[receiver/haproxy] fix the show stat command (#32366)

**Description:**
Fix an issue where we called `show stats` instead of `show stat`.
This also fixes the situation where no records are present by properly
trimming the data.

**Link to tracking Issue:**
Fixes #32291

**Testing:**
Added a unit test.

Author: atoulme

.chloggen/haproxy_stat.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. filelogreceiver)
+component: haproxyreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Fix show stat command on unix socket
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [32291]
+
+# (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/haproxyreceiver/scraper.go

@@ -28,7 +28,7 @@ import (
 )
 
 var (
-	showStatsCommand = []byte("show stats\n")
+	showStatsCommand = []byte("show stat\n")
 )
 
 type scraper struct {
@@ -71,13 +71,14 @@ func (s *scraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 			return pmetric.NewMetrics(), err
 		}
 		buf := make([]byte, 4096)
-		_, err = c.Read(buf)
+		n, err := c.Read(buf)
 		if err != nil {
 			return pmetric.NewMetrics(), err
 		}
+		buf = buf[0:n]
 		records, err = s.readStats(buf)
 		if err != nil {
-			return pmetric.NewMetrics(), err
+			return pmetric.NewMetrics(), fmt.Errorf("error reading stats: %w", err)
 		}
 	}
 
@@ -262,7 +263,7 @@ func (s *scraper) scrape(ctx context.Context) (pmetric.Metrics, error) {
 }
 
 func (s *scraper) readStats(buf []byte) ([]map[string]string, error) {
-	reader := csv.NewReader(bytes.NewReader(buf))
+	reader := csv.NewReader(bytes.NewReader(bytes.TrimSpace(buf)))
 	headers, err := reader.Read()
 	if err != nil {
 		return nil, err

receiver/haproxyreceiver/scraper_test.go

@@ -36,7 +36,7 @@ func Test_scraper_readStats(t *testing.T) {
 
 		data := string(buf[0:nr])
 		switch data {
-		case "show stats\n":
+		case "show stat\n":
 			stats, err2 := os.ReadFile(filepath.Join("testdata", "stats.txt"))
 			require.NoError(t, err2)
 			_, err2 = c.Write(stats)
@@ -79,7 +79,7 @@ func Test_scraper_readStatsWithIncompleteValues(t *testing.T) {
 
 		data := string(buf[0:nr])
 		switch data {
-		case "show stats\n":
+		case "show stat\n":
 			stats, err2 := os.ReadFile(filepath.Join("testdata", "30252_stats.txt"))
 			require.NoError(t, err2)
 			_, err2 = c.Write(stats)
@@ -103,3 +103,41 @@ func Test_scraper_readStatsWithIncompleteValues(t *testing.T) {
 		pmetrictest.IgnoreTimestamp(), pmetrictest.IgnoreResourceAttributeValue("haproxy.addr"),
 		pmetrictest.IgnoreResourceMetricsOrder()))
 }
+
+func Test_scraper_readStatsWithNoValues(t *testing.T) {
+	f, err := os.MkdirTemp("", "haproxytest")
+	require.NoError(t, err)
+	socketAddr := filepath.Join(f, "testhaproxy.sock")
+	l, err := net.Listen("unix", socketAddr)
+	require.NoError(t, err)
+	defer l.Close()
+
+	go func() {
+		c, err2 := l.Accept()
+		require.NoError(t, err2)
+
+		buf := make([]byte, 512)
+		nr, err2 := c.Read(buf)
+		require.NoError(t, err2)
+
+		data := string(buf[0:nr])
+		switch data {
+		case "show stat\n":
+			stats, err2 := os.ReadFile(filepath.Join("testdata", "empty_stats.txt"))
+			require.NoError(t, err2)
+			_, err2 = c.Write(stats)
+			require.NoError(t, err2)
+		default:
+			require.Fail(t, fmt.Sprintf("invalid message: %v", data))
+		}
+	}()
+
+	haProxyCfg := newDefaultConfig().(*Config)
+	haProxyCfg.Endpoint = socketAddr
+	s := newScraper(haProxyCfg, receivertest.NewNopCreateSettings())
+	m, err := s.scrape(context.Background())
+	require.NoError(t, err)
+	require.NotNil(t, m)
+
+	require.Equal(t, 0, m.MetricCount())
+}

receiver/haproxyreceiver/testdata/empty_stats.txt

@@ -0,0 +1,3 @@
+# pxname,svname,qcur,qmax,scur,smax,slim,stot,bin,bout,dreq,dresp,ereq,econ,eresp,wretr,wredis,status,weight,act,bck,chkfail,chkdown,lastchg,downtime,qlimit,pid,iid,sid,throttle,lbtot,tracked,type,rate,rate_lim,rate_max,check_status,check_code,check_duration,hrsp_1xx,hrsp_2xx,hrsp_3xx,hrsp_4xx,hrsp_5xx,hrsp_other,hanafail,req_rate,req_rate_max,req_tot,cli_abrt,srv_abrt,comp_in,comp_out,comp_byp,comp_rsp,lastsess,last_chk,last_agt,qtime,ctime,rtime,ttime,agent_status,agent_code,agent_duration,check_desc,agent_desc,check_rise,check_fall,check_health,agent_rise,agent_fall,agent_health,addr,cookie,mode,algo,conn_rate,conn_rate_max,conn_tot,intercepted,dcon,dses,wrew,connect,reuse,cache_lookups,cache_hits,srv_icur,src_ilim,qtime_max,ctime_max,rtime_max,ttime_max,eint,idle_conn_cur,safe_conn_cur,used_conn_cur,need_conn_est,uweight,agg_server_status,agg_server_check_status,agg_check_status,srid,sess_other,h1sess,h2sess,h3sess,req_other,h1req,h2req,h3req,proto,-,ssl_sess,ssl_reused_sess,ssl_failed_handshake,h2_headers_rcvd,h2_data_rcvd,h2_settings_rcvd,h2_rst_stream_rcvd,h2_goaway_rcvd,h2_detected_conn_protocol_errors,h2_detected_strm_protocol_errors,h2_rst_stream_resp,h2_goaway_resp,h2_open_connections,h2_backend_open_streams,h2_total_connections,h2_backend_total_streams,h1_open_connections,h1_open_streams,h1_total_connections,h1_total_streams,h1_bytes_in,h1_bytes_out,
+
+