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etcdstruct.go
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/*
* Copyright (c) 2017 Sam Kumar <[email protected]>
* Copyright (c) 2017 University of California, Berkeley
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the University of California, Berkeley nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNERS OR CONTRIBUTORS BE LIABLE FOR
* ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
// Package etcdstruct implements tools to retrieve and store structured
// configuration data in etcd.
package etcdstruct
import (
"context"
"github.com/ugorji/go/codec"
etcd "github.com/coreos/etcd/clientv3"
)
var mp codec.Handle = &codec.MsgpackHandle{}
// EtcdStruct abstracts a structured configuration stored in a single
// key-value pair in etcd. It is encoded using the MsgPack standard.
type EtcdStruct interface {
SetRetrievedRevision(rev int64)
GetRetrievedRevision() int64
}
func encodeToken(tok EtcdStruct) ([]byte, error) {
var encoded []byte
encoder := codec.NewEncoderBytes(&encoded, mp)
err := encoder.Encode(tok)
if err != nil {
return nil, err
}
return encoded, nil
}
func decodeToken(encoded []byte, into interface{}) error {
decoder := codec.NewDecoderBytes(encoded, mp)
return decoder.Decode(into)
}
func RetrieveEtcdStruct(ctx context.Context, etcdClient *etcd.Client, etcdKey string, retrieveInto EtcdStruct) (bool, error) {
resp, err := etcdClient.Get(ctx, etcdKey)
if err != nil {
return false, err
}
/* No token with that name exists. */
if len(resp.Kvs) == 0 {
return false, nil
}
err = decodeToken(resp.Kvs[0].Value, retrieveInto)
if err != nil {
return false, err
}
retrieveInto.SetRetrievedRevision(resp.Kvs[0].ModRevision)
return true, nil
}
func RetrieveEtcdStructs(ctx context.Context, etcdClient *etcd.Client, tofill func(key []byte) EtcdStruct, seterror func(es EtcdStruct, key []byte), etcdKey string, opts ...etcd.OpOption) error {
resp, err := etcdClient.Get(ctx, etcdKey, opts...)
if err != nil {
return err
}
for _, kv := range resp.Kvs {
es := tofill(kv.Key)
err := decodeToken(kv.Value, es)
if err != nil {
seterror(es, kv.Key)
}
es.SetRetrievedRevision(kv.ModRevision)
}
return nil
}
func UpsertEtcdStruct(ctx context.Context, etcdClient *etcd.Client, etcdKey string, tok EtcdStruct) error {
encoded, err := encodeToken(tok)
if err != nil {
return err
}
_, err = etcdClient.Put(ctx, etcdKey, string(encoded))
return err
}
func UpsertEtcdStructAtomic(ctx context.Context, etcdClient *etcd.Client, etcdKey string, tok EtcdStruct) (bool, error) {
encoded, err := encodeToken(tok)
if err != nil {
return false, err
}
resp, err := etcdClient.Txn(ctx).
If(etcd.Compare(etcd.ModRevision(etcdKey), "=", tok.GetRetrievedRevision())).
Then(etcd.OpPut(etcdKey, string(encoded))).
Commit()
if resp != nil {
return resp.Succeeded, err
} else {
return false, err
}
}
func DeleteEtcdStructs(ctx context.Context, etcdClient *etcd.Client, etcdKey string, opts ...etcd.OpOption) (int64, error) {
resp, err := etcdClient.Delete(ctx, etcdKey, opts...)
if resp != nil {
return resp.Deleted, err
} else {
return 0, err
}
}