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conn.go
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conn.go
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package statsd
import (
"io"
"math"
"math/rand"
"net"
"strconv"
"strings"
"sync"
"time"
)
type conn struct {
// config
errorHandler func(error)
flushPeriod time.Duration
maxPacketSize int
tagFormat TagFormat
inlineFlush bool
// state
mu sync.Mutex // mu synchronises internal state
closed bool // closed indicates if w has been closed (triggered by first client close)
w io.WriteCloser // w is the writer for the connection
buf []byte // buf is the buffer for the connection
rateCache map[float32]string // rateCache caches string representations of sampling rates
trimTrailingNewline bool // trimTrailingNewline is for UDP, see also conn.flush
}
func newConn(conf connConfig, muted bool) (*conn, error) {
c := &conn{
errorHandler: conf.ErrorHandler,
flushPeriod: conf.FlushPeriod,
maxPacketSize: conf.MaxPacketSize,
tagFormat: conf.TagFormat,
inlineFlush: conf.InlineFlush,
w: conf.WriteCloser,
trimTrailingNewline: conf.TrimTrailingNewline,
}
// exit if muted
if muted {
// close and clear any provided writer
if c.w != nil {
_ = c.w.Close()
c.w = nil
}
// return muted client
return c, nil
}
if c.w == nil {
// initialise writer if not provided
if err := c.connect(conf.Network, conf.Addr, conf.UDPCheck == nil || *conf.UDPCheck); err != nil {
return c, err
}
} else if conf.UDPCheck != nil && *conf.UDPCheck {
// udp check was explicitly set
if err := c.udpCheck(); err != nil {
return c, err
}
}
// To prevent a buffer overflow add some capacity to the buffer to allow for
// an additional metric.
c.buf = make([]byte, 0, c.maxPacketSize+200)
// start the flush worker only if we have a rate and it's not unnecessary
if c.flushPeriod > 0 && !c.inlineFlush {
go c.flushWorker()
}
return c, nil
}
func (c *conn) flushWorker() {
ticker := time.NewTicker(c.flushPeriod)
defer ticker.Stop()
for range ticker.C {
if func() bool {
c.mu.Lock()
defer c.mu.Unlock()
if c.closed {
return true
}
c.flush(0)
return false
}() {
return
}
}
}
// When using UDP do a quick check to see if something is listening on the
// given port to return an error as soon as possible.
//
// See also doc for UDPCheck option (factory func) and https://github.com/alexcesaro/statsd/issues/6
func (c *conn) udpCheck() error {
for i := 0; i < 2; i++ {
if _, err := c.w.Write(nil); err != nil {
_ = c.w.Close()
c.w = nil
return err
}
}
return nil
}
func (c *conn) connect(network string, address string, UDPCheck bool) error {
var err error
c.w, err = dialTimeout(network, address, 5*time.Second)
if err != nil {
return err
}
if strings.HasPrefix(network, "udp") {
// udp retains behavior from the original implementation where it would strip a trailing newline
c.trimTrailingNewline = true
if UDPCheck {
if err := c.udpCheck(); err != nil {
return err
}
}
}
return nil
}
func (c *conn) metric(prefix, bucket string, n interface{}, typ string, rate float32, tags string) {
c.mu.Lock()
l := len(c.buf)
c.appendBucket(prefix, bucket, tags)
c.appendNumber(n)
c.appendType(typ)
c.appendRate(rate)
c.closeMetric(tags)
c.flushIfNecessary(l)
c.mu.Unlock()
}
func (c *conn) gaugeRelative(prefix, bucket string, value interface{}, tags string) {
c.mu.Lock()
l := len(c.buf)
c.appendBucket(prefix, bucket, tags)
// add a (positive) sign if necessary (if there's no negative sign)
// this is complicated by the special case of negative zero (IEEE-754 floating point thing)
// note that NaN ends up "+NaN" and invalid values end up "+" (both probably going to do nothing / error)
if f, ok := floatValue(value); (!ok && !isNegativeInteger(value)) ||
(ok && (f != f || (f == 0 && !math.Signbit(f)) || (f > 0 && f <= math.MaxFloat64))) {
c.appendByte('+')
}
c.appendGauge(value, tags)
c.flushIfNecessary(l)
c.mu.Unlock()
}
func (c *conn) gauge(prefix, bucket string, value interface{}, tags string) {
c.mu.Lock()
l := len(c.buf)
// To set a gauge to a negative value we must first set it to 0.
// https://github.com/etsy/statsd/blob/master/docs/metric_types.md#gauges
// the presence of a sign (/^[-+]/) requires the special case handling
// https://github.com/statsd/statsd/blob/2041f6fb5e64bbf779a8bcb3e9729e63fe207e2f/stats.js#L307
// +Inf doesn't get this special case, no particular reason, it's just existing behavior
if f, ok := floatValue(value); ok && f == 0 {
// special case to handle negative zero (IEEE-754 floating point thing)
value = 0
} else if (ok && f < 0) || (!ok && isNegativeInteger(value)) {
// note this case includes -Inf, which is just existing behavior that's been retained
c.appendBucket(prefix, bucket, tags)
c.appendGauge(0, tags)
}
c.appendBucket(prefix, bucket, tags)
c.appendGauge(value, tags)
c.flushIfNecessary(l)
c.mu.Unlock()
}
func (c *conn) appendGauge(value interface{}, tags string) {
c.appendNumber(value)
c.appendType("g")
c.closeMetric(tags)
}
func (c *conn) unique(prefix, bucket string, value string, tags string) {
c.mu.Lock()
l := len(c.buf)
c.appendBucket(prefix, bucket, tags)
c.appendString(value)
c.appendType("s")
c.closeMetric(tags)
c.flushIfNecessary(l)
c.mu.Unlock()
}
func (c *conn) appendByte(b byte) {
c.buf = append(c.buf, b)
}
func (c *conn) appendString(s string) {
c.buf = append(c.buf, s...)
}
func (c *conn) appendNumber(v interface{}) {
switch n := v.(type) {
case int:
c.buf = strconv.AppendInt(c.buf, int64(n), 10)
case uint:
c.buf = strconv.AppendUint(c.buf, uint64(n), 10)
case int64:
c.buf = strconv.AppendInt(c.buf, n, 10)
case uint64:
c.buf = strconv.AppendUint(c.buf, n, 10)
case int32:
c.buf = strconv.AppendInt(c.buf, int64(n), 10)
case uint32:
c.buf = strconv.AppendUint(c.buf, uint64(n), 10)
case int16:
c.buf = strconv.AppendInt(c.buf, int64(n), 10)
case uint16:
c.buf = strconv.AppendUint(c.buf, uint64(n), 10)
case int8:
c.buf = strconv.AppendInt(c.buf, int64(n), 10)
case uint8:
c.buf = strconv.AppendUint(c.buf, uint64(n), 10)
case float64:
c.buf = strconv.AppendFloat(c.buf, n, 'f', -1, 64)
case float32:
c.buf = strconv.AppendFloat(c.buf, float64(n), 'f', -1, 32)
}
}
func isNegativeInteger(n interface{}) bool {
switch n := n.(type) {
case int:
return n < 0
case int64:
return n < 0
case int32:
return n < 0
case int16:
return n < 0
case int8:
return n < 0
default:
return false
}
}
func floatValue(n interface{}) (float64, bool) {
switch n := n.(type) {
case float64:
return n, true
case float32:
return float64(n), true
default:
return 0, false
}
}
func (c *conn) appendBucket(prefix, bucket string, tags string) {
c.appendString(prefix)
c.appendString(bucket)
if c.tagFormat == InfluxDB {
c.appendString(tags)
}
c.appendByte(':')
}
func (c *conn) appendType(t string) {
c.appendByte('|')
c.appendString(t)
}
func (c *conn) appendRate(rate float32) {
if rate == 1 {
return
}
if c.rateCache == nil {
c.rateCache = make(map[float32]string)
}
c.appendString("|@")
if s, ok := c.rateCache[rate]; ok {
c.appendString(s)
} else {
s = strconv.FormatFloat(float64(rate), 'f', -1, 32)
c.rateCache[rate] = s
c.appendString(s)
}
}
func (c *conn) closeMetric(tags string) {
if c.tagFormat == Datadog {
c.appendString(tags)
}
c.appendByte('\n')
}
func (c *conn) flushNecessary() bool {
if c.inlineFlush {
return true
}
if len(c.buf) > c.maxPacketSize {
return true
}
return false
}
func (c *conn) flushIfNecessary(lastSafeLen int) {
if c.inlineFlush {
lastSafeLen = 0
}
if c.flushNecessary() {
c.flush(lastSafeLen)
}
}
// flush flushes the first n bytes of the buffer.
// If n is 0, the whole buffer is flushed.
func (c *conn) flush(n int) {
if len(c.buf) == 0 {
return
}
if n == 0 {
n = len(c.buf)
}
// write
buffer := c.buf[:n]
if c.trimTrailingNewline {
// https://github.com/cactus/go-statsd-client/issues/17
// Trim the last \n, StatsD does not like it.
buffer = buffer[:len(buffer)-1]
}
_, err := c.w.Write(buffer)
c.handleError(err)
// consume
if n < len(c.buf) {
copy(c.buf, c.buf[n:])
}
c.buf = c.buf[:len(c.buf)-n]
}
func (c *conn) handleError(err error) {
if err != nil && c.errorHandler != nil {
c.errorHandler(err)
}
}
// Stubbed out for testing.
var (
dialTimeout = net.DialTimeout
now = time.Now
randFloat = rand.Float32
resolveUDPAddress = net.ResolveUDPAddr
listenUDP = net.ListenUDP
)