Update a local package
Packages can be arbitrarily customized and later merge updates from upstream.
Topics
Because kpt package contents are resource configuration (data) rather than templates or DSLs (code), it is possible to merge different versions of the package together using the structure of the resources to compute differences.
This allows package consumers to customize their copy, and merge updates from upstream.
The technique of merging fields to perform updates is also how kubectl apply
updates remote cluster resources with local file changes, without overwriting
changes to the resources made by the cluster control-plane (e.g. an autoscaler
can set replicas without apply overwriting them).
See [update strategies] for more choices on how to merge upstream changes.
kpt pkg update explained
Following is a short explanation of the command that will be demonstrated in this guide.
- Copy the staging/cockroachdb subdirectory out of the [kubernetes examples] git repo
- Edit the local package contents
- Commit the changes
- Update the local package with upstream changes from a new version
Steps
- Fetch a remote package
- Edit the contents
- Commit local changes
- Merge upstream changes
- View new package contents
Fetch a remote package
Packages can be fetched at specific versions defined by git tags, and have updated to later versions to merge in upstream changes.
Command
export REPO=https://github.com/GoogleContainerTools/kpt.git
kpt pkg get $REPO/package-examples/helloworld-set@v0.3.0 helloworld
Fetch the helloworld-set package at version v0.3.0.
Output
fetching package /package-examples/helloworld-set from https://github.com/GoogleContainerTools/kpt to helloworld
Each subdirectory within a git repo may be tagged with its own version using the subdirectory path as a tag prefix, and kpt will automatically resolve the subdirectory version.
package-examples/helloworld-set@v0.3.0 is resolved to the tag
package-examples/helloworld-set/v0.3.0 if it exists, otherwise it is
resolved to the tag v0.3.0.
Edit the contents
Edit the contents of the package by making changes to it.
Old local configuration
# helloworld/deploy.yaml (upstream)
...
image: gcr.io/kpt-dev/helloworld-gke:v0.1.0 # {"$ref":"#/definitions/io.k8s.cli.substitutions.image-tag"}
...
env:
- name: PORT
value: "80" # {"$ref":"#/definitions/io.k8s.cli.setters.http-port"}
...
The old package contents without local modifications.
vi helloworld/deploy.yaml
New local configuration
# helloworld/deploy.yaml (locally modified)
...
image: gcr.io/kpt-dev/helloworld-gke:v0.1.0 # {"$ref":"#/definitions/io.k8s.cli.substitutions.image-tag"}
...
env:
- name: PORT
value: "80" # {"$ref":"#/definitions/io.k8s.cli.setters.http-port"}
- name: NEW_ENV # This is a local package addition
value: "local package edits"
...
The new package contents with local modifications.
Commit local changes
In order for updates to be easily undone, configuration must be committed to git prior to performing a package update.
kpt will throw an error if trying to update a package and the git repo has uncommitted changes.
git init
git add .
git commit -m "add helloworld package at v0.3.0"
Merge upstream changes
Package updates are performed by fetching the upstream package at the specified version and applying the upstream changes to the local package.
Command
kpt pkg update helloworld@v0.5.0 --strategy=resource-merge
Update the local package to the upstream version v0.5.0 by doing a 3-way merge between 1) the original upstream commit, 2) the local (customized) package, 3) the new upstream reference.
Output
updating package helloworld to v0.5.0
Changes
--- a/helloworld/deploy.yaml
+++ b/helloworld/deploy.yaml
@@ -31,7 +31,7 @@ spec:
spec:
containers:
- name: helloworld-gke
- image: gcr.io/kpt-dev/helloworld-gke:0.1.0 # {"$ref":"#/definitions/io.k8s.cli.substitutions.image-tag"}
+ image: gcr.io/kpt-dev/helloworld-gke:v0.3.0 # {"$ref":"#/definitions/io.k8s.cli.substitutions.image-tag"}
ports:
- name: http
containerPort: 80 # {"$ref":"#/definitions/io.k8s.cli.setters.http-port"}
diff --git a/helloworld/service.yaml b/helloworld/service.yaml
index 0853ee1..c938fde 100644
--- a/helloworld/service.yaml
+++ b/helloworld/service.yaml
@@ -22,7 +22,7 @@ metadata:
labels:
The Deployment was updated with a new image tag.
--- a/helloworld/service.yaml
+++ b/helloworld/service.yaml
@@ -22,7 +22,7 @@ metadata:
labels:
app: hello
spec:
- type: LoadBalancer
+ type: NodePort
selector:
app: hello
ports:
The Service was updated with a new type.
--- a/helloworld/Kptfile
+++ b/helloworld/Kptfile
@@ -5,10 +5,10 @@ metadata:
upstream:
type: git
git:
- commit: 3d721bafd701deb06aeb43c5ea5afda3134cfdd6
+ commit: 3f173ad974081896b47f6929b2c3cb595d71af94
repo: https://github.com/GoogleContainerTools/kpt
directory: /package-examples/helloworld-set
- ref: v0.3.0
+ ref: v0.5.0
openAPI:
definitions:
io.k8s.cli.setters.http-port:
The Kptfile was updated with the new upstream metadata.
View new package contents
# helloworld/deploy.yaml (updated from upstream)
...
image: gcr.io/kpt-dev/helloworld-gke:v0.3.0 # {"$ref":"#/definitions/io.k8s.cli.substitutions.image-tag"}
...
env:
- name: PORT
value: "80" # {"$ref":"#/definitions/io.k8s.cli.setters.http-port"}
- name: NEW_ENV # This is a local package addition
value: "local package edits"
...
The updated local package contains both the upstream changes (new image tag), and local modifications (additional environment variable).