From a53b27c62e792e09380876db916289c77f2ae2e0 Mon Sep 17 00:00:00 2001 From: Matthew Holt Date: Wed, 9 Oct 2019 19:22:46 -0600 Subject: 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. --- cmd/caddy/main.go | 1 + modules/caddyhttp/httpcache/httpcache.go | 205 +++++++++++++++++++++++++++++++ 2 files changed, 206 insertions(+) create mode 100644 modules/caddyhttp/httpcache/httpcache.go diff --git a/cmd/caddy/main.go b/cmd/caddy/main.go index 93e95e7..87226cd 100644 --- a/cmd/caddy/main.go +++ b/cmd/caddy/main.go @@ -28,6 +28,7 @@ import ( _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/encode/zstd" _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/fileserver" _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/headers" + _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/httpcache" _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/markdown" _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/requestbody" _ "github.com/caddyserver/caddy/v2/modules/caddyhttp/reverseproxy" 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) +) -- cgit v1.2.3