func New()

in api/api.go [97:155]
54 lines of code
9 McCabe index (conditional complexity)

func New(opts Options) (*API, error) {
	if err := opts.validate(); err != nil {
		return nil, fmt.Errorf("invalid API options: %w", err)
	}
	l := opts.Logger
	if l == nil {
		l = log.NewNopLogger()
	}
	concurrency := opts.Concurrency
	if concurrency < 1 {
		concurrency = runtime.GOMAXPROCS(0)
		if concurrency < 8 {
			concurrency = 8
		}
	}

	v2, err := apiv2.NewAPI(
		opts.Alerts,
		opts.GroupFunc,
		opts.StatusFunc,
		opts.Silences,
		opts.Peer,
		log.With(l, "version", "v2"),
		opts.Registry,
	)
	if err != nil {
		return nil, err
	}

	// TODO(beorn7): For now, this hardcodes the method="get" label. Other
	// methods should get the same instrumentation.
	requestsInFlight := prometheus.NewGauge(prometheus.GaugeOpts{
		Name:        "alertmanager_http_requests_in_flight",
		Help:        "Current number of HTTP requests being processed.",
		ConstLabels: prometheus.Labels{"method": "get"},
	})
	concurrencyLimitExceeded := prometheus.NewCounter(prometheus.CounterOpts{
		Name:        "alertmanager_http_concurrency_limit_exceeded_total",
		Help:        "Total number of times an HTTP request failed because the concurrency limit was reached.",
		ConstLabels: prometheus.Labels{"method": "get"},
	})
	if opts.Registry != nil {
		if err := opts.Registry.Register(requestsInFlight); err != nil {
			return nil, err
		}
		if err := opts.Registry.Register(concurrencyLimitExceeded); err != nil {
			return nil, err
		}
	}

	return &API{
		deprecationRouter:        NewV1DeprecationRouter(log.With(l, "version", "v1")),
		v2:                       v2,
		requestsInFlight:         requestsInFlight,
		concurrencyLimitExceeded: concurrencyLimitExceeded,
		timeout:                  opts.Timeout,
		inFlightSem:              make(chan struct{}, concurrency),
	}, nil
}