Table of contents
background
Kubernetes is a popular container orchestration system that automates the deployment, scaling, and management of containerized applications. In Kubernetes, all resources are defined and configured in the form of YAML files. In some cases, we need to extract the YAML data of the created Kubernetes resources for subsequent use.
In this blog post, we will explore how to use the Go programming language to write a function to get the YAML data of a specified resource through the Kubernetes API.
Practical
function definition
func GetResourceYaml(cf *genericclioptions.ConfigFlags, typ, name string) ([]byte, error)
The parameter of the function cfis the client configuration information of Kubernetes, typand represent the type and name of the resource to be obtained namerespectively . The function returns a byte array of the resource's YAML data and possible errors.
function implementation
In the function, we first use the Kubernetes client configuration information cfto get the current namespace ns.
ns, _, _ := cf.ToRawKubeConfigLoader().Namespace()
Then, we use Kubernetes' API to get the object of the specified resource. In this process, we create a stateless resource generator by specifying the type and name of the resource, and then call Do()the method get the resource object.
obj, err := resource.NewBuilder(cf).
DefaultNamespace().
NamespaceParam(ns).
SingleResourceType().
ResourceNames(typ, name).
Unstructured().
Do().
Object()
if err != nil {
return nil, fmt.Errorf("get object: %w", err)
}
Next, we get the metadata object from the resource object metaObj, and call SetManagedFields(nil)the method to delete the management field in the metadata object.
metaObj, err := meta.Accessor(obj)
if err != nil {
return nil, fmt.Errorf("access object: %w", err)
} else {
metaObj.SetManagedFields(nil)
}
Finally, we metaObjserialize b.
b, err := yaml.Marshal(metaObj)
if err != nil {
return nil, fmt.Errorf("marshal object: %w", err)
}
The complete code implementation of the function is as follows:
func GetResourceYaml(cf *genericclioptions.ConfigFlags, typ, name string) ([]byte, error) {
ns, _, _ := cf.ToRawKubeConfigLoader().Namespace()
obj, err := resource.NewBuilder(cf).
DefaultNamespace().
NamespaceParam(ns).
SingleResourceType().
ResourceNames(typ, name).
Unstructured().
Do().
Object()
if err != nil {
return nil, fmt.Errorf("get object: %w", err)
}
metaObj, err := meta.Accessor(obj)
if err != nil {
return nil, fmt.Errorf("access object: %w", err)
} else {
metaObj.SetManagedFields(nil)
}
b, err := yaml.Marshal(metaObj)
if err != nil {
return nil, fmt.Errorf("marshal object: %w", err)
}
return b, nil
}
in conclusion
In this blog post, we use the Kubernetes API to obtain the YAML data of the specified resource through the Go programming language. We first obtain the client configuration information and the current namespace, and then use the resource generator to obtain the object of the specified resource. Next, we get the metadata object from the resource object and delete the admin fields in it. Finally, we serialize the metadata object into a byte array using YAML format as the return value of the function.
This function is used in a wide range of scenarios. For example, when we need to backup or migrate Kubernetes resources, we need to extract the YAML data of the resources. In addition, when we need to quickly copy the created resources, we can also use this function to obtain the YAML data of the resource, and then use the kubectl apply command to perform a quick copy.
It should be noted that this function needs to be used together with the Kubernetes client configuration information in actual use to ensure that the Kubernetes API can be accessed correctly. In addition, for some advanced Kubernetes resources, such as CustomResourceDefinition, this function may have some restrictions and limitations, which need to be adjusted and modified according to the specific situation.