Cleanup collectors (#826)

Fix up `replication` and `process_idle` Update input params to match
the rest of the collectors.

Signed-off-by: SuperQ <superq@gmail.com>

Author: SuperQ

collector/pg_process_idle.go

@@ -43,8 +43,8 @@ var pgProcessIdleSeconds = prometheus.NewDesc(
 	prometheus.Labels{},
 )
 
-func (PGProcessIdleCollector) Update(ctx context.Context, inst *instance, ch chan<- prometheus.Metric) error {
-	db := inst.getDB()
+func (PGProcessIdleCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	row := db.QueryRowContext(ctx,
 		`WITH
 			metrics AS (

collector/pg_replication.go

@@ -15,7 +15,6 @@ package collector
 
 import (
 	"context"
-	"database/sql"
 
 	"github.com/prometheus/client_golang/prometheus"
 )
@@ -64,7 +63,8 @@ var (
 	END as is_replica`
 )
 
-func (c *PGReplicationCollector) Update(ctx context.Context, db *sql.DB, ch chan<- prometheus.Metric) error {
+func (c *PGReplicationCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
+	db := instance.getDB()
 	row := db.QueryRowContext(ctx,
 		pgReplicationQuery,
 	)

collector/pg_replication_test.go

@@ -29,6 +29,8 @@ func TestPgReplicationCollector(t *testing.T) {
 	}
 	defer db.Close()
 
+	inst := &instance{db: db}
+
 	columns := []string{"lag", "is_replica"}
 	rows := sqlmock.NewRows(columns).
 		AddRow(1000, 1)
@@ -39,7 +41,7 @@ func TestPgReplicationCollector(t *testing.T) {
 		defer close(ch)
 		c := PGReplicationCollector{}
 
-		if err := c.Update(context.Background(), db, ch); err != nil {
+		if err := c.Update(context.Background(), inst, ch); err != nil {
 			t.Errorf("Error calling PGReplicationCollector.Update: %s", err)
 		}
 	}()