Support ETags for Azure and Google Cloud [#176, #177] (#183)

* NewRangeReaderEtag for gocloud buckets does provider-specific operations for set/get etag and error.
* use generation ID as string etag for Google Cloud.

pmtiles/bucket.go

@@ -13,12 +13,19 @@ import (
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
 	"strings"
 
+	"cloud.google.com/go/storage"
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
+	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
+	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob/container"
+	"github.com/aws/aws-sdk-go/aws"
 	"github.com/aws/aws-sdk-go/aws/awserr"
 	"github.com/aws/aws-sdk-go/service/s3"
 	"github.com/cespare/xxhash/v2"
 	"gocloud.dev/blob"
+	"google.golang.org/api/googleapi"
 )
 
 // Bucket is an abstration over a gocloud or plain HTTP bucket.
@@ -211,35 +218,86 @@ func (ba BucketAdapter) NewRangeReader(ctx context.Context, key string, offset,
 	return body, err
 }
 
+func etagToGeneration(etag string) int64 {
+	i, _ := strconv.ParseInt(etag, 10, 64)
+	return i
+}
+
+func generationToEtag(generation int64) string {
+	return strconv.FormatInt(generation, 10)
+}
+
+func setProviderEtag(asFunc func(interface{}) bool, etag string) {
+	var awsV1Req *s3.GetObjectInput
+	var azblobReq *azblob.DownloadStreamOptions
+	var gcsHandle **storage.ObjectHandle
+	if asFunc(&awsV1Req) {
+		awsV1Req.IfMatch = aws.String(etag)
+	} else if asFunc(&azblobReq) {
+		azEtag := azcore.ETag(etag)
+		azblobReq.AccessConditions = &azblob.AccessConditions{
+			ModifiedAccessConditions: &container.ModifiedAccessConditions{
+				IfMatch: &azEtag,
+			},
+		}
+	} else if asFunc(&gcsHandle) {
+		*gcsHandle = (*gcsHandle).If(storage.Conditions{
+			GenerationMatch: etagToGeneration(etag),
+		})
+	}
+}
+
+func getProviderErrorStatusCode(err error) int {
+	var awsV1Err awserr.RequestFailure
+	var azureErr *azcore.ResponseError
+	var gcpErr *googleapi.Error
+
+	if errors.As(err, &awsV1Err); awsV1Err != nil {
+		return awsV1Err.StatusCode()
+	} else if errors.As(err, &azureErr); azureErr != nil {
+		return azureErr.StatusCode
+	} else if errors.As(err, &gcpErr); gcpErr != nil {
+		return gcpErr.Code
+	}
+	return 404
+}
+
+func getProviderEtag(reader *blob.Reader) string {
+	var awsV1Resp s3.GetObjectOutput
+	var azureResp azblob.DownloadStreamResponse
+	var gcpResp *storage.Reader
+
+	if reader.As(&awsV1Resp) {
+		return *awsV1Resp.ETag
+	} else if reader.As(&azureResp) {
+		return string(*azureResp.ETag)
+	} else if reader.As(&gcpResp) {
+		return generationToEtag(gcpResp.Attrs.Generation)
+	}
+
+	return ""
+}
+
 func (ba BucketAdapter) NewRangeReaderEtag(ctx context.Context, key string, offset, length int64, etag string) (io.ReadCloser, string, int, error) {
 	reader, err := ba.Bucket.NewRangeReader(ctx, key, offset, length, &blob.ReaderOptions{
 		BeforeRead: func(asFunc func(interface{}) bool) error {
-			var req *s3.GetObjectInput
-			if len(etag) > 0 && asFunc(&req) {
-				req.IfMatch = &etag
+			if len(etag) > 0 {
+				setProviderEtag(asFunc, etag)
 			}
 			return nil
 		},
 	})
 	status := 206
 	if err != nil {
-		var resp awserr.RequestFailure
-		errors.As(err, &resp)
-		status = 404
-		if resp != nil {
-			status = resp.StatusCode()
-			if isRefreshRequiredCode(resp.StatusCode()) {
-				return nil, "", resp.StatusCode(), &RefreshRequiredError{resp.StatusCode()}
-			}
+		status = getProviderErrorStatusCode(err)
+		if isRefreshRequiredCode(status) {
+			return nil, "", status, &RefreshRequiredError{status}
 		}
+
 		return nil, "", status, err
 	}
-	resultETag := ""
-	var resp s3.GetObjectOutput
-	if reader.As(&resp) {
-		resultETag = *resp.ETag
-	}
-	return reader, resultETag, status, nil
+
+	return reader, getProviderEtag(reader), status, nil
 }
 
 func (ba BucketAdapter) Close() error {

pmtiles/bucket_test.go

@@ -2,15 +2,22 @@ package pmtiles
 
 import (
 	"context"
+	"errors"
 	"io"
 	"net/http"
 	"os"
 	"path/filepath"
 	"strings"
 	"testing"
 
+	"github.com/Azure/azure-sdk-for-go/sdk/azcore"
+	"github.com/Azure/azure-sdk-for-go/sdk/storage/azblob"
+	"github.com/aws/aws-sdk-go/aws"
+	"github.com/aws/aws-sdk-go/aws/awserr"
+	"github.com/aws/aws-sdk-go/service/s3"
 	"github.com/stretchr/testify/assert"
 	_ "gocloud.dev/blob/fileblob"
+	"google.golang.org/api/googleapi"
 )
 
 func TestNormalizeLocalFile(t *testing.T) {
@@ -206,3 +213,54 @@ func TestFileShorterThan16K(t *testing.T) {
 	assert.Nil(t, err)
 	assert.Equal(t, 3, len(data))
 }
+
+func TestSetProviderEtagAws(t *testing.T) {
+	var awsV1Req s3.GetObjectInput
+	assert.Nil(t, awsV1Req.IfMatch)
+	asFunc := func(i interface{}) bool {
+		v, ok := i.(**s3.GetObjectInput)
+		if ok {
+			*v = &awsV1Req
+		}
+		return true
+	}
+	setProviderEtag(asFunc, "123")
+	assert.Equal(t, aws.String("123"), awsV1Req.IfMatch)
+}
+
+func TestSetProviderEtagAzure(t *testing.T) {
+	var azOptions azblob.DownloadStreamOptions
+	assert.Nil(t, azOptions.AccessConditions)
+	asFunc := func(i interface{}) bool {
+		v, ok := i.(**azblob.DownloadStreamOptions)
+		if ok {
+			*v = &azOptions
+		}
+		return ok
+	}
+	setProviderEtag(asFunc, "123")
+	assert.Equal(t, azcore.ETag("123"), *azOptions.AccessConditions.ModifiedAccessConditions.IfMatch)
+}
+
+func TestGetProviderErrorStatusCode(t *testing.T) {
+	awsErr := awserr.NewRequestFailure(awserr.New("", "", nil), 500, "")
+	statusCode := getProviderErrorStatusCode(awsErr)
+	assert.Equal(t, 500, statusCode)
+
+	azureErr := &azcore.ResponseError{StatusCode: 500}
+	statusCode = getProviderErrorStatusCode(azureErr)
+	assert.Equal(t, 500, statusCode)
+
+	gcpErr := &googleapi.Error{Code: 500}
+	statusCode = getProviderErrorStatusCode(gcpErr)
+	assert.Equal(t, 500, statusCode)
+
+	err := errors.New("generic error")
+	statusCode = getProviderErrorStatusCode(err)
+	assert.Equal(t, 404, statusCode)
+}
+
+func TestGenerationEtag(t *testing.T) {
+	assert.Equal(t, int64(123), etagToGeneration("123"))
+	assert.Equal(t, "123", generationToEtag(int64(123)))
+}