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leader.go
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leader.go
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package consul
import (
"github.com/armon/go-metrics"
"github.com/hashicorp/consul/consul/structs"
"github.com/hashicorp/raft"
"github.com/hashicorp/serf/serf"
"net"
"strconv"
"time"
)
const (
SerfCheckID = "serfHealth"
SerfCheckName = "Serf Health Status"
ConsulServiceID = "consul"
ConsulServiceName = "consul"
newLeaderEvent = "consul:new-leader"
)
// monitorLeadership is used to monitor if we acquire or lose our role
// as the leader in the Raft cluster. There is some work the leader is
// expected to do, so we must react to changes
func (s *Server) monitorLeadership() {
leaderCh := s.raft.LeaderCh()
var stopCh chan struct{}
for {
select {
case isLeader := <-leaderCh:
if isLeader {
stopCh = make(chan struct{})
go s.leaderLoop(stopCh)
s.logger.Printf("[INFO] consul: cluster leadership acquired")
} else if stopCh != nil {
close(stopCh)
stopCh = nil
s.logger.Printf("[INFO] consul: cluster leadership lost")
}
case <-s.shutdownCh:
return
}
}
}
// leaderLoop runs as long as we are the leader to run various
// maintence activities
func (s *Server) leaderLoop(stopCh chan struct{}) {
// Fire a user event indicating a new leader
payload := []byte(s.config.NodeName)
if err := s.serfLAN.UserEvent(newLeaderEvent, payload, false); err != nil {
s.logger.Printf("[WARN] consul: failed to broadcast new leader event: %v", err)
}
// Reconcile channel is only used once initial reconcile
// has succeeded
var reconcileCh chan serf.Member
RECONCILE:
// Setup a reconciliation timer
reconcileCh = nil
interval := time.After(s.config.ReconcileInterval)
// Apply a raft barrier to ensure our FSM is caught up
start := time.Now()
barrier := s.raft.Barrier(0)
if err := barrier.Error(); err != nil {
s.logger.Printf("[ERR] consul: failed to wait for barrier: %v", err)
goto WAIT
}
metrics.MeasureSince([]string{"consul", "leader", "barrier"}, start)
// Reconcile any missing data
if err := s.reconcile(); err != nil {
s.logger.Printf("[ERR] consul: failed to reconcile: %v", err)
goto WAIT
}
// Initial reconcile worked, now we can process the channel
// updates
reconcileCh = s.reconcileCh
WAIT:
// Periodically reconcile as long as we are the leader,
// or when Serf events arrive
for {
select {
case <-stopCh:
return
case <-s.shutdownCh:
return
case <-interval:
goto RECONCILE
case member := <-reconcileCh:
s.reconcileMember(member)
}
}
}
// reconcile is used to reconcile the differences between Serf
// membership and what is reflected in our strongly consistent store.
// Mainly we need to ensure all live nodes are registered, all failed
// nodes are marked as such, and all left nodes are de-registered.
func (s *Server) reconcile() (err error) {
defer metrics.MeasureSince([]string{"consul", "leader", "reconcile"}, time.Now())
members := s.serfLAN.Members()
knownMembers := make(map[string]struct{})
for _, member := range members {
if err := s.reconcileMember(member); err != nil {
return err
}
knownMembers[member.Name] = struct{}{}
}
// Reconcile any members that have been reaped while we were not the leader
return s.reconcileReaped(knownMembers)
}
// reconcileReaped is used to reconcile nodes that have failed and been reaped
// from Serf but remain in the catalog. This is done by looking for SerfCheckID
// in a crticial state that does not correspond to a known Serf member. We generate
// a "reap" event to cause the node to be cleaned up.
func (s *Server) reconcileReaped(known map[string]struct{}) error {
state := s.fsm.State()
_, critical := state.ChecksInState(structs.HealthCritical)
for _, check := range critical {
// Ignore any non serf checks
if check.CheckID != SerfCheckID {
continue
}
// Check if this node is "known" by serf
if _, ok := known[check.Node]; ok {
continue
}
// Create a fake member
member := serf.Member{
Name: check.Node,
Tags: map[string]string{
"dc": s.config.Datacenter,
"role": "node",
},
}
// Get the node services, look for ConsulServiceID
_, services := state.NodeServices(check.Node)
serverPort := 0
for _, service := range services.Services {
if service.ID == ConsulServiceID {
serverPort = service.Port
break
}
}
// Create the appropriate tags if this was a server node
if serverPort > 0 {
member.Tags["role"] = "consul"
member.Tags["port"] = strconv.FormatUint(uint64(serverPort), 10)
}
// Attempt to reap this member
if err := s.handleReapMember(member); err != nil {
return err
}
}
return nil
}
// reconcileMember is used to do an async reconcile of a single
// serf member
func (s *Server) reconcileMember(member serf.Member) error {
// Check if this is a member we should handle
if !s.shouldHandleMember(member) {
s.logger.Printf("[WARN] consul: skipping reconcile of node %v", member)
return nil
}
defer metrics.MeasureSince([]string{"consul", "leader", "reconcileMember"}, time.Now())
var err error
switch member.Status {
case serf.StatusAlive:
err = s.handleAliveMember(member)
case serf.StatusFailed:
err = s.handleFailedMember(member)
case serf.StatusLeft:
err = s.handleLeftMember(member)
case StatusReap:
err = s.handleReapMember(member)
}
if err != nil {
s.logger.Printf("[ERR] consul: failed to reconcile member: %v: %v",
member, err)
return err
}
return nil
}
// shouldHandleMember checks if this is a Consul pool member
func (s *Server) shouldHandleMember(member serf.Member) bool {
if valid, dc := isConsulNode(member); valid && dc == s.config.Datacenter {
return true
}
if valid, parts := isConsulServer(member); valid && parts.Datacenter == s.config.Datacenter {
return true
}
return false
}
// handleAliveMember is used to ensure the node
// is registered, with a passing health check.
func (s *Server) handleAliveMember(member serf.Member) error {
state := s.fsm.State()
// Register consul service if a server
var service *structs.NodeService
if valid, parts := isConsulServer(member); valid {
service = &structs.NodeService{
ID: ConsulServiceID,
Service: ConsulServiceName,
Port: parts.Port,
}
// Attempt to join the consul server
if err := s.joinConsulServer(member, parts); err != nil {
return err
}
}
// Check if the node exists
_, found, addr := state.GetNode(member.Name)
if found && addr == member.Addr.String() {
// Check if the associated service is available
if service != nil {
match := false
_, services := state.NodeServices(member.Name)
if services != nil {
for id, _ := range services.Services {
if id == service.ID {
match = true
}
}
}
if !match {
goto AFTER_CHECK
}
}
// Check if the serfCheck is in the passing state
_, checks := state.NodeChecks(member.Name)
for _, check := range checks {
if check.CheckID == SerfCheckID && check.Status == structs.HealthPassing {
return nil
}
}
}
AFTER_CHECK:
s.logger.Printf("[INFO] consul: member '%s' joined, marking health alive", member.Name)
// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
Service: service,
Check: &structs.HealthCheck{
Node: member.Name,
CheckID: SerfCheckID,
Name: SerfCheckName,
Status: structs.HealthPassing,
},
}
var out struct{}
return s.endpoints.Catalog.Register(&req, &out)
}
// handleFailedMember is used to mark the node's status
// as being critical, along with all checks as unknown.
func (s *Server) handleFailedMember(member serf.Member) error {
state := s.fsm.State()
// Check if the node exists
_, found, addr := state.GetNode(member.Name)
if found && addr == member.Addr.String() {
// Check if the serfCheck is in the critical state
_, checks := state.NodeChecks(member.Name)
for _, check := range checks {
if check.CheckID == SerfCheckID && check.Status == structs.HealthCritical {
return nil
}
}
}
s.logger.Printf("[INFO] consul: member '%s' failed, marking health critical", member.Name)
// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
Check: &structs.HealthCheck{
Node: member.Name,
CheckID: SerfCheckID,
Name: SerfCheckName,
Status: structs.HealthCritical,
},
}
var out struct{}
return s.endpoints.Catalog.Register(&req, &out)
}
// handleLeftMember is used to handle members that gracefully
// left. They are deregistered if necessary.
func (s *Server) handleLeftMember(member serf.Member) error {
return s.handleDeregisterMember("left", member)
}
// handleReapMember is used to handle members that have been
// reaped after a prolonged failure. They are deregistered.
func (s *Server) handleReapMember(member serf.Member) error {
return s.handleDeregisterMember("reaped", member)
}
// handleDeregisterMember is used to deregister a member of a given reason
func (s *Server) handleDeregisterMember(reason string, member serf.Member) error {
state := s.fsm.State()
// Check if the node does not exists
_, found, _ := state.GetNode(member.Name)
if !found {
return nil
}
s.logger.Printf("[INFO] consul: member '%s' %s, deregistering", member.Name, reason)
// Remove from Raft peers if this was a server
if valid, parts := isConsulServer(member); valid {
if err := s.removeConsulServer(member, parts.Port); err != nil {
return err
}
}
// Deregister the node
req := structs.DeregisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
}
var out struct{}
return s.endpoints.Catalog.Deregister(&req, &out)
}
// joinConsulServer is used to try to join another consul server
func (s *Server) joinConsulServer(m serf.Member, parts *serverParts) error {
// Do not join ourself
if m.Name == s.config.NodeName {
return nil
}
// Check for possibility of multiple bootstrap nodes
if parts.Bootstrap {
members := s.serfLAN.Members()
for _, member := range members {
valid, p := isConsulServer(member)
if valid && member.Name != m.Name && p.Bootstrap {
s.logger.Printf("[ERR] consul: '%v' and '%v' are both in bootstrap mode. Only one node should be in bootstrap mode, not adding Raft peer.", m.Name, member.Name)
return nil
}
}
}
// Attempt to add as a peer
var addr net.Addr = &net.TCPAddr{IP: m.Addr, Port: parts.Port}
future := s.raft.AddPeer(addr)
if err := future.Error(); err != nil && err != raft.KnownPeer {
s.logger.Printf("[ERR] consul: failed to add raft peer: %v", err)
return err
}
return nil
}
// removeConsulServer is used to try to remove a consul server that has left
func (s *Server) removeConsulServer(m serf.Member, port int) error {
// Do not remove ourself
if m.Name == s.config.NodeName {
return nil
}
// Attempt to remove as peer
peer := &net.TCPAddr{IP: m.Addr, Port: port}
future := s.raft.RemovePeer(peer)
if err := future.Error(); err != nil && err != raft.UnknownPeer {
s.logger.Printf("[ERR] consul: failed to remove raft peer '%v': %v",
peer, err)
return err
}
return nil
}