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Fix azblob/download data race #22334

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merged 3 commits into from
Feb 6, 2024
Merged

Fix azblob/download data race #22334

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426cdb3
data race while downloadFile
tanyasethi-msft Jan 23, 2024
4f8a851
changelog update
tanyasethi-msft Feb 2, 2024
36f0b21
cast variable type
tanyasethi-msft Feb 6, 2024
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1 change: 1 addition & 0 deletions sdk/storage/azblob/CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
### Breaking Changes

### Bugs Fixed
* Fix concurrency issue while Downloading File. Fixes [#22156](https://github.com/Azure/azure-sdk-for-go/issues/22156).

### Other Changes

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24 changes: 10 additions & 14 deletions sdk/storage/azblob/blob/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ package blob
import (
"context"
"io"
"math"
"os"
"sync"
"time"
Expand Down Expand Up @@ -469,23 +470,18 @@ func (b *Client) downloadFile(ctx context.Context, writer io.Writer, o downloadO

buffers := shared.NewMMBPool(int(o.Concurrency), o.BlockSize)
defer buffers.Free()
acquireBuffer := func() ([]byte, error) {
select {
case b := <-buffers.Acquire():
// got a buffer
return b, nil
default:
// no buffer available; allocate a new buffer if possible
if _, err := buffers.Grow(); err != nil {
return nil, err
}

// either grab the newly allocated buffer or wait for one to become available
return <-buffers.Acquire(), nil
numChunks := (count-1)/o.BlockSize + 1
for bufferCounter := float64(0); bufferCounter < math.Min(float64(numChunks), float64(o.Concurrency)); bufferCounter++ {
if _, err := buffers.Grow(); err != nil {
return 0, err
}
}

numChunks := uint16((count-1)/o.BlockSize) + 1
acquireBuffer := func() ([]byte, error) {
return <-buffers.Acquire(), nil
}

blocks := make([]chan []byte, numChunks)
for b := range blocks {
blocks[b] = make(chan []byte)
Expand Down Expand Up @@ -525,7 +521,7 @@ func (b *Client) downloadFile(ctx context.Context, writer io.Writer, o downloadO
OperationName: "downloadBlobToWriterAt",
TransferSize: count,
ChunkSize: o.BlockSize,
NumChunks: numChunks,
NumChunks: uint16(numChunks),
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Concurrency: o.Concurrency,
Operation: func(ctx context.Context, chunkStart int64, count int64) error {
buff, err := acquireBuffer()
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