[receiver/postgresqlreceiver] [fix] Support postgres 17 table schema (o…

…pen-telemetry#36813)

<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
#### Description
Support collecting bgwriter metrics from postgres17. 

<!-- Issue number (e.g. open-telemetry#1234) or full URL to issue, if applicable. -->
#### Link to tracking issue
Fixes
open-telemetry#36784

<!--Describe what testing was performed and which tests were added.-->
#### Testing
Updated integration tests, tested locally.

<!--Please delete paragraphs that you did not use before submitting.-->

.chloggen/postgresql-17-bgwriter.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: postgresqlreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Update the postgresqlreceiver to handle new table schema for the bgwriter metrics in pg17+"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [36784]
+
+# (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/postgresqlreceiver/client.go

@@ -9,6 +9,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"strconv"
 	"strings"
 	"time"
 
@@ -56,6 +57,7 @@ type client interface {
 	getMaxConnections(ctx context.Context) (int64, error)
 	getIndexStats(ctx context.Context, database string) (map[indexIdentifer]indexStat, error)
 	listDatabases(ctx context.Context) ([]string, error)
+	getVersion(ctx context.Context) (string, error)
 }
 
 type postgreSQLClient struct {
@@ -442,7 +444,6 @@ type bgStat struct {
 	checkpointWriteTime  float64
 	checkpointSyncTime   float64
 	bgWrites             int64
-	backendWrites        int64
 	bufferBackendWrites  int64
 	bufferFsyncWrites    int64
 	bufferCheckpoints    int64
@@ -451,54 +452,105 @@ type bgStat struct {
 }
 
 func (c *postgreSQLClient) getBGWriterStats(ctx context.Context) (*bgStat, error) {
-	query := `SELECT
-	checkpoints_req AS checkpoint_req,
-	checkpoints_timed AS checkpoint_scheduled,
-	checkpoint_write_time AS checkpoint_duration_write,
-	checkpoint_sync_time AS checkpoint_duration_sync,
-	buffers_clean AS bg_writes,
-	buffers_backend AS backend_writes,
-	buffers_backend_fsync AS buffers_written_fsync,
-	buffers_checkpoint AS buffers_checkpoints,
-	buffers_alloc AS buffers_allocated,
-	maxwritten_clean AS maxwritten_count
-	FROM pg_stat_bgwriter;`
+	version, err := c.getVersion(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	major, err := parseMajorVersion(version)
+	if err != nil {
+		return nil, err
+	}
 
-	row := c.client.QueryRowContext(ctx, query)
 	var (
 		checkpointsReq, checkpointsScheduled               int64
 		checkpointSyncTime, checkpointWriteTime            float64
 		bgWrites, bufferCheckpoints, bufferAllocated       int64
 		bufferBackendWrites, bufferFsyncWrites, maxWritten int64
 	)
-	err := row.Scan(
-		&checkpointsReq,
-		&checkpointsScheduled,
-		&checkpointWriteTime,
-		&checkpointSyncTime,
-		&bgWrites,
-		&bufferBackendWrites,
-		&bufferFsyncWrites,
-		&bufferCheckpoints,
-		&bufferAllocated,
-		&maxWritten,
-	)
-	if err != nil {
-		return nil, err
+
+	if major < 17 {
+		query := `SELECT
+		checkpoints_req AS checkpoint_req,
+		checkpoints_timed AS checkpoint_scheduled,
+		checkpoint_write_time AS checkpoint_duration_write,
+		checkpoint_sync_time AS checkpoint_duration_sync,
+		buffers_clean AS bg_writes,
+		buffers_backend AS backend_writes,
+		buffers_backend_fsync AS buffers_written_fsync,
+		buffers_checkpoint AS buffers_checkpoints,
+		buffers_alloc AS buffers_allocated,
+		maxwritten_clean AS maxwritten_count
+		FROM pg_stat_bgwriter;`
+
+		row := c.client.QueryRowContext(ctx, query)
+
+		if err = row.Scan(
+			&checkpointsReq,
+			&checkpointsScheduled,
+			&checkpointWriteTime,
+			&checkpointSyncTime,
+			&bgWrites,
+			&bufferBackendWrites,
+			&bufferFsyncWrites,
+			&bufferCheckpoints,
+			&bufferAllocated,
+			&maxWritten,
+		); err != nil {
+			return nil, err
+		}
+		return &bgStat{
+			checkpointsReq:       checkpointsReq,
+			checkpointsScheduled: checkpointsScheduled,
+			checkpointWriteTime:  checkpointWriteTime,
+			checkpointSyncTime:   checkpointSyncTime,
+			bgWrites:             bgWrites,
+			bufferBackendWrites:  bufferBackendWrites,
+			bufferFsyncWrites:    bufferFsyncWrites,
+			bufferCheckpoints:    bufferCheckpoints,
+			buffersAllocated:     bufferAllocated,
+			maxWritten:           maxWritten,
+		}, nil
+	} else {
+		query := `SELECT
+		cp.num_requested AS checkpoint_req,
+		cp.num_timed AS checkpoint_scheduled,
+		cp.write_time AS checkpoint_duration_write,
+		cp.sync_time AS checkpoint_duration_sync,
+		cp.buffers_written AS buffers_checkpoints,
+		bg.buffers_clean AS bg_writes,
+		bg.buffers_alloc AS buffers_allocated,
+		bg.maxwritten_clean AS maxwritten_count
+		FROM pg_stat_bgwriter bg, pg_stat_checkpointer cp;`
+
+		row := c.client.QueryRowContext(ctx, query)
+
+		if err = row.Scan(
+			&checkpointsReq,
+			&checkpointsScheduled,
+			&checkpointWriteTime,
+			&checkpointSyncTime,
+			&bufferCheckpoints,
+			&bgWrites,
+			&bufferAllocated,
+			&maxWritten,
+		); err != nil {
+			return nil, err
+		}
+
+		return &bgStat{
+			checkpointsReq:       checkpointsReq,
+			checkpointsScheduled: checkpointsScheduled,
+			checkpointWriteTime:  checkpointWriteTime,
+			checkpointSyncTime:   checkpointSyncTime,
+			bgWrites:             bgWrites,
+			bufferBackendWrites:  -1, // Not found in pg17+ tables
+			bufferFsyncWrites:    -1, // Not found in pg17+ tables
+			bufferCheckpoints:    bufferCheckpoints,
+			buffersAllocated:     bufferAllocated,
+			maxWritten:           maxWritten,
+		}, nil
 	}
-	return &bgStat{
-		checkpointsReq:       checkpointsReq,
-		checkpointsScheduled: checkpointsScheduled,
-		checkpointWriteTime:  checkpointWriteTime,
-		checkpointSyncTime:   checkpointSyncTime,
-		bgWrites:             bgWrites,
-		backendWrites:        bufferBackendWrites,
-		bufferBackendWrites:  bufferBackendWrites,
-		bufferFsyncWrites:    bufferFsyncWrites,
-		bufferCheckpoints:    bufferCheckpoints,
-		buffersAllocated:     bufferAllocated,
-		maxWritten:           maxWritten,
-	}, nil
 }
 
 func (c *postgreSQLClient) getMaxConnections(ctx context.Context) (int64, error) {
@@ -641,6 +693,23 @@ func (c *postgreSQLClient) listDatabases(ctx context.Context) ([]string, error)
 	return databases, nil
 }
 
+func (c *postgreSQLClient) getVersion(ctx context.Context) (string, error) {
+	query := "SHOW server_version;"
+	row := c.client.QueryRowContext(ctx, query)
+	var version string
+	err := row.Scan(&version)
+	return version, err
+}
+
+func parseMajorVersion(ver string) (int, error) {
+	parts := strings.Split(ver, ".")
+	if len(parts) < 2 {
+		return 0, fmt.Errorf("unexpected version string: %s", ver)
+	}
+
+	return strconv.Atoi(parts[0])
+}
+
 func filterQueryByDatabases(baseQuery string, databases []string, groupBy bool) string {
 	if len(databases) > 0 {
 		var queryDatabases []string

receiver/postgresqlreceiver/integration_test.go

@@ -6,6 +6,7 @@
 package postgresqlreceiver
 
 import (
+	"fmt"
 	"net"
 	"path/filepath"
 	"testing"
@@ -22,37 +23,44 @@ import (
 
 const postgresqlPort = "5432"
 
+const (
+	pre17TestVersion  = "13.18"
+	post17TestVersion = "17.2"
+)
+
 func TestIntegration(t *testing.T) {
 	defer testutil.SetFeatureGateForTest(t, separateSchemaAttrGate, false)()
 	defer testutil.SetFeatureGateForTest(t, connectionPoolGate, false)()
-	t.Run("single_db", integrationTest("single_db", []string{"otel"}))
-	t.Run("multi_db", integrationTest("multi_db", []string{"otel", "otel2"}))
-	t.Run("all_db", integrationTest("all_db", []string{}))
+	t.Run("single_db", integrationTest("single_db", []string{"otel"}, pre17TestVersion))
+	t.Run("multi_db", integrationTest("multi_db", []string{"otel", "otel2"}, pre17TestVersion))
+	t.Run("all_db", integrationTest("all_db", []string{}, pre17TestVersion))
+
+	t.Run("single_db_post17", integrationTest("single_db_post17", []string{"otel"}, post17TestVersion))
 }
 
 func TestIntegrationWithSeparateSchemaAttr(t *testing.T) {
 	defer testutil.SetFeatureGateForTest(t, separateSchemaAttrGate, true)()
 	defer testutil.SetFeatureGateForTest(t, connectionPoolGate, false)()
-	t.Run("single_db_schemaattr", integrationTest("single_db_schemaattr", []string{"otel"}))
-	t.Run("multi_db_schemaattr", integrationTest("multi_db_schemaattr", []string{"otel", "otel2"}))
-	t.Run("all_db_schemaattr", integrationTest("all_db_schemaattr", []string{}))
+	t.Run("single_db_schemaattr", integrationTest("single_db_schemaattr", []string{"otel"}, pre17TestVersion))
+	t.Run("multi_db_schemaattr", integrationTest("multi_db_schemaattr", []string{"otel", "otel2"}, pre17TestVersion))
+	t.Run("all_db_schemaattr", integrationTest("all_db_schemaattr", []string{}, pre17TestVersion))
 }
 
 func TestIntegrationWithConnectionPool(t *testing.T) {
 	defer testutil.SetFeatureGateForTest(t, separateSchemaAttrGate, false)()
 	defer testutil.SetFeatureGateForTest(t, connectionPoolGate, true)()
-	t.Run("single_db_connpool", integrationTest("single_db_connpool", []string{"otel"}))
-	t.Run("multi_db_connpool", integrationTest("multi_db_connpool", []string{"otel", "otel2"}))
-	t.Run("all_db_connpool", integrationTest("all_db_connpool", []string{}))
+	t.Run("single_db_connpool", integrationTest("single_db_connpool", []string{"otel"}, pre17TestVersion))
+	t.Run("multi_db_connpool", integrationTest("multi_db_connpool", []string{"otel", "otel2"}, pre17TestVersion))
+	t.Run("all_db_connpool", integrationTest("all_db_connpool", []string{}, pre17TestVersion))
 }
 
-func integrationTest(name string, databases []string) func(*testing.T) {
+func integrationTest(name string, databases []string, pgVersion string) func(*testing.T) {
 	expectedFile := filepath.Join("testdata", "integration", "expected_"+name+".yaml")
 	return scraperinttest.NewIntegrationTest(
 		NewFactory(),
 		scraperinttest.WithContainerRequest(
 			testcontainers.ContainerRequest{
-				Image: "postgres:13.18",
+				Image: fmt.Sprintf("postgres:%s", pgVersion),
 				Env: map[string]string{
 					"POSTGRES_USER":     "root",
 					"POSTGRES_PASSWORD": "otel",

receiver/postgresqlreceiver/scraper.go

@@ -304,9 +304,13 @@ func (p *postgreSQLScraper) collectBGWriterStats(
 	p.mb.RecordPostgresqlBgwriterBuffersAllocatedDataPoint(now, bgStats.buffersAllocated)
 
 	p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bgWrites, metadata.AttributeBgBufferSourceBgwriter)
-	p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bufferBackendWrites, metadata.AttributeBgBufferSourceBackend)
+	if bgStats.bufferBackendWrites >= 0 {
+		p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bufferBackendWrites, metadata.AttributeBgBufferSourceBackend)
+	}
 	p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bufferCheckpoints, metadata.AttributeBgBufferSourceCheckpoints)
-	p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bufferFsyncWrites, metadata.AttributeBgBufferSourceBackendFsync)
+	if bgStats.bufferFsyncWrites >= 0 {
+		p.mb.RecordPostgresqlBgwriterBuffersWritesDataPoint(now, bgStats.bufferFsyncWrites, metadata.AttributeBgBufferSourceBackendFsync)
+	}
 
 	p.mb.RecordPostgresqlBgwriterCheckpointCountDataPoint(now, bgStats.checkpointsReq, metadata.AttributeBgCheckpointTypeRequested)
 	p.mb.RecordPostgresqlBgwriterCheckpointCountDataPoint(now, bgStats.checkpointsScheduled, metadata.AttributeBgCheckpointTypeScheduled)

receiver/postgresqlreceiver/scraper_test.go

@@ -452,6 +452,11 @@ func (m *mockClient) listDatabases(_ context.Context) ([]string, error) {
 	return args.Get(0).([]string), args.Error(1)
 }
 
+func (m *mockClient) getVersion(_ context.Context) (string, error) {
+	args := m.Called()
+	return args.String(0), args.Error(1)
+}
+
 func (m *mockClientFactory) getClient(database string) (client, error) {
 	args := m.Called(database)
 	return args.Get(0).(client), args.Error(1)
@@ -511,7 +516,6 @@ func (m *mockClient) initMocks(database string, schema string, databases []strin
 			checkpointWriteTime:  3.12,
 			checkpointSyncTime:   4.23,
 			bgWrites:             5,
-			backendWrites:        6,
 			bufferBackendWrites:  7,
 			bufferFsyncWrites:    8,
 			bufferCheckpoints:    9,