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go-ansible

Go-ansible is a package for running ansible-playbook or ansible commands from Golang applications. It supports the most of its options for each command.

Install

To install the latest stable version run the command below:

$ go get github.com/apenella/[email protected]

Upgrade to 1.x

Since go-ansible v1.0.0 has introduced many breaking changes read the changelog and the upgrade guide carefully before to proceed to the upgrade.

Packages

Adhoc

github.com/apenella/go-ansible/pkg/adhoc package enables you to run ansible adhoc commands. You can use these adhoc types to run ansible commands:

  • AnsibleAdhocCmd is the main object type which defines the ansible adhoc command and how to execute it. AnsibleAdhocCmd definition is mandatory to run any ansible adhoc command. AnsibleAdhocCmd has a parameter that defines the Executor to use, the worker that launches the execution. If no Executor is specified, is used a bare DefaultExecutor.
  • AnsibleAdhocOptions type has those parameters described on Options section within ansible's man page, and defines how should be the ansible execution behavior and where to find execution configuration.

You could also provide to AnsiblePlaybookCmd privilege escalation options or connection options, defined in github.com/apenella/go-ansible/pkg/options

Playbook

github.com/apenella/go-ansible/pkg/playbook package lets you run ansible-playbook commands. You can use these playbook types to run ansible playbooks:

  • AnsiblePlaybookCmd is the main object type which defines the ansible-playbook command and how to execute it. AnsiblePlaybookCmd definition is mandatory to run any ansible-playbook command. AnsiblePlaybookCmd has a parameter that defines the Executor to use, the worker that launches the execution. If no Executor is specified, a bare DefaultExecutor is used.
  • AnsiblePlaybookOptions type has those parameters described on Options section within ansible-playbook's man page, and defines how should be the ansible-playbook execution behavior and where to find execution configuration.

You could also provide to AnsiblePlaybookCmd escalation privileged options or connection options, defined in github.com/apenella/go-ansible/pkg/options.

Execute

An executor is the component in charge to run the command and return the result received on stdout and stderr. Go-ansible has a default executor implementation under execute package. That executor is named DefaultExecute.

Any executor must comply to the Executor interface.

// Executor interface is satisfied by those types which has a Execute(context.Context,[]string,stdoutcallback.StdoutCallbackResultsFunc,...ExecuteOptions)error method
type Executor interface {
	Execute(ctx context.Context, command []string, resultsFunc stdoutcallback.StdoutCallbackResultsFunc, options ...ExecuteOptions) error
}

DefaultExecute

DefaultExecutor is the executor defined in the go-ansible library. On its most basic setup it just writes the command stdout to system stdout and the same for stderr, but its easy to extend the way of managing the command stdout and stderr. To extend and update its behavior it comes with a bunch of ExecuteOptions functions which can be passed to the executor.

// ExecuteOptions is a function to set executor options
type ExecuteOptions func(Executor)

Another way to extend how to return the results to the user is by using transformers, which can also be added to DefaultExecutor through WithTransformers( ...results.TransformerFunc) ExecuteOptions

Take a look to the examples to see how to do that.

Custom executor

You could write your own executor implementation and set it on AnsiblePlaybookCmd object, whenever DefaultExecutor does not fits to your needs. AnsiblePlaybookCmd expects an object that implements the Executor interface.

Below there is an example of a custom executor which could be configured by ExecuteOptions functions.

type MyExecutor struct {
	Prefix string
}

// Options method is used as a helper to apply a bunch of options to executor
func (e *MyExecutor) Options(options ...execute.ExecuteOptions) {
	// apply all options to the executor
	for _, opt := range options {
		opt(e)
	}
}

// WithPrefix method is used to set the executor prefix attribute
func WithPrefix(prefix string) execute.ExecuteOptions {
	return func(e execute.Executor) {
		e.(*MyExecutor).Prefix = prefix
	}
}

func (e *MyExecutor) Execute(ctx context.Context, command []string, resultsFunc stdoutcallback.StdoutCallbackResultsFunc, options ...execute.ExecuteOptions) error {
	// It is possible to apply extra options when Execute is called
	for _, opt := range options {
		opt(e)
	}
	// that's a dummy work
	fmt.Println(fmt.Sprintf("[%s] %s\n", e.Prefix, "I am MyExecutor and I am doing nothing"))
	return nil
}

Finally, on the next snipped is executed the ansible-playbook using the custom executor

// define an instance for the new executor and set the options
exe := &MyExecutor{}

exe.Options(
	WithPrefix("Go ansible example"),
)

playbook := &ansibler.AnsiblePlaybookCmd{
	Playbook:          "site.yml",
	ConnectionOptions: ansiblePlaybookConnectionOptions,
	Options:           ansiblePlaybookOptions,
	Exec:              exe,
}

playbook.Run(context.TODO())

When you run the playbook using your dummy executor, the output will be as follows:

$ go run myexecutor-ansibleplaybook.go
[Go ansible example] I am MyExecutor and I am doing nothing

Options

The types to define command execution options can be found in github.com/apenella/go-ansible/pkg/options.

ansible adhoc and ansible-playbook common options

  • AnsibleConnectionOptions object has those parameters described on Connections Options section within ansible-playbook's man page, and defines how to connect to hosts.
  • AnsiblePrivilegeEscalationOptions object has those parameters described on Escalation Options section within ansible-playbook's man page, and defines how to become a user.

Stdout Callback

It is possible to define and specific stdout callback method on go-ansible. You can set the StdoutCallback attribute on AnsiblePlaybookCmd object. Depending on the used method, the results are managed by one function or another. The functions to manage ansible-playbook's output are defined in the package github.com/apenella/go-ansible/pkg/stdoutcallback/results and must be defined following the next signature:

// StdoutCallbackResultsFunc defines a function which manages ansible's stdout callbacks. The function expects a context, a reader that receives the data to be wrote and a writer that defines where to write the data coming from reader, Finally a list of transformers could be passed to update the output coming from the executor.
type StdoutCallbackResultsFunc func(context.Context, io.Reader, io.Writer, ...results.TransformerFunc) error

Results

Below are described the methods to manage ansible playbooks outputs:

Transformers

A transformer is a function which purpose is to enrich or update the output coming from the executor, and are defined by the type TransformerFunc.

// TransformerFunc is used to enrich or update messages before to be printed out
type TransformerFunc func(string) string

The output coming from executor is processed line by line and is on that step where are applied all the transformers. results package provides a set of transformers ready to be used, but can also defined by your own and passed through executor.

  • Prepend: Sets a prefix string to the output line
  • Append: Sets a suffix string to the output line
  • LogFormat: Include date time prefix to the output line
  • IgnoreMessage: Ignores the output line based on the patterns it receives as input parameters

Default

By default, any stdout callback results is managed by DefaultStdoutCallbackResults results method. That results method prepends the separator string ── tho each line on stdout, when any transformer is defined, and prepare all the transformers before to call the worker function, which is in charge to write the output to io.Writer.

JSON

When the stdout callback method is defined to be in json format, the output is managed by JSONStdoutCallbackResults results method. That results method prepares the worker output function to use the IgnoreMessage transformer, to ignore those non json lines. Any other transformer will be ignored but JSONStdoutCallbackResults

On JSONStdoutCallbackResults function is defined the skipPatterns array where are placed the matching expressions for the lines to be ignored.

skipPatterns := []string{
		// This pattern skips timer's callback whitelist output
		"^[\\s\\t]*Playbook run took [0-9]+ days, [0-9]+ hours, [0-9]+ minutes, [0-9]+ seconds$",
	}
Manage JSON output

JSONStdoutCallbackResults method writes to io.Writer parameter the json output. Results packages provides a JSONParser that returns an AnsiblePlaybookJSONResults, holding the unmarshalled json on it. You could manipulate AnsiblePlaybookJSONResults object to achieve and format the json output depending on your needs.

The json schema expected from ansible-playbook is the defined in https://github.com/ansible/ansible/blob/v2.9.11/lib/ansible/plugins/callback/json.py.

Examples

Below you could find an step by step example of how to use go-ansible but on examples folder there are more examples.

When is needed to run an ansible-playbook from your Golang application using go-ansible library, you must define a AnsiblePlaybookCmd,AnsiblePlaybookOptions, AnsiblePlaybookConnectionOptions as its shown below.

AnsiblePlaybookConnectionOptions where is defined how to connect to hosts.

ansiblePlaybookConnectionOptions := &options.AnsiblePlaybookConnectionOptions{
	Connection: "local",
}

AnsiblePlaybookOptions where is defined which should be the ansible-playbook execution behavior and where to find execution configuration.

ansiblePlaybookOptions := &playbook.AnsiblePlaybookOptions{
    Inventory: "127.0.0.1,",
}

AnsiblePlaybookPrivilegeEscalationOptions where is defined wether to become another and how to do it.

privilegeEscalationOptions := &options.AnsiblePlaybookPrivilegeEscalationOptions{
    Become:        true,
    BecomeMethod:  "sudo",
}

AnsiblePlaybookCmd where is defined the command execution.

cmd := &playbook.AnsiblePlaybookCmd{
    Playbook:          "site.yml",
    ConnectionOptions: ansiblePlaybookConnectionOptions,
    Options:           ansiblePlaybookOptions,
    PrivilegeEscalationOptions: privilegeEscalationOptions,
}

Once the AnsiblePlaybookCmd is already defined it could be run it using the Run method. Though is not defined an Executor DefaultExecute is used having the default parameters

err := cmd.Run(context.TODO())
if err != nil {
    panic(err)
}

The result of the ansible-playbook execution is shown below.

 ──
 ── PLAY [all] *********************************************************************
 ──
 ── TASK [Gathering Facts] *********************************************************
 ── ok: [127.0.0.1]
 ──
 ── TASK [simple-ansibleplaybook] **************************************************
 ── ok: [127.0.0.1] => {
 ──     "msg": "Your are running 'simple-ansibleplaybook' example"
 ── }
 ──
 ── PLAY RECAP *********************************************************************
 ── 127.0.0.1                  : ok=2    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0
 ──
 ── Playbook run took 0 days, 0 hours, 0 minutes, 0 seconds

License

go-ansible is available under MIT license.


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