/
noop.go
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/
noop.go
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// Mgmt
// Copyright (C) 2013-2024+ James Shubin and the project contributors
// Written by James Shubin <james@shubin.ca> and the project contributors
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
//
// Additional permission under GNU GPL version 3 section 7
//
// If you modify this program, or any covered work, by linking or combining it
// with embedded mcl code and modules (and that the embedded mcl code and
// modules which link with this program, contain a copy of their source code in
// the authoritative form) containing parts covered by the terms of any other
// license, the licensors of this program grant you additional permission to
// convey the resulting work. Furthermore, the licensors of this program grant
// the original author, James Shubin, additional permission to update this
// additional permission if he deems it necessary to achieve the goals of this
// additional permission.
package resources
import (
"context"
"fmt"
"github.com/purpleidea/mgmt/engine"
"github.com/purpleidea/mgmt/engine/traits"
)
func init() {
engine.RegisterResource("noop", func() engine.Res { return &NoopRes{} })
}
// NoopRes is a no-op resource that does nothing.
type NoopRes struct {
traits.Base // add the base methods without re-implementation
traits.Groupable
traits.Refreshable
init *engine.Init
Comment string `lang:"comment" yaml:"comment"` // extra field for example purposes
}
// Default returns some sensible defaults for this resource.
func (obj *NoopRes) Default() engine.Res {
return &NoopRes{}
}
// Validate if the params passed in are valid data.
func (obj *NoopRes) Validate() error {
return nil
}
// Init runs some startup code for this resource.
func (obj *NoopRes) Init(init *engine.Init) error {
obj.init = init // save for later
return nil
}
// Cleanup is run by the engine to clean up after the resource is done.
func (obj *NoopRes) Cleanup() error {
return nil
}
// Watch is the primary listener for this resource and it outputs events.
func (obj *NoopRes) Watch(ctx context.Context) error {
obj.init.Running() // when started, notify engine that we're running
select {
case <-ctx.Done(): // closed by the engine to signal shutdown
}
//obj.init.Event() // notify engine of an event (this can block)
return nil
}
// CheckApply method for Noop resource. Does nothing, returns happy!
func (obj *NoopRes) CheckApply(ctx context.Context, apply bool) (bool, error) {
if obj.init.Refresh() {
obj.init.Logf("received a notification!")
}
return true, nil // state is always okay
}
// Cmp compares two resources and returns an error if they are not equivalent.
func (obj *NoopRes) Cmp(r engine.Res) error {
// we can only compare NoopRes to others of the same resource kind
res, ok := r.(*NoopRes)
if !ok {
return fmt.Errorf("not a %s", obj.Kind())
}
if obj.Comment != res.Comment {
return fmt.Errorf("the Comment differs")
}
return nil
}
// NoopUID is the UID struct for NoopRes.
type NoopUID struct {
engine.BaseUID
name string
}
// UIDs includes all params to make a unique identification of this object. Most
// resources only return one, although some resources can return multiple.
func (obj *NoopRes) UIDs() []engine.ResUID {
x := &NoopUID{
BaseUID: engine.BaseUID{Name: obj.Name(), Kind: obj.Kind()},
name: obj.Name(),
}
return []engine.ResUID{x}
}
// GroupCmp returns whether two resources can be grouped together or not.
func (obj *NoopRes) GroupCmp(r engine.GroupableRes) error {
_, ok := r.(*NoopRes)
if !ok {
// NOTE: technically we could group a noop into any other
// resource, if that resource knew how to handle it, although,
// since the mechanics of inter-kind resource grouping are
// tricky, avoid doing this until there's a good reason.
return fmt.Errorf("resource is not the same kind")
}
return nil // noop resources can always be grouped together!
}
// UnmarshalYAML is the custom unmarshal handler for this struct. It is
// primarily useful for setting the defaults.
func (obj *NoopRes) UnmarshalYAML(unmarshal func(interface{}) error) error {
type rawRes NoopRes // indirection to avoid infinite recursion
def := obj.Default() // get the default
res, ok := def.(*NoopRes) // put in the right format
if !ok {
return fmt.Errorf("could not convert to NoopRes")
}
raw := rawRes(*res) // convert; the defaults go here
if err := unmarshal(&raw); err != nil {
return err
}
*obj = NoopRes(raw) // restore from indirection with type conversion!
return nil
}