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convert.go
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convert.go
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package zktopo
import (
"encoding/json"
"path"
"strings"
"github.com/golang/protobuf/proto"
topodatapb "github.com/youtube/vitess/go/vt/proto/topodata"
vschemapb "github.com/youtube/vitess/go/vt/proto/vschema"
)
// This file contains utility functions to maintain backward compatibility
// with old-style non-Backend Zookeeper topologies. The old
// implementations (before 2016-08-17) used to deal with explicit data
// types. We converted them to a generic []byte and path
// interface. But the zookeeper implementation was not compatible with
// this.
// dataType is an enum for possible data types, used for backward
// compatibility.
type dataType int
// Constants for type conversion
const (
// newType is used to indicate a topology object type of
// anything that is added after the topo.Backend refactor,
// i.e. anything that doesn't require conversion between old
// style topologies and the new style ones. The list of enum
// values after this contain all types that exist at the
// moment (2016-08-17) and doesn't need to be expanded when
// something new is saved in the topology because it will be
// saved in the new style, not in the old one.
newType dataType = iota
srvKeyspaceType
srvVSchemaType
)
// rawDataFromNodeValue convert the data of the given type into an []byte.
// It is mindful of the backward compatibility, i.e. for newer objects
// it doesn't do anything, but for old object types that were stored in JSON
// format in converts them to proto3 binary encoding.
func rawDataFromNodeValue(what dataType, data []byte) ([]byte, error) {
var p proto.Message
switch what {
case srvKeyspaceType:
p = &topodatapb.SrvKeyspace{}
case srvVSchemaType:
p = &vschemapb.SrvVSchema{}
default:
return data, nil
}
if err := json.Unmarshal(data, p); err != nil {
return nil, err
}
return proto.Marshal(p)
}
// oldTypeAndFilePath returns the data type and old file path for a given path.
func oldTypeAndFilePath(cell, filePath string) (dataType, string) {
parts := strings.Split(filePath, "/")
// SrvKeyspace: local cell, keyspaces/<keyspace>/SrvKeyspace
if len(parts) == 3 && parts[0] == "keyspaces" && parts[2] == "SrvKeyspace" {
return srvKeyspaceType, zkPathForSrvKeyspace(cell, parts[1])
}
// SrvVSchema: local cell, SrvVSchema
if len(parts) == 1 && parts[0] == "SrvVSchema" {
return srvVSchemaType, zkPathForSrvVSchema(cell)
}
// General case.
return newType, path.Join("/zk", cell, "vt", filePath)
}