/
collector.go
61 lines (50 loc) · 1.29 KB
/
collector.go
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package collector
import (
"context"
"encoding/json"
"github.com/lovoo/goka"
"github.com/lovoo/goka/examples/3-messaging"
"github.com/lovoo/goka/examples/3-messaging/topicinit"
)
const maxMessages = 5
var (
group goka.Group = "collector"
Table goka.Table = goka.GroupTable(group)
)
type MessageListCodec struct{}
func (c *MessageListCodec) Encode(value interface{}) ([]byte, error) {
return json.Marshal(value)
}
func (c *MessageListCodec) Decode(data []byte) (interface{}, error) {
var m []messaging.Message
err := json.Unmarshal(data, &m)
return m, err
}
func collect(ctx goka.Context, msg interface{}) {
var ml []messaging.Message
if v := ctx.Value(); v != nil {
ml = v.([]messaging.Message)
}
m := msg.(*messaging.Message)
ml = append(ml, *m)
if len(ml) > maxMessages {
ml = ml[len(ml)-maxMessages:]
}
ctx.SetValue(ml)
}
func PrepareTopics(brokers []string) {
topicinit.EnsureStreamExists(string(messaging.ReceivedStream), brokers)
}
func Run(ctx context.Context, brokers []string) func() error {
return func() error {
g := goka.DefineGroup(group,
goka.Input(messaging.ReceivedStream, new(messaging.MessageCodec), collect),
goka.Persist(new(MessageListCodec)),
)
p, err := goka.NewProcessor(brokers, g)
if err != nil {
return err
}
return p.Run(ctx)
}
}