Add database metrics into pgxconn package.

Signed-off-by: Harkishen-Singh <harkishensingh@hotmail.com>

This commit updates the implementation of pgx in pkg/pgxconn
package and implements the following database metrics:
1. promscale_database_requests_total
2. promscale_database_request_errors_total
3. promscale_database_request_duration_seconds

go.sum

@@ -1214,8 +1214,6 @@ github.com/jackc/pgx/v4 v4.0.0-20190420224344-cc3461e65d96/go.mod h1:mdxmSJJuR08
 github.com/jackc/pgx/v4 v4.0.0-20190421002000-1b8f0016e912/go.mod h1:no/Y67Jkk/9WuGR0JG/JseM9irFbnEPbuWV2EELPNuM=
 github.com/jackc/pgx/v4 v4.0.0-pre1.0.20190824185557-6972a5742186/go.mod h1:X+GQnOEnf1dqHGpw7JmHqHc1NxDoalibchSk9/RWuDc=
 github.com/jackc/pgx/v4 v4.12.1-0.20210724153913-640aa07df17c/go.mod h1:1QD0+tgSXP7iUjYm9C1NxKhny7lq6ee99u/z+IHFcgs=
-github.com/jackc/pgx/v4 v4.15.0 h1:B7dTkXsdILD3MF987WGGCcg+tvLW6bZJdEcqVFeU//w=
-github.com/jackc/pgx/v4 v4.15.0/go.mod h1:D/zyOyXiaM1TmVWnOM18p0xdDtdakRBa0RsVGI3U3bw=
 github.com/jackc/pgx/v4 v4.15.1-0.20220219175125-b6b24f9e8a5d h1:8r5Lurk3Ur6K9Tz94Zz3kekJLZ8iVAG/GWHNqtLlmnw=
 github.com/jackc/pgx/v4 v4.15.1-0.20220219175125-b6b24f9e8a5d/go.mod h1:D/zyOyXiaM1TmVWnOM18p0xdDtdakRBa0RsVGI3U3bw=
 github.com/jackc/puddle v0.0.0-20190413234325-e4ced69a3a2b/go.mod h1:m4B5Dj62Y0fbyuIc15OsIqK0+JU8nkqQjsgx7dvjSWk=

pkg/pgclient/client.go

@@ -8,10 +8,15 @@ import (
 	"context"
 	"fmt"
 	"net/url"
+	"os"
+	"time"
 
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v4"
 	"github.com/jackc/pgx/v4/pgxpool"
+	"github.com/prometheus/client_golang/prometheus"
+	"go.opentelemetry.io/collector/model/pdata"
+
 	"github.com/timescale/promscale/pkg/ha"
 	"github.com/timescale/promscale/pkg/log"
 	"github.com/timescale/promscale/pkg/pgmodel/cache"
@@ -25,7 +30,7 @@ import (
 	"github.com/timescale/promscale/pkg/query"
 	"github.com/timescale/promscale/pkg/telemetry"
 	"github.com/timescale/promscale/pkg/tenancy"
-	"go.opentelemetry.io/collector/model/pdata"
+	"github.com/timescale/promscale/pkg/util"
 )
 
 var PromscaleID uuid.UUID
@@ -55,6 +60,7 @@ type Client struct {
 	sigClose          chan struct{}
 	haService         *ha.Service
 	TelemetryEngine   telemetry.Engine
+	stopHealthChecker context.CancelFunc
 }
 
 // NewClient creates a new PostgreSQL client
@@ -179,19 +185,22 @@ func NewClientWithPool(cfg *Config, numCopiers int, connPool *pgxpool.Pool, mt t
 		}
 	}
 
-	healthChecker := health.NewHealthChecker(dbConn)
+	healthCheckerCtx, stopHealthChecker := context.WithCancel(context.Background())
+	healthCheckRoutine(healthCheckerCtx, dbConn)
+
 	client := &Client{
 		Connection:        dbConn,
 		QuerierConnection: dbQuerierConn,
 		ingestor:          dbIngestor,
 		querier:           dbQuerier,
-		healthCheck:       healthChecker,
+		healthCheck:       health.NewHealthChecker(dbConn),
 		queryable:         queryable,
 		metricCache:       metricsCache,
 		labelsCache:       labelsCache,
 		seriesCache:       seriesCache,
 		sigClose:          sigClose,
 		TelemetryEngine:   telemetryEngine,
+		stopHealthChecker: stopHealthChecker,
 	}
 
 	InitClientMetrics(client)
@@ -201,6 +210,9 @@ func NewClientWithPool(cfg *Config, numCopiers int, connPool *pgxpool.Pool, mt t
 // Close closes the client and performs cleanup
 func (c *Client) Close() {
 	log.Info("msg", "Shutting down Client")
+	if c.stopHealthChecker != nil {
+		c.stopHealthChecker()
+	}
 	if c.TelemetryEngine != nil {
 		c.TelemetryEngine.Stop()
 	}
@@ -297,3 +309,43 @@ func observeStatementCacheState(conn *pgx.Conn) bool {
 	statementCacheLen.Observe(float64(statementCacheSize))
 	return true
 }
+
+func healthCheckRoutine(ctx context.Context, conn pgxconn.PgxConn) {
+	r := prometheus.DefaultRegisterer
+	if env := os.Getenv("IS_TEST"); env == "true" {
+		r = prometheus.NewRegistry()
+	}
+	dbHealthChecks := prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: util.PromNamespace,
+			Subsystem: "database",
+			Name:      "health_checks_total",
+			Help:      "Total number of database health checks performed.",
+		},
+	)
+	dbHealthErrors := prometheus.NewCounter(
+		prometheus.CounterOpts{
+			Namespace: util.PromNamespace,
+			Subsystem: "database",
+			Name:      "health_check_errors_total",
+			Help:      "Total number of database health check errors.",
+		},
+	)
+	r.MustRegister(dbHealthChecks, dbHealthErrors)
+	go func() {
+		check := time.NewTicker(time.Minute)
+		defer check.Stop()
+		connection := health.NewHealthChecker(conn)
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-check.C:
+			}
+			dbHealthChecks.Inc()
+			if err := connection(); err != nil {
+				dbHealthErrors.Inc()
+			}
+		}
+	}()
+}

pkg/pgxconn/pgx_conn.go

@@ -13,9 +13,47 @@ import (
 	"github.com/jackc/pgconn"
 	"github.com/jackc/pgx/v4"
 	"github.com/jackc/pgx/v4/pgxpool"
+	"github.com/prometheus/client_golang/prometheus"
+
 	"github.com/timescale/promscale/pkg/log"
+	"github.com/timescale/promscale/pkg/util"
+)
+
+var (
+	requestTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: util.PromNamespace,
+			Subsystem: "database",
+			Name:      "requests_total",
+			Help:      "Total number of database requests.",
+		}, []string{"method"},
+	)
+	errorsTotal = prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Namespace: util.PromNamespace,
+			Subsystem: "database",
+			Name:      "request_errors_total",
+			Help:      "Total number of database request errors.",
+		}, []string{"method"},
+	)
+	duration = prometheus.NewHistogramVec(
+		prometheus.HistogramOpts{
+			Namespace: util.PromNamespace,
+			Subsystem: "database",
+			Name:      "requests_duration_seconds",
+			Help:      "Time taken to complete a database request.",
+		}, []string{"method"},
+	)
 )
 
+func init() {
+	prometheus.MustRegister(requestTotal, errorsTotal, duration)
+}
+
+func getLabelSet(method string) prometheus.Labels {
+	return prometheus.Labels{"method": method}
+}
+
 type PgxBatch interface {
 	Queue(query string, arguments ...interface{})
 	Len() int
@@ -109,15 +147,53 @@ func (p *connImpl) Close() {
 }
 
 func (p *connImpl) Exec(ctx context.Context, sql string, args ...interface{}) (pgconn.CommandTag, error) {
-	return p.Conn.Exec(ctx, sql, args...)
+	lset := getLabelSet("exec")
+	requestTotal.With(lset).Inc()
+	start := time.Now()
+	defer func() {
+		duration.With(lset).Observe(time.Since(start).Seconds())
+	}()
+	tag, err := p.Conn.Exec(ctx, sql, args...)
+	if err != nil {
+		errorsTotal.With(lset).Inc()
+	}
+	return tag, err
 }
 
 func (p *connImpl) Query(ctx context.Context, sql string, args ...interface{}) (PgxRows, error) {
-	return p.Conn.Query(ctx, sql, args...)
+	lset := getLabelSet("query")
+	requestTotal.With(lset).Inc()
+	start := time.Now()
+	defer func() {
+		duration.With(lset).Observe(time.Since(start).Seconds())
+	}()
+	rows, err := p.Conn.Query(ctx, sql, args...)
+	if err != nil {
+		errorsTotal.With(lset).Inc()
+	}
+	return rows, err
 }
 
 func (p *connImpl) QueryRow(ctx context.Context, sql string, args ...interface{}) pgx.Row {
-	return p.Conn.QueryRow(ctx, sql, args...)
+	lset := getLabelSet("query_row")
+	requestTotal.With(lset).Inc()
+	start := time.Now()
+	defer func() {
+		duration.With(lset).Observe(time.Since(start).Seconds())
+	}()
+	return &rowWrapper{p.Conn.QueryRow(ctx, sql, args...)}
+}
+
+type rowWrapper struct {
+	r pgx.Row
+}
+
+func (w *rowWrapper) Scan(dest ...interface{}) error {
+	err := w.r.Scan(dest...)
+	if err != nil {
+		errorsTotal.With(getLabelSet("query_row")).Inc()
+	}
+	return err
 }
 
 func (p *connImpl) CopyFrom(ctx context.Context, tableName pgx.Identifier, columnNames []string, rowSrc pgx.CopyFromSource) (int64, error) {
@@ -133,6 +209,12 @@ func (p *connImpl) NewBatch() PgxBatch {
 }
 
 func (p *connImpl) SendBatch(ctx context.Context, b PgxBatch) (pgx.BatchResults, error) {
+	lset := getLabelSet("send_batch")
+	requestTotal.With(lset).Inc()
+	start := time.Now()
+	defer func() {
+		duration.With(lset).Observe(time.Since(start).Seconds())
+	}()
 	return p.Conn.SendBatch(ctx, b.(*pgx.Batch)), nil
 }