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listoffsets.go
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/
listoffsets.go
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package listoffsets
import (
"sort"
"github.com/segmentio/kafka-go/protocol"
)
func init() {
protocol.Register(&Request{}, &Response{})
}
type Request struct {
ReplicaID int32 `kafka:"min=v1,max=v5"`
IsolationLevel int8 `kafka:"min=v2,max=v5"`
Topics []RequestTopic `kafka:"min=v1,max=v5"`
}
type RequestTopic struct {
Topic string `kafka:"min=v1,max=v5"`
Partitions []RequestPartition `kafka:"min=v1,max=v5"`
}
type RequestPartition struct {
Partition int32 `kafka:"min=v1,max=v5"`
CurrentLeaderEpoch int32 `kafka:"min=v4,max=v5"`
Timestamp int64 `kafka:"min=v1,max=v5"`
// v0 of the API predates kafka 0.10, and doesn't make much sense to
// use so we chose not to support it. It had this extra field to limit
// the number of offsets returned, which has been removed in v1.
//
// MaxNumOffsets int32 `kafka:"min=v0,max=v0"`
}
func (r *Request) ApiKey() protocol.ApiKey { return protocol.ListOffsets }
func (r *Request) Broker(cluster protocol.Cluster) (protocol.Broker, error) {
// Expects r to be a request that was returned by Map, will likely panic
// or produce the wrong result if that's not the case.
partition := r.Topics[0].Partitions[0].Partition
topic := r.Topics[0].Topic
for _, p := range cluster.Topics[topic].Partitions {
if p.ID == partition {
return cluster.Brokers[p.Leader], nil
}
}
return protocol.Broker{ID: -1}, nil
}
func (r *Request) Split(cluster protocol.Cluster) ([]protocol.Message, protocol.Merger, error) {
// Because kafka refuses to answer ListOffsets requests containing multiple
// entries of unique topic/partition pairs, we submit multiple requests on
// the wire and merge their results back.
//
// ListOffsets requests also need to be sent to partition leaders, to keep
// the logic simple we simply split each offset request into a single
// message. This may cause a bit more requests to be sent on the wire but
// it keeps the code sane, we can still optimize the aggregation mechanism
// later if it becomes a problem.
//
// Really the idea here is to shield applications from having to deal with
// the limitation of the kafka server, so they can request any combinations
// of topic/partition/offsets.
requests := make([]Request, 0, 2*len(r.Topics))
for _, t := range r.Topics {
for _, p := range t.Partitions {
requests = append(requests, Request{
ReplicaID: r.ReplicaID,
IsolationLevel: r.IsolationLevel,
Topics: []RequestTopic{{
Topic: t.Topic,
Partitions: []RequestPartition{{
Partition: p.Partition,
CurrentLeaderEpoch: p.CurrentLeaderEpoch,
Timestamp: p.Timestamp,
}},
}},
})
}
}
messages := make([]protocol.Message, len(requests))
for i := range requests {
messages[i] = &requests[i]
}
return messages, new(Response), nil
}
type Response struct {
ThrottleTimeMs int32 `kafka:"min=v2,max=v5"`
Topics []ResponseTopic `kafka:"min=v1,max=v5"`
}
type ResponseTopic struct {
Topic string `kafka:"min=v1,max=v5"`
Partitions []ResponsePartition `kafka:"min=v1,max=v5"`
}
type ResponsePartition struct {
Partition int32 `kafka:"min=v1,max=v5"`
ErrorCode int16 `kafka:"min=v1,max=v5"`
Timestamp int64 `kafka:"min=v1,max=v5"`
Offset int64 `kafka:"min=v1,max=v5"`
LeaderEpoch int32 `kafka:"min=v4,max=v5"`
}
func (r *Response) ApiKey() protocol.ApiKey { return protocol.ListOffsets }
func (r *Response) Merge(requests []protocol.Message, results []interface{}) (protocol.Message, error) {
type topicPartition struct {
topic string
partition int32
}
// Kafka doesn't always return the timestamp in the response, for example
// when the request sends -2 (for the first offset) it always returns -1,
// probably to indicate that the timestamp is unknown. This means that we
// can't correlate the requests and responses based on their timestamps,
// the primary key is the topic/partition pair.
//
// To make the API a bit friendly, we reconstructing an index of topic
// partitions to the timestamps that were requested, and override the
// timestamp value in the response.
timestamps := make([]map[topicPartition]int64, len(requests))
for i, m := range requests {
req := m.(*Request)
ts := make(map[topicPartition]int64, len(req.Topics))
for _, t := range req.Topics {
for _, p := range t.Partitions {
ts[topicPartition{
topic: t.Topic,
partition: p.Partition,
}] = p.Timestamp
}
}
timestamps[i] = ts
}
topics := make(map[string][]ResponsePartition)
errors := 0
for i, res := range results {
m, err := protocol.Result(res)
if err != nil {
for _, t := range requests[i].(*Request).Topics {
partitions := topics[t.Topic]
for _, p := range t.Partitions {
partitions = append(partitions, ResponsePartition{
Partition: p.Partition,
ErrorCode: -1, // UNKNOWN, can we do better?
Timestamp: -1,
Offset: -1,
LeaderEpoch: -1,
})
}
topics[t.Topic] = partitions
}
errors++
continue
}
response := m.(*Response)
if r.ThrottleTimeMs < response.ThrottleTimeMs {
r.ThrottleTimeMs = response.ThrottleTimeMs
}
for _, t := range response.Topics {
for _, p := range t.Partitions {
if timestamp, ok := timestamps[i][topicPartition{
topic: t.Topic,
partition: p.Partition,
}]; ok {
p.Timestamp = timestamp
}
topics[t.Topic] = append(topics[t.Topic], p)
}
}
}
if errors > 0 && errors == len(results) {
_, err := protocol.Result(results[0])
return nil, err
}
r.Topics = make([]ResponseTopic, 0, len(topics))
for topicName, partitions := range topics {
r.Topics = append(r.Topics, ResponseTopic{
Topic: topicName,
Partitions: partitions,
})
}
sort.Slice(r.Topics, func(i, j int) bool {
return r.Topics[i].Topic < r.Topics[j].Topic
})
for _, t := range r.Topics {
sort.Slice(t.Partitions, func(i, j int) bool {
p1 := &t.Partitions[i]
p2 := &t.Partitions[j]
if p1.Partition != p2.Partition {
return p1.Partition < p2.Partition
}
return p1.Offset < p2.Offset
})
}
return r, nil
}
var (
_ protocol.BrokerMessage = (*Request)(nil)
_ protocol.Splitter = (*Request)(nil)
_ protocol.Merger = (*Response)(nil)
)