fix(inputs.socket_listener): fix tracking of unix sockets

This fixes an issue where the code would lose track of unix sockets. The remote end of a unix socket does not have a unique address representation, thus multiple entries may overwrite each other in the map. This changes the map to key off the net.Conn object itself, basically using the map as a set.

Fixes influxdata#13058

plugins/inputs/socket_listener/socket_listener_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"os"
 	"path/filepath"
@@ -15,6 +16,7 @@ import (
 	"time"
 
 	"github.com/google/go-cmp/cmp"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
 	"github.com/influxdata/telegraf"
@@ -181,6 +183,16 @@ func TestSocketListener(t *testing.T) {
 			}, time.Second, 100*time.Millisecond, "did not receive metrics (%d)", acc.NMetrics())
 			actual := acc.GetTelegrafMetrics()
 			testutil.RequireMetricsEqual(t, expected, actual, testutil.SortMetrics())
+
+			plugin.Stop()
+
+			if _, ok := plugin.listener.(*streamListener); ok {
+				// Verify that plugin.Stop() closed the client's connection
+				_ = client.SetReadDeadline(time.Now().Add(time.Second))
+				buf := []byte{1}
+				_, err = client.Read(buf)
+				assert.Equal(t, err, io.EOF)
+			}
 		})
 	}
 }

plugins/inputs/socket_listener/stream_listener.go

@@ -32,7 +32,7 @@ type streamListener struct {
 	Log             telegraf.Logger
 
 	listener    net.Listener
-	connections map[string]net.Conn
+	connections map[net.Conn]struct{}
 	path        string
 
 	wg sync.WaitGroup
@@ -123,7 +123,7 @@ func (l *streamListener) setupConnection(conn net.Conn) error {
 
 	// Store the connection mapped to its address
 	l.Lock()
-	l.connections[addr] = conn
+	l.connections[conn] = struct{}{}
 	l.Unlock()
 
 	return nil
@@ -134,7 +134,7 @@ func (l *streamListener) closeConnection(conn net.Conn) {
 	if err := conn.Close(); err != nil {
 		l.Log.Errorf("Cannot close connection to %q: %v", addr, err)
 	}
-	delete(l.connections, addr)
+	delete(l.connections, conn)
 }
 
 func (l *streamListener) addr() net.Addr {
@@ -147,7 +147,7 @@ func (l *streamListener) close() error {
 	}
 
 	l.Lock()
-	for _, conn := range l.connections {
+	for conn := range l.connections {
 		l.closeConnection(conn)
 	}
 	l.Unlock()
@@ -164,7 +164,7 @@ func (l *streamListener) close() error {
 }
 
 func (l *streamListener) listen(acc telegraf.Accumulator) {
-	l.connections = make(map[string]net.Conn)
+	l.connections = make(map[net.Conn]struct{})
 
 	l.wg.Add(1)
 	defer l.wg.Done()