Package (v1.50.0)

Package managedwriter provides a thick client around the BigQuery storage API's BigQueryWriteClient. More information about this new write client may also be found in the public documentation:

Currently, this client targets the BigQueryWriteClient present in the v1 endpoint, and is intended as a more feature-rich successor to the classic BigQuery streaming interface, which is presented as the Inserter abstraction in, and the tabledata.insertAll method if you're more familiar with the BigQuery v2 REST methods.

Creating a Client

To start working with this package, create a client:

ctx := context.Background()
client, err := managedwriter.NewClient(ctx, projectID)
if err != nil {
    // TODO: Handle error.

Defining the Protocol Buffer Schema

The write functionality of BigQuery Storage requires data to be sent using encoded protocol buffer messages using proto2 wire format. As the protocol buffer is not self-describing, you will need to provide the protocol buffer schema. This is communicated using a DescriptorProto message, defined within the protocol buffer libraries:

More information about protocol buffers can be found in the proto2 language guide:

Details about data type conversions between BigQuery and protocol buffers can be found in the public documentation:

For cases where the protocol buffer is compiled from a static ".proto" definition, this process is straightforward. Instantiate an example message, then convert the descriptor into a descriptor proto:

m := &myprotopackage.MyCompiledMessage{}
descriptorProto := protodesc.ToDescriptorProto(m.ProtoReflect().Descriptor())

If the message uses advanced protocol buffer features like nested messages/groups, or enums, the subpackage contains functionality to normalize the descriptor into a self-contained definition:

m := &myprotopackage.MyCompiledMessage{}
descriptorProto, err := adapt.NormalizeDescriptor(m.ProtoReflect().Descriptor())
if err != nil {
    // TODO: Handle error.

The adapt subpackage also contains functionality for generating a DescriptorProto using a BigQuery table's schema directly.

Constructing a ManagedStream

The ManagedStream handles management of the underlying write connection to the BigQuery Storage service. You can either create a write session explicitly and pass it in, or create the write stream while setting up the ManagedStream.

It's easiest to register the protocol buffer descriptor you'll be using to send data when setting up the managed stream using the WithSchemaDescriptor option, though you can also set/change the schema as part of an append request once the ManagedStream is created.

// Create a ManagedStream using an explicit stream identifer, either a default
// stream or one explicitly created by CreateWriteStream.
managedStream, err := client.NewManagedStream(ctx,
if err != nil {
    // TODO: Handle error.

In addition, NewManagedStream can create new streams implicitly:

// Alternately, allow the ManagedStream to handle stream construction by supplying
// additional options.
tableName := fmt.Sprintf("projects/%s/datasets/%s/tables/%s", myProject, myDataset, myTable)
manageStream, err := client.NewManagedStream(ctx,
if err != nil {
    // TODO: Handle error.

Writing Data

Use the AppendRows function to write one or more serialized proto messages to a stream. You can choose to specify an offset in the stream to handle de-duplication for user-created streams, but a "default" stream neither accepts nor reports offsets.

AppendRows returns a future-like object that blocks until the write is successful or yields an error.

   // Define a couple of messages.
    mesgs := []*myprotopackage.MyCompiledMessage{
            UserName: proto.String("johndoe"),
            EmailAddress: proto.String("jd@mycompany.mydomain",
            FavoriteNumbers: []proto.Int64{1,42,12345},
            UserName: proto.String("janesmith"),
            EmailAddress: proto.String("smith@othercompany.otherdomain",
            FavoriteNumbers: []proto.Int64{1,3,5,7,9},

    // Encode the messages into binary format.
    encoded := make([][]byte, len(mesgs))
    for k, v := range mesgs{
        b, err := proto.Marshal(v)
        if err != nil {
            // TODO: Handle error.
        encoded[k] = b

    // Send the rows to the service, and specify an offset for managing deduplication.
    result, err := managedStream.AppendRows(ctx, encoded, WithOffset(0))

    // Block until the write is complete and return the result.
    returnedOffset, err := result.GetResult(ctx)
    if err != nil {
        // TODO: Handle error.

Buffered Stream Management

For Buffered streams, users control when data is made visible in the destination table/stream independently of when it is written. Use FlushRows on the ManagedStream to advance the flush point ahead in the stream.

// We've written 1500+ rows in the stream, and want to advance the flush point
// ahead to make the first 1000 rows available.
flushOffset, err := managedStream.FlushRows(ctx, 1000)

Pending Stream Management

Pending streams allow users to commit data from multiple streams together once the streams have been finalized, meaning they'll no longer allow further data writes.

// First, finalize the stream we're writing into.
totalRows, err := managedStream.Finalize(ctx)
if err != nil {
    // TODO: Handle error.

req := &storagepb.BatchCommitWriteStreamsRequest{
    Parent: parentName,
    WriteStreams: []string{managedStream.StreamName()},
// Using the client, we can commit data from multple streams to the same
// table atomically.
resp, err := client.BatchCommitWriteStreams(ctx, req)

Error Handling and Automatic Retries

Like other Google Cloud services, this API relies on common components that can provide an enhanced set of errors when communicating about the results of API interactions.

Specifically, the apierror package ( provides convenience methods for extracting structured information about errors.

The BigQuery Storage API service augments applicable errors with service-specific details in the form of a StorageError message. The StorageError message is accessed via the ExtractProtoMessage method in the apierror package. Note that the StorageError messsage does not implement Go's error interface.

An example of accessing the structured error details:

// By way of example, let's assume the response from an append call returns an error.
_, err := result.GetResult(ctx)
if err != nil {
    if apiErr, ok := apierror.FromError(err); ok {
        // We now have an instance of APIError, which directly exposes more specific
        // details about multiple failure conditions include transport-level errors.
        storageErr := &storagepb.StorageError{}
        if e := apiErr.Details().ExtractProtoMessage(storageErr); e != nil {
            // storageErr now contains service-specific information about the error.
            log.Printf("Received service-specific error code %s", storageErr.GetCode().String())

This library supports the ability to retry failed append requests, but this functionality is not enabled by default. You can enable it via the EnableWriteRetries option when constructing a new managed stream. Use of automatic retries can impact correctness when attempting certain exactly-once write patterns, but is generally recommended for workloads that only need at-least-once writing.

With write retries enabled, failed writes will be automatically attempted a finite number of times (currently 4) if the failure is considered retriable.

In support of the retry changes, the AppendResult returned as part of an append call now includes TotalAttempts(), which returns the number of times that specific append was enqueued to the service. Values larger than 1 are indicative of a specific append being enqueued multiple times.



const DetectProjectID = "*detect-project-id*"

DetectProjectID is a sentinel value that instructs NewClient to detect the project ID. It is given in place of the projectID argument. NewClient will use the project ID from the given credentials or the default credentials ( if no credentials were provided. When providing credentials, not all options will allow NewClient to extract the project ID. Specifically a JWT does not have the project ID encoded.


const NoStreamOffset int64 = -1

NoStreamOffset is a sentinel value for signalling we're not tracking stream offset (e.g. a default stream which allows simultaneous append streams).


AppendClientOpenCount, AppendClientOpenRetryCount, AppendRequests, AppendRequestBytes, AppendRequestErrors, AppendRequestRows, AppendResponses, AppendResponseErrors, AppendRetryCount, FlushRequests

var (
	// AppendClientOpenCount is a measure of the number of times the AppendRowsClient was opened.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendClientOpenCount = stats.Int64(statsPrefix+"stream_open_count", "Number of times AppendRowsClient was opened", stats.UnitDimensionless)

	// AppendClientOpenRetryCount is a measure of the number of times the AppendRowsClient open was retried.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendClientOpenRetryCount = stats.Int64(statsPrefix+"stream_open_retry_count", "Number of times AppendRowsClient open was retried", stats.UnitDimensionless)

	// AppendRequests is a measure of the number of append requests sent.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequests = stats.Int64(statsPrefix+"append_requests", "Number of append requests sent", stats.UnitDimensionless)

	// AppendRequestBytes is a measure of the bytes sent as append requests.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestBytes = stats.Int64(statsPrefix+"append_request_bytes", "Number of bytes sent as append requests", stats.UnitBytes)

	// AppendRequestErrors is a measure of the number of append requests that errored on send.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestErrors = stats.Int64(statsPrefix+"append_request_errors", "Number of append requests that yielded immediate error", stats.UnitDimensionless)

	// AppendRequestRows is a measure of the number of append rows sent.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestRows = stats.Int64(statsPrefix+"append_rows", "Number of append rows sent", stats.UnitDimensionless)

	// AppendResponses is a measure of the number of append responses received.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendResponses = stats.Int64(statsPrefix+"append_responses", "Number of append responses sent", stats.UnitDimensionless)

	// AppendResponseErrors is a measure of the number of append responses received with an error attached.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendResponseErrors = stats.Int64(statsPrefix+"append_response_errors", "Number of append responses with errors attached", stats.UnitDimensionless)

	// AppendRetryCount is a measure of the number of appends that were automatically retried by the library
	// after receiving a non-successful response.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRetryCount = stats.Int64(statsPrefix+"append_retry_count", "Number of appends that were retried", stats.UnitDimensionless)

	// FlushRequests is a measure of the number of FlushRows requests sent.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	FlushRequests = stats.Int64(statsPrefix+"flush_requests", "Number of FlushRows requests sent", stats.UnitDimensionless)

AppendClientOpenView, AppendClientOpenRetryView, AppendRequestsView, AppendRequestBytesView, AppendRequestErrorsView, AppendRequestRowsView, AppendResponsesView, AppendResponseErrorsView, AppendRetryView, FlushRequestsView

var (

	// AppendClientOpenView is a cumulative sum of AppendClientOpenCount.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendClientOpenView *view.View

	// AppendClientOpenRetryView is a cumulative sum of AppendClientOpenRetryCount.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendClientOpenRetryView *view.View

	// AppendRequestsView is a cumulative sum of AppendRequests.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestsView *view.View

	// AppendRequestBytesView is a cumulative sum of AppendRequestBytes.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestBytesView *view.View

	// AppendRequestErrorsView is a cumulative sum of AppendRequestErrors.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestErrorsView *view.View

	// AppendRequestRowsView is a cumulative sum of AppendRows.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRequestRowsView *view.View

	// AppendResponsesView is a cumulative sum of AppendResponses.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendResponsesView *view.View

	// AppendResponseErrorsView is a cumulative sum of AppendResponseErrors.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendResponseErrorsView *view.View

	// AppendRetryView is a cumulative sum of AppendRetryCount.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	AppendRetryView *view.View

	// FlushRequestsView is a cumulative sum of FlushRequests.
	// It is EXPERIMENTAL and subject to change or removal without notice.
	FlushRequestsView *view.View


var DefaultOpenCensusViews []*view.View

DefaultOpenCensusViews retains the set of all opencensus views that this library has instrumented, to add view registration for exporters.


func TableParentFromParts

func TableParentFromParts(projectID, datasetID, tableID string) string

TableParentFromParts constructs a table identifier using individual identifiers and returns a string in the form "projects/{project}/datasets/{dataset}/tables/{table}".

func TableParentFromStreamName

func TableParentFromStreamName(streamName string) string

TableParentFromStreamName is a utility function for extracting the parent table prefix from a stream name. When an invalid stream ID is passed, this simply returns the original stream name.


type AppendOption func(*pendingWrite)

AppendOption are options that can be passed when appending data with a managed stream instance.

func UpdateSchemaDescriptor

func UpdateSchemaDescriptor(schema *descriptorpb.DescriptorProto) AppendOption

UpdateSchemaDescriptor is used to update the descriptor message schema associated with a given stream.

func WithOffset

func WithOffset(offset int64) AppendOption

WithOffset sets an explicit offset value for this append request.


type AppendResult struct {
	// contains filtered or unexported fields

AppendResult tracks the status of a batch of data rows.

func (*AppendResult) FullResponse

func (ar *AppendResult) FullResponse(ctx context.Context) (*storagepb.AppendRowsResponse, error)

FullResponse returns the full content of the AppendRowsResponse, and any error encountered while processing the append.

The AppendRowResponse may contain an embedded error. An embedded error in the response will be converted and returned as the error response, so this method may return both the AppendRowsResponse and an error.

This call blocks until the result is ready, or context is no longer valid.

func (*AppendResult) GetResult

func (ar *AppendResult) GetResult(ctx context.Context) (int64, error)

GetResult returns the optional offset of this row, as well as any error encountered while processing the append.

This call blocks until the result is ready, or context is no longer valid.

func (*AppendResult) Ready

func (ar *AppendResult) Ready() <-chan>

Ready blocks until the append request has reached a completed state, which may be a successful append or an error.

func (*AppendResult) TotalAttempts

func (ar *AppendResult) TotalAttempts(ctx context.Context) (int, error)

TotalAttempts returns the number of times this write was attempted.

This call blocks until the result is ready, or context is no longer valid.

func (*AppendResult) UpdatedSchema

func (ar *AppendResult) UpdatedSchema(ctx context.Context) (*storagepb.TableSchema, error)

UpdatedSchema returns the updated schema for a table if supplied by the backend as part of the append response.

This call blocks until the result is ready, or context is no longer valid.


type Client struct {
	// contains filtered or unexported fields

Client is a managed BigQuery Storage write client scoped to a single project.

func NewClient

func NewClient(ctx context.Context, projectID string, opts ...option.ClientOption) (c *Client, err error)

NewClient instantiates a new client.

func (*Client) BatchCommitWriteStreams

BatchCommitWriteStreams atomically commits a group of PENDING streams that belong to the same parent table.

Streams must be finalized before commit and cannot be committed multiple times. Once a stream is committed, data in the stream becomes available for read operations.

func (*Client) Close

func (c *Client) Close() error

Close releases resources held by the client.

func (*Client) CreateWriteStream

func (c *Client) CreateWriteStream(ctx context.Context, req *storagepb.CreateWriteStreamRequest, opts ...gax.CallOption) (*storagepb.WriteStream, error)

CreateWriteStream creates a write stream to the given table. Additionally, every table has a special stream named ‘_default’ to which data can be written. This stream doesn’t need to be created using CreateWriteStream. It is a stream that can be used simultaneously by any number of clients. Data written to this stream is considered committed as soon as an acknowledgement is received.

func (*Client) GetWriteStream

func (c *Client) GetWriteStream(ctx context.Context, req *storagepb.GetWriteStreamRequest, opts ...gax.CallOption) (*storagepb.WriteStream, error)

GetWriteStream returns information about a given WriteStream.

func (*Client) NewManagedStream

func (c *Client) NewManagedStream(ctx context.Context, opts ...WriterOption) (*ManagedStream, error)

NewManagedStream establishes a new managed stream for appending data into a table.

Context here is retained for use by the underlying streaming connections the managed stream may create.


type ManagedStream struct {
	// contains filtered or unexported fields

ManagedStream is the abstraction over a single write stream.

func (*ManagedStream) AppendRows

func (ms *ManagedStream) AppendRows(ctx context.Context, data [][]byte, opts ...AppendOption) (*AppendResult, error)

AppendRows sends the append requests to the service, and returns a single AppendResult for tracking the set of data.

The format of the row data is binary serialized protocol buffer bytes. The message must be compatible with the schema currently set for the stream.

Use the WithOffset() AppendOption to set an explicit offset for this append. Setting an offset for a default stream is unsupported.

The size of a single request must be less than 10 MB in size. Requests larger than this return an error, typically INVALID_ARGUMENT.

func (*ManagedStream) Close

func (ms *ManagedStream) Close() error

Close closes a managed stream.

func (*ManagedStream) Finalize

func (ms *ManagedStream) Finalize(ctx context.Context, opts ...gax.CallOption) (int64, error)

Finalize is used to mark a stream as complete, and thus ensure no further data can be appended to the stream. You cannot finalize a DefaultStream, as it always exists.

Finalizing does not advance the current offset of a BufferedStream, nor does it commit data in a PendingStream.

func (*ManagedStream) FlushRows

func (ms *ManagedStream) FlushRows(ctx context.Context, offset int64, opts ...gax.CallOption) (int64, error)

FlushRows advances the offset at which rows in a BufferedStream are visible. Calling this method for other stream types yields an error.

func (*ManagedStream) StreamName

func (ms *ManagedStream) StreamName() string

StreamName returns the corresponding write stream ID being managed by this writer.

func (*ManagedStream) StreamType

func (ms *ManagedStream) StreamType() StreamType

StreamType returns the configured type for this stream.


type StreamType string

StreamType indicates the type of stream this write client is managing.

DefaultStream, CommittedStream, BufferedStream, PendingStream

var (
	// DefaultStream most closely mimics the legacy bigquery
	// tabledata.insertAll semantics.  Successful inserts are
	// committed immediately, and there's no tracking offsets as
	// all writes go into a "default" stream that always exists
	// for a table.
	DefaultStream StreamType = "DEFAULT"

	// CommittedStream appends data immediately, but creates a
	// discrete stream for the work so that offset tracking can
	// be used to track writes.
	CommittedStream StreamType = "COMMITTED"

	// BufferedStream is a form of checkpointed stream, that allows
	// you to advance the offset of visible rows via Flush operations.
	BufferedStream StreamType = "BUFFERED"

	// PendingStream is a stream in which no data is made visible to
	// readers until the stream is finalized and committed explicitly.
	PendingStream StreamType = "PENDING"


type WriterOption func(*ManagedStream)

WriterOption are variadic options used to configure a ManagedStream instance.

func EnableWriteRetries

func EnableWriteRetries(enable bool) WriterOption

EnableWriteRetries enables ManagedStream to automatically retry failed appends.

Enabling retries is best suited for cases where users want to achieve at-least-once append semantics. Use of automatic retries may complicate patterns where the user is designing for exactly-once append semantics.

func WithAppendRowsCallOption

func WithAppendRowsCallOption(o gax.CallOption) WriterOption

WithAppendRowsCallOption is used to supply additional call options to the ManagedStream when it opens the underlying append stream.

func WithDataOrigin

func WithDataOrigin(dataOrigin string) WriterOption

WithDataOrigin is used to attach an origin context to the instrumentation metrics emitted by the library.

func WithDestinationTable

func WithDestinationTable(destTable string) WriterOption

WithDestinationTable specifies the destination table to which a created stream will append rows. Format of the table:


func WithMaxInflightBytes

func WithMaxInflightBytes(n int) WriterOption

WithMaxInflightBytes bounds the inflight append request bytes on the write connection.

func WithMaxInflightRequests

func WithMaxInflightRequests(n int) WriterOption

WithMaxInflightRequests bounds the inflight appends on the write connection.

func WithSchemaDescriptor

func WithSchemaDescriptor(dp *descriptorpb.DescriptorProto) WriterOption

WithSchemaDescriptor describes the format of the serialized data being sent by AppendRows calls on the stream.

func WithStreamName

func WithStreamName(name string) WriterOption

WithStreamName allows users to set the stream name this writer will append to explicitly. By default, the managed client will create the stream when instantiated if necessary.

Note: Supplying this option causes other options which affect stream construction such as WithStreamType and WithDestinationTable to be ignored.

func WithTraceID

func WithTraceID(traceID string) WriterOption

WithTraceID allows instruments requests to the service with a custom trace prefix. This is generally for diagnostic purposes only.

func WithType

func WithType(st StreamType) WriterOption

WithType sets the stream type for the managed stream.