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cache.go
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/
cache.go
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package middleware
import (
"fmt"
"net/http"
"time"
"github.com/francoganga/pagoda_bun/pkg/context"
"github.com/francoganga/pagoda_bun/pkg/services"
"github.com/go-redis/redis/v8"
"github.com/labstack/echo/v4"
)
// CachedPageGroup stores the cache group for cached pages
const CachedPageGroup = "page"
// CachedPage is what is used to store a rendered Page in the cache
type CachedPage struct {
// URL stores the URL of the requested page
URL string
// HTML stores the complete HTML of the rendered Page
HTML []byte
// StatusCode stores the HTTP status code
StatusCode int
// Headers stores the HTTP headers
Headers map[string]string
}
// ServeCachedPage attempts to load a page from the cache by matching on the complete request URL
// If a page is cached for the requested URL, it will be served here and the request terminated.
// Any request made by an authenticated user or that is not a GET will be skipped.
func ServeCachedPage(ch *services.CacheClient) echo.MiddlewareFunc {
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
// Skip non GET requests
if c.Request().Method != http.MethodGet {
return next(c)
}
// Skip if the user is authenticated
if c.Get(context.AuthenticatedUserKey) != nil {
return next(c)
}
// Attempt to load from cache
res, err := ch.
Get().
Group(CachedPageGroup).
Key(c.Request().URL.String()).
Type(new(CachedPage)).
Fetch(c.Request().Context())
if err != nil {
switch {
case err == redis.Nil:
c.Logger().Info("no cached page found")
case context.IsCanceledError(err):
return nil
default:
c.Logger().Errorf("failed getting cached page: %v", err)
}
return next(c)
}
page, ok := res.(*CachedPage)
if !ok {
c.Logger().Errorf("failed casting cached page")
return next(c)
}
// Set any headers
if page.Headers != nil {
for k, v := range page.Headers {
c.Response().Header().Set(k, v)
}
}
c.Logger().Info("serving cached page")
return c.HTMLBlob(page.StatusCode, page.HTML)
}
}
}
// CacheControl sets a Cache-Control header with a given max age
func CacheControl(maxAge time.Duration) echo.MiddlewareFunc {
return func(next echo.HandlerFunc) echo.HandlerFunc {
return func(c echo.Context) error {
v := "no-cache, no-store"
if maxAge > 0 {
v = fmt.Sprintf("public, max-age=%.0f", maxAge.Seconds())
}
c.Response().Header().Set("Cache-Control", v)
return next(c)
}
}
}