From b74852a5353b4bf2cb2cc944f329d651fbf99064 Mon Sep 17 00:00:00 2001
From: Joe Adams <github@joeadams.io>
Date: Wed, 23 Aug 2023 17:33:47 -0400
Subject: [PATCH] Delay database connection until scrape (#882)
This no longer returns an error when creating a collector.instance when the database cannot be reached for the version query. This will resolve the entire postgresCollector not being registered for metrics collection when a database is not available. If the version query fails, the scrape will fail.
Resolves #880
Signed-off-by: Joe Adams <github@joeadams.io>
---
collector/collector.go | 8 ++++++++
collector/instance.go | 30 ++++++++++++++++++++++--------
collector/probe.go | 8 ++++++++
3 files changed, 38 insertions(+), 8 deletions(-)
diff --git a/collector/collector.go b/collector/collector.go
index c1bf2af9..e06ef7d1 100644
--- a/collector/collector.go
+++ b/collector/collector.go
@@ -166,6 +166,14 @@ func (p PostgresCollector) Describe(ch chan<- *prometheus.Desc) {
// Collect implements the prometheus.Collector interface.
func (p PostgresCollector) Collect(ch chan<- prometheus.Metric) {
ctx := context.TODO()
+
+ // Set up the database connection for the collector.
+ err := p.instance.setup()
+ if err != nil {
+ level.Error(p.logger).Log("msg", "Error opening connection to database", "err", err)
+ return
+ }
+
wg := sync.WaitGroup{}
wg.Add(len(p.Collectors))
for name, c := range p.Collectors {
diff --git a/collector/instance.go b/collector/instance.go
index 9b2bbf47..87eb0591 100644
--- a/collector/instance.go
+++ b/collector/instance.go
@@ -22,29 +22,43 @@ import (
)
type instance struct {
+ dsn string
db *sql.DB
version semver.Version
}
func newInstance(dsn string) (*instance, error) {
- i := &instance{}
+ i := &instance{
+ dsn: dsn,
+ }
+
+ // "Create" a database handle to verify the DSN provided is valid.
+ // Open is not guaranteed to create a connection.
db, err := sql.Open("postgres", dsn)
if err != nil {
return nil, err
}
+ db.Close()
+
+ return i, nil
+}
+
+func (i *instance) setup() error {
+ db, err := sql.Open("postgres", i.dsn)
+ if err != nil {
+ return err
+ }
db.SetMaxOpenConns(1)
db.SetMaxIdleConns(1)
i.db = db
- version, err := queryVersion(db)
+ version, err := queryVersion(i.db)
if err != nil {
- db.Close()
- return nil, err
+ return fmt.Errorf("error querying postgresql version: %w", err)
+ } else {
+ i.version = version
}
-
- i.version = version
-
- return i, nil
+ return nil
}
func (i *instance) getDB() *sql.DB {
diff --git a/collector/probe.go b/collector/probe.go
index 834c6517..a7630272 100644
--- a/collector/probe.go
+++ b/collector/probe.go
@@ -18,6 +18,7 @@ import (
"sync"
"github.com/go-kit/log"
+ "github.com/go-kit/log/level"
"github.com/prometheus-community/postgres_exporter/config"
"github.com/prometheus/client_golang/prometheus"
)
@@ -74,6 +75,13 @@ func (pc *ProbeCollector) Describe(ch chan<- *prometheus.Desc) {
}
func (pc *ProbeCollector) Collect(ch chan<- prometheus.Metric) {
+ // Set up the database connection for the collector.
+ err := pc.instance.setup()
+ if err != nil {
+ level.Error(pc.logger).Log("msg", "Error opening connection to database", "err", err)
+ return
+ }
+
wg := sync.WaitGroup{}
wg.Add(len(pc.collectors))
for name, c := range pc.collectors {