[receiver/statsd] Clean up stale unix socket on startup

Remove any existing socket file before calling net.ListenPacket to
prevent "address already in use" errors when the receiver restarts
after an unclean shutdown (crash, SIGKILL). This is standard practice
for unix socket servers.

Fixes #44866

Author: Vanshul97

.chloggen/fix-statsd-uds-socket-cleanup.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: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. receiver/filelog)
+component: receiver/statsd
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Clean up stale unix socket file on startup to prevent "address already in use" errors after unclean shutdown.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [44866]
+
+# (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/internal/transport/uds_server.go

@@ -22,6 +22,11 @@ func NewUDSServer(transport Transport, socketPath string, socketPermissions os.F
 		return nil, fmt.Errorf("NewUDSServer with %s: %w", transport.String(), ErrUnsupportedPacketTransport)
 	}
 
+	// Remove any stale socket file from a previous instance that didn't
+	// shut down cleanly (e.g., crash, SIGKILL). Ignore errors since the
+	// file may not exist on first startup.
+	_ = os.Remove(socketPath)
+
 	conn, err := net.ListenPacket(transport.String(), socketPath)
 	if err != nil {
 		return nil, fmt.Errorf("starting to listen %s socket: %w", transport.String(), err)

receiver/statsdreceiver/internal/transport/uds_server_test.go

@@ -40,6 +40,32 @@ func Test_UDSServer_Close(t *testing.T) {
 	assert.True(t, os.IsNotExist(err))
 }
 
+func Test_NewUDSServer_CleansUpStaleSocket(t *testing.T) {
+	socketPath := "/tmp/test_socket_stale"
+	defer os.Remove(socketPath)
+
+	// Create first server
+	server1, err := NewUDSServer("unixgram", socketPath, 0o622)
+	require.NoError(t, err)
+	require.NotNil(t, server1)
+
+	// Simulate a crash — close the connection but leave the socket file
+	// (don't call server1.Close() which would remove the file)
+	server1.(*udsServer).packetConn.Close()
+
+	// Verify socket file still exists (simulating stale socket after crash)
+	_, err = os.Stat(socketPath)
+	require.NoError(t, err, "socket file should still exist after simulated crash")
+
+	// Create second server on the same path — should succeed
+	server2, err := NewUDSServer("unixgram", socketPath, 0o622)
+	require.NoError(t, err, "should be able to start a new server on the same socket path")
+	require.NotNil(t, server2)
+
+	err = server2.Close()
+	assert.NoError(t, err)
+}
+
 func Test_NewUDSServer_AppliesChmod(t *testing.T) {
 	socketPath := "/tmp/test_socket_chmod"
 	defer os.Remove(socketPath) // Cleanup after test