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authorMatthew Holt <mholt@users.noreply.github.com>2019-10-09 19:22:46 -0600
committerMatthew Holt <mholt@users.noreply.github.com>2019-10-09 19:22:46 -0600
commita53b27c62e792e09380876db916289c77f2ae2e0 (patch)
tree296a3ddd6beb1bb5fd933060d42e6feb8b06396f /modules/caddyhttp/httpcache
parent03306e646e3ee421f582ef69a2158724bcf2614b (diff)
http: Add work-in-progress cache handler module
This migrates a feature that was previously reserved for enterprise users, according to https://github.com/caddyserver/caddy/issues/2786. The cache HTTP handler will be a high-performing, distributed cache layer for HTTP requests. Right now, the implementation is a very basic proof-of-concept, and further development is required.
Diffstat (limited to 'modules/caddyhttp/httpcache')
-rw-r--r--modules/caddyhttp/httpcache/httpcache.go205
1 files changed, 205 insertions, 0 deletions
diff --git a/modules/caddyhttp/httpcache/httpcache.go b/modules/caddyhttp/httpcache/httpcache.go
new file mode 100644
index 0000000..1b2cfd2
--- /dev/null
+++ b/modules/caddyhttp/httpcache/httpcache.go
@@ -0,0 +1,205 @@
+// Copyright 2015 Matthew Holt and The Caddy Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package httpcache
+
+import (
+ "bytes"
+ "encoding/gob"
+ "fmt"
+ "io"
+ "log"
+ "net/http"
+ "sync"
+
+ "github.com/caddyserver/caddy/v2"
+ "github.com/caddyserver/caddy/v2/modules/caddyhttp"
+ "github.com/golang/groupcache"
+)
+
+func init() {
+ caddy.RegisterModule(Cache{})
+}
+
+// Cache implements a simple distributed cache.
+type Cache struct {
+ group *groupcache.Group
+}
+
+// CaddyModule returns the Caddy module information.
+func (Cache) CaddyModule() caddy.ModuleInfo {
+ return caddy.ModuleInfo{
+ Name: "http.handlers.cache",
+ New: func() caddy.Module { return new(Cache) },
+ }
+}
+
+// Provision provisions c.
+func (c *Cache) Provision(ctx caddy.Context) error {
+ // TODO: proper pool configuration
+ me := "http://localhost:5555"
+ // TODO: Make max size configurable
+ maxSize := int64(512 << 20)
+ poolMu.Lock()
+ if pool == nil {
+ pool = groupcache.NewHTTPPool(me)
+ c.group = groupcache.NewGroup(groupName, maxSize, groupcache.GetterFunc(c.getter))
+ } else {
+ c.group = groupcache.GetGroup(groupName)
+ }
+ pool.Set(me)
+ poolMu.Unlock()
+
+ return nil
+}
+
+// Validate validates c.
+func (c *Cache) Validate() error {
+ // TODO: implement
+ return nil
+}
+
+func (c *Cache) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyhttp.Handler) error {
+ // TODO: proper RFC implementation of cache control headers...
+ if r.Header.Get("Cache-Control") == "no-cache" || r.Method != "GET" {
+ return next.ServeHTTP(w, r)
+ }
+
+ ctx := getterContext{w, r, next}
+
+ // TODO: rigorous performance testing
+
+ // TODO: pretty much everything else to handle the nuances of HTTP caching...
+
+ // TODO: groupcache has no explicit cache eviction, so we need to embed
+ // all information related to expiring cache entries into the key; right
+ // now we just use the request URI as a proof-of-concept
+ key := r.RequestURI
+
+ var cachedBytes []byte
+ err := c.group.Get(ctx, key, groupcache.AllocatingByteSliceSink(&cachedBytes))
+ if err == errUncacheable {
+ return nil
+ }
+ if err != nil {
+ return err
+ }
+
+ // the cached bytes consists of two parts: first a
+ // gob encoding of the status and header, immediately
+ // followed by the raw bytes of the response body
+ rdr := bytes.NewReader(cachedBytes)
+
+ // read the header and status first
+ var hs headerAndStatus
+ err = gob.NewDecoder(rdr).Decode(&hs)
+ if err != nil {
+ return err
+ }
+
+ // set and write the cached headers
+ for k, v := range hs.Header {
+ w.Header()[k] = v
+ }
+ w.WriteHeader(hs.Status)
+
+ // write the cached response body
+ io.Copy(w, rdr)
+
+ return nil
+}
+
+func (c *Cache) getter(ctx groupcache.Context, key string, dest groupcache.Sink) error {
+ combo := ctx.(getterContext)
+
+ // the buffer will store the gob-encoded header, then the body
+ buf := bufPool.Get().(*bytes.Buffer)
+ buf.Reset()
+ defer bufPool.Put(buf)
+
+ // we need to record the response if we are to cache it; only cache if
+ // request is successful (TODO: there's probably much more nuance needed here)
+ var rr caddyhttp.ResponseRecorder
+ rr = caddyhttp.NewResponseRecorder(combo.rw, buf, func(status int) bool {
+ shouldBuf := status < 300
+
+ if shouldBuf {
+ // store the header before the body, so we can efficiently
+ // and conveniently use a single buffer for both; gob
+ // decoder will only read up to end of gob message, and
+ // the rest will be the body, which will be written
+ // implicitly for us by the recorder
+ err := gob.NewEncoder(buf).Encode(headerAndStatus{
+ Header: rr.Header(),
+ Status: status,
+ })
+ if err != nil {
+ log.Printf("[ERROR] Encoding headers for cache entry: %v; not caching this request", err)
+ return false
+ }
+ }
+
+ return shouldBuf
+ })
+
+ // execute next handlers in chain
+ err := combo.next.ServeHTTP(rr, combo.req)
+ if err != nil {
+ return err
+ }
+
+ // if response body was not buffered, response was
+ // already written and we are unable to cache
+ if !rr.Buffered() {
+ return errUncacheable
+ }
+
+ // add to cache
+ dest.SetBytes(buf.Bytes())
+
+ return nil
+}
+
+type headerAndStatus struct {
+ Header http.Header
+ Status int
+}
+
+type getterContext struct {
+ rw http.ResponseWriter
+ req *http.Request
+ next caddyhttp.Handler
+}
+
+var bufPool = sync.Pool{
+ New: func() interface{} {
+ return new(bytes.Buffer)
+ },
+}
+
+var (
+ pool *groupcache.HTTPPool
+ poolMu sync.Mutex
+)
+
+var errUncacheable = fmt.Errorf("uncacheable")
+
+const groupName = "http_requests"
+
+// Interface guards
+var (
+ _ caddy.Provisioner = (*Cache)(nil)
+ _ caddy.Validator = (*Cache)(nil)
+ _ caddyhttp.MiddlewareHandler = (*Cache)(nil)
+)