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datamgr.go
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datamgr.go
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// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package harness
import (
"context"
"io"
"sync"
"time"
"github.com/apache/beam/sdks/go/pkg/beam/core/runtime/exec"
"github.com/apache/beam/sdks/go/pkg/beam/internal/errors"
"github.com/apache/beam/sdks/go/pkg/beam/log"
fnpb "github.com/apache/beam/sdks/go/pkg/beam/model/fnexecution_v1"
)
const (
chunkSize = int(4e6) // Bytes to put in a single gRPC message. Max is slightly higher.
bufElements = 20 // Number of chunks buffered per reader.
)
// ScopedDataManager scopes the global gRPC data manager to a single instruction.
// The indirection makes it easier to control access.
type ScopedDataManager struct {
mgr *DataChannelManager
instID instructionID
closed bool
mu sync.Mutex
}
// NewScopedDataManager returns a ScopedDataManager for the given instruction.
func NewScopedDataManager(mgr *DataChannelManager, instID instructionID) *ScopedDataManager {
return &ScopedDataManager{mgr: mgr, instID: instID}
}
// OpenRead opens an io.ReadCloser on the given stream.
func (s *ScopedDataManager) OpenRead(ctx context.Context, id exec.StreamID) (io.ReadCloser, error) {
ch, err := s.open(ctx, id.Port)
if err != nil {
return nil, err
}
return ch.OpenRead(ctx, id.PtransformID, s.instID), nil
}
// OpenWrite opens an io.WriteCloser on the given stream.
func (s *ScopedDataManager) OpenWrite(ctx context.Context, id exec.StreamID) (io.WriteCloser, error) {
ch, err := s.open(ctx, id.Port)
if err != nil {
return nil, err
}
return ch.OpenWrite(ctx, id.PtransformID, s.instID), nil
}
func (s *ScopedDataManager) open(ctx context.Context, port exec.Port) (*DataChannel, error) {
s.mu.Lock()
if s.closed {
s.mu.Unlock()
return nil, errors.Errorf("instruction %v no longer processing", s.instID)
}
local := s.mgr
s.mu.Unlock()
return local.Open(ctx, port) // don't hold lock over potentially slow operation
}
// Close prevents new IO for this instruction.
func (s *ScopedDataManager) Close() error {
s.mu.Lock()
defer s.mu.Unlock()
s.closed = true
s.mgr.closeInstruction(s.instID)
s.mgr = nil
return nil
}
// DataChannelManager manages data channels over the Data API. A fixed number of channels
// are generally used, each managing multiple logical byte streams. Thread-safe.
type DataChannelManager struct {
ports map[string]*DataChannel
mu sync.Mutex // guards the ports map
}
// Open opens a R/W DataChannel over the given port.
func (m *DataChannelManager) Open(ctx context.Context, port exec.Port) (*DataChannel, error) {
if port.URL == "" {
panic("empty port")
}
m.mu.Lock()
defer m.mu.Unlock()
if m.ports == nil {
m.ports = make(map[string]*DataChannel)
}
if con, ok := m.ports[port.URL]; ok {
return con, nil
}
ch, err := newDataChannel(ctx, port)
if err != nil {
return nil, err
}
ch.forceRecreate = func(id string, err error) {
log.Warnf(ctx, "forcing DataChannel[%v] reconnection on port %v due to %v", id, port, err)
m.mu.Lock()
delete(m.ports, port.URL)
m.mu.Unlock()
}
m.ports[port.URL] = ch
return ch, nil
}
func (m *DataChannelManager) closeInstruction(instID instructionID) {
m.mu.Lock()
defer m.mu.Unlock()
for _, ch := range m.ports {
ch.removeInstruction(instID)
}
}
// clientID identifies a client of a connected channel.
type clientID struct {
ptransformID string
instID instructionID
}
// This is a reduced version of the full gRPC interface to help with testing.
// TODO(wcn): need a compile-time assertion to make sure this stays synced with what's
// in fnpb.BeamFnData_DataClient
type dataClient interface {
Send(*fnpb.Elements) error
Recv() (*fnpb.Elements, error)
}
// DataChannel manages a single gRPC stream over the Data API. Data from
// multiple bundles can be multiplexed over this stream. Data is pushed
// over the channel, so data for a reader may arrive before the reader
// connects.
// Thread-safe.
type DataChannel struct {
id string
client dataClient
writers map[instructionID]map[string]*dataWriter
readers map[instructionID]map[string]*dataReader
// recently terminated instructions
endedInstructions map[instructionID]struct{}
rmQueue []instructionID
// readErr indicates a client.Recv error and is used to prevent new readers.
readErr error
// a closure that forces the data manager to recreate this stream.
forceRecreate func(id string, err error)
cancelFn context.CancelFunc // Allows writers to stop the grpc reading goroutine.
mu sync.Mutex // guards mutable internal data, notably the maps and readErr.
}
func newDataChannel(ctx context.Context, port exec.Port) (*DataChannel, error) {
ctx, cancelFn := context.WithCancel(ctx)
cc, err := dial(ctx, port.URL, 15*time.Second)
if err != nil {
cancelFn()
return nil, errors.Wrapf(err, "failed to connect to data service at %v", port.URL)
}
client, err := fnpb.NewBeamFnDataClient(cc).Data(ctx)
if err != nil {
cc.Close()
cancelFn()
return nil, errors.Wrapf(err, "failed to create data client on %v", port.URL)
}
return makeDataChannel(ctx, port.URL, client, cancelFn), nil
}
func makeDataChannel(ctx context.Context, id string, client dataClient, cancelFn context.CancelFunc) *DataChannel {
ret := &DataChannel{
id: id,
client: client,
writers: make(map[instructionID]map[string]*dataWriter),
readers: make(map[instructionID]map[string]*dataReader),
endedInstructions: make(map[instructionID]struct{}),
cancelFn: cancelFn,
}
go ret.read(ctx)
return ret
}
// terminateStreamOnError requires the lock to be held.
func (c *DataChannel) terminateStreamOnError(err error) {
c.cancelFn() // A context.CancelFunc is threadsafe and indempotent.
if c.forceRecreate != nil {
c.forceRecreate(c.id, err)
c.forceRecreate = nil
}
}
// OpenRead returns an io.ReadCloser of the data elements for the given instruction and ptransform.
func (c *DataChannel) OpenRead(ctx context.Context, ptransformID string, instID instructionID) io.ReadCloser {
c.mu.Lock()
defer c.mu.Unlock()
cid := clientID{ptransformID: ptransformID, instID: instID}
if c.readErr != nil {
log.Errorf(ctx, "opening a reader %v on a closed channel", cid)
return &errReader{c.readErr}
}
return c.makeReader(ctx, cid)
}
// OpenWrite returns an io.WriteCloser of the data elements for the given instruction and ptransform.
func (c *DataChannel) OpenWrite(ctx context.Context, ptransformID string, instID instructionID) io.WriteCloser {
return c.makeWriter(ctx, clientID{ptransformID: ptransformID, instID: instID})
}
func (c *DataChannel) read(ctx context.Context) {
cache := make(map[clientID]*dataReader)
for {
msg, err := c.client.Recv()
if err != nil {
// This connection is bad, so we should close and delete all extant streams.
c.mu.Lock()
c.readErr = err // prevent not yet opened readers from hanging.
// Readers must be closed from this goroutine, since we can't
// close the r.buf channels twice, or send on a closed channel.
// Any other approach is racy, and may cause one of the above
// panics.
for _, m := range c.readers {
for _, r := range m {
log.Errorf(ctx, "DataChannel.read %v reader %v closing due to error on channel", c.id, r.id)
if !r.completed {
r.completed = true
r.err = err
close(r.buf)
}
delete(cache, r.id)
}
}
c.terminateStreamOnError(err)
c.mu.Unlock()
if err == io.EOF {
log.Warnf(ctx, "DataChannel.read %v closed", c.id)
return
}
log.Errorf(ctx, "DataChannel.read %v bad: %v", c.id, err)
return
}
recordStreamReceive(msg)
// Each message may contain segments for multiple streams, so we
// must treat each segment in isolation. We maintain a local cache
// to reduce lock contention.
for _, elm := range msg.GetData() {
id := clientID{ptransformID: elm.TransformId, instID: instructionID(elm.GetInstructionId())}
var r *dataReader
if local, ok := cache[id]; ok {
r = local
} else {
c.mu.Lock()
r = c.makeReader(ctx, id)
c.mu.Unlock()
cache[id] = r
}
if elm.GetIsLast() {
// If this reader hasn't closed yet, do so now.
if !r.completed {
// Sentinel EOF segment for stream. Close buffer to signal EOF.
r.completed = true
close(r.buf)
}
// Clean up local bookkeeping. We'll never see another message
// for it again. We have to be careful not to remove the real
// one, because readers may be initialized after we've seen
// the full stream.
delete(cache, id)
continue
}
if r.completed {
// The local reader has closed but the remote is still sending data.
// Just ignore it. We keep the reader config in the cache so we don't
// treat it as a new reader. Eventually the stream will finish and go
// through normal teardown.
continue
}
// This send is deliberately blocking, if we exceed the buffering for
// a reader. We can't buffer the entire main input, if some user code
// is slow (or gets stuck). If the local side closes, the reader
// will be marked as completed and further remote data will be ignored.
select {
case r.buf <- elm.GetData():
case <-r.done:
r.completed = true
close(r.buf)
}
}
}
}
type errReader struct {
err error
}
func (r *errReader) Read(_ []byte) (int, error) {
return 0, r.err
}
func (r *errReader) Close() error {
return r.err
}
// makeReader creates a dataReader. It expects to be called while c.mu is held.
func (c *DataChannel) makeReader(ctx context.Context, id clientID) *dataReader {
var m map[string]*dataReader
var ok bool
if m, ok = c.readers[id.instID]; !ok {
m = make(map[string]*dataReader)
c.readers[id.instID] = m
}
if r, ok := m[id.ptransformID]; ok {
return r
}
r := &dataReader{id: id, buf: make(chan []byte, bufElements), done: make(chan bool, 1), channel: c}
// Just in case initial data for an instruction arrives *after* an instructon has ended.
// eg. it was blocked by another reader being slow, or the other instruction failed.
// So we provide a pre-completed reader, and do not cache it, as there's no further cleanup for it.
if _, ok := c.endedInstructions[id.instID]; ok {
r.completed = true
close(r.buf)
r.err = io.EOF // In case of any actual data readers, so they terminate without error.
return r
}
m[id.ptransformID] = r
return r
}
func (c *DataChannel) removeReader(id clientID) {
c.mu.Lock()
if m, ok := c.readers[id.instID]; ok {
delete(m, id.ptransformID)
}
c.mu.Unlock()
}
const endedInstructionCap = 32
// removeInstruction closes all readers and writers registered for the instruction
// and deletes this instruction from the channel's reader and writer maps.
func (c *DataChannel) removeInstruction(instID instructionID) {
c.mu.Lock()
// We don't want to leak memory, so cap the endedInstructions list.
if len(c.rmQueue) >= endedInstructionCap {
toRemove := c.rmQueue[0]
c.rmQueue = c.rmQueue[1:]
delete(c.endedInstructions, toRemove)
}
c.endedInstructions[instID] = struct{}{}
c.rmQueue = append(c.rmQueue, instID)
rs := c.readers[instID]
ws := c.writers[instID]
// Prevent other users while we iterate.
delete(c.readers, instID)
delete(c.writers, instID)
c.mu.Unlock()
// Close grabs the channel lock, so this must be outside the critical section.
for _, r := range rs {
r.Close()
}
for _, w := range ws {
w.Close()
}
}
func (c *DataChannel) makeWriter(ctx context.Context, id clientID) *dataWriter {
c.mu.Lock()
defer c.mu.Unlock()
var m map[string]*dataWriter
var ok bool
if m, ok = c.writers[id.instID]; !ok {
m = make(map[string]*dataWriter)
c.writers[id.instID] = m
}
if w, ok := m[id.ptransformID]; ok {
return w
}
// We don't check for ended instructions for writers, as writers
// can only be created if an instruction is in scope, and aren't
// runner or user directed.
w := &dataWriter{ch: c, id: id}
m[id.ptransformID] = w
return w
}
type dataReader struct {
id clientID
buf chan []byte
done chan bool
cur []byte
channel *DataChannel
completed bool
err error
}
func (r *dataReader) Close() error {
r.done <- true
r.channel.removeReader(r.id)
return nil
}
func (r *dataReader) Read(buf []byte) (int, error) {
if r.cur == nil {
b, ok := <-r.buf
if !ok {
if r.err == nil {
return 0, io.EOF
}
return 0, r.err
}
r.cur = b
}
// We don't need to check for a 0 length copy from r.cur here, since that's
// checked before buffers are handed to the r.buf channel.
n := copy(buf, r.cur)
switch {
case len(r.cur) == n:
r.cur = nil
default:
r.cur = r.cur[n:]
}
return n, nil
}
type dataWriter struct {
buf []byte
id clientID
ch *DataChannel
}
// send requires the ch.mu lock to be held.
func (w *dataWriter) send(msg *fnpb.Elements) error {
recordStreamSend(msg)
if err := w.ch.client.Send(msg); err != nil {
if err == io.EOF {
log.Warnf(context.TODO(), "dataWriter[%v;%v] EOF on send; fetching real error", w.id, w.ch.id)
err = nil
for err == nil {
// Per GRPC stream documentation, if there's an EOF, we must call Recv
// until a non-nil error is returned, to ensure resources are cleaned up.
// https://godoc.org/google.golang.org/grpc#ClientConn.NewStream
_, err = w.ch.client.Recv()
}
}
log.Warnf(context.TODO(), "dataWriter[%v;%v] error on send: %v", w.id, w.ch.id, err)
w.ch.terminateStreamOnError(err)
return err
}
return nil
}
func (w *dataWriter) Close() error {
// Don't acquire the locks as Flush will do so.
l := len(w.buf)
err := w.Flush()
if err != nil {
return errors.Wrapf(err, "dataWriter[%v;%v].Close: error flushing buffer of length %d", w.id, w.ch.id, l)
}
// Now acquire the locks since we're sending.
w.ch.mu.Lock()
defer w.ch.mu.Unlock()
delete(w.ch.writers[w.id.instID], w.id.ptransformID)
msg := &fnpb.Elements{
Data: []*fnpb.Elements_Data{
{
InstructionId: string(w.id.instID),
TransformId: w.id.ptransformID,
// Empty data == sentinel
IsLast: true,
},
},
}
return w.send(msg)
}
const largeBufferNotificationThreshold = 1024 * 1024 * 1024 // 1GB
func (w *dataWriter) Flush() error {
w.ch.mu.Lock()
defer w.ch.mu.Unlock()
if w.buf == nil {
return nil
}
msg := &fnpb.Elements{
Data: []*fnpb.Elements_Data{
{
InstructionId: string(w.id.instID),
TransformId: w.id.ptransformID,
Data: w.buf,
},
},
}
if l := len(w.buf); l > largeBufferNotificationThreshold {
log.Infof(context.TODO(), "dataWriter[%v;%v].Flush flushed large buffer of length %d", w.id, w.ch.id, l)
}
w.buf = nil
return w.send(msg)
}
func (w *dataWriter) Write(p []byte) (n int, err error) {
if len(w.buf)+len(p) > chunkSize {
l := len(w.buf)
// We can't fit this message into the buffer. We need to flush the buffer
if err := w.Flush(); err != nil {
return 0, errors.Wrapf(err, "datamgr.go [%v]: error flushing buffer of length %d", w.id, l)
}
}
// At this point there's room in the buffer one way or another.
w.buf = append(w.buf, p...)
return len(p), nil
}