Start building out the packages.

pkg/servers/server.go

@@ -4,14 +4,17 @@ import (
 	"database/sql"
 	"fmt"
 	"github.com/blang/semver"
+	"github.com/pkg/errors"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/common/log"
+	"github.com/wrouesnel/postgres_exporter/pkg/pgdbconv"
+	"github.com/wrouesnel/postgres_exporter/pkg/queries/metricmaps"
 	"sync"
+	"time"
 )
 
 // Server describes a connection to a Postgresql database, and describes the
 // metric maps and overrides in-place for it.
-// Also it contains metrics map and query overrides.
 type Server struct {
 	db     *sql.DB
 	labels prometheus.Labels
@@ -21,7 +24,7 @@ type Server struct {
 	// then maps are recalculated.
 	lastMapVersion semver.Version
 	// Currently active metric map
-	metricMap map[string]MetricMapNamespace
+	metricMap map[string]metricmaps.MetricMapNamespace
 	// Currently active query overrides
 	queryOverrides map[string]string
 	mappingMtx     sync.RWMutex
@@ -50,7 +53,7 @@ func NewServer(dsn string, opts ...ServerOpt) (*Server, error) {
 		db:     db,
 		master: false,
 		labels: prometheus.Labels{
-			serverLabelName: fingerprint,
+			metricmaps.ServerLabelName: fingerprint,
 		},
 		metricCache: make(map[string]cachedMetrics),
 	}
@@ -80,7 +83,7 @@ func (s *Server) Ping() error {
 
 // String returns server's fingerprint.
 func (s *Server) String() string {
-	return s.labels[serverLabelName]
+	return s.labels[metricmaps.ServerLabelName]
 }
 
 // Scrape loads metrics.
@@ -104,9 +107,211 @@ func (s *Server) Scrape(ch chan<- prometheus.Metric, disableSettingsMetrics bool
 	return err
 }
 
+// Query within a namespace mapping and emit metrics. Returns fatal errors if
+// the scrape fails, and a slice of errors if they were non-fatal.
+func (s *Server) queryNamespaceMapping(namespace string, mapping MetricMapNamespace) ([]prometheus.Metric, []error, error) {
+	// Check for a query override for this namespace
+	query, found := s.queryOverrides[namespace]
+
+	// Was this query disabled (i.e. nothing sensible can be queried on cu
+	// version of PostgreSQL?
+	if query == "" && found {
+		// Return success (no pertinent data)
+		return []prometheus.Metric{}, []error{}, nil
+	}
+
+	// Don't fail on a bad scrape of one metric
+	var rows *sql.Rows
+	var err error
+
+	if !found {
+		// I've no idea how to avoid this properly at the moment, but this is
+		// an admin tool so you're not injecting SQL right?
+		rows, err = s.db.Query(fmt.Sprintf("SELECT * FROM %s;", namespace)) // nolint: gas, safesql
+	} else {
+		rows, err = s.db.Query(query) // nolint: safesql
+	}
+	if err != nil {
+		return []prometheus.Metric{}, []error{}, fmt.Errorf("Error running query on database %q: %s %v", s, namespace, err)
+	}
+	defer rows.Close() // nolint: errcheck
+
+	var columnNames []string
+	columnNames, err = rows.Columns()
+	if err != nil {
+		return []prometheus.Metric{}, []error{}, errors.New(fmt.Sprintln("Error retrieving column list for: ", namespace, err))
+	}
+
+	// Make a lookup map for the column indices
+	var columnIdx = make(map[string]int, len(columnNames))
+	for i, n := range columnNames {
+		columnIdx[n] = i
+	}
+
+	var columnData = make([]interface{}, len(columnNames))
+	var scanArgs = make([]interface{}, len(columnNames))
+	for i := range columnData {
+		scanArgs[i] = &columnData[i]
+	}
+
+	nonfatalErrors := []error{}
+
+	metrics := make([]prometheus.Metric, 0)
+
+	for rows.Next() {
+		err = rows.Scan(scanArgs...)
+		if err != nil {
+			return []prometheus.Metric{}, []error{}, errors.New(fmt.Sprintln("Error retrieving rows:", namespace, err))
+		}
+
+		// Get the label values for this row.
+		labels := make([]string, len(mapping.labels))
+		for idx, label := range mapping.labels {
+			labels[idx], _ = pgdbconv.DBToString(columnData[columnIdx[label]])
+		}
+
+		// Loop over column names, and match to scan data. Unknown columns
+		// will be filled with an untyped metric number *if* they can be
+		// converted to float64s. NULLs are allowed and treated as NaN.
+		for idx, columnName := range columnNames {
+			var metric prometheus.Metric
+			if metricMapping, ok := mapping.columnMappings[columnName]; ok {
+				// Is this a metricy metric?
+				if metricMapping.discard {
+					continue
+				}
+
+				value, ok := pgdbconv.DBToFloat64(columnData[idx])
+				if !ok {
+					nonfatalErrors = append(nonfatalErrors, errors.New(fmt.Sprintln("Unexpected error parsing column: ", namespace, columnName, columnData[idx])))
+					continue
+				}
+				// Generate the metric
+				metric = prometheus.MustNewConstMetric(metricMapping.desc, metricMapping.vtype, value, labels...)
+			} else {
+				// Unknown metric. Report as untyped if scan to float64 works, else note an error too.
+				metricLabel := fmt.Sprintf("%s_%s", namespace, columnName)
+				desc := prometheus.NewDesc(metricLabel, fmt.Sprintf("Unknown metric from %s", namespace), mapping.labels, s.labels)
+
+				// Its not an error to fail here, since the values are
+				// unexpected anyway.
+				value, ok := pgdbconv.DBToFloat64(columnData[idx])
+				if !ok {
+					nonfatalErrors = append(nonfatalErrors, errors.New(fmt.Sprintln("Unparseable column type - discarding: ", namespace, columnName, err)))
+					continue
+				}
+				metric = prometheus.MustNewConstMetric(desc, prometheus.UntypedValue, value, labels...)
+			}
+			metrics = append(metrics, metric)
+		}
+	}
+	return metrics, nonfatalErrors, nil
+}
+
+// Iterate through all the namespace mappings in the exporter and run their
+// queries.
+func (s *Server) queryNamespaceMappings(ch chan<- prometheus.Metric) map[string]error {
+	// Return a map of namespace -> errors
+	namespaceErrors := make(map[string]error)
+
+	scrapeStart := time.Now()
+
+	for namespace, mapping := range s.metricMap {
+		log.Debugln("Querying namespace: ", namespace)
+
+		if mapping.master && !s.master {
+			log.Debugln("Query skipped...")
+			continue
+		}
+
+		scrapeMetric := false
+		// Check if the metric is cached
+		s.cacheMtx.Lock()
+		cachedMetric, found := s.metricCache[namespace]
+		s.cacheMtx.Unlock()
+		// If found, check if needs refresh from cache
+		if found {
+			if scrapeStart.Sub(cachedMetric.lastScrape).Seconds() > float64(mapping.cacheSeconds) {
+				scrapeMetric = true
+			}
+		} else {
+			scrapeMetric = true
+		}
+
+		var metrics []prometheus.Metric
+		var nonFatalErrors []error
+		var err error
+		if scrapeMetric {
+			metrics, nonFatalErrors, err = s.queryNamespaceMapping(namespace, mapping)
+		} else {
+			metrics = cachedMetric.metrics
+		}
+
+		// Serious error - a namespace disappeared
+		if err != nil {
+			namespaceErrors[namespace] = err
+			log.Infoln(err)
+		}
+		// Non-serious errors - likely version or parsing problems.
+		if len(nonFatalErrors) > 0 {
+			for _, err := range nonFatalErrors {
+				log.Infoln(err.Error())
+			}
+		}
+
+		// Emit the metrics into the channel
+		for _, metric := range metrics {
+			ch <- metric
+		}
+
+		if scrapeMetric {
+			// Only cache if metric is meaningfully cacheable
+			if mapping.cacheSeconds > 0 {
+				s.cacheMtx.Lock()
+				s.metricCache[namespace] = cachedMetrics{
+					metrics:    metrics,
+					lastScrape: scrapeStart,
+				}
+				s.cacheMtx.Unlock()
+			}
+		}
+	}
+
+	return namespaceErrors
+}
+
+
 // AddQueries adds queries to the builtinMetricMaps and queryOverrides maps.
 // Added queries do not respect version requirements, because it is assumed
 // that the user knows what they are doing with their version of postgres.
 func (s *Server) AddQueries() {
 
+}
+
+// Query the pg_settings view containing runtime variables
+func (s *Server) querySettings(ch chan<- prometheus.Metric) error {
+	log.Debugf("Querying pg_setting view on %q", s)
+
+	// pg_settings docs: https://www.postgresql.org/docs/current/static/view-pg-settings.html
+	//
+	// NOTE: If you add more vartypes here, you must update the supported
+	// types in normaliseUnit() below
+	query := "SELECT name, setting, COALESCE(unit, ''), short_desc, vartype FROM pg_settings WHERE vartype IN ('bool', 'integer', 'real');"
+
+	rows, err := s.db.Query(query)
+	if err != nil {
+		return fmt.Errorf("Error running query on database %q: %s %v", s, metricmaps.ExporterNamespaceLabel, err)
+	}
+	defer rows.Close() // nolint: errcheck
+
+	for rows.Next() {
+		setting := &pgSetting{}
+		err = rows.Scan(&setting.name, &setting.setting, &setting.unit, &setting.shortDesc, &setting.vartype)
+		if err != nil {
+			return fmt.Errorf("Error retrieving rows on %q: %s %v", s, metricmaps.ExporterNamespaceLabel, err)
+		}
+
+		ch <- setting.metric(s.labels)
+	}
+	return nil
 }