Statsdreceiver optimizations (#33683)

**Description:**
Optimize statsdreceiver code to reduce heap usage
Also reduce failCnt increment to reduce memory footprint in cases of
tons of malformed statsd messages

**Link to tracking Issue:** <Issue number if applicable>

**Testing:**
- Tested internally and saw a 17% reduction in object allocation from
our workloads (with ~2.5k/s statsd metrics input) mostly from reduction
of strings.Split
Screenshot is from `go tool pprof -http:8081 -diff_base baseline.heap.gz
optimized.heap.gz`
![Screenshot 2024-06-20 at 12 45
17 PM](https://github.com/open-telemetry/opentelemetry-collector-contrib/assets/142453/e8065097-2533-4934-9b78-c0e828e075ac)

Note: I also saw lots of allocations from attribute.NewSet but idk the
best way to go about reducing that. (Screenshot below is from
unoptimized statsdreceiver)
![Screenshot 2024-06-20 at 12 44
32 PM](https://github.com/open-telemetry/opentelemetry-collector-contrib/assets/142453/293553c0-92c8-465b-872a-ddb7b68299a0)

I tried changing statsDMetricDescription's attrs field to
`map[string]any` in the hopes of using attributes.FromRaw in
buildGaugeMetric but it would require replacing statsDMetricDescription
as the type of the map key in instruments.gauges, etc.

.chloggen/feature-statsdreceiver-optimizations.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: statsdreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Optimize statsdreceiver to reduce object allocations
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [33683]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

receiver/statsdreceiver/internal/protocol/statsd_parser.go

@@ -356,41 +356,41 @@ func (p *StatsDParser) Aggregate(line string, addr net.Addr) error {
 func parseMessageToMetric(line string, enableMetricType bool, enableSimpleTags bool) (statsDMetric, error) {
 	result := statsDMetric{}
 
-	parts := strings.Split(line, "|")
-	if len(parts) < 2 {
+	nameValue, rest, foundName := strings.Cut(line, "|")
+	if !foundName {
 		return result, fmt.Errorf("invalid message format: %s", line)
 	}
 
-	separatorIndex := strings.IndexByte(parts[0], ':')
-	if separatorIndex < 0 {
-		return result, fmt.Errorf("invalid <name>:<value> format: %s", parts[0])
+	name, valueStr, foundValue := strings.Cut(nameValue, ":")
+	if !foundValue {
+		return result, fmt.Errorf("invalid <name>:<value> format: %s", nameValue)
 	}
 
-	result.description.name = parts[0][0:separatorIndex]
-	if result.description.name == "" {
+	if name == "" {
 		return result, errEmptyMetricName
 	}
-	valueStr := parts[0][separatorIndex+1:]
+	result.description.name = name
 	if valueStr == "" {
 		return result, errEmptyMetricValue
 	}
 	if strings.HasPrefix(valueStr, "-") || strings.HasPrefix(valueStr, "+") {
 		result.addition = true
 	}
 
-	inType := MetricType(parts[1])
+	var metricType, additionalParts, _ = strings.Cut(rest, "|")
+	inType := MetricType(metricType)
 	switch inType {
 	case CounterType, GaugeType, HistogramType, TimingType, DistributionType:
 		result.description.metricType = inType
 	default:
 		return result, fmt.Errorf("unsupported metric type: %s", inType)
 	}
 
-	additionalParts := parts[2:]
-
 	var kvs []attribute.KeyValue
 
-	for _, part := range additionalParts {
+	var part string
+	part, additionalParts, _ = strings.Cut(additionalParts, "|")
+	for ; len(part) > 0; part, additionalParts, _ = strings.Cut(additionalParts, "|") {
 		switch {
 		case strings.HasPrefix(part, "@"):
 			sampleRateStr := strings.TrimPrefix(part, "@")
@@ -402,30 +402,24 @@ func parseMessageToMetric(line string, enableMetricType bool, enableSimpleTags b
 
 			result.sampleRate = f
 		case strings.HasPrefix(part, "#"):
-			tagsStr := strings.TrimPrefix(part, "#")
+			var tagsStr = strings.TrimPrefix(part, "#")
 
 			// handle an empty tag set
 			// where the tags part was still sent (some clients do this)
 			if len(tagsStr) == 0 {
 				continue
 			}
 
-			tagSets := strings.Split(tagsStr, ",")
-
-			for _, tagSet := range tagSets {
-				tagParts := strings.SplitN(tagSet, ":", 2)
-				k := tagParts[0]
+			var tagSet string
+			tagSet, tagsStr, _ = strings.Cut(tagsStr, ",")
+			for ; len(tagSet) > 0; tagSet, tagsStr, _ = strings.Cut(tagsStr, ",") {
+				k, v, _ := strings.Cut(tagSet, ":")
 				if k == "" {
 					return result, fmt.Errorf("invalid tag format: %q", tagSet)
 				}
 
 				// support both simple tags (w/o value) and dimension tags (w/ value).
 				// dogstatsd notably allows simple tags.
-				var v string
-				if len(tagParts) == 2 {
-					v = tagParts[1]
-				}
-
 				if v == "" && !enableSimpleTags {
 					return result, fmt.Errorf("invalid tag format: %q", tagSet)
 				}

receiver/statsdreceiver/internal/transport/split_bytes.go

@@ -0,0 +1,59 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package transport // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/statsdreceiver/internal/transport"
+
+import "bytes"
+
+// SplitBytes iterates over a byte buffer, returning chunks split by a given
+// delimiter byte. It does not perform any allocations, and does not modify the
+// buffer it is given. It is not safe for use by concurrent goroutines.
+//
+//	sb := NewSplitBytes(buf, '\n')
+//	for sb.Next() {
+//	    fmt.Printf("%q\n", sb.Chunk())
+//	}
+//
+// The sequence of chunks returned by SplitBytes is equivalent to calling
+// bytes.Split, except without allocating an intermediate slice.
+type SplitBytes struct {
+	buf          []byte
+	delim        byte
+	currentChunk []byte
+	lastChunk    bool
+}
+
+// NewSplitBytes initializes a SplitBytes struct with the provided buffer and delimiter.
+func NewSplitBytes(buf []byte, delim byte) *SplitBytes {
+	return &SplitBytes{
+		buf:   buf,
+		delim: delim,
+	}
+}
+
+// Next advances SplitBytes to the next chunk, returning true if a new chunk
+// actually exists and false otherwise.
+func (sb *SplitBytes) Next() bool {
+	if sb.lastChunk {
+		// we do not check the length here, this ensures that we return the
+		// last chunk in the sequence (even if it's empty)
+		return false
+	}
+
+	next := bytes.IndexByte(sb.buf, sb.delim)
+	if next == -1 {
+		// no newline, consume the entire buffer
+		sb.currentChunk = sb.buf
+		sb.buf = nil
+		sb.lastChunk = true
+	} else {
+		sb.currentChunk = sb.buf[:next]
+		sb.buf = sb.buf[next+1:]
+	}
+	return true
+}
+
+// Chunk returns the current chunk.
+func (sb *SplitBytes) Chunk() []byte {
+	return sb.currentChunk
+}

receiver/statsdreceiver/internal/transport/udp_server.go

@@ -4,12 +4,9 @@
 package transport // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/statsdreceiver/internal/transport"
 
 import (
-	"bytes"
 	"errors"
 	"fmt"
-	"io"
 	"net"
-	"strings"
 
 	"go.opentelemetry.io/collector/consumer"
 )
@@ -53,9 +50,7 @@ func (u *udpServer) ListenAndServe(
 	for {
 		n, addr, err := u.packetConn.ReadFrom(buf)
 		if n > 0 {
-			bufCopy := make([]byte, n)
-			copy(bufCopy, buf)
-			u.handlePacket(bufCopy, addr, transferChan)
+			u.handlePacket(n, buf, addr, transferChan)
 		}
 		if err != nil {
 			reporter.OnDebugf("%s Transport (%s) - ReadFrom error: %v",
@@ -80,22 +75,16 @@ func (u *udpServer) Close() error {
 
 // handlePacket is helper that parses the buffer and split it line by line to be parsed upstream.
 func (u *udpServer) handlePacket(
+	numBytes int,
 	data []byte,
 	addr net.Addr,
 	transferChan chan<- Metric,
 ) {
-	buf := bytes.NewBuffer(data)
-	for {
-		bytes, err := buf.ReadBytes((byte)('\n'))
-		if errors.Is(err, io.EOF) {
-			if len(bytes) == 0 {
-				// Completed without errors.
-				break
-			}
-		}
-		line := strings.TrimSpace(string(bytes))
-		if line != "" {
-			transferChan <- Metric{line, addr}
+	splitPacket := NewSplitBytes(data[:numBytes], '\n')
+	for splitPacket.Next() {
+		chunk := splitPacket.Chunk()
+		if len(chunk) > 0 {
+			transferChan <- Metric{string(chunk), addr}
 		}
 	}
 }

receiver/statsdreceiver/receiver.go

@@ -119,7 +119,7 @@ func (r *statsdReceiver) Start(ctx context.Context, _ component.Host) error {
 		}
 	}()
 	go func() {
-		var successCnt int64
+		var failCnt, successCnt int64
 		for {
 			select {
 			case <-ticker.C:
@@ -137,7 +137,11 @@ func (r *statsdReceiver) Start(ctx context.Context, _ component.Host) error {
 			case metric := <-transferChan:
 				err := r.parser.Aggregate(metric.Raw, metric.Addr)
 				if err != nil {
-					r.reporter.RecordParseFailure()
+					failCnt++
+					if failCnt%100 == 0 {
+						r.reporter.RecordParseFailure()
+						failCnt = 0
+					}
 					r.reporter.OnDebugf("Error aggregating pmetric", zap.Error(err))
 				} else {
 					successCnt++