/
str.go
97 lines (84 loc) · 3.67 KB
/
str.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 str
import (
"context"
"fmt"
"github.com/purpleidea/mgmt/etcd/interfaces"
"github.com/purpleidea/mgmt/util/errwrap"
etcd "go.etcd.io/etcd/clientv3"
etcdutil "go.etcd.io/etcd/clientv3/clientv3util"
)
const (
ns = "" // in case we want to add one back in
)
// WatchStr returns a channel which spits out events on key activity.
// FIXME: It should close the channel when it's done, and spit out errors when
// something goes wrong.
// XXX: since the caller of this (via the World API) has no way to tell it it's
// done, does that mean we leak go-routines since it might still be running, but
// perhaps even blocked??? Could this cause a dead-lock? Should we instead
// return some sort of struct which has a close method with it to ask for a
// shutdown?
func WatchStr(ctx context.Context, client interfaces.Client, key string) (chan error, error) {
// new key structure is $NS/strings/$key = $data
path := fmt.Sprintf("%s/strings/%s", ns, key)
return client.Watcher(ctx, path)
}
// GetStr collects the string which matches a global namespace in etcd.
func GetStr(ctx context.Context, client interfaces.Client, key string) (string, error) {
// new key structure is $NS/strings/$key = $data
path := fmt.Sprintf("%s/strings/%s", ns, key)
keyMap, err := client.Get(ctx, path, etcd.WithPrefix())
if err != nil {
return "", errwrap.Wrapf(err, "could not get strings in: %s", key)
}
if len(keyMap) == 0 {
return "", interfaces.ErrNotExist
}
if count := len(keyMap); count != 1 {
return "", fmt.Errorf("returned %d entries", count)
}
val, exists := keyMap[path]
if !exists {
return "", fmt.Errorf("path `%s` is missing", path)
}
return val, nil
}
// SetStr sets a key and hostname pair to a certain value. If the value is nil,
// then it deletes the key. Otherwise the value should point to a string.
// TODO: TTL or delete disconnect?
func SetStr(ctx context.Context, client interfaces.Client, key string, data *string) error {
// key structure is $NS/strings/$key = $data
path := fmt.Sprintf("%s/strings/%s", ns, key)
ifs := []etcd.Cmp{} // list matching the desired state
ops := []etcd.Op{} // list of ops in this transaction (then)
els := []etcd.Op{} // list of ops in this transaction (else)
if data == nil { // perform a delete
ifs = append(ifs, etcdutil.KeyExists(path))
//ifs = append(ifs, etcd.Compare(etcd.Version(path), ">", 0))
ops = append(ops, etcd.OpDelete(path))
} else {
data := *data // get the real value
ifs = append(ifs, etcd.Compare(etcd.Value(path), "=", data)) // desired state
els = append(els, etcd.OpPut(path, data))
}
// it's important to do this in one transaction, and atomically, because
// this way, we only generate one watch event, and only when it's needed
_, err := client.Txn(ctx, ifs, ops, els) // TODO: do we need to look at response?
return errwrap.Wrapf(err, "could not set strings in: %s", key)
}