0af9af44e5
It's up to the end user to decide who is writing and/or overwriting them. It could also be useful to reimplement (refactor) some of the existing World API's to be implemented in terms of these primitives.
106 lines
3.9 KiB
Go
106 lines
3.9 KiB
Go
// Mgmt
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// Copyright (C) 2013-2017+ 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 Affero 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 Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package etcd
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import (
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"errors"
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"fmt"
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etcd "github.com/coreos/etcd/clientv3"
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errwrap "github.com/pkg/errors"
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)
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// ErrNotExist is returned when GetStr can not find the requested key.
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// TODO: https://dave.cheney.net/2016/04/07/constant-errors
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var ErrNotExist = errors.New("errNotExist")
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// WatchStr returns a channel which spits out events on key activity.
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// FIXME: It should close the channel when it's done, and spit out errors when
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// something goes wrong.
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func WatchStr(obj *EmbdEtcd, key string) chan error {
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// new key structure is /$NS/strings/$key = $data
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path := fmt.Sprintf("/%s/strings/%s", NS, key)
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ch := make(chan error, 1)
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// FIXME: fix our API so that we get a close event on shutdown.
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callback := func(re *RE) error {
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// TODO: is this even needed? it used to happen on conn errors
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//log.Printf("Etcd: Watch: Path: %v", path) // event
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if re == nil || re.response.Canceled {
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return fmt.Errorf("watch is empty") // will cause a CtxError+retry
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}
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if len(ch) == 0 { // send event only if one isn't pending
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ch <- nil // event
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}
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return nil
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}
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_, _ = obj.AddWatcher(path, callback, true, false, etcd.WithPrefix()) // no need to check errors
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return ch
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}
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// GetStr collects the string which matches a gloabl namespace in etcd.
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func GetStr(obj *EmbdEtcd, key string) (string, error) {
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// new key structure is /$NS/strings/$key = $data
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path := fmt.Sprintf("/%s/strings/%s", NS, key)
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keyMap, err := obj.Get(path, etcd.WithPrefix())
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if err != nil {
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return "", errwrap.Wrapf(err, "could not get strings in: %s", key)
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}
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if len(keyMap) == 0 {
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return "", ErrNotExist
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}
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if count := len(keyMap); count != 1 {
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return "", fmt.Errorf("returned %d entries", count)
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}
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val, exists := keyMap[path]
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if !exists {
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return "", fmt.Errorf("path `%s` is missing", path)
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}
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//log.Printf("Etcd: GetStr(%s): %s", key, val)
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return val, nil
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}
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// SetStr sets a key and hostname pair to a certain value. If the value is
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// nil, then it deletes the key. Otherwise the value should point to a string.
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// TODO: TTL or delete disconnect?
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func SetStr(obj *EmbdEtcd, key string, data *string) error {
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// key structure is /$NS/strings/$key = $data
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path := fmt.Sprintf("/%s/strings/%s", NS, key)
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ifs := []etcd.Cmp{} // list matching the desired state
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ops := []etcd.Op{} // list of ops in this transaction (then)
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els := []etcd.Op{} // list of ops in this transaction (else)
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if data == nil { // perform a delete
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// TODO: use https://github.com/coreos/etcd/pull/7417 if merged
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//ifs = append(ifs, etcd.KeyExists(path))
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ifs = append(ifs, etcd.Compare(etcd.Version(path), ">", 0))
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ops = append(ops, etcd.OpDelete(path))
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} else {
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data := *data // get the real value
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ifs = append(ifs, etcd.Compare(etcd.Value(path), "=", data)) // desired state
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els = append(els, etcd.OpPut(path, data))
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}
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// it's important to do this in one transaction, and atomically, because
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// this way, we only generate one watch event, and only when it's needed
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_, err := obj.Txn(ifs, ops, els) // TODO: do we need to look at response?
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return errwrap.Wrapf(err, "could not set strings in: %s", key)
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}
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