://github.com/paketo-buildpacks/ca-certificates  Launch Helper: Contributing to layer    Creating /layers/paketo-buildpacks_ca-certificates/helper/exec.d/ca-certificates-helperPaketo BellSoft Liberica Buildpack 8.0.0  https://github.com/paketo-buildpacks/bellsoft-liberica  Build Configuration:    $BP_JVM_VERSION              11              the Java version  Launch Configuration:    $BPL_JVM_HEAD_ROOM           0               the headroom in memory calculation    $BPL_JVM_LOADED_CLASS_COUNT  35% of classes  the number of loaded classes in memory calculation    $BPL_JVM_THREAD_COUNT        250             the number of threads in memory calculation    $JAVA_TOOL_OPTIONS                           the JVM launch flags  BellSoft Liberica JDK 11.0.11: Contributing to layer    Downloading from https://github.com/bell-sw/Liberica/releases/download/11.0.11+9/bellsoft-jdk11.0.11+9-linux-amd64.tar.gz    Verifying checksum    Expanding to /layers/paketo-buildpacks_bellsoft-liberica/jdk    Adding 129 container CA certificates to JVM truststore    Writing env.build/JAVA_HOME.override    Writing env.build/JDK_HOME.override  BellSoft Liberica JRE 11.0.11: Contributing to layer    Downloading from https://github.com/bell-sw/Liberica/releases/download/11.0.11+9/bellsoft-jre11.0.11+9-linux-amd64.tar.gz    Verifying checksum    Expanding to /layers/paketo-buildpacks_bellsoft-liberica/jre    Adding 129 container CA certificates to JVM truststore    Writing env.launch/BPI_APPLICATION_PATH.default    Writing env.launch/BPI_JVM_CACERTS.default    Writing env.launch/BPI_JVM_CLASS_COUNT.default    Writing env.launch/BPI_JVM_SECURITY_PROVIDERS.default    Writing env.launch/JAVA_HOME.default    Writing env.launch/MALLOC_ARENA_MAX.default  Launch Helper: Contributing to layer    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/active-processor-count    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/java-opts    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/link-local-dns    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/memory-calculator    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/openssl-certificate-loader    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/security-providers-configurer    Creating /layers/paketo-buildpacks_bellsoft-liberica/helper/exec.d/security-providers-classpath-9  JVMKill Agent 1.16.0: Contributing to layer    Downloading from https://github.com/cloudfoundry/jvmkill/releases/download/v1.16.0.RELEASE/jvmkill-1.16.0-RELEASE.so    Verifying checksum    Copying to /layers/paketo-buildpacks_bellsoft-liberica/jvmkill    Writing env.launch/JAVA_TOOL_OPTIONS.append    Writing env.launch/JAVA_TOOL_OPTIONS.delim  Java Security Properties: Contributing to layer    Writing env.launch/JAVA_SECURITY_PROPERTIES.default    Writing env.launch/JAVA_TOOL_OPTIONS.append    Writing env.launch/JAVA_TOOL_OPTIONS.delimPaketo Maven Buildpack 5.1.0  https://github.com/paketo-buildpacks/maven  Build Configuration:    $BP_MAVEN_BUILD_ARGUMENTS  -Dmaven.test.skip=true package  the arguments to pass to Maven    $BP_MAVEN_BUILT_ARTIFACT   target/*.[jw]ar                 the built application artifact explicitly.  Supersedes $BP_MAVEN_BUILT_MODULE    $BP_MAVEN_BUILT_MODULE                                     the module to find application artifact in    Creating cache directory /home/cnb/.m2  Compiled Application: Contributing to layer    Executing mvnw --batch-mode -Dmaven.test.skip=true package[INFO] Scanning for projects...[INFO] Downloading from central: https://repo.maven.apache.org/maven2/org/springframework/boot/spring-boot-starter-parent/2.2.7.RELEASE/spring-boot-starter-parent-2.2.7.RELEASE.pom[INFO] -----------------------< com.txconsole:helloapp >-----------------------[INFO] Building helloapp 0.0.1-SNAPSHOT[INFO] --------------------------------[ jar ]---------------------------------[INFO] Downloading from central: https://repo.maven.apache.org/maven2/org/springframework/boot/spring-boot-maven-plugin/2.2.7.RELEASE/spring-boot-maven-plugin-2.2.7.RELEASE.pom[INFO] Replacing main artifact with repackaged archive[INFO] ------------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] ------------------------------------------------------------------------[INFO] Total time:  02:50 min[INFO] Finished at: 2021-05-12T16:22:04Z[INFO] ------------------------------------------------------------------------  Removing source codePaketo Executable JAR Buildpack 5.0.0  https://github.com/paketo-buildpacks/executable-jar  Class Path: Contributing to layer    Writing env/CLASSPATH.delim    Writing env/CLASSPATH.prepend  Process types:    executable-jar: java org.springframework.boot.loader.JarLauncher (direct)    task:           java org.springframework.boot.loader.JarLauncher (direct)    web:            java org.springframework.boot.loader.JarLauncher (direct)Paketo Spring Boot Buildpack 4.2.0  https://github.com/paketo-buildpacks/spring-boot  Launch Helper: Contributing to layer    Creating /layers/paketo-buildpacks_spring-boot/helper/exec.d/spring-cloud-bindings  Spring Cloud Bindings 1.7.1: Contributing to layer    Downloading from https://repo.spring.io/release/org/springframework/cloud/spring-cloud-bindings/1.7.1/spring-cloud-bindings-1.7.1.jar    Verifying checksum    Copying to /layers/paketo-buildpacks_spring-boot/spring-cloud-bindings  Web Application Type: Contributing to layer    Servlet web application detected    Writing env.launch/BPL_JVM_THREAD_COUNT.default  Image labels:    org.opencontainers.image.title    org.opencontainers.image.version    org.springframework.boot.spring-configuration-metadata.json    org.springframework.boot.version===> EXPORTAdding layer 'paketo-buildpacks/ca-certificates:helper'Adding layer 'paketo-buildpacks/bellsoft-liberica:helper'Adding layer 'paketo-buildpacks/bellsoft-liberica:java-security-properties'Adding layer 'paketo-buildpacks/bellsoft-liberica:jre'Adding layer 'paketo-buildpacks/bellsoft-liberica:jvmkill'Adding layer 'paketo-buildpacks/executable-jar:classpath'Adding layer 'paketo-buildpacks/spring-boot:helper'Adding layer 'paketo-buildpacks/spring-boot:spring-cloud-bindings'Adding layer 'paketo-buildpacks/spring-boot:web-application-type'Adding 1/1 app layer(s)Adding layer 'launcher'Adding layer 'config'Adding layer 'process-types'Adding label 'io.buildpacks.lifecycle.metadata'Adding label 'io.buildpacks.build.metadata'Adding label 'io.buildpacks.project.metadata'Adding label 'org.opencontainers.image.title'Adding label 'org.opencontainers.image.version'Adding label 'org.springframework.boot.spring-configuration-metadata.json'Adding label 'org.springframework.boot.version'Setting default process type 'web'*** Images (sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe):      txconsole/helloapp      index.docker.io/txconsole/helloapp:b1.20210512.161819Adding cache layer 'paketo-buildpacks/bellsoft-liberica:jdk'Adding cache layer 'paketo-buildpacks/maven:application'Adding cache layer 'paketo-buildpacks/maven:cache'===> COMPLETIONBuild successful

Once the build is successful, then the resultant resource status can be verified in k8s namespace :

$ kubectl get pod,builds,image -n helloapp-projectNAME                                   READY   STATUS      RESTARTS   AGEpod/helloapp-build-1-jtsdc-build-pod   0/1     Completed   0          4m55sNAME                                    IMAGE                                                                                                        SUCCEEDEDbuild.kpack.io/helloapp-build-1-jtsdc   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe   TrueNAME                      LATESTIMAGE                                                                                                  READYimage.kpack.io/helloapp   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe   True

Thus, the image helloapp:b1.20210512.161819 is built and pushed to the configured docker registry. The build details are configured in the build resource.

Spec:  Builder:    Image:     pvtregistry.txvlab.com/kpack/builder@sha256:f819bc21837c2faf9858934c810bfc3ee9739455a18aa835a578bbcc0bf0866e  Cache Name:  helloapp-cache  Resources:  Service Account:  app-sa  Source:    Git:      Revision:  76e91560cce2abe386af0d133d3ede96599277e2      URL:       https://github.com/txconsole/helloapp.git  Tags:    txconsole/helloapp    index.docker.io/txconsole/helloapp:b1.20210512.161819

The build job’s pod has moved to completed state after successful image build.

The image resource specify the latest image detail and status.

Spec:  Builder:    Kind:                      ClusterBuilder    Name:                      default  Cache Size:                  2G  Failed Build History Limit:  10  Image Tagging Strategy:      BuildNumber  Service Account:             app-sa  Source:    Git:      Revision:                 master      URL:                      https://github.com/txconsole/helloapp.git  Success Build History Limit:  10  Tag:                          txconsole/helloappStatus:  Build Cache Name:  helloapp-cache  Build Counter:     1  Conditions:    Last Transition Time:         2021-05-12T16:22:52Z    Status:                       True    Type:                         Ready    Last Transition Time:         2021-05-12T16:22:52Z    Status:                       True    Type:                         BuilderReady  Latest Build Image Generation:  1  Latest Build Reason:            CONFIG  Latest Build Ref:               helloapp-build-1-jtsdc  Latest Image:                   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe  Latest Stack:                   io.buildpacks.stacks.bionic  Observed Generation:            1

Perform image rebuild

Time to perform some app source code change to auto-trigger kpack webhook and create another app image version with the new source code revision.

$ kubectl get pod,builds,image -n helloapp-projectNAME                                   READY   STATUS      RESTARTS   AGEpod/helloapp-build-1-jtsdc-build-pod   0/1     Completed   0          23mpod/helloapp-build-2-zcwd7-build-pod   0/1     Init:0/6    0          5sNAME                                    IMAGE                                                                                                        SUCCEEDEDbuild.kpack.io/helloapp-build-1-jtsdc   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe   Truebuild.kpack.io/helloapp-build-2-zcwd7                                                                                                                UnknownNAME                      LATESTIMAGE                                                                                                  READYimage.kpack.io/helloapp   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe   Unknown

The above app revision should auto-trigger another app image build. The build logs can be still verified with the logs utility.

===> PREPAREBuild reason(s): COMMITCOMMIT:	- 76e91560cce2abe386af0d133d3ede96599277e2	+ 1c3b53849a0b8ebc274a1928a5225581e6b35cd6Loading secret for "https://index.docker.io/v1/" from secret "regcreddoc" at location "/var/build-secrets/regcreddoc"Loading secret for "https://pvtregistry.txvlab.com" from secret "regcredhbr" at location "/var/build-secrets/regcredhbr"Cloning "https://github.com/txconsole/helloapp.git" @ "1c3b53849a0b8ebc274a1928a5225581e6b35cd6"...Successfully cloned "https://github.com/txconsole/helloapp.git" @ "1c3b53849a0b8ebc274a1928a5225581e6b35cd6" in path "/workspace"===> DETECT7 of 18 buildpacks participatingpaketo-buildpacks/ca-certificates   2.2.0paketo-buildpacks/bellsoft-liberica 8.0.0paketo-buildpacks/maven             5.1.0paketo-buildpacks/executable-jar    5.0.0paketo-buildpacks/apache-tomcat     5.3.0paketo-buildpacks/dist-zip          4.0.0paketo-buildpacks/spring-boot       4.2.0===> ANALYZERestoring metadata for "paketo-buildpacks/ca-certificates:helper" from app imageRestoring metadata for "paketo-buildpacks/bellsoft-liberica:helper" from app imageRestoring metadata for "paketo-buildpacks/bellsoft-liberica:java-security-properties" from app imageRestoring metadata for "paketo-buildpacks/bellsoft-liberica:jre" from app imageRestoring metadata for "paketo-buildpacks/bellsoft-liberica:jvmkill" from app imageRestoring metadata for "paketo-buildpacks/bellsoft-liberica:jdk" from cacheRestoring metadata for "paketo-buildpacks/maven:application" from cacheRestoring metadata for "paketo-buildpacks/maven:cache" from cacheRestoring metadata for "paketo-buildpacks/spring-boot:helper" from app imageRestoring metadata for "paketo-buildpacks/spring-boot:spring-cloud-bindings" from app imageRestoring metadata for "paketo-buildpacks/spring-boot:web-application-type" from app image===> RESTORERestoring data for "paketo-buildpacks/bellsoft-liberica:jdk" from cacheRestoring data for "paketo-buildpacks/maven:application" from cacheRestoring data for "paketo-buildpacks/maven:cache" from cache===> BUILDPaketo CA Certificates Buildpack 2.2.0  https://github.com/paketo-buildpacks/ca-certificates  Launch Helper: Reusing cached layerPaketo BellSoft Liberica Buildpack 8.0.0  https://github.com/paketo-buildpacks/bellsoft-liberica  Build Configuration:    $BP_JVM_VERSION              11              the Java version  Launch Configuration:    $BPL_JVM_HEAD_ROOM           0               the headroom in memory calculation    $BPL_JVM_LOADED_CLASS_COUNT  35% of classes  the number of loaded classes in memory calculation    $BPL_JVM_THREAD_COUNT        250             the number of threads in memory calculation    $JAVA_TOOL_OPTIONS                           the JVM launch flags  BellSoft Liberica JDK 11.0.11: Reusing cached layer  BellSoft Liberica JRE 11.0.11: Reusing cached layer  Launch Helper: Reusing cached layer  JVMKill Agent 1.16.0: Reusing cached layer  Java Security Properties: Reusing cached layerPaketo Maven Buildpack 5.1.0  https://github.com/paketo-buildpacks/maven  Build Configuration:    $BP_MAVEN_BUILD_ARGUMENTS  -Dmaven.test.skip=true package  the arguments to pass to Maven    $BP_MAVEN_BUILT_ARTIFACT   target/*.[jw]ar                 the built application artifact explicitly.  Supersedes $BP_MAVEN_BUILT_MODULE    $BP_MAVEN_BUILT_MODULE                                     the module to find application artifact in    Creating cache directory /home/cnb/.m2  Compiled Application: Contributing to layer    Executing mvnw --batch-mode -Dmaven.test.skip=true package[INFO] Scanning for projects...[INFO][INFO] -----------------------< com.txconsole:helloapp >-----------------------[INFO] Building helloapp 0.0.1-SNAPSHOT[INFO] --------------------------------[ jar ]---------------------------------[INFO][INFO] --- maven-resources-plugin:3.1.0:resources (default-resources) @ helloapp ---[INFO] Using 'UTF-8' encoding to copy filtered resources.[INFO] Copying 1 resource[INFO] Copying 5 resources[INFO][INFO] --- maven-compiler-plugin:3.8.1:compile (default-compile) @ helloapp ---[INFO] Changes detected - recompiling the module![INFO] Compiling 3 source files to /workspace/target/classes[INFO][INFO] --- maven-resources-plugin:3.1.0:testResources (default-testResources) @ helloapp ---[INFO] Not copying test resources[INFO][INFO] --- maven-compiler-plugin:3.8.1:testCompile (default-testCompile) @ helloapp ---[INFO] Not compiling test sources[INFO][INFO] --- maven-surefire-plugin:2.22.2:test (default-test) @ helloapp ---[INFO] Tests are skipped.[INFO][INFO] --- maven-jar-plugin:3.1.2:jar (default-jar) @ helloapp ---[INFO] Building jar: /workspace/target/helloapp-0.0.1-SNAPSHOT.jar[INFO][INFO] --- spring-boot-maven-plugin:2.2.7.RELEASE:repackage (repackage) @ helloapp ---[INFO] Replacing main artifact with repackaged archive[INFO] ------------------------------------------------------------------------[INFO] BUILD SUCCESS[INFO] ------------------------------------------------------------------------[INFO] Total time:  2.880 s[INFO] Finished at: 2021-05-12T16:42:05Z[INFO] ------------------------------------------------------------------------  Removing source codePaketo Executable JAR Buildpack 5.0.0  https://github.com/paketo-buildpacks/executable-jar  Class Path: Contributing to layer    Writing env/CLASSPATH.delim    Writing env/CLASSPATH.prepend  Process types:    executable-jar: java org.springframework.boot.loader.JarLauncher (direct)    task:           java org.springframework.boot.loader.JarLauncher (direct)    web:            java org.springframework.boot.loader.JarLauncher (direct)Paketo Spring Boot Buildpack 4.2.0  https://github.com/paketo-buildpacks/spring-boot  Launch Helper: Reusing cached layer  Spring Cloud Bindings 1.7.1: Reusing cached layer  Web Application Type: Reusing cached layer  Image labels:    org.opencontainers.image.title    org.opencontainers.image.version    org.springframework.boot.spring-configuration-metadata.json    org.springframework.boot.version===> EXPORTReusing layers from image 'index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe'Reusing layer 'paketo-buildpacks/ca-certificates:helper'Reusing layer 'paketo-buildpacks/bellsoft-liberica:helper'Reusing layer 'paketo-buildpacks/bellsoft-liberica:java-security-properties'Reusing layer 'paketo-buildpacks/bellsoft-liberica:jre'Reusing layer 'paketo-buildpacks/bellsoft-liberica:jvmkill'Reusing layer 'paketo-buildpacks/executable-jar:classpath'Reusing layer 'paketo-buildpacks/spring-boot:helper'Reusing layer 'paketo-buildpacks/spring-boot:spring-cloud-bindings'Reusing layer 'paketo-buildpacks/spring-boot:web-application-type'Reusing 1/1 app layer(s)Reusing layer 'launcher'Reusing layer 'config'Reusing layer 'process-types'Adding label 'io.buildpacks.lifecycle.metadata'Adding label 'io.buildpacks.build.metadata'Adding label 'io.buildpacks.project.metadata'Adding label 'org.opencontainers.image.title'Adding label 'org.opencontainers.image.version'Adding label 'org.springframework.boot.spring-configuration-metadata.json'Adding label 'org.springframework.boot.version'Setting default process type 'web'*** Images (sha256:1d9f6c0627cb98721a6ad7c12c67476d55b3fb2fc12c70a478f318c8e2e98fa8):      txconsole/helloapp      index.docker.io/txconsole/helloapp:b2.20210512.164127Reusing cache layer 'paketo-buildpacks/bellsoft-liberica:jdk'Adding cache layer 'paketo-buildpacks/maven:application'Reusing cache layer 'paketo-buildpacks/maven:cache'===> COMPLETIONBuild successful

Thus, the image resource is updated with the newly created and pushed image helloapp:b2.20200717.143231. We can observe another entry of build resource showing the specs as configured and used in the 2nd build. It also shows the status “SUCCEEDED” as “true” which proves that all the image build lifecycle stages were performed successfully.

$ kubectl get pod,builds,image -n helloapp-projectNAME                                   READY   STATUS      RESTARTS   AGEpod/helloapp-build-1-jtsdc-build-pod   0/1     Completed   0          24mpod/helloapp-build-2-zcwd7-build-pod   0/1     Completed   0          97sNAME                                    IMAGE                                                                                                        SUCCEEDEDbuild.kpack.io/helloapp-build-1-jtsdc   index.docker.io/txconsole/helloapp@sha256:5cb7b0605f985ebb3261cd5f4f5249e02656f828530b92189822038de8f132fe   Truebuild.kpack.io/helloapp-build-2-zcwd7   index.docker.io/txconsole/helloapp@sha256:1d9f6c0627cb98721a6ad7c12c67476d55b3fb2fc12c70a478f318c8e2e98fa8   TrueNAME                      LATESTIMAGE                                                                                                  READYimage.kpack.io/helloapp   index.docker.io/txconsole/helloapp@sha256:1d9f6c0627cb98721a6ad7c12c67476d55b3fb2fc12c70a478f318c8e2e98fa8   True

Conclusion

We performed the poc on installing kpack and using it to perform app image build/rebuild which is ready to be consumed for microservice deployment.