fix(inputs.postgresql_extensible): Use same timestamp for each gather

Rather than using a different timestamp for each query, this uses a
single timestamp determined at the start of gather, for any and all
metrics generated during that gather.

While the timestamp might be off from when the actual queries are run,
it combines all metrics around a single timestamp to better understand
when data was captured.

fixes: #9737

plugins/inputs/postgresql_extensible/postgresql_extensible.go

@@ -114,17 +114,21 @@ func (p *Postgresql) Gather(acc telegraf.Accumulator) error {
 		dbVersion = 0
 	}
 
+	// set default timestamp to Now and use for all generated metrics during
+	// the same Gather call
+	timestamp := time.Now()
+
 	// We loop in order to process each query
 	// Query is not run if Database version does not match the query version.
 	for _, q := range p.Query {
 		if q.MinVersion <= dbVersion && (q.MaxVersion == 0 || q.MaxVersion > dbVersion) {
-			acc.AddError(p.gatherMetricsFromQuery(acc, q))
+			acc.AddError(p.gatherMetricsFromQuery(acc, q, timestamp))
 		}
 	}
 	return nil
 }
 
-func (p *Postgresql) gatherMetricsFromQuery(acc telegraf.Accumulator, q query) error {
+func (p *Postgresql) gatherMetricsFromQuery(acc telegraf.Accumulator, q query, timestamp time.Time) error {
 	rows, err := p.service.DB.Query(q.Sqlquery)
 	if err != nil {
 		return err
@@ -139,7 +143,7 @@ func (p *Postgresql) gatherMetricsFromQuery(acc telegraf.Accumulator, q query) e
 	}
 
 	for rows.Next() {
-		if err := p.accRow(acc, rows, columns, q); err != nil {
+		if err := p.accRow(acc, rows, columns, q, timestamp); err != nil {
 			return err
 		}
 	}
@@ -150,7 +154,7 @@ type scanner interface {
 	Scan(dest ...interface{}) error
 }
 
-func (p *Postgresql) accRow(acc telegraf.Accumulator, row scanner, columns []string, q query) error {
+func (p *Postgresql) accRow(acc telegraf.Accumulator, row scanner, columns []string, q query, timestamp time.Time) error {
 	// this is where we'll store the column name with its *interface{}
 	columnMap := make(map[string]*interface{})
 
@@ -188,9 +192,6 @@ func (p *Postgresql) accRow(acc telegraf.Accumulator, row scanner, columns []str
 		"db":     dbname.String(),
 	}
 
-	// set default timestamp to Now
-	timestamp := time.Now()
-
 	fields := make(map[string]interface{})
 	for col, val := range columnMap {
 		p.Log.Debugf("Column: %s = %T: %v\n", col, *val, *val)

plugins/inputs/postgresql_extensible/postgresql_extensible_test.go

@@ -338,7 +338,7 @@ func TestAccRow(t *testing.T) {
 	}
 	for _, tt := range tests {
 		q := query{Measurement: "pgTEST", additionalTags: make(map[string]bool)}
-		require.NoError(t, p.accRow(&acc, tt.fields, columns, q))
+		require.NoError(t, p.accRow(&acc, tt.fields, columns, q, time.Now()))
 		require.Len(t, acc.Metrics, 1)
 		metric := acc.Metrics[0]
 		require.Equal(t, tt.dbName, metric.Tags["db"])