Merge pull request #833 from mgood/dns-startup-hooks
Simplify DNS server startup check
This commit is contained in:
Armon Dadgar
commit
325e87cdaa
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@ -7,6 +7,7 @@ import (
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"math/rand"
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"net"
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"strings"
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"sync"
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"time"
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"github.com/hashicorp/consul/consul/structs"
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@ -14,8 +15,6 @@ import (
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)
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const (
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testQuery = "_test.consul."
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consulDomain = "consul."
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maxServiceResponses = 3 // For UDP only
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maxRecurseRecords = 3
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)
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@ -51,17 +50,21 @@ func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain s
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// Construct the DNS components
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mux := dns.NewServeMux()
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var wg sync.WaitGroup
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// Setup the servers
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server := &dns.Server{
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Addr: bind,
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Net: "udp",
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Handler: mux,
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UDPSize: 65535,
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Addr: bind,
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Net: "udp",
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Handler: mux,
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UDPSize: 65535,
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NotifyStartedFunc: wg.Done,
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}
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serverTCP := &dns.Server{
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Addr: bind,
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Net: "tcp",
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Handler: mux,
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Addr: bind,
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Net: "tcp",
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Handler: mux,
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NotifyStartedFunc: wg.Done,
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}
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// Create the server
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@ -79,11 +82,8 @@ func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain s
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// Register mux handler, for reverse lookup
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mux.HandleFunc("arpa.", srv.handlePtr)
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// Register mux handlers, always handle "consul."
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// Register mux handlers
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mux.HandleFunc(domain, srv.handleQuery)
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if domain != consulDomain {
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mux.HandleFunc(consulDomain, srv.handleTest)
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}
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if len(recursors) > 0 {
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validatedRecursors := make([]string, len(recursors))
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@ -99,6 +99,8 @@ func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain s
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mux.HandleFunc(".", srv.handleRecurse)
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}
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wg.Add(2)
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// Async start the DNS Servers, handle a potential error
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errCh := make(chan error, 1)
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go func() {
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@ -116,28 +118,11 @@ func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain s
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}
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}()
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// Check the server is running, do a test lookup
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checkCh := make(chan error, 1)
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// Wait for NotifyStartedFunc callbacks indicating server has started
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startCh := make(chan struct{})
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go func() {
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// This is jank, but we have no way to edge trigger on
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// the start of our server, so we just wait and hope it is up.
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time.Sleep(50 * time.Millisecond)
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m := new(dns.Msg)
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m.SetQuestion(testQuery, dns.TypeANY)
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c := new(dns.Client)
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in, _, err := c.Exchange(m, bind)
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if err != nil {
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checkCh <- fmt.Errorf("dns test query failed: %v", err)
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return
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}
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if len(in.Answer) == 0 {
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checkCh <- fmt.Errorf("no response to test message")
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return
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}
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close(checkCh)
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wg.Wait()
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close(startCh)
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}()
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// Wait for either the check, listen error, or timeout
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@ -146,8 +131,8 @@ func NewDNSServer(agent *Agent, config *DNSConfig, logOutput io.Writer, domain s
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return srv, e
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case e := <-errChTCP:
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return srv, e
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case e := <-checkCh:
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return srv, e
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case <-startCh:
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return srv, nil
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case <-time.After(time.Second):
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return srv, fmt.Errorf("timeout setting up DNS server")
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}
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@ -234,12 +219,6 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
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d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
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}(time.Now())
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// Check if this is potentially a test query
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if q.Name == testQuery {
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d.handleTest(resp, req)
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return
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}
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// Switch to TCP if the client is
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network := "udp"
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if _, ok := resp.RemoteAddr().(*net.TCPAddr); ok {
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@ -266,34 +245,6 @@ func (d *DNSServer) handleQuery(resp dns.ResponseWriter, req *dns.Msg) {
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}
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}
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// handleTest is used to handle DNS queries in the ".consul." domain
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func (d *DNSServer) handleTest(resp dns.ResponseWriter, req *dns.Msg) {
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q := req.Question[0]
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defer func(s time.Time) {
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d.logger.Printf("[DEBUG] dns: request for %v (%v)", q, time.Now().Sub(s))
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}(time.Now())
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if !(q.Qtype == dns.TypeANY || q.Qtype == dns.TypeTXT) {
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return
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}
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if q.Name != testQuery {
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return
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}
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// Always respond with TXT "ok"
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m := new(dns.Msg)
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m.SetReply(req)
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m.Authoritative = true
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m.RecursionAvailable = true
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header := dns.RR_Header{Name: q.Name, Rrtype: dns.TypeTXT, Class: dns.ClassINET, Ttl: 0}
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txt := &dns.TXT{Hdr: header, Txt: []string{"ok"}}
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m.Answer = append(m.Answer, txt)
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d.addSOA(consulDomain, m)
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if err := resp.WriteMsg(m); err != nil {
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d.logger.Printf("[WARN] dns: failed to respond: %v", err)
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}
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}
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// addSOA is used to add an SOA record to a message for the given domain
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func (d *DNSServer) addSOA(domain string, msg *dns.Msg) {
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soa := &dns.SOA{
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@ -39,34 +39,6 @@ func TestRecursorAddr(t *testing.T) {
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}
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}
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func TestDNS_IsAlive(t *testing.T) {
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dir, srv := makeDNSServer(t)
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defer os.RemoveAll(dir)
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defer srv.agent.Shutdown()
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m := new(dns.Msg)
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m.SetQuestion("_test.consul.", dns.TypeANY)
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c := new(dns.Client)
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addr, _ := srv.agent.config.ClientListener("", srv.agent.config.Ports.DNS)
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in, _, err := c.Exchange(m, addr.String())
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if err != nil {
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t.Fatalf("err: %v", err)
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}
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if len(in.Answer) != 1 {
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t.Fatalf("Bad: %#v", in)
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}
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txt, ok := in.Answer[0].(*dns.TXT)
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if !ok {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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if txt.Txt[0] != "ok" {
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t.Fatalf("Bad: %#v", in.Answer[0])
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}
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}
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func TestDNS_NodeLookup(t *testing.T) {
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dir, srv := makeDNSServer(t)
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defer os.RemoveAll(dir)
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