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) } err = proc.Wait() elog.Printf("lost the backend: %s", err) w.Close() } |