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kafkatarget.go
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kafkatarget.go
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package kafkatarget
// This code is copied from Promtail (https://github.com/grafana/loki/commit/065bee7e72b00d800431f4b70f0d673d6e0e7a2b). The kafkatarget package is used to
// configure and run the targets that can read kafka entries and forward them
// to other loki components.
import (
"fmt"
"time"
"github.com/IBM/sarama"
"github.com/go-kit/log"
"github.com/grafana/alloy/internal/alloy/logging/level"
"github.com/grafana/alloy/internal/component/common/loki"
"github.com/grafana/loki/clients/pkg/promtail/targets/target"
"github.com/prometheus/common/model"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/model/relabel"
)
type runnableDroppedTarget struct {
target.Target
runFn func()
}
func (d *runnableDroppedTarget) run() {
d.runFn()
}
type KafkaTarget struct {
logger log.Logger
discoveredLabels model.LabelSet
lbs model.LabelSet
details ConsumerDetails
claim sarama.ConsumerGroupClaim
session sarama.ConsumerGroupSession
client loki.EntryHandler
relabelConfig []*relabel.Config
useIncomingTimestamp bool
messageParser MessageParser
}
func NewKafkaTarget(
logger log.Logger,
session sarama.ConsumerGroupSession,
claim sarama.ConsumerGroupClaim,
discoveredLabels, lbs model.LabelSet,
relabelConfig []*relabel.Config,
client loki.EntryHandler,
useIncomingTimestamp bool,
messageParser MessageParser,
) *KafkaTarget {
return &KafkaTarget{
logger: logger,
discoveredLabels: discoveredLabels,
lbs: lbs,
details: newDetails(session, claim),
claim: claim,
session: session,
client: client,
relabelConfig: relabelConfig,
useIncomingTimestamp: useIncomingTimestamp,
messageParser: messageParser,
}
}
const (
defaultKafkaMessageKey = "none"
labelKeyKafkaMessageKey = "__meta_kafka_message_key"
labelKeyKafkaOffset = "__meta_kafka_message_offset"
)
func (t *KafkaTarget) run() {
defer t.client.Stop()
for message := range t.claim.Messages() {
mk := string(message.Key)
if len(mk) == 0 {
mk = defaultKafkaMessageKey
}
// TODO: Possibly need to format after merging with discovered labels because we can specify multiple labels in source labels
// https://github.com/grafana/loki/pull/4745#discussion_r750022234
lbs := format([]labels.Label{
{Name: labelKeyKafkaMessageKey, Value: mk},
{Name: labelKeyKafkaOffset, Value: fmt.Sprintf("%v", message.Offset)},
}, t.relabelConfig)
out := t.lbs.Clone()
if len(lbs) > 0 {
out = out.Merge(lbs)
}
entries, err := t.messageParser.Parse(message, out, t.relabelConfig, t.useIncomingTimestamp)
if err != nil {
level.Error(t.logger).Log("msg", "message parsing error", "err", err)
} else {
for _, entry := range entries {
t.client.Chan() <- entry
}
}
t.session.MarkMessage(message, "")
}
}
func timestamp(useIncoming bool, incoming time.Time) time.Time {
if useIncoming {
return incoming
}
return time.Now()
}
func (t *KafkaTarget) Type() target.TargetType {
return target.KafkaTargetType
}
func (t *KafkaTarget) Ready() bool {
return true
}
func (t *KafkaTarget) DiscoveredLabels() model.LabelSet {
return t.discoveredLabels
}
func (t *KafkaTarget) Labels() model.LabelSet {
return t.lbs
}
// Details returns target-specific details.
func (t *KafkaTarget) Details() interface{} {
return t.details
}
type ConsumerDetails struct {
// MemberID returns the cluster member ID.
MemberID string
// GenerationID returns the current generation ID.
GenerationID int32
Topic string
Partition int32
InitialOffset int64
}
func (c ConsumerDetails) String() string {
return fmt.Sprintf("member_id=%s generation_id=%d topic=%s partition=%d initial_offset=%d", c.MemberID, c.GenerationID, c.Topic, c.Partition, c.InitialOffset)
}
func newDetails(session sarama.ConsumerGroupSession, claim sarama.ConsumerGroupClaim) ConsumerDetails {
return ConsumerDetails{
MemberID: session.MemberID(),
GenerationID: session.GenerationID(),
Topic: claim.Topic(),
Partition: claim.Partition(),
InitialOffset: claim.InitialOffset(),
}
}