Close #74: Add maintenance window

config/maintenance/maintenance.go

@@ -0,0 +1,133 @@
+package maintenance
+
+import (
+	"errors"
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+	"time"
+)
+
+var (
+	errInvalidMaintenanceStartFormat = errors.New("invalid maintenance start format: must be hh:mm, between 00:00 and 23:59 inclusively (e.g. 23:00)")
+	errInvalidMaintenanceDuration    = errors.New("invalid maintenance duration: must be bigger than 0 (e.g. 30m)")
+	errInvalidDayName                = fmt.Errorf("invalid value specified for 'on'. supported values are %s", longDayNames)
+
+	longDayNames = []string{
+		"Sunday",
+		"Monday",
+		"Tuesday",
+		"Wednesday",
+		"Thursday",
+		"Friday",
+		"Saturday",
+	}
+)
+
+// Config allows for the configuration of a maintenance period.
+// During this maintenance period, no alerts will be sent.
+//
+// Uses UTC.
+type Config struct {
+	Enabled  *bool         `yaml:"enabled"`  // Whether the maintenance period is enabled. Enabled by default if nil.
+	Start    string        `yaml:"start"`    // Time at which the maintenance period starts (e.g. 23:00)
+	Duration time.Duration `yaml:"duration"` // Duration of the maintenance period (e.g. 4h)
+
+	// Every is a list of days of the week during which maintenance period applies.
+	// See longDayNames for list of valid values.
+	// Every day if empty.
+	Every []string `yaml:"every"`
+
+	durationToStartFromMidnight time.Duration
+	timeLocation                *time.Location
+}
+
+func GetDefaultConfig() *Config {
+	defaultValue := false
+	return &Config{
+		Enabled: &defaultValue,
+	}
+}
+
+// IsEnabled returns whether maintenance is enabled or not
+func (c Config) IsEnabled() bool {
+	if c.Enabled == nil {
+		return true
+	}
+	return *c.Enabled
+}
+
+// ValidateAndSetDefaults validates the maintenance configuration and sets the default values if necessary.
+//
+// Must be called once in the application's lifecycle before IsUnderMaintenance is called, since it
+// also sets durationToStartFromMidnight.
+func (c *Config) ValidateAndSetDefaults() error {
+	if c == nil || !c.IsEnabled() {
+		// Don't waste time validating if maintenance is not enabled.
+		return nil
+	}
+	for _, day := range c.Every {
+		isDayValid := false
+		for _, longDayName := range longDayNames {
+			if day == longDayName {
+				isDayValid = true
+				break
+			}
+		}
+		if !isDayValid {
+			return errInvalidDayName
+		}
+	}
+	var err error
+	c.durationToStartFromMidnight, err = hhmmToDuration(c.Start)
+	if err != nil {
+		return err
+	}
+	if c.Duration <= 0 || c.Duration >= 24*time.Hour {
+		return errInvalidMaintenanceDuration
+	}
+	return nil
+}
+
+// IsUnderMaintenance checks whether the services that Gatus monitors are within the configured maintenance window
+func (c Config) IsUnderMaintenance() bool {
+	if !c.IsEnabled() {
+		return false
+	}
+	now := time.Now().UTC()
+	dayWhereMaintenancePeriodWouldStart := now.Add(-c.Duration).Truncate(24 * time.Hour)
+	hasMaintenanceEveryDay := len(c.Every) == 0
+	hasMaintenancePeriodScheduledForThatWeekday := sort.SearchStrings(c.Every, dayWhereMaintenancePeriodWouldStart.Weekday().String()) != len(c.Every)
+	if !hasMaintenanceEveryDay && !hasMaintenancePeriodScheduledForThatWeekday {
+		// The day when the maintenance period would start is not scheduled
+		// to have any maintenance, so we can just return false.
+		return false
+	}
+	startOfMaintenancePeriod := dayWhereMaintenancePeriodWouldStart.Add(c.durationToStartFromMidnight)
+	endOfMaintenancePeriod := startOfMaintenancePeriod.Add(c.Duration)
+	return now.After(startOfMaintenancePeriod) && now.Before(endOfMaintenancePeriod)
+}
+
+func hhmmToDuration(s string) (time.Duration, error) {
+	if len(s) != 5 {
+		return 0, errInvalidMaintenanceStartFormat
+	}
+	var hours, minutes int
+	var err error
+	if hours, err = extractNumericalValueFromPotentiallyZeroPaddedString(s[:2]); err != nil {
+		return 0, err
+	}
+	if minutes, err = extractNumericalValueFromPotentiallyZeroPaddedString(s[3:5]); err != nil {
+		return 0, err
+	}
+	duration := (time.Duration(hours) * time.Hour) + (time.Duration(minutes) * time.Minute)
+	if hours < 0 || hours > 23 || minutes < 0 || minutes > 59 || duration < 0 || duration >= 24*time.Hour {
+		return 0, errInvalidMaintenanceStartFormat
+	}
+	return duration, nil
+}
+
+func extractNumericalValueFromPotentiallyZeroPaddedString(s string) (int, error) {
+	return strconv.Atoi(strings.TrimPrefix(s, "0"))
+}