error-pages/internal/checkers/health.go

package checkers

import (
	"context"
	"fmt"
	"net/http"
	"time"
)

type httpClient interface {
	Do(*http.Request) (*http.Response, error)
}

// HealthChecker is a heals checker.
type HealthChecker struct {
	ctx        context.Context
	httpClient httpClient
}

const defaultHTTPClientTimeout = time.Second * 3

// NewHealthChecker creates heals checker.
func NewHealthChecker(ctx context.Context, client ...httpClient) *HealthChecker {
	var c httpClient

	if len(client) == 1 {
		c = client[0]
	} else {
		c = &http.Client{Timeout: defaultHTTPClientTimeout} // default
	}

	return &HealthChecker{ctx: ctx, httpClient: c}
}

// Check application using liveness probe.
func (c *HealthChecker) Check(port uint16) error {
	req, err := http.NewRequestWithContext(c.ctx, http.MethodGet, fmt.Sprintf("http://127.0.0.1:%d/healthz", port), nil) //nolint:lll
	if err != nil {
		return err
	}

	req.Header.Set("User-Agent", "HealthChecker/internal")

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return err
	}

	_ = resp.Body.Close()

	if code := resp.StatusCode; code != http.StatusOK {
		return fmt.Errorf("wrong status code [%d] from live endpoint", code)
	}

	return nil
}