Fix last scraped caching for all metrics modes (#370)

* Fix last scraped caching for all metrics modes

Signed-off-by: Anders Swanson <[email protected]>

Author: anders-swanson

collector/collector.go

@@ -168,7 +168,8 @@ func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	// otherwise do a normal scrape per request
 	e.mu.Lock() // ensure no simultaneous scrapes
 	defer e.mu.Unlock()
-	e.scrape(ch, nil)
+	now := time.Now()
+	e.scrape(ch, &now)
 	ch <- e.duration
 	ch <- e.totalScrapes
 	ch <- e.error
@@ -390,34 +391,6 @@ func hashFile(h hash.Hash, fn string) error {
 	return nil
 }
 
-func (e *Exporter) reloadMetrics() {
-	// Truncate metricsToScrape
-	e.metricsToScrape.Metric = []*Metric{}
-
-	// Load default metrics
-	defaultMetrics := e.DefaultMetrics()
-	e.metricsToScrape.Metric = defaultMetrics.Metric
-
-	// If custom metrics, load it
-	if len(e.CustomMetricsFiles()) > 0 {
-		for _, _customMetrics := range e.CustomMetricsFiles() {
-			metrics := &Metrics{}
-
-			if err := loadMetricsConfig(_customMetrics, metrics); err != nil {
-				e.logger.Error("failed to load custom metrics", "error", err)
-				panic(errors.New("Error while loading " + _customMetrics))
-			} else {
-				e.logger.Info("Successfully loaded custom metrics from " + _customMetrics)
-			}
-
-			e.metricsToScrape.Metric = append(e.metricsToScrape.Metric, metrics.Metric...)
-		}
-	} else {
-		e.logger.Debug("No custom metrics defined.")
-	}
-	e.initCache()
-}
-
 // ScrapeMetric is an interface method to call scrapeGenericValues using Metric struct values
 func (e *Exporter) ScrapeMetric(d *Database, ch chan<- prometheus.Metric, m *Metric) error {
 	e.logger.Debug("Calling function ScrapeGenericValues()")

collector/config.go

@@ -200,7 +200,7 @@ func LoadMetricsConfiguration(logger *slog.Logger, cfg *Config, path string, fla
 			return m, yerr
 		}
 	} else {
-		logger.Warn("Configuring default database from CLI parameters is deprecated. Use of the '--config.file' argument is preferred. See https://github.com/oracle/oracle-db-appdev-monitoring?tab=readme-ov-file#standalone-binary")
+		logger.Warn("Configuring default database from CLI parameters is deprecated. Use of the '--config.file' argument is preferred. See https://oracle.github.io/oracle-db-appdev-monitoring/docs/getting-started/basics#standalone-binary")
 		m.Databases = make(map[string]DatabaseConfig)
 		m.Databases["default"] = m.defaultDatabase(cfg)
 	}

collector/data_loader.go

@@ -4,6 +4,7 @@
 package collector
 
 import (
+	"errors"
 	"fmt"
 	"os"
 	"strings"
@@ -12,6 +13,34 @@ import (
 	"gopkg.in/yaml.v2"
 )
 
+func (e *Exporter) reloadMetrics() {
+	// Truncate metricsToScrape
+	e.metricsToScrape.Metric = []*Metric{}
+
+	// Load default metrics
+	defaultMetrics := e.DefaultMetrics()
+	e.metricsToScrape.Metric = defaultMetrics.Metric
+
+	// If custom metrics, load it
+	if len(e.CustomMetricsFiles()) > 0 {
+		for _, _customMetrics := range e.CustomMetricsFiles() {
+			metrics := &Metrics{}
+
+			if err := loadMetricsConfig(_customMetrics, metrics); err != nil {
+				e.logger.Error("failed to load custom metrics", "error", err)
+				panic(errors.New("Error while loading " + _customMetrics))
+			} else {
+				e.logger.Info("Successfully loaded custom metrics from " + _customMetrics)
+			}
+
+			e.metricsToScrape.Metric = append(e.metricsToScrape.Metric, metrics.Metric...)
+		}
+	} else {
+		e.logger.Debug("No custom metrics defined.")
+	}
+	e.initCache()
+}
+
 func loadYamlMetricsConfig(_metricsFileName string, metrics *Metrics) error {
 	yamlBytes, err := os.ReadFile(_metricsFileName)
 	if err != nil {

collector/metrics.go

@@ -34,7 +34,7 @@ func (e *Exporter) isScrapeMetric(tick *time.Time, metric *Metric, d *Database)
 		// we should scrape the metric.
 		interval < tick.Sub(*lastScraped)
 	if shouldScrape {
-		d.MetricsCache.SetLastScraped(metric, lastScraped)
+		d.MetricsCache.SetLastScraped(metric, tick)
 	}
 	return shouldScrape
 }
@@ -78,6 +78,15 @@ func (e *Exporter) parseFloat(metric, metricHelp string, row map[string]string)
 	return valueFloat, true
 }
 
+func (m *Metric) ID() string {
+	sb := strings.Builder{}
+	sb.WriteString(m.Context)
+	for desc := range m.MetricsDesc {
+		sb.WriteString(desc)
+	}
+	return sb.String()
+}
+
 func (m *Metric) GetLabels() []string {
 	if len(m.FieldToAppend) == 0 {
 		return m.Labels

site/docs/configuration/config-file.md

@@ -1,9 +1,9 @@
 ---
-title: Exporter Config File
+title: Exporter Configuration
 sidebar_position: 1
 ---
 
-# Exporter Config File
+# Exporter Configuration
 
 The recommended way to configure the exporter is with the `--config.file` argument, specifying a YAML configuration file.
 
@@ -92,6 +92,20 @@ log:
 #  configFile: /path/to/webconfigfile
 ```
 
+### Scrape on request vs. Scrape on interval
+
+The metrics exporter has two scraping modes: scrape on request, and scrape on interval. By default, the metrics exporter scrapes metrics on request, when the `/metrics` endpoint is invoked.
+
+To scrape metrics on a given interval, set the `metrics.scrapeInterval` property to a valid interval:
+
+```yaml
+metrics:
+  # Metrics will be scraped every 30s.
+  scrapeInterval: 30s
+```
+
+An individual metric may have its own scrape interval separate from the exporter's scrape interval. See the [metric schema](custom-metrics.md#metric-schema) for details on configuring per-metric scrape intervals.
+
 ### Config file in a container image
 
 To add your custom config file to a container image, you can layer the base exporter image and include that config:

site/docs/configuration/custom-metrics.md

@@ -38,7 +38,7 @@ Metrics files must contain a series of `[[metric]]` definitions, in TOML, or the
 | request          | Oracle database query to run for metrics scraping                                                                                                                                                                                                                                   | String                            | Yes      |                                   |
 | ignorezeroresult | Whether or not an error will be printed if the request does not return any results                                                                                                                                                                                                  | Boolean                           | No       | false                             |
 | querytimeout     | Oracle Database query timeout duration, e.g., 300ms, 0.5h                                                                                                                                                                                                                           | String duration                   | No       | Value of query.timeout in seconds |
-| scrapeinterval   | Custom metric scrape interval, used if scrape.interval is provided, otherwise metrics are always scraped on request.                                                                                                                                                                | String duration                   | No       |                                   |
+| scrapeinterval   | Custom metric scrape interval. If the metric was already scraped during the specified interval, a cached value is provided.                                                                                                                                                         | String duration                   | No       |                                   |
 | databases        | Array of databases the metric will be scraped from, using the database name from the exporter config file. If not present, the metric is scraped from all databases. If the databases array is empty (`databases = []`) the metric will not be scraped, effectively being disabled. | Array of Strings                  | No       |                                   |
 
 ### Example Metric Definition

site/docs/releases/changelog.md

@@ -15,14 +15,17 @@ Our current priorities to support metrics for advanced database features and use
 - Standardize multi-arch builds and document supported database versions.
 - Metrics with an empty databases array (`databases = []`) are now considered disabled, and will not be scraped.
 - Increased the default query timeout for the `top_sql` metric to 10 seconds (previously 5 seconds).
+- Metrics using the `scrapeinterval` property will no longer be scraped on every request if they have a cached value. This only applies when the metrics exporter is configured to scrape metrics _on request_, rather than on a global interval.
 - Metrics using the `fieldtoappend` property now support labels. The `wait_time` and `activity` default metrics use the `fieldtoappend` property, and now properly display their labels. 
 - Fix `wait_time` default metric to work with Oracle Database 19c.
+- Fix an issue where the exporter would unnecessarily scrape metrics with a custom scrape interval.
 
 Thank you to the following people for their suggestions and contributions:
 - [@romankspb](https://github.com/romankspb)
 - [@muhammadabdullah-amjad](https://github.com/muhammadabdullah-amjad)
 - [@MansuyDavid](https://github.com/MansuyDavid)
 - [@borkoz](https://github.com/borkoz)
+- [@ristagg](https://github.com/ristagg)
 
 ### Version 2.0.4, September 8, 2025