engine: Resources package rewrite
This giant patch makes some much needed improvements to the code base. * The engine has been rewritten and lives within engine/graph/ * All of the common interfaces and code now live in engine/ * All of the resources are in one package called engine/resources/ * The Res API can use different "traits" from engine/traits/ * The Res API has been simplified to hide many of the old internals * The Watch & Process loops were previously inverted, but is now fixed * The likelihood of package cycles has been reduced drastically * And much, much more... Unfortunately, some code had to be temporarily removed. The remote code had to be taken out, as did the prometheus code. We hope to have these back in new forms as soon as possible.
This commit is contained in:
James Shubin
333
engine/resources/augeas.go
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333
engine/resources/augeas.go
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// Mgmt
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// Copyright (C) 2013-2018+ James Shubin and the project contributors
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// Written by James Shubin <james@shubin.ca> and the project contributors
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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// +build !noaugeas
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package resources
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import (
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"fmt"
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"os"
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"strings"
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"github.com/purpleidea/mgmt/engine"
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"github.com/purpleidea/mgmt/engine/traits"
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"github.com/purpleidea/mgmt/recwatch"
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errwrap "github.com/pkg/errors"
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// FIXME: we vendor go/augeas because master requires augeas 1.6.0
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// and libaugeas-dev-1.6.0 is not yet available in a PPA.
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"honnef.co/go/augeas"
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)
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const (
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// NS is a namespace for augeas operations
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NS = "Xmgmt"
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)
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func init() {
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engine.RegisterResource("augeas", func() engine.Res { return &AugeasRes{} })
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}
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// AugeasRes is a resource that enables you to use the augeas resource.
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// Currently only allows you to change simple files (e.g sshd_config).
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type AugeasRes struct {
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traits.Base // add the base methods without re-implementation
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init *engine.Init
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// File is the path to the file targeted by this resource.
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File string `yaml:"file"`
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// Lens is the lens used by this resource. If specified, mgmt
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// will lower the augeas overhead by only loading that lens.
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Lens string `yaml:"lens"`
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// Sets is a list of changes that will be applied to the file, in the form of
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// ["path", "value"]. mgmt will run augeas.Get() before augeas.Set(), to
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// prevent changing the file when it is not needed.
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Sets []*AugeasSet `yaml:"sets"`
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recWatcher *recwatch.RecWatcher // used to watch the changed files
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}
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// AugeasSet represents a key/value pair of settings to be applied.
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type AugeasSet struct {
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Path string `yaml:"path"` // The relative path to the value to be changed.
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Value string `yaml:"value"` // The value to be set on the given Path.
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}
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// Cmp compares this set with another one.
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func (obj *AugeasSet) Cmp(set *AugeasSet) error {
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if obj == nil && set == nil {
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return nil
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}
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if obj == nil && set != nil {
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return fmt.Errorf("can't compare nil set to set")
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}
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if obj != nil && set == nil {
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return fmt.Errorf("can't compare set to nil set")
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}
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if obj.Path != set.Path {
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return fmt.Errorf("the Path values differ")
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}
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if obj.Value != set.Value {
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return fmt.Errorf("the Value values differ")
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}
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return nil
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}
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// Default returns some sensible defaults for this resource.
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func (obj *AugeasRes) Default() engine.Res {
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return &AugeasRes{}
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}
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// Validate if the params passed in are valid data.
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func (obj *AugeasRes) Validate() error {
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if !strings.HasPrefix(obj.File, "/") {
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return fmt.Errorf("the File param should start with a slash")
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}
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if obj.Lens != "" && !strings.HasSuffix(obj.Lens, ".lns") {
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return fmt.Errorf("the Lens param should have a .lns suffix")
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}
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if (obj.Lens == "") != (obj.File == "") {
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return fmt.Errorf("the File and Lens params must be specified together")
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}
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return nil
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}
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// Init initializes the resource.
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func (obj *AugeasRes) Init(init *engine.Init) error {
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obj.init = init // save for later
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return nil
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}
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// Close is run by the engine to clean up after the resource is done.
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func (obj *AugeasRes) Close() error {
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return nil
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}
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// Watch is the primary listener for this resource and it outputs events.
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// Taken from the File resource.
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// FIXME: DRY - This is taken from the file resource
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func (obj *AugeasRes) Watch() error {
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var err error
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obj.recWatcher, err = recwatch.NewRecWatcher(obj.File, false)
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if err != nil {
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return err
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}
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defer obj.recWatcher.Close()
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// notify engine that we're running
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if err := obj.init.Running(); err != nil {
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return err // exit if requested
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}
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var send = false // send event?
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for {
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if obj.init.Debug {
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obj.init.Logf("Watching: %s", obj.File) // attempting to watch...
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}
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select {
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case event, ok := <-obj.recWatcher.Events():
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if !ok { // channel shutdown
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return nil
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}
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if err := event.Error; err != nil {
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return errwrap.Wrapf(err, "Unknown %s watcher error", obj)
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}
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if obj.init.Debug { // don't access event.Body if event.Error isn't nil
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obj.init.Logf("Event(%s): %v", event.Body.Name, event.Body.Op)
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}
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send = true
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obj.init.Dirty() // dirty
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case event, ok := <-obj.init.Events:
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if !ok {
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return nil
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}
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if err := obj.init.Read(event); err != nil {
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return err
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}
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}
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// do all our event sending all together to avoid duplicate msgs
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if send {
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send = false
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if err := obj.init.Event(); err != nil {
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return err // exit if requested
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}
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}
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}
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}
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// checkApplySet runs CheckApply for one element of the AugeasRes.Set
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func (obj *AugeasRes) checkApplySet(apply bool, ag *augeas.Augeas, set *AugeasSet) (bool, error) {
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fullpath := fmt.Sprintf("/files/%v/%v", obj.File, set.Path)
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// We do not check for errors because errors are also thrown when
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// the path does not exist.
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if getValue, _ := ag.Get(fullpath); set.Value == getValue {
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// The value is what we expect, return directly
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return true, nil
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}
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if !apply {
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// If noop, we can return here directly. We return with
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// nil even if err is not nil because it does not mean
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// there is an error.
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return false, nil
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}
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if err := ag.Set(fullpath, set.Value); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while setting value")
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}
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return false, nil
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}
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// CheckApply method for Augeas resource.
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func (obj *AugeasRes) CheckApply(apply bool) (bool, error) {
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obj.init.Logf("CheckApply: %s", obj.File)
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// By default we do not set any option to augeas, we use the defaults.
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opts := augeas.None
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if obj.Lens != "" {
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// if the lens is specified, we can speed up augeas by not
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// loading everything. Without this option, augeas will try to
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// read all the files it knows in the complete filesystem.
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// e.g. to change /etc/ssh/sshd_config, it would load /etc/hosts, /etc/ntpd.conf, etc...
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opts = augeas.NoModlAutoload
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}
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// Initiate augeas
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ag, err := augeas.New("/", "", opts)
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if err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while initializing")
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}
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defer ag.Close()
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if obj.Lens != "" {
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// If the lens is set, load the lens for the file we want to edit.
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// We pick Xmgmt, as this name will not collide with any other lens name.
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// We do not pick Mgmt as in the future there might be an Mgmt lens.
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// https://github.com/hercules-team/augeas/wiki/Loading-specific-files
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if err = ag.Set(fmt.Sprintf("/augeas/load/%s/lens", NS), obj.Lens); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while initializing lens")
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}
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if err = ag.Set(fmt.Sprintf("/augeas/load/%s/incl", NS), obj.File); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while initializing incl")
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}
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if err = ag.Load(); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while loading")
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}
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}
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checkOK := true
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for _, set := range obj.Sets {
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if setCheckOK, err := obj.checkApplySet(apply, &ag, set); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error during CheckApply of one Set")
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} else if !setCheckOK {
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checkOK = false
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}
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}
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// If the state is correct or we can't apply, return early.
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if checkOK || !apply {
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return checkOK, nil
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}
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obj.init.Logf("changes needed, saving")
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if err = ag.Save(); err != nil {
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return false, errwrap.Wrapf(err, "augeas: error while saving augeas values")
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}
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// FIXME: Workaround for https://github.com/dominikh/go-augeas/issues/13
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// To be fixed upstream.
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if obj.File != "" {
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if _, err := os.Stat(obj.File); os.IsNotExist(err) {
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return false, errwrap.Wrapf(err, "augeas: error: file does not exist")
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}
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}
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return false, nil
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}
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// Cmp compares two resources and returns an error if they are not equivalent.
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func (obj *AugeasRes) Cmp(r engine.Res) error {
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// we can only compare to others of the same resource kind
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res, ok := r.(*AugeasRes)
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if !ok {
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return fmt.Errorf("resource is not the same kind")
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}
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if obj.File != res.File {
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return fmt.Errorf("the File params differ")
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}
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if obj.Lens != res.Lens {
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return fmt.Errorf("the Lens params differ")
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}
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if len(obj.Sets) != len(res.Sets) {
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return fmt.Errorf("the length of the two Sets params differs")
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}
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for i := 0; i < len(obj.Sets); i++ {
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if err := obj.Sets[i].Cmp(res.Sets[i]); err != nil {
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return errwrap.Wrapf(err, "the Sets item at index %d differs", i)
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}
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}
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return nil
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}
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// AugeasUID is the UID struct for AugeasRes.
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type AugeasUID struct {
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engine.BaseUID
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name string
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}
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// UIDs includes all params to make a unique identification of this object.
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func (obj *AugeasRes) UIDs() []engine.ResUID {
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x := &AugeasUID{
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BaseUID: engine.BaseUID{Name: obj.Name(), Kind: obj.Kind()},
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name: obj.Name(),
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}
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return []engine.ResUID{x}
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}
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// UnmarshalYAML is the custom unmarshal handler for this struct.
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// It is primarily useful for setting the defaults.
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func (obj *AugeasRes) UnmarshalYAML(unmarshal func(interface{}) error) error {
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type rawRes AugeasRes // indirection to avoid infinite recursion
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def := obj.Default() // get the default
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res, ok := def.(*AugeasRes) // put in the right format
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if !ok {
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return fmt.Errorf("could not convert to AugeasRes")
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}
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raw := rawRes(*res) // convert; the defaults go here
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if err := unmarshal(&raw); err != nil {
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return err
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}
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*obj = AugeasRes(raw) // restore from indirection with type conversion!
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return nil
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}
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