Support creating an iterator with an initial timestamp (#99)

* Allow setting initial timestamp

* Fix writing to closed channel

* Allow cancelling of request

consumer.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"io/ioutil"
 	"log"
+	"sync"
+	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
@@ -61,6 +63,7 @@ func New(streamName string, opts ...Option) (*Consumer, error) {
 type Consumer struct {
 	streamName               string
 	initialShardIteratorType string
+	initialTimestamp         *time.Time
 	client                   kinesisiface.KinesisAPI
 	counter                  Counter
 	group                    Group
@@ -98,22 +101,29 @@ func (c *Consumer) Scan(ctx context.Context, fn ScanFunc) error {
 		close(shardc)
 	}()
 
+	wg := new(sync.WaitGroup)
 	// process each of the shards
 	for shard := range shardc {
+		wg.Add(1)
 		go func(shardID string) {
+			defer wg.Done()
 			if err := c.ScanShard(ctx, shardID, fn); err != nil {
 				select {
 				case errc <- fmt.Errorf("shard %s error: %v", shardID, err):
 					// first error to occur
 					cancel()
 				default:
-					// error has already occured
+					// error has already occurred
 				}
 			}
 		}(aws.StringValue(shard.ShardId))
 	}
 
-	close(errc)
+	go func() {
+		wg.Wait()
+		close(errc)
+	}()
+
 	return <-errc
 }
 
@@ -127,7 +137,7 @@ func (c *Consumer) ScanShard(ctx context.Context, shardID string, fn ScanFunc) e
 	}
 
 	// get shard iterator
-	shardIterator, err := c.getShardIterator(c.streamName, shardID, lastSeqNum)
+	shardIterator, err := c.getShardIterator(ctx, c.streamName, shardID, lastSeqNum)
 	if err != nil {
 		return fmt.Errorf("get shard iterator error: %v", err)
 	}
@@ -156,7 +166,7 @@ func (c *Consumer) ScanShard(ctx context.Context, shardID string, fn ScanFunc) e
 					}
 				}
 
-				shardIterator, err = c.getShardIterator(c.streamName, shardID, lastSeqNum)
+				shardIterator, err = c.getShardIterator(ctx, c.streamName, shardID, lastSeqNum)
 				if err != nil {
 					return fmt.Errorf("get shard iterator error: %v", err)
 				}
@@ -205,7 +215,7 @@ func isShardClosed(nextShardIterator, currentShardIterator *string) bool {
 	return nextShardIterator == nil || currentShardIterator == nextShardIterator
 }
 
-func (c *Consumer) getShardIterator(streamName, shardID, seqNum string) (*string, error) {
+func (c *Consumer) getShardIterator(ctx context.Context, streamName, shardID, seqNum string) (*string, error) {
 	params := &kinesis.GetShardIteratorInput{
 		ShardId:    aws.String(shardID),
 		StreamName: aws.String(streamName),
@@ -214,10 +224,13 @@ func (c *Consumer) getShardIterator(streamName, shardID, seqNum string) (*string
 	if seqNum != "" {
 		params.ShardIteratorType = aws.String(kinesis.ShardIteratorTypeAfterSequenceNumber)
 		params.StartingSequenceNumber = aws.String(seqNum)
+	} else if c.initialTimestamp != nil {
+		params.ShardIteratorType = aws.String(kinesis.ShardIteratorTypeAtTimestamp)
+		params.Timestamp = c.initialTimestamp
 	} else {
 		params.ShardIteratorType = aws.String(c.initialShardIteratorType)
 	}
 
-	res, err := c.client.GetShardIterator(params)
+	res, err := c.client.GetShardIteratorWithContext(aws.Context(ctx), params)
 	return res.ShardIterator, err
 }

consumer_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
+	"github.com/aws/aws-sdk-go/aws/request"
 	"github.com/aws/aws-sdk-go/service/kinesis"
 	"github.com/aws/aws-sdk-go/service/kinesis/kinesisiface"
 )
@@ -330,6 +331,10 @@ func (c *kinesisClientMock) GetShardIterator(in *kinesis.GetShardIteratorInput)
 	return c.getShardIteratorMock(in)
 }
 
+func (c *kinesisClientMock) GetShardIteratorWithContext(ctx aws.Context, in *kinesis.GetShardIteratorInput, options ...request.Option) (*kinesis.GetShardIteratorOutput, error) {
+	return c.getShardIteratorMock(in)
+}
+
 // implementation of checkpoint
 type fakeCheckpoint struct {
 	cache map[string]string

options.go

@@ -1,6 +1,10 @@
 package consumer
 
-import "github.com/aws/aws-sdk-go/service/kinesis/kinesisiface"
+import (
+	"time"
+
+	"github.com/aws/aws-sdk-go/service/kinesis/kinesisiface"
+)
 
 // Option is used to override defaults when creating a new Consumer
 type Option func(*Consumer)
@@ -46,3 +50,10 @@ func WithShardIteratorType(t string) Option {
 		c.initialShardIteratorType = t
 	}
 }
+
+// Timestamp overrides the starting point for the consumer
+func WithTimestamp(t time.Time) Option {
+	return func(c *Consumer) {
+		c.initialTimestamp = &t
+	}
+}