b19583e7d3
This is an initial implementation of the mgmt language. It is a declarative (immutable) functional, reactive, domain specific programming language. It is intended to be a language that is: * safe * powerful * easy to reason about With these properties, we hope this language, and the mgmt engine will allow you to model the real-time systems that you'd like to automate. This also includes a number of other associated changes. Sorry for the large size of this patch.
110 lines
4.2 KiB
Go
110 lines
4.2 KiB
Go
// 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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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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// XXX: since the caller of this (via the World API) has no way to tell it it's
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// done, does that mean we leak go-routines since it might still be running, but
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// perhaps even blocked??? Could this cause a dead-lock? Should we instead return
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// some sort of struct which has a close method with it to ask for a shutdown?
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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 global 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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