forked from purpleidea/mgmt
/
kv.go
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/
kv.go
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// Mgmt
// Copyright (C) 2013-2018+ 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 resources
import (
"fmt"
"strconv"
"github.com/purpleidea/mgmt/engine"
"github.com/purpleidea/mgmt/engine/traits"
errwrap "github.com/pkg/errors"
)
func init() {
engine.RegisterResource("kv", func() engine.Res { return &KVRes{} })
}
// KVResSkipCmpStyle represents the different styles of comparison when using SkipLessThan.
type KVResSkipCmpStyle int
// These are the different allowed comparison styles. Most folks will want SkipCmpStyleInt.
const (
SkipCmpStyleInt KVResSkipCmpStyle = iota
SkipCmpStyleString
)
// KVRes is a resource which writes a key/value pair into cluster wide storage.
// It will ensure that the key is set to the requested value. The one exception
// is that if you use the SkipLessThan parameter, then it will only replace the
// stored value with the requested value if it is greater than that stored one.
// This allows the KV resource to be used in fast acting, finite state machines
// which have monotonically increasing state values that represent progression.
// The one exception is that when this resource receives a refresh signal, then
// it will set the value to be the exact one if they are not identical already.
type KVRes struct {
traits.Base // add the base methods without re-implementation
//traits.Groupable // TODO: it could be useful to group our writes and watches!
traits.Refreshable
traits.Recvable
init *engine.Init
// XXX: shouldn't the name be the key?
Key string `yaml:"key"` // key to set
Value *string `yaml:"value"` // value to set (nil to delete)
SkipLessThan bool `yaml:"skiplessthan"` // skip updates as long as stored value is greater
SkipCmpStyle KVResSkipCmpStyle `yaml:"skipcmpstyle"` // how to do the less than cmp
// TODO: does it make sense to have different backends here? (eg: local)
}
// Default returns some sensible defaults for this resource.
func (obj *KVRes) Default() engine.Res {
return &KVRes{}
}
// Validate if the params passed in are valid data.
func (obj *KVRes) Validate() error {
if obj.Key == "" {
return fmt.Errorf("key must not be empty")
}
if obj.SkipLessThan {
if obj.SkipCmpStyle != SkipCmpStyleInt && obj.SkipCmpStyle != SkipCmpStyleString {
return fmt.Errorf("the SkipCmpStyle of %v is invalid", obj.SkipCmpStyle)
}
if v := obj.Value; obj.SkipCmpStyle == SkipCmpStyleInt && v != nil {
if _, err := strconv.Atoi(*v); err != nil {
return fmt.Errorf("the set value of %v can't convert to int", v)
}
}
}
return nil
}
// Init initializes the resource.
func (obj *KVRes) Init(init *engine.Init) error {
obj.init = init // save for later
return nil
}
// Close is run by the engine to clean up after the resource is done.
func (obj *KVRes) Close() error {
return nil
}
// Watch is the primary listener for this resource and it outputs events.
func (obj *KVRes) Watch() error {
// notify engine that we're running
if err := obj.init.Running(); err != nil {
return err // exit if requested
}
ch := obj.init.World.StrMapWatch(obj.Key) // get possible events!
var send = false // send event?
for {
select {
// NOTE: this part is very similar to the file resource code
case err, ok := <-ch:
if !ok { // channel shutdown
return nil
}
if err != nil {
return errwrap.Wrapf(err, "unknown %s watcher error", obj)
}
if obj.init.Debug {
obj.init.Logf("Event!")
}
send = true
obj.init.Dirty() // dirty
case event, ok := <-obj.init.Events:
if !ok {
return nil
}
if err := obj.init.Read(event); err != nil {
return err
}
}
// do all our event sending all together to avoid duplicate msgs
if send {
send = false
if err := obj.init.Event(); err != nil {
return err // exit if requested
}
}
}
}
// lessThanCheck checks for less than validity.
func (obj *KVRes) lessThanCheck(value string) (checkOK bool, err error) {
v := *obj.Value
if value == v { // redundant check for safety
return true, nil
}
var refresh = obj.init.Refresh() // do we have a pending reload to apply?
if !obj.SkipLessThan || refresh { // update lessthan on refresh
return false, nil
}
switch obj.SkipCmpStyle {
case SkipCmpStyleInt:
intValue, err := strconv.Atoi(value)
if err != nil {
// NOTE: We don't error here since we're going to write
// over the value anyways. It could be from an old run!
return false, nil // value is bad (old/corrupt), fix it
}
if vint, err := strconv.Atoi(v); err != nil {
return false, errwrap.Wrapf(err, "can't convert %v to int", v)
} else if vint < intValue {
return true, nil
}
case SkipCmpStyleString:
if v < value { // weird way to cmp, but valid
return true, nil
}
default:
return false, fmt.Errorf("unmatches SkipCmpStyle style %v", obj.SkipCmpStyle)
}
return false, nil
}
// CheckApply method for Password resource. Does nothing, returns happy!
func (obj *KVRes) CheckApply(apply bool) (checkOK bool, err error) {
obj.init.Logf("CheckApply(%t)", apply)
if val, exists := obj.init.Recv()["Value"]; exists && val.Changed {
// if we received on Value, and it changed, wooo, nothing to do.
obj.init.Logf("CheckApply: `Value` was updated!")
}
hostname := obj.init.Hostname // me
keyMap, err := obj.init.World.StrMapGet(obj.Key)
if err != nil {
return false, errwrap.Wrapf(err, "check error during StrGet")
}
if value, ok := keyMap[hostname]; ok && obj.Value != nil {
if value == *obj.Value {
return true, nil
}
if c, err := obj.lessThanCheck(value); err != nil {
return false, err
} else if c {
return true, nil
}
} else if !ok && obj.Value == nil {
return true, nil // nothing to delete, we're good!
} else if ok && obj.Value == nil { // delete
err := obj.init.World.StrMapDel(obj.Key)
return false, errwrap.Wrapf(err, "apply error during StrDel")
}
if !apply {
return false, nil
}
if err := obj.init.World.StrMapSet(obj.Key, *obj.Value); err != nil {
return false, errwrap.Wrapf(err, "apply error during StrSet")
}
return false, nil
}
// Cmp compares two resources and returns an error if they are not equivalent.
func (obj *KVRes) Cmp(r engine.Res) error {
if !obj.Compare(r) {
return fmt.Errorf("did not compare")
}
return nil
}
// Compare two resources and return if they are equivalent.
func (obj *KVRes) Compare(r engine.Res) bool {
// we can only compare KVRes to others of the same resource kind
res, ok := r.(*KVRes)
if !ok {
return false
}
if obj.Key != res.Key {
return false
}
if (obj.Value == nil) != (res.Value == nil) { // xor
return false
}
if obj.Value != nil && res.Value != nil {
if *obj.Value != *res.Value { // compare the strings
return false
}
}
if obj.SkipLessThan != res.SkipLessThan {
return false
}
if obj.SkipCmpStyle != res.SkipCmpStyle {
return false
}
return true
}
// KVUID is the UID struct for KVRes.
type KVUID 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 *KVRes) UIDs() []engine.ResUID {
x := &KVUID{
BaseUID: engine.BaseUID{Name: obj.Name(), Kind: obj.Kind()},
name: obj.Name(),
}
return []engine.ResUID{x}
}
// UnmarshalYAML is the custom unmarshal handler for this struct.
// It is primarily useful for setting the defaults.
func (obj *KVRes) UnmarshalYAML(unmarshal func(interface{}) error) error {
type rawRes KVRes // indirection to avoid infinite recursion
def := obj.Default() // get the default
res, ok := def.(*KVRes) // put in the right format
if !ok {
return fmt.Errorf("could not convert to KVRes")
}
raw := rawRes(*res) // convert; the defaults go here
if err := unmarshal(&raw); err != nil {
return err
}
*obj = KVRes(raw) // restore from indirection with type conversion!
return nil
}