Waylon  Bruen

Waylon Bruen

1654819980

Ko: Build and Deploy Go Applications on Kubernetes

ko: Easy Go Containers  

ko is a simple, fast container image builder for Go applications.

It's ideal for use cases where your image contains a single Go application without any/many dependencies on the OS base image (e.g., no cgo, no OS package dependencies).

ko builds images by effectively executing go build on your local machine, and as such doesn't require docker to be installed. This can make it a good fit for lightweight CI/CD use cases.

ko also includes support for simple YAML templating which makes it a powerful tool for Kubernetes applications (See below).

Setup

Install

Install from Releases

VERSION=TODO # choose the latest version
OS=Linux     # or Darwin
ARCH=x86_64  # or arm64, i386, s390x
curl -L https://github.com/google/ko/releases/download/v${VERSION}/ko_${VERSION}_${OS}_${ARCH}.tar.gz | tar xzf - ko
chmod +x ./ko

Install using Homebrew

brew install ko

Build and Install from Source

With Go 1.16+, build and install the latest released version:

go install github.com/google/ko@latest

Setup on GitHub Actions

You can use the setup-ko action to install ko and setup auth to GitHub Container Registry in a GitHub Action workflow:

steps:
- uses: imjasonh/setup-ko@v0.4

Authenticate

ko depends on the authentication configured in your Docker config (typically ~/.docker/config.json). If you can push an image with docker push, you are already authenticated for ko.

Since ko doesn't require docker, ko login also provides a surface for logging in to a container image registry with a username and password, similar to docker login.

Additionally, if auth is not configured in the Docker config, ko includes built-in support for authenticating to the following container registries using credentials configured in the environment:

Choose Destination

ko depends on an environment variable, KO_DOCKER_REPO, to identify where it should push images that it builds. Typically this will be a remote registry, e.g.:

  • KO_DOCKER_REPO=gcr.io/my-project, or
  • KO_DOCKER_REPO=my-dockerhub-user

Build an Image

ko build ./cmd/app builds and pushes a container image, and prints the resulting image digest to stdout.

In this example, ./cmd/app must be a package main that defines func main().

ko build ./cmd/app
...
gcr.io/my-project/app-099ba5bcefdead87f92606265fb99ac0@sha256:6e398316742b7aa4a93161dce4a23bc5c545700b862b43347b941000b112ec3e

NB: Prior to v0.10, the command was called ko publish -- this is equivalent to ko build, and both commands will work and do the same thing.

The executable binary that was built from ./cmd/app is available in the image at /ko-app/app -- the binary name matches the base import path name -- and that binary is the image's entrypoint.

Because the output of ko build is an image reference, you can easily pass it to other tools that expect to take an image reference.

To run the container locally:

docker run -p 8080:8080 $(ko build ./cmd/app)

Or to deploy it to other services like Cloud Run:

gcloud run deploy --image=$(ko build ./cmd/app)

Or fly.io:

flyctl launch --image=$(ko build ./cmd/app)
  • Note: The image must be publicly available.

Or AWS Lambda:

aws lambda update-function-code \
  --function-name=my-function-name \
  --image-uri=$(ko build ./cmd/app)
  • Note: The image must be pushed to ECR, based on the AWS provided base image, and use the aws-lambda-go framework. See official docs for more information.

Or Azure Container Apps:

az containerapp update \
  --name my-container-app
  --resource-group my-resource-group
  --image $(ko build ./cmd/app)
  • Note: The image must be pushed to ACR or other registry service. See official docs for more information.

Configuration

Aside from KO_DOCKER_REPO, you can configure ko's behavior using a .ko.yaml file. The location of this file can be overridden with KO_CONFIG_PATH.

Overriding Base Images

By default, ko bases images on gcr.io/distroless/static:nonroot. This is a small image that provides the bare necessities to run your Go binary.

You can override this base image in two ways:

  1. To override the base image for all images ko builds, add this line to your .ko.yaml file:
defaultBaseImage: registry.example.com/base/image
  1. To override the base image for certain importpaths:
baseImageOverrides:
  github.com/my-user/my-repo/cmd/app: registry.example.com/base/for/app
  github.com/my-user/my-repo/cmd/foo: registry.example.com/base/for/foo

Overriding Go build settings

By default, ko builds the binary with no additional build flags other than -trimpath. You can replace the default build arguments by providing build flags and ldflags using a GoReleaser influenced builds configuration section in your .ko.yaml.

builds:
- id: foo
  dir: .  # default is .
  main: ./foobar/foo
  env:
  - GOPRIVATE=git.internal.example.com,source.developers.google.com
  flags:
  - -tags
  - netgo
  ldflags:
  - -s -w
  - -extldflags "-static"
  - -X main.version={{.Env.VERSION}}
- id: bar
  dir: ./bar
  main: .  # default is .
  env:
  - GOCACHE=/workspace/.gocache
  ldflags:
  - -s
  - -w

If your repository contains multiple modules (multiple go.mod files in different directories), use the dir field to specify the directory where ko should run go build.

ko picks the entry from builds based on the import path you request. The import path is matched against the result of joining dir and main.

The paths specified in dir and main are relative to the working directory of the ko process.

The ldflags default value is [].

Please note: Even though the configuration section is similar to the GoReleaser builds section, only the env, flags and ldflags fields are currently supported. Also, the templating support is currently limited to using environment variables only.

Naming Images

ko provides a few different strategies for naming the image it pushes, to workaround certain registry limitations and user preferences:

Given KO_DOCKER_REPO=registry.example.com/repo, by default, ko build ./cmd/app will produce an image named like registry.example.com/repo/app-<md5>, which includes the MD5 hash of the full import path, to avoid collisions.

  • --preserve-import-path (-P) will include the entire importpath: registry.example.com/repo/github.com/my-user/my-repo/cmd/app
  • --base-import-paths (-B) will omit the MD5 portion: registry.example.com/repo/app
  • --bare will only include the KO_DOCKER_REPO: registry.example.com/repo

Local Publishing Options

ko is normally used to publish images to container image registries, identified by KO_DOCKER_REPO.

ko can also load images to a local Docker daemon, if available, by setting KO_DOCKER_REPO=ko.local, or by passing the --local (-L) flag.

Local images can be used as a base image for other ko images:

defaultBaseImage: ko.local/example/base/image

ko can also load images into a local KinD cluster, if available, by setting KO_DOCKER_REPO=kind.local. By default this loads into the default KinD cluster name (kind). To load into another KinD cluster, set KIND_CLUSTER_NAME=my-other-cluster.

Multi-Platform Images

Because Go supports cross-compilation to other CPU architectures and operating systems, ko excels at producing multi-platform images.

To build and push an image for all platforms supported by the configured base image, simply add --platform=all. This will instruct ko to look up all the supported platforms in the base image, execute GOOS=<os> GOARCH=<arch> GOARM=<variant> go build for each platform, and produce a manifest list containing an image for each platform.

You can also select specific platforms, for example, --platform=linux/amd64,linux/arm64

Generating SBOMs

A Software Bill of Materials (SBOM) is a list of software components that a software artifact depends on. Having a list of dependencies can be helpful in determining whether any vulnerable components were used to build the software artifact.

From v0.9+, ko generates and uploads an SBOM for every image it produces by default.

ko will generate an SBOM in the SPDX format by default, but you can select the CycloneDX format instead with the --sbom=cyclonedx flag. To disable SBOM generation, pass --sbom=none.

These SBOMs can be downloaded using the cosign download sbom command.

Static Assets

ko can also bundle static assets into the images it produces.

By convention, any contents of a directory named <importpath>/kodata/ will be bundled into the image, and the path where it's available in the image will be identified by the environment variable KO_DATA_PATH.

As an example, you can bundle and serve static contents in your image:

cmd/
  app/
    main.go
    kodata/
      favicon.ico
      index.html

Then, in your main.go:

func main() {
    http.Handle("/", http.FileServer(http.Dir(os.Getenv("KO_DATA_PATH"))))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

You can simulate ko's behavior outside of the container image by setting the KO_DATA_PATH environment variable yourself:

KO_DATA_PATH=cmd/app/kodata/ go run ./cmd/app

Tip: Symlinks in kodata are followed and included as well. For example, you can include Git commit information in your image with:

ln -s -r .git/HEAD ./cmd/app/kodata/

Also note that http.FileServer will not serve the Last-Modified header (or validate If-Modified-Since request headers) because ko does not embed timestamps by default.

This can be supported by manually setting the KO_DATA_DATE_EPOCH environment variable during build (See below).

Kubernetes Integration

You could stop at just building and pushing images.

But, because building images is so easy with ko, and because building with ko only requires a string importpath to identify the image, we can integrate this with YAML generation to make Kubernetes use cases much simpler.

YAML Changes

Traditionally, you might have a Kubernetes deployment, defined in a YAML file, that runs an image:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  ...
  template:
    spec:
      containers:
      - name: my-app
        image: registry.example.com/my-app:v1.2.3

...which you apply to your cluster with kubectl apply:

kubectl apply -f deployment.yaml

With ko, you can instead reference your Go binary by its importpath, prefixed with ko://:

    ...
    spec:
      containers:
      - name: my-app
        image: ko://github.com/my-user/my-repo/cmd/app

ko resolve

With this small change, running ko resolve -f deployment.yaml will instruct ko to:

  1. scan the YAML file(s) for values with the ko:// prefix,
  2. for each unique ko://-prefixed string, execute ko build <importpath> to build and push an image,
  3. replace ko://-prefixed string(s) in the input YAML with the fully-specified image reference of the built image(s), for example:
spec:
  containers:
    - name: my-app
      image: registry.example.com/github.com/my-user/my-repo/cmd/app@sha256:deadb33f...
  1. Print the resulting resolved YAML to stdout.

The result can be redirected to a file, to distribute to others:

ko resolve -f config/ > release.yaml

Taken together, ko resolve aims to make packaging, pushing, and referencing container images an invisible implementation detail of your Kubernetes deployment, and let you focus on writing code in Go.

ko apply

To apply the resulting resolved YAML config, you can redirect the output of ko resolve to kubectl apply:

ko resolve -f config/ | kubectl apply -f -

Since this is a relatively common use case, the same functionality is available using ko apply:

ko apply -f config/

NB: This requires that kubectl is available.

ko delete

To teardown resources applied using ko apply, you can run ko delete:

ko delete -f config/

This is purely a convenient alias for kubectl delete, and doesn't perform any builds, or delete any previously built images.

Frequently Asked Questions

How can I set ldflags?

Using -ldflags is a common way to embed version info in go binaries (In fact, we do this for ko!). Unfortunately, because ko wraps go build, it's not possible to use this flag directly; however, you can use the GOFLAGS environment variable instead:

GOFLAGS="-ldflags=-X=main.version=1.2.3" ko build .

How can I set multiple ldflags?

Currently, there is a limitation that does not allow to set multiple arguments in ldflags using GOFLAGS. Using -ldflags multiple times also does not work. In this use case, it works best to use the builds section in the .ko.yaml file.

Why are my images all created in 1970?

In order to support reproducible builds, ko doesn't embed timestamps in the images it produces by default.

However, ko does respect the SOURCE_DATE_EPOCH environment variable, which will set the container image's timestamp accordingly.

Similarly, the KO_DATA_DATE_EPOCH environment variable can be used to set the modtime timestamp of the files in KO_DATA_PATH.

For example, you can set the container image's timestamp to the current timestamp by executing:

export SOURCE_DATE_EPOCH=$(date +%s)

or set the timestamp of the files in KO_DATA_PATH to the latest git commit's timestamp with:

export KO_DATA_DATE_EPOCH=$(git log -1 --format='%ct')

Can I build Windows containers?

Yes, but support for Windows containers is new, experimental, and tenuous. Be prepared to file bugs. 🐛

The default base image does not provide a Windows image. You can try out building a Windows container image by setting the base image to a Windows base image and building with --platform=windows/amd64 or --platform=all:

For example, to build a Windows container image for ko, from within this repo:

ko build ./ --platform=windows/amd64

This works because the ko image is configured in .ko.yaml to be based on a golang base image, which provides platform-specific images for both Linux and Windows.

Known issues 🐛

  • Symlinks in kodata are ignored when building Windows images; only regular files and directories will be included in the Windows image.

Can I optimize images for eStargz support?

Yes! Set the environment variable GGCR_EXPERIMENT_ESTARGZ=1 to produce eStargz-optimized images.

Does ko support autocompletion?

Yes! ko completion generates a Bash/Zsh/Fish/PowerShell completion script. You can get how to load it from help document.

ko completion [bash|zsh|fish|powershell] --help

Or, you can source it directly:

source <(ko completion)

Does ko work with Kustomize?

Yes! ko resolve -f - will read and process input from stdin, so you can have ko easily process the output of the kustomize command.

kustomize build config | ko resolve -f -

Does ko integrate with other build and development tools?

Oh, you betcha. Here's a partial list:

Does ko work with OpenShift Internal Registry?

Yes! Follow these steps:

oc registry login --to=$HOME/.docker/config.json
  • Create a namespace where you will push your images, i.e: ko-images
  • Execute this command to set KO_DOCKER_REPO to publish images to the internal registry.
   export KO_DOCKER_REPO=$(oc registry info --public)/ko-images

Acknowledgements

This work is based heavily on experience from having built the Docker and Kubernetes support for Bazel. That work was presented here.

Discuss

Questions? Comments? Ideas? Come discuss ko with us in the #ko-project channel on the Kubernetes Slack! See you there!

Author: Google
Source Code: https://github.com/google/ko 
License: Apache-2.0 license

#go #golang #kubernetes #deploy #container 

What is GEEK

Buddha Community

Ko: Build and Deploy Go Applications on Kubernetes
Christa  Stehr

Christa Stehr

1602964260

50+ Useful Kubernetes Tools for 2020 - Part 2

Introduction

Last year, we provided a list of Kubernetes tools that proved so popular we have decided to curate another list of some useful additions for working with the platform—among which are many tools that we personally use here at Caylent. Check out the original tools list here in case you missed it.

According to a recent survey done by Stackrox, the dominance Kubernetes enjoys in the market continues to be reinforced, with 86% of respondents using it for container orchestration.

(State of Kubernetes and Container Security, 2020)

And as you can see below, more and more companies are jumping into containerization for their apps. If you’re among them, here are some tools to aid you going forward as Kubernetes continues its rapid growth.

(State of Kubernetes and Container Security, 2020)

#blog #tools #amazon elastic kubernetes service #application security #aws kms #botkube #caylent #cli #container monitoring #container orchestration tools #container security #containers #continuous delivery #continuous deployment #continuous integration #contour #developers #development #developments #draft #eksctl #firewall #gcp #github #harbor #helm #helm charts #helm-2to3 #helm-aws-secret-plugin #helm-docs #helm-operator-get-started #helm-secrets #iam #json #k-rail #k3s #k3sup #k8s #keel.sh #keycloak #kiali #kiam #klum #knative #krew #ksniff #kube #kube-prod-runtime #kube-ps1 #kube-scan #kube-state-metrics #kube2iam #kubeapps #kubebuilder #kubeconfig #kubectl #kubectl-aws-secrets #kubefwd #kubernetes #kubernetes command line tool #kubernetes configuration #kubernetes deployment #kubernetes in development #kubernetes in production #kubernetes ingress #kubernetes interfaces #kubernetes monitoring #kubernetes networking #kubernetes observability #kubernetes plugins #kubernetes secrets #kubernetes security #kubernetes security best practices #kubernetes security vendors #kubernetes service discovery #kubernetic #kubesec #kubeterminal #kubeval #kudo #kuma #microsoft azure key vault #mozilla sops #octant #octarine #open source #palo alto kubernetes security #permission-manager #pgp #rafay #rakess #rancher #rook #secrets operations #serverless function #service mesh #shell-operator #snyk #snyk container #sonobuoy #strongdm #tcpdump #tenkai #testing #tigera #tilt #vert.x #wireshark #yaml

Waylon  Bruen

Waylon Bruen

1654819980

Ko: Build and Deploy Go Applications on Kubernetes

ko: Easy Go Containers  

ko is a simple, fast container image builder for Go applications.

It's ideal for use cases where your image contains a single Go application without any/many dependencies on the OS base image (e.g., no cgo, no OS package dependencies).

ko builds images by effectively executing go build on your local machine, and as such doesn't require docker to be installed. This can make it a good fit for lightweight CI/CD use cases.

ko also includes support for simple YAML templating which makes it a powerful tool for Kubernetes applications (See below).

Setup

Install

Install from Releases

VERSION=TODO # choose the latest version
OS=Linux     # or Darwin
ARCH=x86_64  # or arm64, i386, s390x
curl -L https://github.com/google/ko/releases/download/v${VERSION}/ko_${VERSION}_${OS}_${ARCH}.tar.gz | tar xzf - ko
chmod +x ./ko

Install using Homebrew

brew install ko

Build and Install from Source

With Go 1.16+, build and install the latest released version:

go install github.com/google/ko@latest

Setup on GitHub Actions

You can use the setup-ko action to install ko and setup auth to GitHub Container Registry in a GitHub Action workflow:

steps:
- uses: imjasonh/setup-ko@v0.4

Authenticate

ko depends on the authentication configured in your Docker config (typically ~/.docker/config.json). If you can push an image with docker push, you are already authenticated for ko.

Since ko doesn't require docker, ko login also provides a surface for logging in to a container image registry with a username and password, similar to docker login.

Additionally, if auth is not configured in the Docker config, ko includes built-in support for authenticating to the following container registries using credentials configured in the environment:

Choose Destination

ko depends on an environment variable, KO_DOCKER_REPO, to identify where it should push images that it builds. Typically this will be a remote registry, e.g.:

  • KO_DOCKER_REPO=gcr.io/my-project, or
  • KO_DOCKER_REPO=my-dockerhub-user

Build an Image

ko build ./cmd/app builds and pushes a container image, and prints the resulting image digest to stdout.

In this example, ./cmd/app must be a package main that defines func main().

ko build ./cmd/app
...
gcr.io/my-project/app-099ba5bcefdead87f92606265fb99ac0@sha256:6e398316742b7aa4a93161dce4a23bc5c545700b862b43347b941000b112ec3e

NB: Prior to v0.10, the command was called ko publish -- this is equivalent to ko build, and both commands will work and do the same thing.

The executable binary that was built from ./cmd/app is available in the image at /ko-app/app -- the binary name matches the base import path name -- and that binary is the image's entrypoint.

Because the output of ko build is an image reference, you can easily pass it to other tools that expect to take an image reference.

To run the container locally:

docker run -p 8080:8080 $(ko build ./cmd/app)

Or to deploy it to other services like Cloud Run:

gcloud run deploy --image=$(ko build ./cmd/app)

Or fly.io:

flyctl launch --image=$(ko build ./cmd/app)
  • Note: The image must be publicly available.

Or AWS Lambda:

aws lambda update-function-code \
  --function-name=my-function-name \
  --image-uri=$(ko build ./cmd/app)
  • Note: The image must be pushed to ECR, based on the AWS provided base image, and use the aws-lambda-go framework. See official docs for more information.

Or Azure Container Apps:

az containerapp update \
  --name my-container-app
  --resource-group my-resource-group
  --image $(ko build ./cmd/app)
  • Note: The image must be pushed to ACR or other registry service. See official docs for more information.

Configuration

Aside from KO_DOCKER_REPO, you can configure ko's behavior using a .ko.yaml file. The location of this file can be overridden with KO_CONFIG_PATH.

Overriding Base Images

By default, ko bases images on gcr.io/distroless/static:nonroot. This is a small image that provides the bare necessities to run your Go binary.

You can override this base image in two ways:

  1. To override the base image for all images ko builds, add this line to your .ko.yaml file:
defaultBaseImage: registry.example.com/base/image
  1. To override the base image for certain importpaths:
baseImageOverrides:
  github.com/my-user/my-repo/cmd/app: registry.example.com/base/for/app
  github.com/my-user/my-repo/cmd/foo: registry.example.com/base/for/foo

Overriding Go build settings

By default, ko builds the binary with no additional build flags other than -trimpath. You can replace the default build arguments by providing build flags and ldflags using a GoReleaser influenced builds configuration section in your .ko.yaml.

builds:
- id: foo
  dir: .  # default is .
  main: ./foobar/foo
  env:
  - GOPRIVATE=git.internal.example.com,source.developers.google.com
  flags:
  - -tags
  - netgo
  ldflags:
  - -s -w
  - -extldflags "-static"
  - -X main.version={{.Env.VERSION}}
- id: bar
  dir: ./bar
  main: .  # default is .
  env:
  - GOCACHE=/workspace/.gocache
  ldflags:
  - -s
  - -w

If your repository contains multiple modules (multiple go.mod files in different directories), use the dir field to specify the directory where ko should run go build.

ko picks the entry from builds based on the import path you request. The import path is matched against the result of joining dir and main.

The paths specified in dir and main are relative to the working directory of the ko process.

The ldflags default value is [].

Please note: Even though the configuration section is similar to the GoReleaser builds section, only the env, flags and ldflags fields are currently supported. Also, the templating support is currently limited to using environment variables only.

Naming Images

ko provides a few different strategies for naming the image it pushes, to workaround certain registry limitations and user preferences:

Given KO_DOCKER_REPO=registry.example.com/repo, by default, ko build ./cmd/app will produce an image named like registry.example.com/repo/app-<md5>, which includes the MD5 hash of the full import path, to avoid collisions.

  • --preserve-import-path (-P) will include the entire importpath: registry.example.com/repo/github.com/my-user/my-repo/cmd/app
  • --base-import-paths (-B) will omit the MD5 portion: registry.example.com/repo/app
  • --bare will only include the KO_DOCKER_REPO: registry.example.com/repo

Local Publishing Options

ko is normally used to publish images to container image registries, identified by KO_DOCKER_REPO.

ko can also load images to a local Docker daemon, if available, by setting KO_DOCKER_REPO=ko.local, or by passing the --local (-L) flag.

Local images can be used as a base image for other ko images:

defaultBaseImage: ko.local/example/base/image

ko can also load images into a local KinD cluster, if available, by setting KO_DOCKER_REPO=kind.local. By default this loads into the default KinD cluster name (kind). To load into another KinD cluster, set KIND_CLUSTER_NAME=my-other-cluster.

Multi-Platform Images

Because Go supports cross-compilation to other CPU architectures and operating systems, ko excels at producing multi-platform images.

To build and push an image for all platforms supported by the configured base image, simply add --platform=all. This will instruct ko to look up all the supported platforms in the base image, execute GOOS=<os> GOARCH=<arch> GOARM=<variant> go build for each platform, and produce a manifest list containing an image for each platform.

You can also select specific platforms, for example, --platform=linux/amd64,linux/arm64

Generating SBOMs

A Software Bill of Materials (SBOM) is a list of software components that a software artifact depends on. Having a list of dependencies can be helpful in determining whether any vulnerable components were used to build the software artifact.

From v0.9+, ko generates and uploads an SBOM for every image it produces by default.

ko will generate an SBOM in the SPDX format by default, but you can select the CycloneDX format instead with the --sbom=cyclonedx flag. To disable SBOM generation, pass --sbom=none.

These SBOMs can be downloaded using the cosign download sbom command.

Static Assets

ko can also bundle static assets into the images it produces.

By convention, any contents of a directory named <importpath>/kodata/ will be bundled into the image, and the path where it's available in the image will be identified by the environment variable KO_DATA_PATH.

As an example, you can bundle and serve static contents in your image:

cmd/
  app/
    main.go
    kodata/
      favicon.ico
      index.html

Then, in your main.go:

func main() {
    http.Handle("/", http.FileServer(http.Dir(os.Getenv("KO_DATA_PATH"))))
    log.Fatal(http.ListenAndServe(":8080", nil))
}

You can simulate ko's behavior outside of the container image by setting the KO_DATA_PATH environment variable yourself:

KO_DATA_PATH=cmd/app/kodata/ go run ./cmd/app

Tip: Symlinks in kodata are followed and included as well. For example, you can include Git commit information in your image with:

ln -s -r .git/HEAD ./cmd/app/kodata/

Also note that http.FileServer will not serve the Last-Modified header (or validate If-Modified-Since request headers) because ko does not embed timestamps by default.

This can be supported by manually setting the KO_DATA_DATE_EPOCH environment variable during build (See below).

Kubernetes Integration

You could stop at just building and pushing images.

But, because building images is so easy with ko, and because building with ko only requires a string importpath to identify the image, we can integrate this with YAML generation to make Kubernetes use cases much simpler.

YAML Changes

Traditionally, you might have a Kubernetes deployment, defined in a YAML file, that runs an image:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: my-deployment
spec:
  replicas: 3
  ...
  template:
    spec:
      containers:
      - name: my-app
        image: registry.example.com/my-app:v1.2.3

...which you apply to your cluster with kubectl apply:

kubectl apply -f deployment.yaml

With ko, you can instead reference your Go binary by its importpath, prefixed with ko://:

    ...
    spec:
      containers:
      - name: my-app
        image: ko://github.com/my-user/my-repo/cmd/app

ko resolve

With this small change, running ko resolve -f deployment.yaml will instruct ko to:

  1. scan the YAML file(s) for values with the ko:// prefix,
  2. for each unique ko://-prefixed string, execute ko build <importpath> to build and push an image,
  3. replace ko://-prefixed string(s) in the input YAML with the fully-specified image reference of the built image(s), for example:
spec:
  containers:
    - name: my-app
      image: registry.example.com/github.com/my-user/my-repo/cmd/app@sha256:deadb33f...
  1. Print the resulting resolved YAML to stdout.

The result can be redirected to a file, to distribute to others:

ko resolve -f config/ > release.yaml

Taken together, ko resolve aims to make packaging, pushing, and referencing container images an invisible implementation detail of your Kubernetes deployment, and let you focus on writing code in Go.

ko apply

To apply the resulting resolved YAML config, you can redirect the output of ko resolve to kubectl apply:

ko resolve -f config/ | kubectl apply -f -

Since this is a relatively common use case, the same functionality is available using ko apply:

ko apply -f config/

NB: This requires that kubectl is available.

ko delete

To teardown resources applied using ko apply, you can run ko delete:

ko delete -f config/

This is purely a convenient alias for kubectl delete, and doesn't perform any builds, or delete any previously built images.

Frequently Asked Questions

How can I set ldflags?

Using -ldflags is a common way to embed version info in go binaries (In fact, we do this for ko!). Unfortunately, because ko wraps go build, it's not possible to use this flag directly; however, you can use the GOFLAGS environment variable instead:

GOFLAGS="-ldflags=-X=main.version=1.2.3" ko build .

How can I set multiple ldflags?

Currently, there is a limitation that does not allow to set multiple arguments in ldflags using GOFLAGS. Using -ldflags multiple times also does not work. In this use case, it works best to use the builds section in the .ko.yaml file.

Why are my images all created in 1970?

In order to support reproducible builds, ko doesn't embed timestamps in the images it produces by default.

However, ko does respect the SOURCE_DATE_EPOCH environment variable, which will set the container image's timestamp accordingly.

Similarly, the KO_DATA_DATE_EPOCH environment variable can be used to set the modtime timestamp of the files in KO_DATA_PATH.

For example, you can set the container image's timestamp to the current timestamp by executing:

export SOURCE_DATE_EPOCH=$(date +%s)

or set the timestamp of the files in KO_DATA_PATH to the latest git commit's timestamp with:

export KO_DATA_DATE_EPOCH=$(git log -1 --format='%ct')

Can I build Windows containers?

Yes, but support for Windows containers is new, experimental, and tenuous. Be prepared to file bugs. 🐛

The default base image does not provide a Windows image. You can try out building a Windows container image by setting the base image to a Windows base image and building with --platform=windows/amd64 or --platform=all:

For example, to build a Windows container image for ko, from within this repo:

ko build ./ --platform=windows/amd64

This works because the ko image is configured in .ko.yaml to be based on a golang base image, which provides platform-specific images for both Linux and Windows.

Known issues 🐛

  • Symlinks in kodata are ignored when building Windows images; only regular files and directories will be included in the Windows image.

Can I optimize images for eStargz support?

Yes! Set the environment variable GGCR_EXPERIMENT_ESTARGZ=1 to produce eStargz-optimized images.

Does ko support autocompletion?

Yes! ko completion generates a Bash/Zsh/Fish/PowerShell completion script. You can get how to load it from help document.

ko completion [bash|zsh|fish|powershell] --help

Or, you can source it directly:

source <(ko completion)

Does ko work with Kustomize?

Yes! ko resolve -f - will read and process input from stdin, so you can have ko easily process the output of the kustomize command.

kustomize build config | ko resolve -f -

Does ko integrate with other build and development tools?

Oh, you betcha. Here's a partial list:

Does ko work with OpenShift Internal Registry?

Yes! Follow these steps:

oc registry login --to=$HOME/.docker/config.json
  • Create a namespace where you will push your images, i.e: ko-images
  • Execute this command to set KO_DOCKER_REPO to publish images to the internal registry.
   export KO_DOCKER_REPO=$(oc registry info --public)/ko-images

Acknowledgements

This work is based heavily on experience from having built the Docker and Kubernetes support for Bazel. That work was presented here.

Discuss

Questions? Comments? Ideas? Come discuss ko with us in the #ko-project channel on the Kubernetes Slack! See you there!

Author: Google
Source Code: https://github.com/google/ko 
License: Apache-2.0 license

#go #golang #kubernetes #deploy #container 

Aida  Stamm

Aida Stamm

1590207561

How to Deploy a Resilient Go Application to Kubernetes on DigitalOcean

How to Deploy a Resilient Go Application to Kubernetes on DigitalOcean

Subscribe to the channel https://www.youtube.com/watch?v=g_-U5jddSuM

#deploy #application #go #kubernetes #digitalocean

Fannie  Zemlak

Fannie Zemlak

1599854400

What's new in the go 1.15

Go announced Go 1.15 version on 11 Aug 2020. Highlighted updates and features include Substantial improvements to the Go linker, Improved allocation for small objects at high core counts, X.509 CommonName deprecation, GOPROXY supports skipping proxies that return errors, New embedded tzdata package, Several Core Library improvements and more.

As Go promise for maintaining backward compatibility. After upgrading to the latest Go 1.15 version, almost all existing Golang applications or programs continue to compile and run as older Golang version.

#go #golang #go 1.15 #go features #go improvement #go package #go new features

Maud  Rosenbaum

Maud Rosenbaum

1601051854

Kubernetes in the Cloud: Strategies for Effective Multi Cloud Implementations

Kubernetes is a highly popular container orchestration platform. Multi cloud is a strategy that leverages cloud resources from multiple vendors. Multi cloud strategies have become popular because they help prevent vendor lock-in and enable you to leverage a wide variety of cloud resources. However, multi cloud ecosystems are notoriously difficult to configure and maintain.

This article explains how you can leverage Kubernetes to reduce multi cloud complexities and improve stability, scalability, and velocity.

Kubernetes: Your Multi Cloud Strategy

Maintaining standardized application deployments becomes more challenging as your number of applications and the technologies they are based on increase. As environments, operating systems, and dependencies differ, management and operations require more effort and extensive documentation.

In the past, teams tried to get around these difficulties by creating isolated projects in the data center. Each project, including its configurations and requirements were managed independently. This required accurately predicting performance and the number of users before deployment and taking down applications to update operating systems or applications. There were many chances for error.

Kubernetes can provide an alternative to the old method, enabling teams to deploy applications independent of the environment in containers. This eliminates the need to create resource partitions and enables teams to operate infrastructure as a unified whole.

In particular, Kubernetes makes it easier to deploy a multi cloud strategy since it enables you to abstract away service differences. With Kubernetes deployments you can work from a consistent platform and optimize services and applications according to your business needs.

The Compelling Attributes of Multi Cloud Kubernetes

Multi cloud Kubernetes can provide multiple benefits beyond a single cloud deployment. Below are some of the most notable advantages.

Stability

In addition to the built-in scalability, fault tolerance, and auto-healing features of Kubernetes, multi cloud deployments can provide service redundancy. For example, you can mirror applications or split microservices across vendors. This reduces the risk of a vendor-related outage and enables you to create failovers.

#kubernetes #multicloud-strategy #kubernetes-cluster #kubernetes-top-story #kubernetes-cluster-install #kubernetes-explained #kubernetes-infrastructure #cloud