Add context to ErrLeaseNotAcquired (#87)

* clientlibrary/checkpoint: convert ErrLeaseAcquired to struct

Signed-off-by: Aurélien Rainone <aurelien.rainone@gmail.com>

* clientlibrary/checkpoint: add context to ErrLeaseNotAcquired

Signed-off-by: Aurélien Rainone <aurelien.rainone@gmail.com>

* Use errors.As to check for ErrLeaseNotAcquired error

Signed-off-by: Aurélien Rainone <aurelien.rainone@gmail.com>

clientlibrary/checkpoint/checkpointer.go

@@ -29,6 +29,8 @@ package checkpoint
 
 import (
 	"errors"
+	"fmt"
+
 	par "github.com/vmware/vmware-go-kcl/clientlibrary/partition"
 )
 
@@ -41,11 +43,16 @@ const (
 
 	// We've completely processed all records in this shard.
 	ShardEnd = "SHARD_END"
-
-	// ErrLeaseNotAcquired is returned when we failed to get a lock on the shard
-	ErrLeaseNotAcquired = "lease is already held by another node"
 )
 
+type ErrLeaseNotAcquired struct {
+	cause string
+}
+
+func (e ErrLeaseNotAcquired) Error() string {
+	return fmt.Sprintf("lease not acquired: %s", e.cause)
+}
+
 // Checkpointer handles checkpointing when a record has been processed
 type Checkpointer interface {
 	// Init initialises the Checkpoint

clientlibrary/checkpoint/dynamodb-checkpointer.go

@@ -28,7 +28,6 @@
 package checkpoint
 
 import (
-	"errors"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
@@ -142,7 +141,7 @@ func (checkpointer *DynamoCheckpoint) GetLease(shard *par.ShardStatus, newAssign
 		}
 
 		if time.Now().UTC().Before(currentLeaseTimeout) && assignedTo != newAssignTo {
-			return errors.New(ErrLeaseNotAcquired)
+			return ErrLeaseNotAcquired{"current lease timeout not yet expired"}
 		}
 
 		checkpointer.log.Debugf("Attempting to get a lock for shard: %s, leaseTimeout: %s, assignedTo: %s", shard.ID, currentLeaseTimeout, assignedTo)
@@ -186,7 +185,7 @@ func (checkpointer *DynamoCheckpoint) GetLease(shard *par.ShardStatus, newAssign
 	if err != nil {
 		if awsErr, ok := err.(awserr.Error); ok {
 			if awsErr.Code() == dynamodb.ErrCodeConditionalCheckFailedException {
-				return errors.New(ErrLeaseNotAcquired)
+				return ErrLeaseNotAcquired{dynamodb.ErrCodeConditionalCheckFailedException}
 			}
 		}
 		return err

clientlibrary/checkpoint/dynamodb-checkpointer_test.go

@@ -29,11 +29,12 @@ package checkpoint
 
 import (
 	"errors"
-	"github.com/stretchr/testify/assert"
 	"sync"
 	"testing"
 	"time"
 
+	"github.com/stretchr/testify/assert"
+
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/dynamodb"
@@ -85,7 +86,7 @@ func TestGetLeaseNotAquired(t *testing.T) {
 		Checkpoint: "",
 		Mux:        &sync.Mutex{},
 	}, "ijkl-mnop")
-	if err == nil || err.Error() != ErrLeaseNotAcquired {
+	if err == nil || !errors.As(err, &ErrLeaseNotAcquired{}) {
 		t.Errorf("Got a lease when it was already held by abcd-efgh: %s", err)
 	}
 }

clientlibrary/worker/shard-consumer.go

@@ -28,6 +28,7 @@
 package worker
 
 import (
+	"errors"
 	"math"
 	"sync"
 	"time"
@@ -162,7 +163,7 @@ func (sc *ShardConsumer) getRecords(shard *par.ShardStatus) error {
 			log.Debugf("Refreshing lease on shard: %s for worker: %s", shard.ID, sc.consumerID)
 			err = sc.checkpointer.GetLease(shard, sc.consumerID)
 			if err != nil {
-				if err.Error() == chk.ErrLeaseNotAcquired {
+				if errors.As(err, &chk.ErrLeaseNotAcquired{}) {
 					log.Warnf("Failed in acquiring lease on shard: %s for worker: %s", shard.ID, sc.consumerID)
 					return nil
 				}

clientlibrary/worker/worker.go

@@ -28,6 +28,7 @@
 package worker
 
 import (
+	"errors"
 	"math/rand"
 	"sync"
 	"time"
@@ -277,7 +278,7 @@ func (w *Worker) eventLoop() {
 				err = w.checkpointer.GetLease(shard, w.workerID)
 				if err != nil {
 					// cannot get lease on the shard
-					if err.Error() != chk.ErrLeaseNotAcquired {
+					if !errors.As(err, &chk.ErrLeaseNotAcquired{}) {
 						log.Errorf("Cannot get lease: %+v", err)
 					}
 					continue