add table waiters (#193)

* add table waiters

createtable.go

@@ -229,13 +229,14 @@ func (ct *CreateTable) SSEEncryption(enabled bool, keyID string, sseType SSEType
 	return ct
 }
 
-// Run creates this table or returns and error.
+// Run creates this table or returns an error.
 func (ct *CreateTable) Run() error {
 	ctx, cancel := defaultContext()
 	defer cancel()
 	return ct.RunWithContext(ctx)
 }
 
+// RunWithContext creates this table or returns an error.
 func (ct *CreateTable) RunWithContext(ctx aws.Context) error {
 	if ct.err != nil {
 		return ct.err
@@ -248,6 +249,21 @@ func (ct *CreateTable) RunWithContext(ctx aws.Context) error {
 	})
 }
 
+// Wait creates this table and blocks until it exists and is ready to use.
+func (ct *CreateTable) Wait() error {
+	ctx, cancel := defaultContext()
+	defer cancel()
+	return ct.WaitWithContext(ctx)
+}
+
+// WaitWithContext creates this table and blocks until it exists and is ready to use.
+func (ct *CreateTable) WaitWithContext(ctx aws.Context) error {
+	if err := ct.RunWithContext(ctx); err != nil {
+		return err
+	}
+	return ct.db.Table(ct.tableName).WaitWithContext(ctx)
+}
+
 func (ct *CreateTable) from(rv reflect.Value) error {
 	switch rv.Kind() {
 	case reflect.Struct: // ok

go.mod

@@ -7,4 +7,4 @@ require (
 	golang.org/x/net v0.0.0-20220127200216-cd36cc0744dd
 )
 
-go 1.12
+go 1.13

retry.go

@@ -1,6 +1,7 @@
 package dynamo
 
 import (
+	"errors"
 	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
@@ -46,7 +47,14 @@ func retry(ctx aws.Context, f func() error) error {
 	}
 }
 
+// errRetry is a sentinel error to retry, should never be returned to user
+var errRetry = errors.New("dynamo: retry")
+
 func canRetry(err error) bool {
+	if errors.Is(err, errRetry) {
+		return true
+	}
+
 	if ae, ok := err.(awserr.RequestFailure); ok {
 		switch ae.StatusCode() {
 		case 500, 503:

table.go

@@ -1,16 +1,20 @@
 package dynamo
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"sync/atomic"
 
 	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/dynamodb"
 )
 
 // Status is an enumeration of table and index statuses.
 type Status string
 
+// Table and index statuses.
 const (
 	// The table or index is ready for use.
 	ActiveStatus Status = "ACTIVE"
@@ -20,6 +24,10 @@ const (
 	UpdatingStatus Status = "UPDATING"
 	// The table or index is being deleted.
 	DeletingStatus Status = "DELETING"
+
+	// NotExistsStatus is a special status you can pass to table.Wait() to wait until a table doesn't exist.
+	// DescribeTable will return a ResourceNotFound AWS error instead of this.
+	NotExistsStatus Status = "_gone"
 )
 
 // Table is a DynamoDB table.
@@ -44,6 +52,52 @@ func (table Table) Name() string {
 	return table.name
 }
 
+// Wait blocks until this table's status matches any status provided by want.
+// If no statuses are specified, the active status is used.
+func (table Table) Wait(want ...Status) error {
+	ctx, cancel := defaultContext()
+	defer cancel()
+	return table.WaitWithContext(ctx, want...)
+}
+
+// Wait blocks until this table's status matches any status provided by want.
+// If no statuses are specified, the active status is used.
+func (table Table) WaitWithContext(ctx aws.Context, want ...Status) error {
+	if len(want) == 0 {
+		want = []Status{ActiveStatus}
+	}
+	wantGone := false
+	for _, status := range want {
+		if status == NotExistsStatus {
+			wantGone = true
+		}
+	}
+
+	err := retry(ctx, func() error {
+		desc, err := table.Describe().RunWithContext(ctx)
+		var aerr awserr.RequestFailure
+		if errors.As(err, &aerr) {
+			if aerr.Code() == "ResourceNotFoundException" {
+				if wantGone {
+					return nil
+				}
+				return errRetry
+			}
+		}
+		if err != nil {
+			return err
+		}
+
+		for _, status := range want {
+			if status == desc.Status {
+				return nil
+			}
+		}
+		return errRetry
+	})
+	return err
+}
+
 // primaryKeys attempts to determine this table's primary keys.
 // It will try:
 // - output LastEvaluatedKey
@@ -142,6 +196,21 @@ func (dt *DeleteTable) RunWithContext(ctx aws.Context) error {
 	})
 }
 
+// Wait executes this request and blocks until the table is finished deleting.
+func (dt *DeleteTable) Wait() error {
+	ctx, cancel := defaultContext()
+	defer cancel()
+	return dt.WaitWithContext(ctx)
+}
+
+// WaitWithContext executes this request and blocks until the table is finished deleting.
+func (dt *DeleteTable) WaitWithContext(ctx context.Context) error {
+	if err := dt.RunWithContext(ctx); err != nil {
+		return err
+	}
+	return dt.table.WaitWithContext(ctx, NotExistsStatus)
+}
+
 func (dt *DeleteTable) input() *dynamodb.DeleteTableInput {
 	name := dt.table.Name()
 	return &dynamodb.DeleteTableInput{

table_test.go

@@ -1,13 +1,48 @@
 package dynamo
 
 import (
+	"fmt"
 	"reflect"
 	"testing"
+	"time"
 
 	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/service/dynamodb"
 )
 
+func TestTableLifecycle(t *testing.T) {
+	if testDB == nil {
+		t.Skip(offlineSkipMsg)
+	}
+
+	now := time.Now().UTC()
+	name := fmt.Sprintf("TestDB-%d", now.UnixNano())
+
+	// example from the docs
+	type UserAction struct {
+		UserID string    `dynamo:"ID,hash" index:"Seq-ID-index,range"`
+		Time   time.Time `dynamo:",range"`
+		Seq    int64     `localIndex:"ID-Seq-index,range" index:"Seq-ID-index,hash"`
+		UUID   string    `index:"UUID-index,hash"`
+	}
+
+	// create & wait
+	if err := testDB.CreateTable(name, UserAction{}).Wait(); err != nil {
+		t.Fatal(err)
+	}
+
+	// make sure it really works
+	table := testDB.Table(name)
+	if err := table.Put(UserAction{UserID: "test", Time: now, Seq: 1, UUID: "42"}).Run(); err != nil {
+		t.Fatal(err)
+	}
+
+	// delete & wait
+	if err := testDB.Table(name).DeleteTable().Wait(); err != nil {
+		t.Fatal(err)
+	}
+}
+
 func TestAddConsumedCapacity(t *testing.T) {
 	raw := &dynamodb.ConsumedCapacity{
 		TableName: aws.String("TestTable"),