package main import ( "log" "math" "os/exec" "time" ) // Monitor represents a particular periodic check of a command type Monitor struct { // Config values Name string Command []string CommandShell string `yaml:"command_shell"` AlertDown []string `yaml:"alert_down"` AlertUp []string `yaml:"alert_up"` CheckInterval float64 `yaml:"check_interval"` AlertAfter int16 `yaml:"alert_after"` AlertEvery int16 `yaml:"alert_every"` // Other values lastCheck time.Time lastOutput string alertCount int16 failureCount int16 lastSuccess time.Time } // IsValid returns a boolean indicating if the Monitor has been correctly // configured func (monitor Monitor) IsValid() bool { atLeastOneCommand := (monitor.CommandShell != "" || monitor.Command != nil) atMostOneCommand := (monitor.CommandShell == "" || monitor.Command == nil) return atLeastOneCommand && atMostOneCommand && monitor.getAlertAfter() > 0 } // ShouldCheck returns a boolean indicating if the Monitor is ready to be // be checked again func (monitor Monitor) ShouldCheck() bool { if monitor.lastCheck.IsZero() { return true } sinceLastCheck := time.Now().Sub(monitor.lastCheck).Seconds() return sinceLastCheck >= monitor.CheckInterval } // Check will run the command configured by the Monitor and return a status // and a possible AlertNotice func (monitor *Monitor) Check() (bool, *AlertNotice) { var cmd *exec.Cmd if monitor.Command != nil { cmd = exec.Command(monitor.Command[0], monitor.Command[1:]...) } else { cmd = ShellCommand(monitor.CommandShell) } output, err := cmd.CombinedOutput() monitor.lastCheck = time.Now() monitor.lastOutput = string(output) var alertNotice *AlertNotice isSuccess := (err == nil) if isSuccess { alertNotice = monitor.success() } else { alertNotice = monitor.failure() } if LogDebug { log.Printf("DEBUG: Command output: %s", monitor.lastOutput) } if err != nil { if LogDebug { log.Printf("DEBUG: Command result: %v", err) } } log.Printf( "INFO: %s success=%t, alert=%t", monitor.Name, isSuccess, alertNotice != nil, ) return isSuccess, alertNotice } func (monitor Monitor) isUp() bool { return monitor.alertCount == 0 } func (monitor *Monitor) success() (notice *AlertNotice) { if !monitor.isUp() { // Alert that we have recovered notice = monitor.createAlertNotice(true) } monitor.failureCount = 0 monitor.alertCount = 0 monitor.lastSuccess = time.Now() return } func (monitor *Monitor) failure() (notice *AlertNotice) { monitor.failureCount++ // If we haven't hit the minimum failures, we can exit if monitor.failureCount < monitor.getAlertAfter() { if LogDebug { log.Printf( "DEBUG: %s failed but did not hit minimum failures. "+ "Count: %v alert after: %v", monitor.Name, monitor.failureCount, monitor.getAlertAfter(), ) } return } // Take number of failures after minimum failureCount := (monitor.failureCount - monitor.getAlertAfter()) // Use alert cadence to determine if we should alert if monitor.AlertEvery > 0 { // Handle integer number of failures before alerting if failureCount%monitor.AlertEvery == 0 { notice = monitor.createAlertNotice(false) } } else if monitor.AlertEvery == 0 { // Handle alerting on first failure only if failureCount == 0 { notice = monitor.createAlertNotice(false) } } else { // Handle negative numbers indicating an exponential backoff if failureCount >= int16(math.Pow(2, float64(monitor.alertCount))-1) { notice = monitor.createAlertNotice(false) } } // If we're going to alert, increment count if notice != nil { monitor.alertCount++ } return } func (monitor Monitor) getAlertAfter() int16 { // TODO: Come up with a better way than this method // Zero is one! if monitor.AlertAfter == 0 { return 1 } else { return monitor.AlertAfter } } // GetAlertNames gives a list of alert names for a given monitor status func (monitor Monitor) GetAlertNames(up bool) []string { if up { return monitor.AlertUp } else { return monitor.AlertDown } } func (monitor Monitor) createAlertNotice(isUp bool) *AlertNotice { // TODO: Maybe add something about recovery status here return &AlertNotice{ MonitorName: monitor.Name, AlertCount: monitor.alertCount, FailureCount: monitor.failureCount, LastCheckOutput: monitor.lastOutput, LastSuccess: monitor.lastSuccess, IsUp: isUp, } }