backend.go (view raw)
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//
// 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"
"net"
"net/rpc"
"os"
"os/exec"
"humungus.tedunangst.com/r/webs/gate"
"humungus.tedunangst.com/r/webs/image"
)
type Shrinker struct {
}
type ShrinkerArgs struct {
Buf []byte
Params image.Params
}
type ShrinkerResult struct {
Image *image.Image
}
var shrinkgate = gate.NewLimiter(4)
func (s *Shrinker) Shrink(args *ShrinkerArgs, res *ShrinkerResult) error {
shrinkgate.Start()
defer shrinkgate.Finish()
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
}
var backendhooks []func()
func orphancheck() {
var b [1]byte
os.Stdin.Read(b[:])
dlog.Printf("backend shutting down")
os.Exit(0)
}
func backendServer() {
dlog.Printf("backend server running")
go orphancheck()
shrinker := new(Shrinker)
srv := rpc.NewServer()
err := srv.Register(shrinker)
if err != nil {
elog.Panicf("unable to register shrinker: %s", err)
}
sockname := backendSockname()
err = os.Remove(sockname)
if err != nil && !os.IsNotExist(err) {
elog.Panicf("unable to unlink socket: %s", err)
}
lis, err := net.Listen("unix", sockname)
if err != nil {
elog.Panicf("unable to register shrinker: %s", err)
}
err = setLimits()
if err != nil {
elog.Printf("error setting backend limits: %s", err)
}
for _, h := range backendhooks {
h()
}
srv.Accept(lis)
}
func runBackendServer() {
r, w, err := os.Pipe()
if err != nil {
elog.Panicf("can't pipe: %s", err)
}
proc := exec.Command(os.Args[0], reexecArgs("backend")...)
proc.Stdout = os.Stdout
proc.Stderr = os.Stderr
proc.Stdin = r
err = proc.Start()
if err != nil {
elog.Panicf("can't exec backend: %s", err)
}
go func() {
proc.Wait()
elog.Printf("lost the backend: %s", err)
w.Close()
}()
}
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