feat(firestore): adds Bulkwriter support to Firestore client

firestore/bulkwriter.go

@@ -0,0 +1,325 @@
+package firestore
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"sync"
+	"time"
+
+	vkit "cloud.google.com/go/firestore/apiv1"
+	"golang.org/x/time/rate"
+	"google.golang.org/api/support/bundler"
+	pb "google.golang.org/genproto/googleapis/firestore/v1"
+)
+
+const (
+	// maxBatchSize is the max number of writes to send in a request
+	maxBatchSize = 20
+	// maxRetryAttempts is the max number of times to retry a write
+	maxRetryAttempts = 10
+	// defaultStartingMaximumOpsPerSecond is the starting max number of requests to the service per second
+	defaultStartingMaximumOpsPerSecond = 500
+	// maxWritesPerSecond is the starting limit of writes allowed to callers per second
+	maxWritesPerSecond = maxBatchSize * defaultStartingMaximumOpsPerSecond
+)
+
+// bulkWriterResult contains the WriteResult or error results from an individual
+// write to the database.
+type bulkWriterResult struct {
+	result *pb.WriteResult // (cached) result from the operation
+	err    error           // (cached) any errors that occurred
+}
+
+// BulkWriterJob provides read-only access to the results of a BulkWriter write attempt.
+type BulkWriterJob struct {
+	resultChan  chan bulkWriterResult // send errors and results to this channel
+	write       *pb.Write             // the writes to apply to the database
+	attempts    int                   // number of times this write has been attempted
+	resultsLock sync.Mutex            // guards the cached wr and e values for the job
+	result      *WriteResult          // (cached) result from the operation
+	err         error                 // (cached) any errors that occurred
+	ctx         context.Context       // context for canceling/timing out results
+}
+
+// Results gets the results of the BulkWriter write attempt.
+// This method blocks if the results for this BulkWriterJob haven't been
+// received.
+func (j *BulkWriterJob) Results() (*WriteResult, error) {
+	j.resultsLock.Lock()
+	defer j.resultsLock.Unlock()
+	if j.result == nil && j.err == nil {
+		j.result, j.err = j.processResults() // cache the results for additional calls
+	}
+	return j.result, j.err
+}
+
+// processResults checks for errors returned from send() and packages up the
+// results as WriteResult objects
+func (j *BulkWriterJob) processResults() (*WriteResult, error) {
+	select {
+	case <-j.ctx.Done():
+		return nil, j.ctx.Err()
+	case bwr := <-j.resultChan:
+		if bwr.err != nil {
+			return nil, bwr.err
+		}
+		return writeResultFromProto(bwr.result)
+	}
+}
+
+// setError ensures that an error is returned on the error channel of BulkWriterJob.
+func (j *BulkWriterJob) setError(e error) {
+	bwr := bulkWriterResult{
+		err:    e,
+		result: nil,
+	}
+	j.resultChan <- bwr
+	close(j.resultChan)
+}
+
+// A BulkWriter supports concurrent writes to multiple documents. The BulkWriter
+// submits document writes in maximum batches of 20 writes per request. Each
+// request can contain many different document writes: create, delete, update,
+// and set are all supported.
+//
+// Only one operation (create, set, update, delete) per document is allowed.
+// BulkWriter cannot promise atomicity: individual writes can fail or succeed
+// independent of each other. Bulkwriter does not apply writes in any set order;
+// thus a document can't have set on it immediately after creation.
+type BulkWriter struct {
+	database        string           // the database as resource name: projects/[PROJECT]/databases/[DATABASE]
+	start           time.Time        // when this BulkWriter was started; used to calculate qps and rate increases
+	vc              *vkit.Client     // internal client
+	maxOpsPerSecond int              // number of requests that can be sent per second
+	docUpdatePaths  map[string]bool  // document paths with corresponding writes in the queue
+	limiter         rate.Limiter     // limit requests to server to <= 500 qps
+	bundler         *bundler.Bundler // handle bundling up writes to Firestore
+	ctx             context.Context  // context for canceling all BulkWriter operations
+	isOpenLock      sync.Mutex       // guards against setting isOpen concurrently
+	isOpen          bool             // flag that the BulkWriter is closed
+}
+
+// newBulkWriter creates a new instance of the BulkWriter.
+func newBulkWriter(ctx context.Context, c *Client, database string) *BulkWriter {
+	// Although typically we shouldn't store Context objects, in this case we
+	// need to pass this Context through to the Bundler handler.
+	ctx = withResourceHeader(ctx, c.path())
+
+	bw := &BulkWriter{
+		database:        database,
+		start:           time.Now(),
+		vc:              c.c,
+		isOpen:          true,
+		maxOpsPerSecond: defaultStartingMaximumOpsPerSecond,
+		docUpdatePaths:  make(map[string]bool),
+		ctx:             ctx,
+		limiter:         *rate.NewLimiter(rate.Limit(maxWritesPerSecond), 1),
+	}
+
+	// can't initialize within struct above; need instance reference to BulkWriter.send()
+	bw.bundler = bundler.NewBundler(&BulkWriterJob{}, bw.send)
+	bw.bundler.HandlerLimit = bw.maxOpsPerSecond
+	bw.bundler.BundleCountThreshold = maxBatchSize
+
+	return bw
+}
+
+// End sends all enqueued writes in parallel and closes the BulkWriter to new requests.
+// After calling End(), calling any additional method automatically returns
+// with an error. This method completes when there are no more pending writes
+// in the queue.
+func (bw *BulkWriter) End() {
+	bw.isOpenLock.Lock()
+	bw.isOpen = false
+	bw.isOpenLock.Unlock()
+	bw.Flush()
+}
+
+// Flush commits all writes that have been enqueued up to this point in parallel.
+// This method blocks execution.
+func (bw *BulkWriter) Flush() {
+	bw.bundler.Flush()
+}
+
+// Create adds a document creation write to the queue of writes to send.
+// Note: You cannot write to (Create, Update, Set, or Delete) the same document more than once.
+func (bw *BulkWriter) Create(doc *DocumentRef, datum interface{}) (*BulkWriterJob, error) {
+	err := bw.checkWriteConditions(doc)
+	if err != nil {
+		return nil, err
+	}
+
+	w, err := doc.newCreateWrites(datum)
+	if err != nil {
+		return nil, fmt.Errorf("firestore: cannot create %v with %v", doc.ID, datum)
+	}
+
+	if len(w) > 1 {
+		return nil, fmt.Errorf("firestore: too many document writes sent to bulkwriter")
+	}
+
+	j := bw.write(w[0])
+	return j, nil
+}
+
+// Delete adds a document deletion write to the queue of writes to send.
+// Note: You cannot write to (Create, Update, Set, or Delete) the same document more than once.
+func (bw *BulkWriter) Delete(doc *DocumentRef, preconds ...Precondition) (*BulkWriterJob, error) {
+	err := bw.checkWriteConditions(doc)
+	if err != nil {
+		return nil, err
+	}
+
+	w, err := doc.newDeleteWrites(preconds)
+	if err != nil {
+		return nil, fmt.Errorf("firestore: cannot delete doc %v", doc.ID)
+	}
+
+	if len(w) > 1 {
+		return nil, fmt.Errorf("firestore: too many document writes sent to bulkwriter")
+	}
+
+	j := bw.write(w[0])
+	return j, nil
+}
+
+// Set adds a document set write to the queue of writes to send.
+// Note: You cannot write to (Create, Update, Set, or Delete) the same document more than once.
+func (bw *BulkWriter) Set(doc *DocumentRef, datum interface{}, opts ...SetOption) (*BulkWriterJob, error) {
+	err := bw.checkWriteConditions(doc)
+	if err != nil {
+		return nil, err
+	}
+
+	w, err := doc.newSetWrites(datum, opts)
+	if err != nil {
+		return nil, fmt.Errorf("firestore: cannot set %v on doc %v", datum, doc.ID)
+	}
+
+	if len(w) > 1 {
+		return nil, fmt.Errorf("firestore: too many writes sent to bulkwriter")
+	}
+
+	j := bw.write(w[0])
+	return j, nil
+}
+
+// Update adds a document update write to the queue of writes to send.
+// Note: You cannot write to (Create, Update, Set, or Delete) the same document more than once.
+func (bw *BulkWriter) Update(doc *DocumentRef, updates []Update, preconds ...Precondition) (*BulkWriterJob, error) {
+	err := bw.checkWriteConditions(doc)
+	if err != nil {
+		return nil, err
+	}
+
+	w, err := doc.newUpdatePathWrites(updates, preconds)
+	if err != nil {
+		return nil, fmt.Errorf("firestore: cannot update doc %v", doc.ID)
+	}
+
+	if len(w) > 1 {
+		return nil, fmt.Errorf("firestore: too many writes sent to bulkwriter")
+	}
+
+	j := bw.write(w[0])
+	return j, nil
+}
+
+// checkConditions determines whether this write attempt is valid. It returns
+// an error if either the BulkWriter has already been closed or if it
+// receives a nil document reference.
+func (bw *BulkWriter) checkWriteConditions(doc *DocumentRef) error {
+	bw.isOpenLock.Lock()
+	open := bw.isOpen
+	bw.isOpenLock.Unlock()
+	if !open {
+		return errors.New("firestore: BulkWriter has been closed")
+	}
+
+	if doc == nil {
+		return errors.New("firestore: nil document contents")
+	}
+
+	_, havePath := bw.docUpdatePaths[doc.shortPath]
+	if havePath {
+		return fmt.Errorf("firestore: BulkWriter received duplicate write for path: %v", doc.shortPath)
+	}
+
+	bw.docUpdatePaths[doc.shortPath] = true
+
+	return nil
+}
+
+// write packages up write requests into bulkWriterJob objects.
+func (bw *BulkWriter) write(w *pb.Write) *BulkWriterJob {
+
+	j := &BulkWriterJob{
+		resultChan: make(chan bulkWriterResult, 1),
+		write:      w,
+		ctx:        bw.ctx,
+	}
+
+	bw.limiter.Wait(bw.ctx)
+	// ignore operation size constraints and related errors; can't be inferred at compile time
+	// Bundler is set to accept an unlimited amount of bytes
+	_ = bw.bundler.Add(j, 0)
+
+	return j
+}
+
+// send transmits writes to the service and matches response results to job channels.
+func (bw *BulkWriter) send(i interface{}) {
+	bwj := i.([]*BulkWriterJob)
+
+	if len(bwj) == 0 {
+		return
+	}
+
+	var ws []*pb.Write
+	for _, w := range bwj {
+		ws = append(ws, w.write)
+	}
+
+	bwr := &pb.BatchWriteRequest{
+		Database: bw.database,
+		Writes:   ws,
+		Labels:   map[string]string{},
+	}
+
+	select {
+	case <-bw.ctx.Done():
+		return
+	default:
+		resp, err := bw.vc.BatchWrite(bw.ctx, bwr)
+		if err != nil {
+			// Do we need to be selective about what kind of errors we send?
+			for _, j := range bwj {
+				j.setError(err)
+			}
+			return
+		}
+		// Match write results with BulkWriterJob objects
+		for i, res := range resp.WriteResults {
+			s := resp.Status[i]
+			c := s.GetCode()
+			if c != 0 { // Should we do an explicit check against rpc.Code enum?
+				j := bwj[i]
+				j.attempts++
+
+				// Do we need separate retry bundler?
+				if j.attempts < maxRetryAttempts {
+					// ignore operation size constraints and related errors; job size can't be inferred at compile time
+					// Bundler is set to accept an unlimited amount of bytes
+					_ = bw.bundler.Add(j, 0)
+				} else {
+					j.setError(fmt.Errorf("firestore: write failed with status: %v", s))
+				}
+				continue
+			}
+
+			bwj[i].resultChan <- bulkWriterResult{err: nil, result: res}
+			close(bwj[i].resultChan)
+		}
+	}
+}