package main import ( "bytes" "errors" "fmt" "os/exec" "text/template" "time" "git.iamthefij.com/iamthefij/slog" ) var ( errNoTemplate = errors.New("no template") // ErrAlertFailed indicates that an alert failed to send ErrAlertFailed = errors.New("alert failed") ) // Alert is a config driven mechanism for sending a notice type Alert struct { Name string Command CommandOrShell commandTemplate []*template.Template commandShellTemplate *template.Template } // AlertNotice captures the context for an alert to be sent type AlertNotice struct { AlertCount int16 FailureCount int16 IsUp bool LastSuccess time.Time MonitorName string LastCheckOutput string } // IsValid returns a boolean indicating if the Alert has been correctly // configured func (alert Alert) IsValid() bool { return !alert.Command.Empty() } // BuildTemplates compiles command templates for the Alert func (alert *Alert) BuildTemplates() error { slog.Debugf("Building template for alert %s", alert.Name) switch { case alert.commandTemplate == nil && alert.Command.Command != nil: alert.commandTemplate = []*template.Template{} for i, cmdPart := range alert.Command.Command { alert.commandTemplate = append(alert.commandTemplate, template.Must( template.New(alert.Name+fmt.Sprint(i)).Parse(cmdPart), )) } case alert.commandShellTemplate == nil && alert.Command.ShellCommand != "": shellCmd := alert.Command.ShellCommand alert.commandShellTemplate = template.Must( template.New(alert.Name).Parse(shellCmd), ) default: return fmt.Errorf("No template provided for alert %s: %w", alert.Name, errNoTemplate) } return nil } // Send will send an alert notice by executing the command template func (alert Alert) Send(notice AlertNotice) (outputStr string, err error) { slog.Infof("Sending alert %s for %s", alert.Name, notice.MonitorName) var cmd *exec.Cmd switch { case alert.commandTemplate != nil: command := []string{} for _, cmdTmp := range alert.commandTemplate { var commandBuffer bytes.Buffer err = cmdTmp.Execute(&commandBuffer, notice) if err != nil { return } command = append(command, commandBuffer.String()) } cmd = exec.Command(command[0], command[1:]...) case alert.commandShellTemplate != nil: var commandBuffer bytes.Buffer err = alert.commandShellTemplate.Execute(&commandBuffer, notice) if err != nil { return } shellCommand := commandBuffer.String() cmd = ShellCommand(shellCommand) default: err = fmt.Errorf("No templates compiled for alert %s: %w", alert.Name, errNoTemplate) return } // Exit if we're not ready to run the command if cmd == nil || err != nil { return } var output []byte output, err = cmd.CombinedOutput() outputStr = string(output) slog.Debugf("Alert output for: %s\n---\n%s\n---", alert.Name, outputStr) if err != nil { err = fmt.Errorf( "Alert '%s' failed to send. Returned %v: %w", alert.Name, err, ErrAlertFailed, ) } return outputStr, err } // NewLogAlert creates an alert that does basic logging using echo func NewLogAlert() *Alert { return &Alert{ Name: "log", Command: CommandOrShell{ Command: []string{ "echo", "{{.MonitorName}} {{if .IsUp}}has recovered{{else}}check has failed {{.FailureCount}} times{{end}}", }, }, } }