fix(azure): append method on azure backend

CHANGELOG.md

@@ -15,6 +15,7 @@
 * [BUGFIX] Fix Query Frontend grpc settings to avoid noisy error log. [#690](https://github.com/grafana/tempo/pull/690)
 * [BUGFIX] Zipkin Support - CombineTraces. [#688](https://github.com/grafana/tempo/pull/688)
 * [BUGFIX] Zipkin support - Dedupe span IDs based on span.Kind (client/server) in Query Frontend. [#687](https://github.com/grafana/tempo/pull/687)
+* [BUGFIX] Azure Backend - Fix an issue with the append method on the Azure backend. [#736](https://github.com/grafana/tempo/pull/736)
 
 ## v0.7.0
 

tempodb/backend/azure/azure.go

@@ -4,6 +4,8 @@ import (
 	"bufio"
 	"bytes"
 	"context"
+	"encoding/base64"
+	"encoding/binary"
 	"encoding/json"
 	"io"
 	"strings"
@@ -91,7 +93,7 @@ func (rw *readerWriter) Append(ctx context.Context, name string, blockID uuid.UU
 	} else {
 		a = tracker.(appendTracker)
 
-		_, err := rw.append(ctx, buffer, a.Name)
+		err := rw.append(ctx, buffer, a.Name)
 		if err != nil {
 			return nil, err
 		}
@@ -222,16 +224,45 @@ func (rw *readerWriter) writeAll(ctx context.Context, name string, b []byte) err
 	return nil
 }
 
-func (rw *readerWriter) append(ctx context.Context, src []byte, name string) (string, error) {
-	appendBlobURL := rw.containerURL.NewAppendBlobURL(name)
+func (rw *readerWriter) append(ctx context.Context, src []byte, name string) error {
+	appendBlobURL := rw.containerURL.NewBlockBlobURL(name)
 
-	resp, err := appendBlobURL.AppendBlock(ctx, bytes.NewReader(src), blob.AppendBlobAccessConditions{}, nil)
+	// These helper functions convert a binary block ID to a base-64 string and vice versa
+	// NOTE: The blockID must be <= 64 bytes and ALL blockIDs for the block must be the same length
+	blockIDBinaryToBase64 := func(blockID []byte) string { return base64.StdEncoding.EncodeToString(blockID) }
 
+	blockIDIntToBase64 := func(blockID int) string {
+		binaryBlockID := (&[64]byte{})[:]
+		binary.LittleEndian.PutUint32(binaryBlockID, uint32(blockID))
+		return blockIDBinaryToBase64(binaryBlockID)
+	}
+
+	l, err := appendBlobURL.GetBlockList(ctx, blob.BlockListAll, blob.LeaseAccessConditions{})
+	if err != nil {
+		return err
+	}
+
+	// generate the next block id
+	id := blockIDIntToBase64(len(l.CommittedBlocks) + 1)
+
+	_, err = appendBlobURL.StageBlock(ctx, id, bytes.NewReader(src), blob.LeaseAccessConditions{}, nil)
 	if err != nil {
-		return "", err
+		return err
 	}
-	return resp.RequestID(), nil
 
+	base64BlockIDs := make([]string, len(l.CommittedBlocks)+1)
+	for i := 0; i < len(l.CommittedBlocks); i++ {
+		base64BlockIDs[i] = l.CommittedBlocks[i].Name
+	}
+
+	base64BlockIDs[len(l.CommittedBlocks)] = id
+
+	// After all the blocks are uploaded, atomically commit them to the blob.
+	_, err = appendBlobURL.CommitBlockList(ctx, base64BlockIDs, blob.BlobHTTPHeaders{}, blob.Metadata{}, blob.BlobAccessConditions{})
+	if err != nil {
+		return err
+	}
+	return nil
 }
 
 func (rw *readerWriter) writer(ctx context.Context, src io.Reader, name string) error {