fix: protect publish path from mysql exhaustion

server/metrics/db_pool_test.go

@@ -0,0 +1,47 @@
+package metrics
+
+import (
+	"database/sql"
+	"testing"
+	"time"
+)
+
+type fixedDBStats struct {
+	stats sql.DBStats
+}
+
+func (s fixedDBStats) Stats() sql.DBStats { return s.stats }
+
+func TestDBPoolCollector(t *testing.T) {
+	RegisterDBPool("test", fixedDBStats{stats: sql.DBStats{
+		MaxOpenConnections: 32,
+		OpenConnections:    12,
+		InUse:              7,
+		Idle:               5,
+		WaitCount:          9,
+		WaitDuration:       1500 * time.Millisecond,
+	}})
+
+	families, err := Registry.Gather()
+	if err != nil {
+		t.Fatal(err)
+	}
+	want := map[string]bool{
+		"im_db_pool_max_open_connections":        false,
+		"im_db_pool_open_connections":            false,
+		"im_db_pool_in_use_connections":          false,
+		"im_db_pool_idle_connections":            false,
+		"im_db_pool_wait_total":                  false,
+		"im_db_pool_wait_duration_seconds_total": false,
+	}
+	for _, family := range families {
+		if _, ok := want[family.GetName()]; ok {
+			want[family.GetName()] = true
+		}
+	}
+	for name, found := range want {
+		if !found {
+			t.Errorf("metric %s was not gathered", name)
+		}
+	}
+}