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reverse.go
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reverse.go
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// Mgmt
// Copyright (C) 2013-2021+ 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 <http://www.gnu.org/licenses/>.
package graph
import (
"fmt"
"io/ioutil"
"os"
"path"
"sort"
"github.com/purpleidea/mgmt/engine"
engineUtil "github.com/purpleidea/mgmt/engine/util"
"github.com/purpleidea/mgmt/pgraph"
"github.com/purpleidea/mgmt/util/errwrap"
)
const (
// ReverseFile is the file name in the resource state dir where any
// reversal information is stored.
ReverseFile = "reverse"
// ReversePerm is the permissions mode used to create the ReverseFile.
ReversePerm = 0600
)
// Reversals adds the reversals onto the loaded graph. This should happen last,
// and before Commit.
func (obj *Engine) Reversals() error {
if obj.nextGraph == nil {
return fmt.Errorf("there is no active graph to add reversals to")
}
// Initially get all of the reversals to seek out all possible errors.
// XXX: The engine needs to know where data might have been stored if we
// XXX: want to potentially allow alternate read/write paths, like etcd.
// XXX: In this scenario, we'd have to store a token somewhere to let us
// XXX: know to look elsewhere for the special ReversalList read method.
data, err := obj.ReversalList() // (map[string]string, error)
if err != nil {
return errwrap.Wrapf(err, "the reversals had errors")
}
if len(data) == 0 {
return nil // end early
}
resMatch := func(r1, r2 engine.Res) bool { // simple match on UID only!
if r1.Kind() != r2.Kind() {
return false
}
if r1.Name() != r2.Name() {
return false
}
return true
}
resInList := func(needle engine.Res, haystack []engine.Res) bool {
for _, res := range haystack {
if resMatch(needle, res) {
return true
}
}
return false
}
if obj.Debug {
obj.Logf("decoding %d reversals...", len(data))
}
resources := []engine.Res{}
// do this in a sorted order so that it errors deterministically
sorted := []string{}
for key := range data {
sorted = append(sorted, key)
}
sort.Strings(sorted)
for _, key := range sorted {
val := data[key]
// XXX: replace this ResToB64 method with one that stores it in
// a human readable format, in case someone wants to hack and
// edit it manually.
// XXX: we probably want this to be YAML, it works with the diff
// too...
r, err := engineUtil.B64ToRes(val)
if err != nil {
return errwrap.Wrapf(err, "error decoding res with UID: `%s`", key)
}
res, ok := r.(engine.ReversibleRes)
if !ok {
// this requirement is here to keep things simpler...
return errwrap.Wrapf(err, "decoded res with UID: `%s` was not reversible", key)
}
matchFn := func(vertex pgraph.Vertex) (bool, error) {
r, ok := vertex.(engine.Res)
if !ok {
return false, fmt.Errorf("not a Res")
}
if !resMatch(r, res) {
return false, nil
}
return true, nil
}
// FIXME: not efficient, we could build a cache-map first
vertex, err := obj.nextGraph.VertexMatchFn(matchFn) // (Vertex, error)
if err != nil {
return errwrap.Wrapf(err, "error searching graph for match")
}
if vertex != nil { // found one!
continue // it doesn't need reversing yet
}
// TODO: check for (incompatible?) duplicates instead
if resInList(res, resources) { // we've already got this one...
continue
}
// We set this in two different places to be safe. It ensures
// that we erase the reversal state file after we've used it.
res.ReversibleMeta().Reversal = true // set this for later...
resources = append(resources, res)
}
if len(resources) == 0 {
return nil // end early
}
// Now that we've passed the chance of any errors, we modify the graph.
obj.Logf("adding %d reversals...", len(resources))
for _, res := range resources {
obj.nextGraph.AddVertex(res)
}
// TODO: Do we want a way for stored reversals to add edges too?
// It would be great to ensure we didn't add any graph cycles here, but
// instead of checking now, we'll move the check into the main loop.
return nil
}
// ReversalList returns all the available pending reversal data on this host. It
// can then be decoded by whatever method is appropriate for.
func (obj *Engine) ReversalList() (map[string]string, error) {
result := make(map[string]string) // some key to contents
dir := obj.statePrefix() // loop through this dir...
files, err := ioutil.ReadDir(dir)
if err != nil && !os.IsNotExist(err) {
return nil, errwrap.Wrapf(err, "error reading list of state dirs")
} else if err != nil {
return result, nil // nothing found, no state dir exists yet
}
for _, x := range files {
key := x.Name() // some uid for the resource
file := path.Join(dir, key, ReverseFile)
content, err := ioutil.ReadFile(file)
if err != nil && !os.IsNotExist(err) {
return nil, errwrap.Wrapf(err, "could not read reverse file: %s", file)
} else if err != nil {
continue // file does not exist, skip
}
// file exists!
str := string(content)
result[key] = str // save
}
return result, nil
}
// ReversalInit performs the reversal initialization steps if necessary for this
// resource.
func (obj *State) ReversalInit() error {
res, ok := obj.Vertex.(engine.ReversibleRes)
if !ok {
return nil // nothing to do
}
if res.ReversibleMeta().Disabled {
return nil // nothing to do, reversal isn't enabled
}
// If the reversal is enabled, but we are the result of a previous
// reversal, then this will overwrite that older reversal request, and
// our resource should be designed to deal with that. This happens if we
// return a reversible resource as the reverse of a resource that was
// reversed. It's probably fairly rare.
if res.ReversibleMeta().Reversal {
obj.Logf("triangle reversal") // warn!
}
r, err := res.Reversed()
if err != nil {
return errwrap.Wrapf(err, "could not reverse: %s", res.String())
}
if r == nil {
return nil // this can't be reversed, or isn't implemented here
}
// We set this in two different places to be safe. It ensures that we
// erase the reversal state file after we've used it.
r.ReversibleMeta().Reversal = true // set this for later...
// XXX: replace this ResToB64 method with one that stores it in a human
// readable format, in case someone wants to hack and edit it manually.
// XXX: we probably want this to be YAML, it works with the diff too...
str, err := engineUtil.ResToB64(r)
if err != nil {
return errwrap.Wrapf(err, "could not encode: %s", res.String())
}
// TODO: put this method on traits.Reversible as part of the interface?
return obj.ReversalWrite(str, res.ReversibleMeta().Overwrite) // Store!
}
// ReversalClose performs the reversal shutdown steps if necessary for this
// resource.
func (obj *State) ReversalClose() error {
res, ok := obj.Vertex.(engine.ReversibleRes)
if !ok {
return nil // nothing to do
}
// Don't check res.ReversibleMeta().Disabled because we're removing the
// previous one. That value only applies if we're doing a new reversal.
if !res.ReversibleMeta().Reversal {
return nil // nothing to erase, we're not a reversal resource
}
if !obj.isStateOK { // did we successfully reverse?
obj.Logf("did not complete reversal") // warn
return nil
}
// TODO: put this method on traits.Reversible as part of the interface?
return obj.ReversalDelete() // Erase our reversal instructions.
}
// ReversalWrite stores the reversal state information for this resource.
func (obj *State) ReversalWrite(str string, overwrite bool) error {
dir, err := obj.varDir("") // private version
if err != nil {
return errwrap.Wrapf(err, "could not get VarDir for reverse")
}
file := path.Join(dir, ReverseFile) // return a unique file
content, err := ioutil.ReadFile(file)
if err != nil && !os.IsNotExist(err) {
return errwrap.Wrapf(err, "could not read reverse file: %s", file)
}
// file exists and we shouldn't overwrite if different
if err == nil && !overwrite {
// compare to existing file
oldStr := string(content)
if str != oldStr {
obj.Logf("existing, pending, reversible resource exists")
//obj.Logf("diff:")
//obj.Logf("") // TODO: print the diff w/o and secret values
return fmt.Errorf("existing, pending, reversible resource exists")
}
}
return ioutil.WriteFile(file, []byte(str), ReversePerm)
}
// ReversalDelete removes the reversal state information for this resource.
func (obj *State) ReversalDelete() error {
dir, err := obj.varDir("") // private version
if err != nil {
return errwrap.Wrapf(err, "could not get VarDir for reverse")
}
file := path.Join(dir, ReverseFile) // return a unique file
// FIXME: why do we see these removals when there isn't a state file?
if err = os.Remove(file); os.IsNotExist(err) {
return nil // ignore missing files
}
return errwrap.Wrapf(err, "could not remove reverse state file")
}