// FileChecker checks the existence of a file and returns an error
// if the file exists.
func FileChecker(f string) health.Checker {
return health.CheckFunc(func() error {
if _, err := os.Stat(f); err == nil {
return errors.New("file exists")
}
return nil
})
}
// TCPChecker attempts to open a TCP connection.
func TCPChecker(addr string, timeout time.Duration) health.Checker {
return health.CheckFunc(func() error {
conn, err := net.DialTimeout("tcp", addr, timeout)
if err != nil {
return errors.New("connection to " + addr + " failed")
}
conn.Close()
return nil
})
}
// HTTPChecker does a HEAD request and verifies if the HTTP status
// code return is a 200, taking the application out of rotation if
// otherwise
func HTTPChecker(r string) health.Checker {
return health.CheckFunc(func() error {
response, err := http.Head(r)
if err != nil {
return errors.New("error while checking: " + r)
}
if response.StatusCode != http.StatusOK {
return errors.New("downstream service returned unexpected status: " + string(response.StatusCode))
}
return nil
})
}
// Start checks the modules for the following interfaces and registers and/or starts:
// Startable:
// health.Checker:
// Endpoint: Register the handler function of the Endpoint in the http service at prefix
func (s *Service) Start() error {
el := protocol.NewErrorList("service: errors occured while starting: ")
if s.healthEndpoint != "" {
loggerService.WithField("healthEndpoint", s.healthEndpoint).Info("Health endpoint")
s.webserver.Handle(s.healthEndpoint, http.HandlerFunc(health.StatusHandler))
} else {
loggerService.Info("Health endpoint disabled")
}
if s.metricsEndpoint != "" {
loggerService.WithField("metricsEndpoint", s.metricsEndpoint).Info("Metrics endpoint")
s.webserver.Handle(s.metricsEndpoint, http.HandlerFunc(metrics.HttpHandler))
} else {
loggerService.Info("Metrics endpoint disabled")
}
for _, module := range s.modules {
name := reflect.TypeOf(module).String()
if startable, ok := module.(Startable); ok {
loggerService.WithFields(log.Fields{
"name": name,
}).Info("Starting module")
if err := startable.Start(); err != nil {
loggerService.WithFields(log.Fields{
"name": name,
"err": err,
}).Error("Error while starting module")
el.Add(err)
}
}
if checker, ok := module.(health.Checker); ok && s.healthEndpoint != "" {
loggerService.WithField("name", name).Info("Registering module as Health-Checker")
health.RegisterPeriodicThresholdFunc(name, s.healthFrequency, s.healthThreshold, health.CheckFunc(checker.Check))
}
if endpoint, ok := module.(Endpoint); ok {
prefix := endpoint.GetPrefix()
loggerService.WithFields(log.Fields{
"name": name,
"prefix": prefix,
}).Info("Registering module as Endpoint")
s.webserver.Handle(prefix, endpoint)
}
}
return el.ErrorOrNil()
}
// Start checks the modules for the following interfaces and registers and/or starts:
// Startable:
// health.Checker:
// Endpoint: Register the handler function of the Endpoint in the http service at prefix
func (s *Service) Start() error {
var multierr *multierror.Error
if s.healthEndpoint != "" {
logger.WithField("healthEndpoint", s.healthEndpoint).Info("Health endpoint")
s.webserver.Handle(s.healthEndpoint, http.HandlerFunc(health.StatusHandler))
} else {
logger.Info("Health endpoint disabled")
}
if s.metricsEndpoint != "" {
logger.WithField("metricsEndpoint", s.metricsEndpoint).Info("Metrics endpoint")
s.webserver.Handle(s.metricsEndpoint, http.HandlerFunc(metrics.HttpHandler))
} else {
logger.Info("Metrics endpoint disabled")
}
for order, iface := range s.ModulesSortedByStartOrder() {
name := reflect.TypeOf(iface).String()
if s, ok := iface.(Startable); ok {
logger.WithFields(log.Fields{"name": name, "order": order}).Info("Starting module")
if err := s.Start(); err != nil {
logger.WithError(err).WithField("name", name).Error("Error while starting module")
multierr = multierror.Append(multierr, err)
}
} else {
logger.WithFields(log.Fields{"name": name, "order": order}).Debug("Module is not startable")
}
if c, ok := iface.(health.Checker); ok && s.healthEndpoint != "" {
logger.WithField("name", name).Info("Registering module as Health-Checker")
health.RegisterPeriodicThresholdFunc(name, s.healthFrequency, s.healthThreshold, health.CheckFunc(c.Check))
}
if e, ok := iface.(Endpoint); ok {
prefix := e.GetPrefix()
logger.WithFields(log.Fields{"name": name, "prefix": prefix}).Info("Registering module as Endpoint")
s.webserver.Handle(prefix, e)
}
}
return multierr.ErrorOrNil()
}
// HTTPChecker does a HEAD request and verifies that the HTTP status code
// returned matches statusCode.
func HTTPChecker(r string, statusCode int, timeout time.Duration, headers http.Header) health.Checker {
return health.CheckFunc(func() error {
client := http.Client{
Timeout: timeout,
}
req, err := http.NewRequest("HEAD", r, nil)
if err != nil {
return errors.New("error creating request: " + r)
}
for headerName, headerValues := range headers {
for _, headerValue := range headerValues {
req.Header.Add(headerName, headerValue)
}
}
response, err := client.Do(req)
if err != nil {
return errors.New("error while checking: " + r)
}
if response.StatusCode != statusCode {
return errors.New("downstream service returned unexpected status: " + strconv.Itoa(response.StatusCode))
}
return nil
})
}