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consumer.go
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consumer.go
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package kafka
import (
"github.com/Shopify/sarama"
"github.com/iheartradio/cog"
"github.com/iheartradio/cog/cio/eio"
)
// Consumer implements a kafka consumer
type Consumer struct {
c sarama.Consumer
msgs chan []byte
errs chan error
exit *cog.Exit
Args struct {
// List of brokers to connect to
Brokers []string
// Name of the topic to read from.
Topic string
}
}
func init() {
eio.RegisterConsumer("kafka", newConsumer)
}
func newConsumer(args eio.Args) (eio.Consumer, error) {
c := &Consumer{
msgs: make(chan []byte, 32),
errs: make(chan error, 8),
exit: cog.NewExit(),
}
err := args.ApplyTo(&c.Args)
if err != nil {
return nil, err
}
c.c, err = sarama.NewConsumer(c.Args.Brokers, nil)
if err != nil {
return nil, err
}
parts, err := c.c.Partitions(c.Args.Topic)
if err == nil {
c.exit.Add(len(parts))
for _, part := range parts {
go c.consume(part)
}
go c.waitForExit()
} else {
c.waitForExit()
c.Close()
c = nil
}
return c, err
}
func (c *Consumer) waitForExit() {
c.exit.Wait()
c.c.Close()
close(c.errs)
}
func (c *Consumer) consume(partID int32) {
defer c.exit.Done()
pc, err := c.c.ConsumePartition(
c.Args.Topic,
partID,
sarama.OffsetNewest)
if err != nil {
c.errs <- err
return
}
defer pc.Close()
msgs := pc.Messages()
errs := pc.Errors()
for {
select {
case msg := <-msgs:
select {
case c.msgs <- msg.Value:
case <-c.exit.C:
return
}
case err := <-errs:
c.errs <- err.Err
case <-c.exit.C:
return
}
}
}
// Next implemnets Consumer.Next
func (c *Consumer) Next() ([]byte, error) {
select {
case msg := <-c.msgs:
return msg, nil
case err := <-c.errs:
return nil, err
}
}
// Close implemnets Consumer.Close
func (c *Consumer) Close() (es cog.Errors) {
c.exit.Signal()
es.Drain(c.errs)
return
}