Add statsdreceiver Unixgram Support (#36608)

#### Description

Adds `unixgram` transport for the `statsdreceiver`. Additionally,
creates a new `packetServer` base class for both `UDS` and `UDP*`
transport types

#### Link to tracking issue

#21385

#### Testing

Added a unit test

---------

Co-authored-by: Christos Markou <chrismarkou92@gmail.com>

.chloggen/statsdreceiver-uds.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: Add UDS support to statsdreceiver
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [21385]
+
+# (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: []

receiver/statsdreceiver/README.md

@@ -19,12 +19,13 @@ Use case: it does not support horizontal pool of collectors. Desired work case i
 
 ## Configuration
 
-The following settings are required:
-
-- `endpoint` (default = `localhost:8125`): Address and port to listen on.
+The Following settings are optional:
 
+- `endpoint`: Address and port to listen on.
+  - For `udp` and `tcp` based `transport`, this config will default to `localhost:8125`
+  - For `unixgram` `transport`, this config will default to `/var/run/statsd-receiver.sock`
 
-The Following settings are optional:
+- `transport` (default = `udp`): Protocol used by the StatsD server. Currently supported transports can be found in [this file](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/receiver/statsdreceiver/internal/transport/transport.go).
 
 - `aggregation_interval: 70s`(default value is 60s): The aggregation time that the receiver aggregates the metrics (similar to the flush interval in StatsD server)
 

receiver/statsdreceiver/internal/transport/client/client.go

@@ -51,6 +51,15 @@ func (s *StatsD) connect() error {
 		if err != nil {
 			return err
 		}
+	case "unixgram":
+		unixAddr, err := net.ResolveUnixAddr(s.transport, s.address)
+		if err != nil {
+			return err
+		}
+		s.conn, err = net.DialUnix(s.transport, nil, unixAddr)
+		if err != nil {
+			return err
+		}
 	default:
 		return fmt.Errorf("unknown/unsupported transport: %s", s.transport)
 	}

receiver/statsdreceiver/internal/transport/packet_server.go

@@ -0,0 +1,84 @@
+// 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 (
+	"errors"
+	"net"
+
+	"go.opentelemetry.io/collector/consumer"
+)
+
+type packetServer struct {
+	packetConn net.PacketConn
+	transport  Transport
+}
+
+// ListenAndServe starts the server ready to receive metrics.
+func (u *packetServer) ListenAndServe(
+	nextConsumer consumer.Metrics,
+	reporter Reporter,
+	transferChan chan<- Metric,
+) error {
+	if nextConsumer == nil || reporter == nil {
+		return errNilListenAndServeParameters
+	}
+
+	buf := make([]byte, 65527) // max size for udp packet body (assuming ipv6)
+	for {
+		n, addr, err := u.packetConn.ReadFrom(buf)
+		if addr == nil && u.transport == UDS {
+			addr = &udsAddr{
+				network: u.transport.String(),
+				address: u.packetConn.LocalAddr().String(),
+			}
+		}
+
+		if n > 0 {
+			u.handlePacket(n, buf, addr, transferChan)
+		}
+		if err != nil {
+			reporter.OnDebugf("%s Transport (%s) - ReadFrom error: %v",
+				u.transport,
+				u.packetConn.LocalAddr(),
+				err)
+			var netErr net.Error
+			if errors.As(err, &netErr) {
+				if netErr.Timeout() {
+					continue
+				}
+			}
+			return err
+		}
+	}
+}
+
+// handlePacket is helper that parses the buffer and split it line by line to be parsed upstream.
+func (u *packetServer) handlePacket(
+	numBytes int,
+	data []byte,
+	addr net.Addr,
+	transferChan chan<- Metric,
+) {
+	splitPacket := NewSplitBytes(data[:numBytes], '\n')
+	for splitPacket.Next() {
+		chunk := splitPacket.Chunk()
+		if len(chunk) > 0 {
+			transferChan <- Metric{string(chunk), addr}
+		}
+	}
+}
+
+type udsAddr struct {
+	network string
+	address string
+}
+
+func (u *udsAddr) Network() string {
+	return u.network
+}
+
+func (u *udsAddr) String() string {
+	return u.address
+}

receiver/statsdreceiver/internal/transport/transport.go

@@ -21,6 +21,7 @@ const (
 	TCP  Transport = "tcp"
 	TCP4 Transport = "tcp4"
 	TCP6 Transport = "tcp6"
+	UDS  Transport = "unixgram"
 )
 
 // NewTransport creates a Transport based on the transport string or returns an empty Transport.
@@ -31,14 +32,16 @@ func NewTransport(ts string) Transport {
 		return trans
 	case TCP, TCP4, TCP6:
 		return trans
+	case UDS:
+		return trans
 	}
 	return Transport("")
 }
 
 // String casts the transport to a String if the Transport is supported. Return an empty Transport overwise.
 func (trans Transport) String() string {
 	switch trans {
-	case UDP, UDP4, UDP6, TCP, TCP4, TCP6:
+	case UDP, UDP4, UDP6, TCP, TCP4, TCP6, UDS:
 		return string(trans)
 	}
 	return ""
@@ -47,7 +50,7 @@ func (trans Transport) String() string {
 // IsPacketTransport returns true if the transport is packet based.
 func (trans Transport) IsPacketTransport() bool {
 	switch trans {
-	case UDP, UDP4, UDP6:
+	case UDP, UDP4, UDP6, UDS:
 		return true
 	}
 	return false

receiver/statsdreceiver/internal/transport/udp_server.go

@@ -4,16 +4,12 @@
 package transport // import "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/statsdreceiver/internal/transport"
 
 import (
-	"errors"
 	"fmt"
 	"net"
-
-	"go.opentelemetry.io/collector/consumer"
 )
 
 type udpServer struct {
-	packetConn net.PacketConn
-	transport  Transport
+	packetServer
 }
 
 // Ensure that Server is implemented on UDP Server.
@@ -31,60 +27,14 @@ func NewUDPServer(transport Transport, address string) (Server, error) {
 	}
 
 	return &udpServer{
-		packetConn: conn,
-		transport:  transport,
+		packetServer: packetServer{
+			packetConn: conn,
+			transport:  transport,
+		},
 	}, nil
 }
 
-// ListenAndServe starts the server ready to receive metrics.
-func (u *udpServer) ListenAndServe(
-	nextConsumer consumer.Metrics,
-	reporter Reporter,
-	transferChan chan<- Metric,
-) error {
-	if nextConsumer == nil || reporter == nil {
-		return errNilListenAndServeParameters
-	}
-
-	buf := make([]byte, 65527) // max size for udp packet body (assuming ipv6)
-	for {
-		n, addr, err := u.packetConn.ReadFrom(buf)
-		if n > 0 {
-			u.handlePacket(n, buf, addr, transferChan)
-		}
-		if err != nil {
-			reporter.OnDebugf("%s Transport (%s) - ReadFrom error: %v",
-				u.transport,
-				u.packetConn.LocalAddr(),
-				err)
-			var netErr net.Error
-			if errors.As(err, &netErr) {
-				if netErr.Timeout() {
-					continue
-				}
-			}
-			return err
-		}
-	}
-}
-
 // Close closes the server.
 func (u *udpServer) Close() error {
 	return u.packetConn.Close()
 }
-
-// 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,
-) {
-	splitPacket := NewSplitBytes(data[:numBytes], '\n')
-	for splitPacket.Next() {
-		chunk := splitPacket.Chunk()
-		if len(chunk) > 0 {
-			transferChan <- Metric{string(chunk), addr}
-		}
-	}
-}

receiver/statsdreceiver/internal/transport/uds_server.go

@@ -0,0 +1,42 @@
+// 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 (
+	"fmt"
+	"net"
+	"os"
+)
+
+type udsServer struct {
+	packetServer
+}
+
+// Ensure that Server is implemented on UDS Server.
+var _ (Server) = (*udsServer)(nil)
+
+// NewUDSServer creates a transport.Server using Unixgram as its transport.
+func NewUDSServer(transport Transport, socketPath string) (Server, error) {
+	if !transport.IsPacketTransport() {
+		return nil, fmt.Errorf("NewUDSServer with %s: %w", transport.String(), ErrUnsupportedPacketTransport)
+	}
+
+	conn, err := net.ListenPacket(transport.String(), socketPath)
+	if err != nil {
+		return nil, fmt.Errorf("starting to listen %s socket: %w", transport.String(), err)
+	}
+
+	return &udsServer{
+		packetServer: packetServer{
+			packetConn: conn,
+			transport:  transport,
+		},
+	}, nil
+}
+
+// Close closes the server.
+func (u *udsServer) Close() error {
+	os.Remove(u.packetConn.LocalAddr().String())
+	return u.packetConn.Close()
+}

receiver/statsdreceiver/receiver.go

@@ -46,16 +46,21 @@ func newReceiver(
 	config Config,
 	nextConsumer consumer.Metrics,
 ) (receiver.Metrics, error) {
+	trans := transport.NewTransport(strings.ToLower(string(config.NetAddr.Transport)))
+
 	if config.NetAddr.Endpoint == "" {
-		config.NetAddr.Endpoint = "localhost:8125"
+		if trans == transport.UDS {
+			config.NetAddr.Endpoint = "/var/run/statsd-receiver.sock"
+		} else {
+			config.NetAddr.Endpoint = "localhost:8125"
+		}
 	}
 
 	rep, err := newReporter(set)
 	if err != nil {
 		return nil, err
 	}
 
-	trans := transport.NewTransport(strings.ToLower(string(config.NetAddr.Transport)))
 	obsrecv, err := receiverhelper.NewObsReport(receiverhelper.ObsReportSettings{
 		LongLivedCtx:           true,
 		ReceiverID:             set.ID,
@@ -80,13 +85,14 @@ func newReceiver(
 }
 
 func buildTransportServer(config Config) (transport.Server, error) {
-	// TODO: Add unix socket transport implementations
 	trans := transport.NewTransport(strings.ToLower(string(config.NetAddr.Transport)))
 	switch trans {
 	case transport.UDP, transport.UDP4, transport.UDP6:
 		return transport.NewUDPServer(trans, config.NetAddr.Endpoint)
 	case transport.TCP, transport.TCP4, transport.TCP6:
 		return transport.NewTCPServer(trans, config.NetAddr.Endpoint)
+	case transport.UDS:
+		return transport.NewUDSServer(trans, config.NetAddr.Endpoint)
 	}
 
 	return nil, fmt.Errorf("unsupported transport %q", string(config.NetAddr.Transport))

receiver/statsdreceiver/receiver_test.go

@@ -106,6 +106,24 @@ func Test_statsdreceiver_EndToEnd(t *testing.T) {
 				return c
 			},
 		},
+		{
+			name: "UDS server with 4s interval",
+			addr: "/tmp/statsd_test.sock",
+			configFn: func() *Config {
+				return &Config{
+					NetAddr: confignet.AddrConfig{
+						Endpoint:  "/tmp/statsd_test.sock",
+						Transport: confignet.TransportTypeUnixgram,
+					},
+					AggregationInterval: 4 * time.Second,
+				}
+			},
+			clientFn: func(t *testing.T, addr string) *client.StatsD {
+				c, err := client.NewStatsD("unixgram", addr)
+				require.NoError(t, err)
+				return c
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {