telegraf/internal/models/buffer.go

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package models
import (
"sync"
"github.com/influxdata/telegraf"
"github.com/influxdata/telegraf/selfstat"
)
var (
AgentMetricsWritten = selfstat.Register("agent", "metrics_written", map[string]string{})
AgentMetricsDropped = selfstat.Register("agent", "metrics_dropped", map[string]string{})
)
// Buffer stores metrics in a circular buffer.
type Buffer struct {
sync.Mutex
buf []telegraf.Metric
first int // index of the first/oldest metric
last int // one after the index of the last/newest metric
size int // number of metrics currently in the buffer
cap int // the capacity of the buffer
batchFirst int // index of the first metric in the batch
batchSize int // number of metrics currently in the batch
MetricsAdded selfstat.Stat
MetricsWritten selfstat.Stat
MetricsDropped selfstat.Stat
BufferSize selfstat.Stat
BufferLimit selfstat.Stat
}
// NewBuffer returns a new empty Buffer with the given capacity.
func NewBuffer(name string, capacity int) *Buffer {
b := &Buffer{
buf: make([]telegraf.Metric, capacity),
first: 0,
last: 0,
size: 0,
cap: capacity,
MetricsAdded: selfstat.Register(
"write",
"metrics_added",
map[string]string{"output": name},
),
MetricsWritten: selfstat.Register(
"write",
"metrics_written",
map[string]string{"output": name},
),
MetricsDropped: selfstat.Register(
"write",
"metrics_dropped",
map[string]string{"output": name},
),
BufferSize: selfstat.Register(
"write",
"buffer_size",
map[string]string{"output": name},
),
BufferLimit: selfstat.Register(
"write",
"buffer_limit",
map[string]string{"output": name},
),
}
b.BufferSize.Set(int64(0))
b.BufferLimit.Set(int64(capacity))
return b
}
// Len returns the number of metrics currently in the buffer.
func (b *Buffer) Len() int {
b.Lock()
defer b.Unlock()
return b.length()
}
func (b *Buffer) length() int {
return min(b.size+b.batchSize, b.cap)
}
func (b *Buffer) metricAdded() {
b.MetricsAdded.Incr(1)
}
func (b *Buffer) metricWritten(metric telegraf.Metric) {
AgentMetricsWritten.Incr(1)
b.MetricsWritten.Incr(1)
metric.Accept()
}
func (b *Buffer) metricDropped(metric telegraf.Metric) {
AgentMetricsDropped.Incr(1)
b.MetricsDropped.Incr(1)
metric.Reject()
}
func (b *Buffer) add(m telegraf.Metric) {
// Check if Buffer is full
if b.size == b.cap {
b.metricDropped(b.buf[b.last])
if b.last == b.batchFirst && b.batchSize > 0 {
b.batchSize--
b.batchFirst = b.next(b.batchFirst)
}
}
b.metricAdded()
b.buf[b.last] = m
b.last = b.next(b.last)
if b.size == b.cap {
b.first = b.next(b.first)
}
b.size = min(b.size+1, b.cap)
}
// Add adds metrics to the buffer
func (b *Buffer) Add(metrics ...telegraf.Metric) {
b.Lock()
defer b.Unlock()
for i := range metrics {
b.add(metrics[i])
}
b.BufferSize.Set(int64(b.length()))
}
// Batch returns a slice containing up to batchSize of the most recently added
// metrics. Metrics are ordered from newest to oldest in the batch. The
// batch must not be modified by the client.
func (b *Buffer) Batch(batchSize int) []telegraf.Metric {
b.Lock()
defer b.Unlock()
outLen := min(b.size, batchSize)
out := make([]telegraf.Metric, outLen)
if outLen == 0 {
return out
}
b.batchFirst = b.cap + b.last - outLen
b.batchFirst %= b.cap
b.batchSize = outLen
batchIndex := b.batchFirst
for i := range out {
out[len(out)-1-i] = b.buf[batchIndex]
b.buf[batchIndex] = nil
batchIndex = b.next(batchIndex)
}
b.last = b.batchFirst
b.size -= outLen
return out
}
// Accept marks the batch, acquired from Batch(), as successfully written.
func (b *Buffer) Accept(batch []telegraf.Metric) {
b.Lock()
defer b.Unlock()
for _, m := range batch {
b.metricWritten(m)
}
b.resetBatch()
b.BufferSize.Set(int64(b.length()))
}
// Reject returns the batch, acquired from Batch(), to the buffer and marks it
// as unsent.
func (b *Buffer) Reject(batch []telegraf.Metric) {
b.Lock()
defer b.Unlock()
older := b.dist(b.first, b.batchFirst)
free := b.cap - b.size
restore := min(len(batch), free+older)
// Rotate newer metrics forward the number of metrics that we can restore.
rb := b.batchFirst
rp := b.last
re := b.nextby(rp, restore)
b.last = re
for rb != rp {
rp = b.prev(rp)
re = b.prev(re)
if b.buf[re] != nil {
b.metricDropped(b.buf[re])
b.first = b.next(b.first)
}
b.buf[re] = b.buf[rp]
b.buf[rp] = nil
}
// Copy metrics from the batch back into the buffer; recall that the
// batch is in reverse order compared to b.buf
for i := range batch {
if i < restore {
re = b.prev(re)
b.buf[re] = batch[i]
b.size = min(b.size+1, b.cap)
} else {
b.metricDropped(batch[i])
}
}
b.resetBatch()
b.BufferSize.Set(int64(b.length()))
}
// dist returns the distance between two indexes. Because this data structure
// uses a half open range the arguments must both either left side or right
// side pairs.
func (b *Buffer) dist(begin, end int) int {
if begin <= end {
return end - begin
} else {
return b.cap - begin + end
}
}
// next returns the next index with wrapping.
func (b *Buffer) next(index int) int {
index++
if index == b.cap {
return 0
}
return index
}
// next returns the index that is count newer with wrapping.
func (b *Buffer) nextby(index, count int) int {
index += count
index %= b.cap
return index
}
// next returns the prev index with wrapping.
func (b *Buffer) prev(index int) int {
index--
if index < 0 {
return b.cap - 1
}
return index
}
func (b *Buffer) resetBatch() {
b.batchFirst = 0
b.batchSize = 0
}
func min(a, b int) int {
if b < a {
return b
}
return a
}