From 8a6eaf5fe1b3bd366ce1bba8e4b145b4dd11b8d7 Mon Sep 17 00:00:00 2001
From: Ted Unangst <tedu@tedunangst.com>
Date: Sat, 9 Nov 2019 02:15:15 -0500
Subject: [PATCH] move the memory intensive and sometimes fragile image code to
 a special backend process

---
 activity.go |   4 +--
 backend.go  | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 honk.go     |   2 ++
 web.go      |   4 +--
 4 files changed, 106 insertions(+), 5 deletions(-)
 create mode 100644 backend.go

diff --git a/activity.go b/activity.go
index 4094bdc..31f91f1 100644
--- a/activity.go
+++ b/activity.go
@@ -34,7 +34,6 @@ import (
 	"humungus.tedunangst.com/r/webs/cache"
 	"humungus.tedunangst.com/r/webs/gate"
 	"humungus.tedunangst.com/r/webs/httpsig"
-	"humungus.tedunangst.com/r/webs/image"
 	"humungus.tedunangst.com/r/webs/junk"
 )
 
@@ -175,8 +174,7 @@ func savedonk(url string, name, desc, media string, localize bool) *Donk {
 			log.Printf("truncation likely")
 		}
 		if strings.HasPrefix(media, "image") {
-			img, err := image.Vacuum(&buf,
-				image.Params{LimitSize: 4200 * 4200, MaxWidth: 2048, MaxHeight: 2048})
+			img, err := shrinkit(data)
 			if err != nil {
 				log.Printf("unable to decode image: %s", err)
 				localize = false
diff --git a/backend.go b/backend.go
new file mode 100644
index 0000000..b101ccc
--- /dev/null
+++ b/backend.go
@@ -0,0 +1,101 @@
+//
+// Copyright (c) 2019 Ted Unangst <tedu@tedunangst.com>
+//
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+package main
+
+import (
+	"bytes"
+	"log"
+	"net"
+	"net/rpc"
+	"os"
+	"os/exec"
+
+	"humungus.tedunangst.com/r/webs/image"
+)
+
+type Shrinker struct {
+}
+
+type ShrinkerArgs struct {
+	Buf    []byte
+	Params image.Params
+}
+
+type ShrinkerResult struct {
+	Image *image.Image
+}
+
+func (s *Shrinker) Shrink(args *ShrinkerArgs, res *ShrinkerResult) error {
+	img, err := image.Vacuum(bytes.NewReader(args.Buf), args.Params)
+	if err != nil {
+		return err
+	}
+	res.Image = img
+	return nil
+}
+
+func backendSockname() string {
+	return dataDir + "/backend.sock"
+}
+
+func shrinkit(data []byte) (*image.Image, error) {
+	cl, err := rpc.Dial("unix", backendSockname())
+	if err != nil {
+		return nil, err
+	}
+	defer cl.Close()
+	var res ShrinkerResult
+	err = cl.Call("Shrinker.Shrink", &ShrinkerArgs{
+		Buf:    data,
+		Params: image.Params{LimitSize: 4200 * 4200, MaxWidth: 2048, MaxHeight: 2048},
+	}, &res)
+	if err != nil {
+		return nil, err
+	}
+	return res.Image, nil
+}
+
+func backendServer() {
+	log.Printf("backend server running")
+	shrinker := new(Shrinker)
+	srv := rpc.NewServer()
+	err := srv.Register(shrinker)
+	if err != nil {
+		log.Panicf("unable to register shrinker: %s", err)
+	}
+
+	sockname := backendSockname()
+	err = os.Remove(sockname)
+	if err != nil && !os.IsNotExist(err) {
+		log.Panicf("unable to unlink socket: %s", err)
+	}
+
+	lis, err := net.Listen("unix", sockname)
+	if err != nil {
+		log.Panicf("unable to register shrinker: %s", err)
+	}
+	srv.Accept(lis)
+}
+
+func startBackendServer() {
+	proc := exec.Command(os.Args[0], "-datadir", dataDir, "backend")
+	proc.Stdout = os.Stdout
+	proc.Stderr = os.Stderr
+	err := proc.Start()
+	if err != nil {
+		log.Panicf("can't exec backend: %s", err)
+	}
+}
diff --git a/honk.go b/honk.go
index 5ccfcbb..d76799d 100644
--- a/honk.go
+++ b/honk.go
@@ -269,6 +269,8 @@ func main() {
 		ping(user, targ)
 	case "run":
 		serve()
+	case "backend":
+		backendServer()
 	case "test":
 		ElaborateUnitTests()
 	default:
diff --git a/web.go b/web.go
index 6824a7c..7a62fdf 100644
--- a/web.go
+++ b/web.go
@@ -36,7 +36,6 @@ import (
 	"github.com/gorilla/mux"
 	"humungus.tedunangst.com/r/webs/cache"
 	"humungus.tedunangst.com/r/webs/httpsig"
-	"humungus.tedunangst.com/r/webs/image"
 	"humungus.tedunangst.com/r/webs/junk"
 	"humungus.tedunangst.com/r/webs/login"
 	"humungus.tedunangst.com/r/webs/rss"
@@ -1399,7 +1398,7 @@ func submithonk(w http.ResponseWriter, r *http.Request) {
 			data := buf.Bytes()
 			xid := xfiltrate()
 			var media, name string
-			img, err := image.Vacuum(&buf, image.Params{MaxWidth: 2048, MaxHeight: 2048})
+			img, err := shrinkit(data)
 			if err == nil {
 				data = img.Data
 				format := img.Format
@@ -2060,6 +2059,7 @@ func serve() {
 	if err != nil {
 		log.Fatal(err)
 	}
+	startBackendServer()
 	go enditall()
 	go redeliverator()
 	go tracker()