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belly.go
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belly.go
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package main
import (
"cloud.google.com/go/storage"
"compress/gzip"
"context"
"fmt"
"github.com/caarlos0/env/v6"
"github.com/confluentinc/confluent-kafka-go/kafka"
"github.com/segmentio/ksuid"
"log"
"sync"
"time"
)
func merge(cs ...<-chan error) <-chan error {
var wg sync.WaitGroup
out := make(chan error)
output := func(c <-chan error) {
for n := range c {
out <- n
}
wg.Done()
}
wg.Add(len(cs))
for _, c := range cs {
go output(c)
}
go func() {
wg.Wait()
close(out)
}()
return out
}
type BellyWriter struct {
gz *gzip.Writer
gc *storage.Writer
}
type WriteChan struct {
In chan<- *BellyData
Errs <-chan error
}
func (t *BellyWriter) Write(dat *BellyData) error {
_, err := t.gz.Write(dat.Value)
if err != nil {
return err
}
_, err = t.gz.Write([]byte{'\n'})
return err
}
func (t *BellyWriter) Close() error {
if err := t.gz.Close(); err != nil {
return err
}
if err := t.gc.Close(); err != nil {
return err
}
return nil
}
func NewWriteChan(bkt *storage.BucketHandle, date string) *WriteChan {
filename := ksuid.New()
// TODO: add source (topic) as a partitioned column...?
object := fmt.Sprintf("datestamp=%v/%v.json.gz", date, filename)
gc := bkt.Object(object).NewWriter(context.Background())
gz := gzip.NewWriter(gc)
inch := make(chan *BellyData)
errs := make(chan error)
writer := BellyWriter{gz, gc}
go func() {
defer close(errs)
for dat := range inch {
if err := writer.Write(dat); err != nil {
log.Print("Error while writing tweet: \n")
log.Println(err)
errs <- err
}
}
// close writer when inchan closes
if err := writer.Close(); err != nil {
panic(err)
}
}()
return &WriteChan{inch, errs}
}
func WriteData(bkt *storage.BucketHandle, data chan *BellyData) {
writers := make(map[string]*WriteChan)
for d := range data {
w, ok := writers[d.Key]
if ok == false {
w = NewWriteChan(bkt, d.Key)
writers[d.Key] = w
}
w.In <- d
}
// close in chans and block
// until all the writer out chans close
// we ignore write errors in the out chans
outs := []<-chan error{}
for _, w := range writers {
close(w.In)
outs = append(outs, w.Errs)
}
for _ = range merge(outs...) {
}
}
func monitor(errs <-chan error) {
e := <-errs
log.Fatalf("Belly failed with error: %v", e)
}
type Config struct {
Size int `env:"BELLY_SIZE,required"`
Location string `env:"BELLY_LOCATION,required"`
KafkaBrokers string `env:"KAFKA_BROKERS,required"`
KafkaPollTimeout time.Duration `env:"KAFKA_POLL_TIMEOUT,required"`
Topic string `env:"BELLY_TOPIC,required"`
Group string `env:"BELLY_GROUP,required"`
}
func getConfig() Config {
cfg := Config{}
if err := env.Parse(&cfg); err != nil {
panic(err)
}
return cfg
}
func handleCommitError(err error) bool {
if err == nil {
return true
}
if e, ok := err.(kafka.Error); ok && e.Code() == kafka.ErrNoOffset {
log.Print("Belly consumed no messages and is committing no messages")
return false
}
panic(err)
}
func main() {
cnf := getConfig()
client, _ := storage.NewClient(context.Background())
bkt := client.Bucket(cnf.Location)
errs := make(chan error)
go monitor(errs)
c := NewKafkaConsumer(cnf.Topic, cnf.KafkaBrokers, cnf.Group)
data := c.Consume(cnf.Size, cnf.KafkaPollTimeout, errs)
WriteData(bkt, data)
tp, err := c.Consumer.Commit()
ok := handleCommitError(err)
if ok {
log.Printf("Committed topic partition: %v", tp)
}
}