Merge pull request #47 from fastly/joeshaw/to-upstream/cache-and-purge-api

Author: joeshaw

_examples/corecache/main.go

@@ -0,0 +1,140 @@
+package main
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+	"time"
+
+	"github.com/fastly/compute-sdk-go/cache/core"
+	"github.com/fastly/compute-sdk-go/fsthttp"
+	"github.com/fastly/compute-sdk-go/purge"
+)
+
+func main() {
+	fsthttp.ServeFunc(func(ctx context.Context, w fsthttp.ResponseWriter, r *fsthttp.Request) {
+		key := keyForRequest(r)
+		switch r.Method {
+
+		// Fetch content from the cache.
+		case "GET":
+			tx, err := core.NewTransaction(key, core.LookupOptions{})
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+			defer tx.Close()
+
+			f, err := tx.Found()
+			if errors.Is(err, core.ErrNotFound) {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusNotFound)
+				return
+			}
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+			defer f.Body.Close()
+
+			msg, err := io.ReadAll(f.Body)
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+
+			w.Header().Set("Content-Type", "text/plain")
+			fmt.Fprintf(w, "%s's message for %s is: %s\n", getPOP(), r.URL.Path, msg)
+
+		// Write data to the cache and stream it back to the client.
+		case "POST":
+			if r.Header.Get("Content-Type") != "text/plain" && r.Header.Get("Content-Type") != "text/plain; charset=utf-8" {
+				w.WriteHeader(fsthttp.StatusUnsupportedMediaType)
+				return
+			}
+
+			msg, err := io.ReadAll(r.Body)
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+
+			tx, err := core.NewTransaction(key, core.LookupOptions{})
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+			defer tx.Close()
+
+			if !tx.MustInsert() {
+				w.WriteHeader(fsthttp.StatusConflict)
+				return
+			}
+
+			// We call InsertAndStreamBack to create both a handle to
+			// write the content into the cache and a Found object to
+			// stream the contents back out to the client.  As soon as
+			// data is written to the insert body, it is immediately
+			// streamed to all clients waiting on this transaction,
+			// including this one.
+			//
+			// This is preferable to using an io.MultiWriter because a
+			// MultiWriter is constrained by the slowest writer.  If
+			// other transactions are waiting on the content to be
+			// written to the cache and streamed, we don't want that
+			// process to be delayed by a slow client for this request.
+			insertBody, found, err := tx.InsertAndStreamBack(core.WriteOptions{
+				TTL:           600 * time.Second,
+				Length:        uint64(len(msg)),
+				SurrogateKeys: []string{hex.EncodeToString(key)},
+			})
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+			defer found.Body.Close()
+
+			insertBody.Write(msg)
+
+			if err := insertBody.Close(); err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+
+			msg, err = io.ReadAll(found.Body)
+			if err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+
+			w.Header().Set("Content-Type", "text/plain")
+			w.WriteHeader(fsthttp.StatusCreated)
+			fmt.Fprintf(w, "%s's message for %s is: %s\n", getPOP(), r.URL.Path, msg)
+
+		// Purge the key from the cache.
+		case "DELETE":
+			if err := purge.PurgeSurrogateKey(hex.EncodeToString(key), purge.PurgeOptions{}); err != nil {
+				fsthttp.Error(w, err.Error(), fsthttp.StatusInternalServerError)
+				return
+			}
+			w.WriteHeader(fsthttp.StatusAccepted)
+
+		default:
+			w.WriteHeader(fsthttp.StatusMethodNotAllowed)
+		}
+	})
+}
+
+func keyForRequest(r *fsthttp.Request) []byte {
+	h := sha256.New()
+	h.Write([]byte(r.URL.Path))
+	h.Write([]byte(getPOP()))
+	return h.Sum(nil)
+}
+
+func getPOP() string {
+	return os.Getenv("FASTLY_POP")
+}