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unaggregated_iterator.go
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/
unaggregated_iterator.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package migration
import (
"fmt"
"github.com/m3db/m3/src/metrics/encoding"
"github.com/m3db/m3/src/metrics/encoding/msgpack"
"github.com/m3db/m3/src/metrics/encoding/protobuf"
)
// UnaggregatedIterator decodes unaggregated metrics.
type UnaggregatedIterator interface {
// Next returns true if there are more items to decode.
Next() bool
// Current returns the current decoded value.
Current() encoding.UnaggregatedMessageUnion
// Err returns the error encountered during decoding, if any.
Err() error
// Close closes the iterator.
Close()
}
type unaggregatedIterator struct {
reader encoding.ByteReadScanner
msgpackIt msgpack.UnaggregatedIterator
protobufIt protobuf.UnaggregatedIterator
msg encoding.UnaggregatedMessageUnion
closed bool
err error
}
// NewUnaggregatedIterator creates a new unaggregated iterator.
func NewUnaggregatedIterator(
reader encoding.ByteReadScanner,
msgpackItOpts msgpack.UnaggregatedIteratorOptions,
protobufItOpts protobuf.UnaggregatedOptions,
) UnaggregatedIterator {
msgpackIt := msgpack.NewUnaggregatedIterator(reader, msgpackItOpts)
protobufIt := protobuf.NewUnaggregatedIterator(reader, protobufItOpts)
return &unaggregatedIterator{
reader: reader,
msgpackIt: msgpackIt,
protobufIt: protobufIt,
}
}
func (it *unaggregatedIterator) Next() bool {
if it.closed || it.Err() != nil {
return false
}
protocol, err := it.decodeProtocolType()
if err != nil {
return false
}
switch protocol {
case msgpackProtocol:
if !it.msgpackIt.Next() {
return false
}
metric := it.msgpackIt.Metric()
policiesList := it.msgpackIt.PoliciesList()
msg, err := toUnaggregatedMessageUnion(metric, policiesList)
if err != nil {
it.err = err
return false
}
it.msg = msg
return true
case protobufProtocol:
if !it.protobufIt.Next() {
return false
}
it.msg = it.protobufIt.Current()
return true
default:
it.err = fmt.Errorf("unexpected protocol type: %v", protocol)
return false
}
}
func (it *unaggregatedIterator) Current() encoding.UnaggregatedMessageUnion { return it.msg }
func (it *unaggregatedIterator) Err() error {
if it.err != nil {
return it.err
}
if err := it.msgpackIt.Err(); err != nil {
return err
}
return it.protobufIt.Err()
}
func (it *unaggregatedIterator) Close() {
if it.closed {
return
}
it.closed = true
it.msgpackIt.Close()
it.msgpackIt = nil
it.protobufIt.Close()
it.protobufIt = nil
it.msg = encoding.UnaggregatedMessageUnion{}
it.err = nil
}
func (it *unaggregatedIterator) decodeProtocolType() (protocolType, error) {
// Peek the first byte of the message.
b, err := it.reader.ReadByte()
if err != nil {
it.err = err
return unknownProtocolType, err
}
// Put the byte back.
if err := it.reader.UnreadByte(); err != nil {
it.err = err
return unknownProtocolType, err
}
// NB: currently the msgpack encoder always encodes the version first as the first byte
// of the msgpack message, and since we are currently at version 1, the first byte will
// always be an odd number (i.e., 1). On the other hand, the protobuf encoder always
// encodes the message length as a varint, in which case the first byte will always
// be an even number. As such we can use the last bit of the byte to distinguish the
// different protocols.
protocol := msgpackProtocol
if (b & 1) == 0 {
protocol = protobufProtocol
}
return protocol, nil
}
type protocolType int
const (
unknownProtocolType protocolType = iota
msgpackProtocol
protobufProtocol
)