OCM SDK

This project contains a Go library that simplifies the use of the OCM API, available in api.openshift.com.

Usage

To use it import the github.com/openshift-online/ocm-sdk-go package, and then use it to send requests to the API.

Note that the name of the directory is ocm-sdk-go but the name of the package is just sdk, so to use it you will have to import it and then use sdk as the package selector.

For example, if you need to create a cluster you can use the following code:

package main

import (
        "fmt"
        "os"

        sdk "github.com/openshift-online/ocm-sdk-go"
	cmv1 "github.com/openshift-online/ocm-sdk-go/clustersmgmt/v1"
)

func main() {
	// Create a logger that has the debug level enabled:
	logger, err := sdk.NewGoLoggerBuilder().
		Debug(true).
		Build()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Can't build logger: %v\n", err)
		os.Exit(1)
	}

	// Create the connection, and remember to close it:
	token := os.Getenv("OCM_TOKEN")
	connection, err := sdk.NewConnectionBuilder().
		Logger(logger).
		Tokens(token).
		Build()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Can't build connection: %v\n", err)
		os.Exit(1)
	}
	defer connection.Close()

	// Get the client for the resource that manages the collection of clusters:
	collection := connection.ClustersMgmt().V1().Clusters()

	// Prepare the description of the cluster to create:
	cluster, err := cmv1.NewCluster().
		Name("mycluster").
		CloudProvider(
			cmv1.NewCloudProvider().
				ID("aws"),
		).
		Region(
			cmv1.NewCloudRegion().
				ID("us-east-1"),
		).
		Version(
			cmv1.NewVersion().
				ID("openshift-v4.0-beta4"),
		).
		Build()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Can't create cluster description: %v\n", err)
		os.Exit(1)
	}

	// Send a request to create the cluster:
	response, err := collection.Add().
		Body(cluster).
		Send()
	if err != nil {
		fmt.Fprintf(os.Stderr, "Can't create cluster: %v\n", err)
		os.Exit(1)
	}

	// Print the result:
	cluster = response.Body()
	fmt.Printf("%s - %s\n", cluster.ID(), cluster.Name())
}

There are more examples in the examples directory.

Packages

The following are the packages that are most frequently needed in order to use the SDK:

main

This is the top level package. The most important element is the Connection type, as it is the mechanism to connect to the server and to get the reference to the clients for the services that are part of the API.

errors

Contains the Error type that is used by the SDK to report errors.

accesstransparency/v1

This package contains the types and clients for version 1 of the access transparency service.

accountsmgmt/v1

This package contains the types and clients for version 1 of the accounts management service.

authorizations/v1

This package contains the types and clients for version 1 of the authorizations service.

clustersmgmt/v1

This package contains the types and clients for version 1 of the clusters management service.

There are other packages, like helpers and internal. Those contain internal implementation details of the SDK. Refrain from using them, as they may change in the future: backwards compatibility isn't guaranteed.

Connecting to the server

To connect to the server import the sdk package. That contains the Connection type, which is the entry point of the SDK, and gives you access to the clients for the services that are part of the API:

import (
	"github.com/openshift-online/ocm-sdk-go"
)

// Create the connection:
connection, err := sdk.NewConnectionBuilder().
	Tokens(token).
	Build()
if err != nil {
        fmt.Fprintf(os.Stderr, "Can't build connection: %v\n", err)
        os.Exit(1)
}

The connection holds expensive resources, including a pool of HTTP connections to the server and an authentication token. It is important to release those resources when they are no longer in use:

// Close the connection:
connection.Close()

Consider using the defer mechanism to ensure that the connection is always closed when no longer needed.

Using types

The Go types that correspond to the API data types live in the accountsmgmt/v1, authorizations/v1, and clustersmgmt/v1 packages. These types are pure data containers, they don't have any logic or operation. Instances can be created at will.

Creation of objects of these types does not have any effect in the server side, unless the object is explicitly passed to a call to one of the resource methods described below. Changes in the server side are not automatically reflected in the instances that already exist in memory.

Creation of objects of these types is done using the corresponding builder type. For example, to create an object of the Cluster type create an object of the ClusterBuilder type (using the NewCluster function) populate and then build the object calling the Build method:

// Create a new object of the `Cluster` type:
cluster, err := cmv1.NewCluster().
	Name("mycluster").
	CloudProvider(
		cmv1.NewCloudProvider().
			ID("aws"),
	).
	Region(
		cmv1.NewCloudRegion().
			ID("us-east-1"),
	).
	Version(
		cmv1.NewVersion().
			ID("openshift-v4.9.7"),
	).
	Build()
if err != nil {
	fmt.Fprintf(os.Stderr, "Can't create cluster object: %v\n", err)
	os.Exit(1)
}

Once created objects are immutable.

The fields containing the values of the attributes of these types are private. To read them use the access methods. For example, to read the value of the name attribute of a cluster:

// Get the value of the `name` attribute:
name := cluster.Name()
fmt.Printf("Cluster name is '%s'\n", name)

The access methods return the value of the attribute, if it has a value, or the zero value of the type ("" for strings, false for booleans, 0 for integers, etc) if the attribute doesn't have a value. That makes it impossible to know if the attribute has a value or not. If you need that, use the Get... variant of the accessor. For example, to get the value of the name attribute and also check if the attribute has a value:

// Get the value of the `name` attribute, and check if it has a value:
name, ok := cluster.GetName()
if !ok {
	fmt.Printf("Cluster has no name\n")
} else {
	fmt.Printf("Cluster name is '%s'\n", name)
}

Attributes that are defined as list of objects in the specification of the API are implemented as objects of a ...List type. For example, the value of the groups attribute of the Cluster type is implemented as the GroupList type. These list types provide methods to process the elements of the list. For example, to print the names of a list of groups:

// Get the list of groups:
groups := ...

// Print the name of each group:
groups.Each(func(group *cmv1.Group) bool {
	fmt.Printf("Group name is '%s'\n", group.Name())
	return true
})

The function passed to the Each method will be called once for each item of the list. If it returns true the iteration will continue, otherwise will stop. This is intended to mimic a for loop with an optional break.

If it is necessary to have access to the index of the item, then it is better to use the Range method:

// Get the list of groups:
groups := ...

// Print index and name of each group:
groups.Range(func(int i, group *cmv1.Group) bool {
	fmt.Printf("Group index is %d and is '%s'\n", i, group.Name())
	return true
})

It is also possible to convert the list to an slice, using the Slice method, and the process it as usual:

// Get the list of groups:
groups := ...

// Print the name of each group:
slice := groups.Slice()
for _, group := range slice {
	fmt.Printf("Group name is '%s'\n", group.Name())
}

It is in general better to use the Each or Range methods instead of the Slice method, because Slice has the additional cost of allocating that slice and copying the internal representation into it.

CLI

See also the command-line tool https://github.com/openshift-online/ocm-cli built on top of this SDK.