apps/app-runner/server.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
	"os/exec"
	"sync"
	"syscall"
	"time"

	"golang.org/x/crypto/ssh"
)

type Server struct {
	l           sync.Locker
	port        int
	appId       string
	ready       bool
	cmd         *exec.Cmd
	repoAddr    string
	branch      string
	signer      ssh.Signer
	appDir      string
	runCommands []Command
	self        string
	managerAddr string
	logs        *Log
	currDir     string
}

func NewServer(port int, appId string, repoAddr, branch string, signer ssh.Signer, appDir string, runCommands []Command, self string, manager string) *Server {
	return &Server{
		l:           &sync.Mutex{},
		port:        port,
		ready:       false,
		appId:       appId,
		repoAddr:    repoAddr,
		branch:      branch,
		signer:      signer,
		appDir:      appDir,
		runCommands: runCommands,
		self:        self,
		managerAddr: manager,
		logs:        &Log{},
		currDir:     "",
	}
}

func (s *Server) Start() error {
	http.HandleFunc("/update", s.handleUpdate)
	http.HandleFunc("/ready", s.handleReady)
	http.HandleFunc("/logs", s.handleLogs)
	if err := s.run(); err != nil {
		return err
	}
	go s.pingManager()
	return http.ListenAndServe(fmt.Sprintf(":%d", s.port), nil)
}

func (s *Server) handleLogs(w http.ResponseWriter, r *http.Request) {
	fmt.Fprint(w, s.logs.Contents())
}

func (s *Server) handleReady(w http.ResponseWriter, r *http.Request) {
	s.l.Lock()
	defer s.l.Unlock()
	if s.ready {
		fmt.Fprintln(w, "ok")
	} else {
		http.Error(w, "not ready", http.StatusInternalServerError)
	}
}

func (s *Server) handleUpdate(w http.ResponseWriter, r *http.Request) {
	fmt.Println("update")
	s.l.Lock()
	s.ready = false
	s.l.Unlock()
	if err := s.run(); err != nil {
		http.Error(w, err.Error(), http.StatusInternalServerError)
		return
	}
	s.l.Lock()
	s.ready = true
	s.l.Unlock()
}

func (s *Server) run() error {
	newDir, err := os.MkdirTemp(s.appDir, "code-*")
	if err != nil {
		return err
	}
	if err := CloneRepositoryBranch(s.repoAddr, s.branch, s.signer, newDir); err != nil {
		return err
	}
	logM := io.MultiWriter(os.Stdout, s.logs)
	for i, c := range s.runCommands {
		args := []string{c.Bin}
		args = append(args, c.Args...)
		cmd := &exec.Cmd{
			Dir:    newDir,
			Path:   c.Bin,
			Args:   args,
			Env:    append(os.Environ(), c.Env...),
			Stdout: logM,
			Stderr: logM,
		}
		cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
		fmt.Printf("Running: %s %s\n", c.Bin, c.Args)
		if i < len(s.runCommands)-1 {
			if err := cmd.Run(); err != nil {
				return err
			}
		} else {
			if s.cmd != nil {
				// TODO(gio): make this point configurable
				if err := s.kill(); err != nil {
					return err
				}
				if err := os.RemoveAll(s.currDir); err != nil {
					return err
				}
			}
			if err := cmd.Start(); err != nil {
				return err
			}
			s.cmd = cmd
		}
	}
	s.currDir = newDir
	return nil
}

type pingReq struct {
	Address string `json:"address"`
	Logs    string `json:"logs"`
}

func (s *Server) pingManager() {
	defer func() {
		go func() {
			time.Sleep(5 * time.Second)
			s.pingManager()
		}()
	}()
	buf, err := json.Marshal(pingReq{
		Address: fmt.Sprintf("%s:%d", s.self, s.port),
		Logs:    s.logs.Contents(),
	})
	if err != nil {
		return
	}
	registerWorkerAddr := fmt.Sprintf("%s/api/apps/%s/workers", s.managerAddr, s.appId)
	http.Post(registerWorkerAddr, "application/json", bytes.NewReader(buf))
}

func (s *Server) kill() error {
	if s.cmd == nil {
		return nil
	}

	err := syscall.Kill(-s.cmd.Process.Pid, syscall.SIGKILL)
	if err != nil {
		return err
	}
	// NOTE(gio): No need to check err as we just killed the process
	s.cmd.Wait()
	s.cmd = nil
	return nil
}