Better error handling in goroutines (#122)

* More robust goroutine error handling using channels

* Fix tests and make startup log msg saner

* Clarification to README and config file

.travis.yml

@@ -1,6 +1,7 @@
 language: go
 go:
  - 1.9
+ - 1.11
 env:
  - "PATH=/home/travis/gopath/bin:$PATH"
 before_install:

README.md

@@ -212,7 +212,9 @@ $ dig @auth.example.org d420c923-bbd7-4056-ab64-c3ca54c9b3cf.auth.example.org
 
 ```bash
 [general]
-# dns interface
+# DNS interface. Note that systemd-resolved may reserve port 53 on 127.0.0.53
+# In this case acme-dns will error out and you will need to define the listening interface
+# for example: listen = "127.0.0.1:53"
 listen = ":53"
 # protocol, "udp", "udp4", "udp6" or "tcp", "tcp4", "tcp6"
 protocol = "udp"

config.cfg

@@ -1,5 +1,7 @@
 [general]
-# dns interface
+# DNS interface. Note that systemd-resolved may reserve port 53 on 127.0.0.53
+# In this case acme-dns will error out and you will need to define the listening interface
+# for example: listen = "127.0.0.1:53"
 listen = ":53"
 # protocol, "udp", "udp4", "udp6" or "tcp", "tcp4", "tcp6"
 protocol = "udp"

main.go

@@ -11,6 +11,7 @@ import (
  "syscall"
 
  "github.com/julienschmidt/httprouter"
+ "github.com/miekg/dns"
  "github.com/rs/cors"
  log "github.com/sirupsen/logrus"
  "golang.org/x/crypto/acme/autocert"
@@ -55,16 +56,41 @@ func main() {
  DB = newDB
  defer DB.Close()
 
+ // Error channel for servers
+ errChan := make(chan error, 1)
+
  // DNS server
- startDNS(Config.General.Listen, Config.General.Proto)
+ dnsServer := setupDNSServer()
+ go startDNS(dnsServer, errChan)
 
  // HTTP API
- startHTTPAPI()
+ go startHTTPAPI(errChan)
 
+ // block waiting for error
+ select {
+ case err = <-errChan:
+ if err != nil {
+ log.Fatal(err)
+ }
+ }
  log.Debugf("Shutting down...")
 }
 
-func startHTTPAPI() {
+func startDNS(server *dns.Server, errChan chan error) {
+ // DNS server part
+ dns.HandleFunc(".", handleRequest)
+ log.WithFields(log.Fields{"addr": Config.General.Listen}).Info("Listening DNS")
+ err := server.ListenAndServe()
+ if err != nil {
+ errChan <- err
+ }
+}
+
+func setupDNSServer() *dns.Server {
+ return &dns.Server{Addr: Config.General.Listen, Net: Config.General.Proto}
+}
+
+func startHTTPAPI(errChan chan error) {
  // Setup http logger
  logger := log.New()
  logwriter := logger.Writer()
@@ -90,7 +116,7 @@ func startHTTPAPI() {
  cfg := &tls.Config{
  MinVersion: tls.VersionTLS12,
  }
-
+ var err error
  switch Config.API.TLS {
  case "letsencrypt":
  m := autocert.Manager{
@@ -109,7 +135,7 @@ func startHTTPAPI() {
  ErrorLog: stdlog.New(logwriter, "", 0),
  }
  log.WithFields(log.Fields{"host": host, "domain": Config.API.Domain}).Info("Listening HTTPS, using certificate from autocert")
- log.Fatal(srv.ListenAndServeTLS("", ""))
+ err = srv.ListenAndServeTLS("", "")
  case "cert":
  srv := &http.Server{
  Addr: host,
@@ -118,9 +144,12 @@ func startHTTPAPI() {
  ErrorLog: stdlog.New(logwriter, "", 0),
  }
  log.WithFields(log.Fields{"host": host}).Info("Listening HTTPS")
- log.Fatal(srv.ListenAndServeTLS(Config.API.TLSCertFullchain, Config.API.TLSCertPrivkey))
+ err = srv.ListenAndServeTLS(Config.API.TLSCertFullchain, Config.API.TLSCertPrivkey)
  default:
  log.WithFields(log.Fields{"host": host}).Info("Listening HTTP")
- log.Fatal(http.ListenAndServe(host, c.Handler(api)))
+ err = http.ListenAndServe(host, c.Handler(api))
+ }
+ if err != nil {
+ errChan <- err
  }
 }

main_test.go

@@ -7,6 +7,7 @@ import (
  logrustest "github.com/sirupsen/logrus/hooks/test"
  "io/ioutil"
  "os"
+ "sync"
  "testing"
 )
 
@@ -42,7 +43,15 @@ func TestMain(m *testing.M) {
  _ = newDb.Init("sqlite3", ":memory:")
  }
  DB = newDb
- server := startDNS("0.0.0.0:15353", "udp")
+ server := setupDNSServer()
+ // Make sure that we're not creating a race condition in tests
+ var wg sync.WaitGroup
+ wg.Add(1)
+ server.NotifyStartedFunc = func() {
+ wg.Done()
+ }
+ go startDNS(server, make(chan error, 1))
+ wg.Wait()
  exitval := m.Run()
  server.Shutdown()
  DB.Close()
@@ -57,6 +66,8 @@ func setupConfig() {
 
  var generalcfg = general{
  Domain: "auth.example.org",
+ Listen: "127.0.0.1:15353",
+ Proto: "udp",
  Nsname: "ns1.auth.example.org",
  Nsadmin: "admin.example.org",
  StaticRecords: records,

util.go

@@ -10,7 +10,6 @@ import (
  "strings"
 
  "github.com/BurntSushi/toml"
- "github.com/miekg/dns"
  log "github.com/sirupsen/logrus"
 )
 
@@ -108,14 +107,6 @@ func setupLogging(format string, level string) {
  // TODO: file logging
 }
 
-func startDNS(listen string, proto string) *dns.Server {
- // DNS server part
- dns.HandleFunc(".", handleRequest)
- server := &dns.Server{Addr: listen, Net: proto}
- go server.ListenAndServe()
- return server
-}
-
 func getIPListFromHeader(header string) []string {
  iplist := []string{}
  for _, v := range strings.Split(header, ",") {