feat: export bad ip count per jail

Update exported metrics to spit the number of bad IPs per jail using metric
value labels. This includes a change to the database code to use a
different query that groups the count by the `jail` column.

db/db.go

@@ -3,10 +3,9 @@ package db
 import (
 	"database/sql"
 	"log"
-	"strconv"
 )
 
-const queryCountTotalBadIps = "SELECT COUNT(1) FROM bips"
+const queryBadIpsPerJail = "SELECT jail, COUNT(1) FROM bips GROUP BY jail"
 
 type Fail2BanDB struct {
 	DatabasePath string
@@ -24,22 +23,37 @@ func MustConnectToDb(databasePath string) *Fail2BanDB {
 	}
 }
 
-func (db *Fail2BanDB) CountTotalBadIps() (int, error) {
-	stmt, err := db.sqliteDB.Prepare(queryCountTotalBadIps)
+func (db *Fail2BanDB) CountBadIpsPerJail() (map[string]int, error) {
+	stmt, err := db.sqliteDB.Prepare(queryBadIpsPerJail)
 	defer db.mustCloseStatement(stmt)
 
 	if err != nil {
-		return -1, err
+		return nil, err
 	}
 
-	result := ""
-	err = stmt.QueryRow().Scan(&result)
-
+	jailNameToCountMap := map[string]int{}
+	rows, err := stmt.Query()
 	if err != nil {
-		return -1, err
+		return nil, err
+	}
+	if rows == nil {
+		return jailNameToCountMap, nil
 	}
 
-	return strconv.Atoi(result)
+	for rows.Next() {
+		if rows.Err() != nil {
+			return nil, err
+		}
+		jailName := ""
+		count := 0
+		err = rows.Scan(&jailName, &count)
+		if err != nil {
+			return nil, err
+		}
+
+		jailNameToCountMap[jailName] = count
+	}
+	return jailNameToCountMap, nil
 }
 
 func (db *Fail2BanDB) mustCloseStatement(stmt *sql.Stmt) {

exporter.go

@@ -18,10 +18,10 @@ var (
 		"Was the last fail2ban query successful.",
 		nil, nil,
 	)
-	metricBadIpTotal = prometheus.NewDesc(
-		prometheus.BuildFQName(namespace, "", "badip_total"),
-		"Total number of bad IPs stored in the database.",
-		nil, nil,
+	metricBadIpsPerJail = prometheus.NewDesc(
+		prometheus.BuildFQName(namespace, "", "bad_ips"),
+		"Number of bad IPs stored in the database (per jail).",
+		[]string{"jail"}, nil,
 	)
 )
 
@@ -30,22 +30,27 @@ type Exporter struct {
 
 func (e *Exporter) Describe(ch chan<- *prometheus.Desc) {
 	ch <- metricUp
-	ch <- metricBadIpTotal
+	ch <- metricBadIpsPerJail
 }
 
 func (e *Exporter) Collect(ch chan<- prometheus.Metric) {
 	ch <- prometheus.MustNewConstMetric(
 		metricUp, prometheus.GaugeValue, 1,
 	)
-	ch <- *collectTotalBadIpMetric()
+	collectBadIpsPerJailMetrics(ch)
 }
 
-func collectTotalBadIpMetric() *prometheus.Metric {
-	count, _ := db.CountTotalBadIps()
-	metric := prometheus.MustNewConstMetric(
-		metricBadIpTotal, prometheus.GaugeValue, float64(count),
-	)
-	return &metric
+func collectBadIpsPerJailMetrics(ch chan<- prometheus.Metric) {
+	jailNameToCountMap, err := db.CountBadIpsPerJail()
+	if err != nil {
+		log.Print(err)
+	}
+
+	for jailName, count := range jailNameToCountMap {
+		ch <- prometheus.MustNewConstMetric(
+			metricBadIpsPerJail, prometheus.GaugeValue, float64(count), jailName,
+		)
+	}
 }
 
 func main() {