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sample_merger.go
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/
sample_merger.go
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package steps
import (
"container/list"
"fmt"
"math"
"strconv"
"sync"
"time"
"github.com/bitflow-stream/go-bitflow/bitflow"
"github.com/bitflow-stream/go-bitflow/script/reg"
log "github.com/sirupsen/logrus"
)
type SynchronizedStreamMerger struct {
bitflow.NoopProcessor
MergeTag string
MergeInterval time.Duration
ExpectedStreams int
MergeSamples func([]*bitflow.Sample, []*bitflow.Header) (*bitflow.Sample, *bitflow.Header)
Description string
DebugQueueLengths bool
DebugWaitingQueues bool
queues map[string]*mergeQueue
readyQueues map[string]bool
readyQueuesLock sync.Mutex
start time.Time
end time.Time
samples []queueElem // Reused slice to avoid reallocations
}
func RegisterSubpipelineStreamMerger(b reg.ProcessorRegistry) {
create := func(p *bitflow.SamplePipeline, params map[string]string) error {
intervalStr := params["interval"]
tag := params["tag"]
numStr := params["num"]
debug := params["debug"] == "true"
num, err := strconv.Atoi(numStr)
if err != nil {
return reg.ParameterError("num", err)
}
interval, err := time.ParseDuration(intervalStr)
if err != nil {
return reg.ParameterError("interval", err)
}
merger := &SynchronizedStreamMerger{
MergeTag: tag,
MergeInterval: interval,
ExpectedStreams: num,
Description: fmt.Sprintf("Merge %v Streams (tag: %v, interval: %v)", num, tag, interval),
DebugQueueLengths: debug,
DebugWaitingQueues: debug,
MergeSamples: func(samples []*bitflow.Sample, headers []*bitflow.Header) (*bitflow.Sample, *bitflow.Header) {
if len(samples) == 0 {
return nil, nil
}
var outHeader []string
var valueCounts []int
outSample := new(bitflow.Sample)
indices := make(map[string]int)
for sampleNum, sample := range samples {
header := headers[sampleNum]
streamTag := sample.Tag(tag)
for fieldNum, field := range header.Fields {
newField := streamTag + "/" + field
index, ok := indices[newField]
if !ok {
index := len(outHeader)
indices[newField] = index
outHeader = append(outHeader, newField)
outSample.Values = append(outSample.Values, 0)
valueCounts = append(valueCounts, 0)
}
outSample.Values[index] += sample.Values[fieldNum]
valueCounts[index]++
}
}
for i, value := range outSample.Values {
outSample.Values[i] = value / bitflow.Value(valueCounts[i])
}
return outSample, &bitflow.Header{Fields: outHeader}
},
}
p.Add(merger)
return nil
}
b.RegisterAnalysisParamsErr("merge_streams", create, "Merge multiple streams, identified by a given tag. Output samples are generated in a given interval, all incoming metrics are averaged within that window, incoming metric names are prefixes with the respective tag value.", reg.RequiredParams("tag", "num", "interval"))
}
func (p *SynchronizedStreamMerger) Sample(sample *bitflow.Sample, header *bitflow.Header) error {
if !sample.HasTag(p.MergeTag) {
log.Warnln("Dropping sample without", p.MergeTag, "tag")
return nil
}
if p.queues == nil {
p.queues = make(map[string]*mergeQueue)
}
tag := sample.Tag(p.MergeTag)
queue, ok := p.queues[tag]
if !ok {
queue = new(mergeQueue)
queue.queue.Init()
p.queues[tag] = queue
}
queue.push(sample, header)
// Check if the new sample completes its queue, i.e. was recorded after the end of the current merge interval
if p.canMergeSamples() && sample.Time.After(p.end) {
p.readyQueuesLock.Lock()
p.readyQueues[tag] = true
allReady := len(p.readyQueues) >= len(p.queues)
p.readyQueuesLock.Unlock()
if allReady {
// All queues have enough data, so output a sample and flush queues.
sample, header = p.createSample()
if sample != nil {
if p.DebugQueueLengths {
p.logQueueLengths()
}
return p.NoopProcessor.Sample(sample, header)
} else if p.DebugWaitingQueues {
p.logWaitingQueues()
}
}
}
return nil
}
func (p *SynchronizedStreamMerger) Close() {
for {
if !p.canMergeSamples() {
break
}
sample, header := p.createSample()
if sample == nil {
break
}
if err := p.NoopProcessor.Sample(sample, header); err != nil {
p.Error(err)
break
}
}
p.CloseSink()
}
func (p *SynchronizedStreamMerger) StreamClosed(name string) {
p.readyQueuesLock.Lock()
defer p.readyQueuesLock.Unlock()
if queue, ok := p.queues[name]; ok {
queue.closed = true
p.readyQueues[name] = true
}
}
func (p *SynchronizedStreamMerger) StreamOfSampleClosed(lastSample *bitflow.Sample, lastHeader *bitflow.Header) {
p.StreamClosed(lastSample.Tag("client"))
}
func (p *SynchronizedStreamMerger) String() string {
return p.Description
}
func (p *SynchronizedStreamMerger) logQueueLengths() {
min := math.MaxInt32
max := 0
var avg float64
for _, q := range p.queues {
l := q.queue.Len()
avg += float64(l) / float64(len(p.queues))
if max < l {
max = l
}
if min > l {
min = l
}
}
log.Printf("%v: Outputting merged sample, avg queue length: %v (min: %v max: %v)", p, avg, min, max)
}
func (p *SynchronizedStreamMerger) logWaitingQueues() {
waitingQueues := make([]string, 0, len(p.queues))
for name := range p.queues {
if _, ok := p.readyQueues[name]; !ok {
waitingQueues = append(waitingQueues, name)
}
}
log.Printf("Waiting for %v queue(s): %v", len(waitingQueues), waitingQueues)
}
func (p *SynchronizedStreamMerger) canMergeSamples() bool {
if len(p.queues) < p.ExpectedStreams {
// Still waiting for every input stream to deliver at least one sample
return false
}
if p.readyQueues == nil {
// Lazy initialize
p.readyQueues = make(map[string]bool)
}
if p.start.IsZero() {
// We now received one sample on each queue, initialize the first merge window.
p.storeStart()
return false
}
return true
}
func (p *SynchronizedStreamMerger) createSample() (*bitflow.Sample, *bitflow.Header) {
queueElements := p.collectQueuedSamples(p.queues)
if len(queueElements) == 0 {
return nil, nil
}
samples := make([]*bitflow.Sample, len(queueElements))
headers := make([]*bitflow.Header, len(queueElements))
for i, elem := range queueElements {
samples[i] = elem.sample
headers[i] = elem.header
}
outSample, outHeader := p.MergeSamples(samples, headers)
// Store the start + end times for the next interval, record which queues already have enough data
p.storeStart()
p.readyQueuesLock.Lock()
defer p.readyQueuesLock.Unlock()
p.readyQueues = make(map[string]bool)
for queueName, queue := range p.queues {
// Some queues might already have enough samples for the next interval
isReady := queue.closed
if !isReady {
newest := queue.peekNewest()
if newest.sample != nil && newest.sample.Time.After(p.end) {
isReady = true
}
}
if isReady {
p.readyQueues[queueName] = true
}
}
return outSample, outHeader
}
func (p *SynchronizedStreamMerger) collectQueuedSamples(queues map[string]*mergeQueue) []queueElem {
res := p.samples[:0]
for _, queue := range queues {
for {
sample := queue.popYoungerThan(p.end)
if sample.sample == nil {
break
}
res = append(res, sample)
}
}
p.samples = res // Reuse (possibly extended buffer) next time
return res
}
func (p *SynchronizedStreamMerger) storeStart() {
p.start = time.Time{}
p.end = time.Time{}
for _, queue := range p.queues {
sample := queue.peek().sample
if sample != nil && (p.start.IsZero() || sample.Time.Before(p.start)) {
p.start = sample.Time
}
}
p.end = p.start.Add(p.MergeInterval)
}
type mergeQueue struct {
queue list.List
closed bool
}
type queueElem struct {
sample *bitflow.Sample
header *bitflow.Header
}
func (m *mergeQueue) push(sample *bitflow.Sample, header *bitflow.Header) {
m.queue.PushBack(queueElem{sample, header})
}
func (m *mergeQueue) peek() queueElem {
if elem := m.queue.Front(); elem != nil {
return elem.Value.(queueElem)
}
return queueElem{}
}
func (m *mergeQueue) peekNewest() queueElem {
if elem := m.queue.Back(); elem != nil {
return elem.Value.(queueElem)
}
return queueElem{}
}
func (m *mergeQueue) popYoungerThan(endTime time.Time) queueElem {
peekedElem := m.queue.Front()
if peekedElem == nil {
return queueElem{}
}
peeked := peekedElem.Value.(queueElem)
if !peeked.sample.Time.After(endTime) {
m.queue.Remove(peekedElem)
return peeked
}
return queueElem{}
}