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engine.go
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engine.go
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package ssp
import (
"context"
"fmt"
"reflect"
"sync"
"sync/atomic"
"github.com/affo/ssp/values"
)
func Execute(ctx context.Context) error {
e := &Engine{}
return e.Execute(ctx)
}
type Engine struct{}
func (e *Engine) Execute(ctx context.Context) error {
g := GetGraph(ctx)
ops := make(map[Node]*ParallelOperator)
ins := make(map[Node][]Node)
Walk(g, func(a *Arch) {
if from := a.From(); from != nil {
if _, ok := ops[from]; !ok {
par := from.GetParallelism()
ops[from] = NewParallelOperator(par, func() *Operator {
return NewOperator(from)
})
}
}
if to := a.To(); to != nil {
if _, ok := ops[to]; !ok {
par := to.GetParallelism()
ops[to] = NewParallelOperator(par, func() *Operator {
return NewOperator(to)
}, WithInKeySelector(a.ks))
}
}
if from, to := a.From(), a.To(); from != nil && to != nil {
if _, ok := ins[to]; !ok {
ins[to] = make([]Node, 0, 1)
}
ins[to] = append(ins[to], from)
}
})
outs := make(map[Node][]Collector)
for n, in := range ins {
inss := make([]*infiniteStream, 0, len(in))
to := ops[n]
for _, from := range in {
is := NewInfiniteStream()
inss = append(inss, is)
if _, ok := outs[from]; !ok {
outs[from] = make([]Collector, 0, 1)
}
outs[from] = append(outs[from], is)
}
to.In(newWatermarker(newDataStreams(inss...), len(inss)), func() Transport {
return NewInfiniteStream()
})
}
for n, out := range outs {
ops[n].Out(out)
}
for _, op := range ops {
op.Open()
}
var werr error
for _, op := range ops {
if err := op.Close(); err != nil {
werr = fmt.Errorf("error on operator close: %w", err)
}
}
return werr
}
// dataStreams joins multiple streams from different sources offering a DataStream.
// It manages tagging records with a values.Source.
type dataStreams struct {
ss []*infiniteStream
cases []reflect.SelectCase
n int64
}
func newDataStreams(ss ...*infiniteStream) *dataStreams {
cases := make([]reflect.SelectCase, len(ss))
for i, s := range ss {
cases[i] = reflect.SelectCase{
Dir: reflect.SelectRecv,
Chan: reflect.ValueOf(s.s),
}
}
return &dataStreams{
ss: ss,
cases: cases,
n: int64(len(ss)),
}
}
func (d *dataStreams) Next() values.Value {
if n := atomic.LoadInt64(&d.n); n == 0 {
return nil
}
i, value, ok := reflect.Select(d.cases)
// !ok means the channel has been closed.
if !ok {
panic("unexpected close")
}
v := value.Interface().(values.Value)
if v.Type() == values.Close {
atomic.AddInt64(&d.n, -1)
return d.Next()
}
return values.SetSource(values.Source(i), v)
}
// watermarker sets correct watermarks on timestamped values based on their source.
// Resulting values (obtained via Next()) will have a monotonically increasing watermark equal to
// the minimum of the watermark of the sources.
// This makes time flow in one direction, and ensures that all sources agree on time passing.
type watermarker struct {
DataStream
nSources int
wms map[values.Source]values.Timestamp
}
func newWatermarker(dataStream DataStream, nSources int) *watermarker {
return &watermarker{
DataStream: dataStream,
nSources: nSources,
wms: make(map[values.Source]values.Timestamp, nSources),
}
}
// handleTimestamp replaces the watermark with the minimum watermark received for each source.
// It also makes watermarks monotonically increasing for every record that passes in.
func (w *watermarker) handleTimestamp(tsv values.TimestampedValue, source values.Source) values.Value {
wm, ok := w.wms[source]
if !ok || tsv.Watermark() > wm {
wm = tsv.Watermark()
w.wms[source] = wm
}
minWm := wm
for _, wm := range w.wms {
if wm < minWm {
minWm = wm
}
}
return values.SetTime(tsv.Timestamp(), minWm, tsv)
}
func (w *watermarker) Next() values.Value {
v := w.DataStream.Next()
if v == nil {
return nil
}
s, err := values.GetSource(v)
if err != nil {
s = values.Source(0)
}
if tsv, err := values.GetTimestampedValue(v); err == nil {
v = w.handleTimestamp(tsv, s)
}
return v
}
// sharedCollector de-multiplies Close signals.
type sharedCollector struct {
c Collector
par int64
}
func newSharedCollector(c Collector, par int) *sharedCollector {
return &sharedCollector{
c: c,
par: int64(par),
}
}
func (s *sharedCollector) Collect(v values.Value) {
if v.Type() == values.Close {
par := atomic.AddInt64(&s.par, -1)
if par > 0 {
return
}
}
s.c.Collect(v)
}
// broadcastCollector broadcasts values to multiple collectors.
type broadcastCollector struct {
cs []Collector
}
func newBroadCastCollector(cs []Collector) broadcastCollector {
return broadcastCollector{
cs: cs,
}
}
func (s broadcastCollector) Collect(v values.Value) {
for _, c := range s.cs {
c.Collect(v)
}
}
type Operator struct {
bn Node
ns map[values.Key]Node
in DataStream
out Collector
wg sync.WaitGroup
err error
}
func NewOperator(n Node) *Operator {
op := &Operator{
bn: n,
ns: make(map[values.Key]Node),
}
return op
}
func (o *Operator) In(ds DataStream) {
o.in = ds
}
func (o *Operator) Out(c Collector) {
o.out = c
}
func (o *Operator) getNode(key values.Key) Node {
if _, ok := o.ns[key]; !ok {
o.ns[key] = o.bn.Clone()
}
return o.ns[key]
}
func (o *Operator) do() error {
// This is a source, the provided value is useless.
if o.in == nil {
return o.bn.Do(o.out, values.NewNull(values.Int64))
}
for {
v := o.in.Next()
if v == nil {
return nil
}
k, err := values.GetKey(v)
if err != nil {
return err
}
n := o.getNode(k)
if err := n.Do(o.out, v); err != nil {
return err
}
}
}
func (o *Operator) Open() {
o.wg.Add(1)
go func() {
o.err = o.do()
// Propagate close. Note that sinks have nil collector.
if o.out != nil {
SendClose(o.out)
}
o.wg.Done()
}()
}
func (o *Operator) Close() error {
o.wg.Wait()
return o.err
}
type operatorOptions struct {
inKs KeySelector
}
type OperatorOption func(options *operatorOptions)
func WithInKeySelector(ks KeySelector) OperatorOption {
return func(o *operatorOptions) {
o.inKs = ks
}
}
type ParallelOperator struct {
ops []*Operator
opts operatorOptions
}
func NewParallelOperator(par int, f func() *Operator, opts ...OperatorOption) *ParallelOperator {
ops := make([]*Operator, par)
for i := 0; i < len(ops); i++ {
ops[i] = f()
}
pop := &ParallelOperator{
ops: ops,
}
for _, opt := range opts {
opt(&pop.opts)
}
return pop
}
func (o *ParallelOperator) In(ds DataStream, f func() Transport) {
ps := NewPartitionedStream(len(o.ops), o.opts.inKs, ds, f)
for i, o := range o.ops {
o.In(ps.Stream(i))
}
}
func (o *ParallelOperator) Out(cs []Collector) {
bc := newBroadCastCollector(cs)
sc := newSharedCollector(bc, len(o.ops))
for _, o := range o.ops {
o.Out(sc)
}
}
func (o *ParallelOperator) Open() {
for _, op := range o.ops {
op.Open()
}
}
func (o *ParallelOperator) Close() error {
var err error
for _, op := range o.ops {
if oerr := op.Close(); oerr != nil {
err = oerr
}
}
return err
}
type partitionedStream struct {
ds DataStream
ts []Transport
ks KeySelector
}
func NewPartitionedStream(par int, ks KeySelector, ds DataStream, f func() Transport) *partitionedStream {
if ks == nil {
ks = NewRoundRobinKeySelector(par)
}
ts := make([]Transport, par)
for i := 0; i < len(ts); i++ {
ts[i] = f()
}
ps := &partitionedStream{
ds: ds,
ts: ts,
ks: ks,
}
go ps.do()
return ps
}
func (s *partitionedStream) Stream(partition int) DataStream {
return s.ts[partition]
}
func (s *partitionedStream) do() {
for v := s.ds.Next(); v != nil; v = s.ds.Next() {
// Apply new keying.
k := s.ks.GetKey(v)
kv := values.SetKey(k, v)
i := uint64(k) % uint64(len(s.ts))
t := s.ts[i]
t.Collect(kv)
}
for _, t := range s.ts {
SendClose(t)
}
}