open-consul/consul/leader.go

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package consul
import (
"fmt"
"net"
"strconv"
"strings"
"time"
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"github.com/armon/go-metrics"
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"github.com/hashicorp/consul/consul/agent"
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"github.com/hashicorp/consul/consul/structs"
"github.com/hashicorp/raft"
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"github.com/hashicorp/serf/serf"
)
const (
SerfCheckID = "serfHealth"
SerfCheckName = "Serf Health Status"
SerfCheckAliveOutput = "Agent alive and reachable"
SerfCheckFailedOutput = "Agent not live or unreachable"
ConsulServiceID = "consul"
ConsulServiceName = "consul"
newLeaderEvent = "consul:new-leader"
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)
// 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
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// maintenance activities
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func (s *Server) leaderLoop(stopCh chan struct{}) {
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// Ensure we revoke leadership on stepdown
defer s.revokeLeadership()
// 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
establishedLeader := false
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RECONCILE:
// Setup a reconciliation timer
reconcileCh = nil
interval := time.After(s.config.ReconcileInterval)
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// Apply a raft barrier to ensure our FSM is caught up
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start := time.Now()
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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
}
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metrics.MeasureSince([]string{"consul", "leader", "barrier"}, start)
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// Check if we need to handle initial leadership actions
if !establishedLeader {
if err := s.establishLeadership(); err != nil {
s.logger.Printf("[ERR] consul: failed to establish leadership: %v",
err)
goto WAIT
}
establishedLeader = true
}
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// 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
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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)
case index := <-s.tombstoneGC.ExpireCh():
go s.reapTombstones(index)
}
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}
}
// establishLeadership is invoked once we become leader and are able
// to invoke an initial barrier. The barrier is used to ensure any
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// previously inflight transactions have been committed and that our
// state is up-to-date.
func (s *Server) establishLeadership() error {
// Hint the tombstone expiration timer. When we freshly establish leadership
// we become the authoritative timer, and so we need to start the clock
// on any pending GC events.
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s.tombstoneGC.SetEnabled(true)
lastIndex := s.raft.LastIndex()
s.tombstoneGC.Hint(lastIndex)
s.logger.Printf("[DEBUG] consul: reset tombstone GC to index %d", lastIndex)
// Setup ACLs if we are the leader and need to
if err := s.initializeACL(); err != nil {
s.logger.Printf("[ERR] consul: ACL initialization failed: %v", err)
return err
}
// Setup the session timers. This is done both when starting up or when
// a leader fail over happens. Since the timers are maintained by the leader
// node along, effectively this means all the timers are renewed at the
// time of failover. The TTL contract is that the session will not be expired
// before the TTL, so expiring it later is allowable.
//
// This MUST be done after the initial barrier to ensure the latest Sessions
// are available to be initialized. Otherwise initialization may use stale
// data.
if err := s.initializeSessionTimers(); err != nil {
s.logger.Printf("[ERR] consul: Session Timers initialization failed: %v",
err)
return err
}
return nil
}
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// revokeLeadership is invoked once we step down as leader.
// This is used to cleanup any state that may be specific to a leader.
func (s *Server) revokeLeadership() error {
// Disable the tombstone GC, since it is only useful as a leader
s.tombstoneGC.SetEnabled(false)
// Clear the session timers on either shutdown or step down, since we
// are no longer responsible for session expirations.
if err := s.clearAllSessionTimers(); err != nil {
s.logger.Printf("[ERR] consul: Clearing session timers failed: %v", err)
return err
}
return nil
}
// initializeACL is used to setup the ACLs if we are the leader
// and need to do this.
func (s *Server) initializeACL() error {
// Bail if not configured or we are not authoritative
authDC := s.config.ACLDatacenter
if len(authDC) == 0 || authDC != s.config.Datacenter {
return nil
}
// Purge the cache, since it could've changed while we
// were not the leader
s.aclAuthCache.Purge()
// Look for the anonymous token
state := s.fsm.State()
_, acl, err := state.ACLGet(anonymousToken)
if err != nil {
return fmt.Errorf("failed to get anonymous token: %v", err)
}
// Create anonymous token if missing
if acl == nil {
req := structs.ACLRequest{
Datacenter: authDC,
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Op: structs.ACLSet,
ACL: structs.ACL{
ID: anonymousToken,
Name: "Anonymous Token",
Type: structs.ACLTypeClient,
},
}
_, err := s.raftApply(structs.ACLRequestType, &req)
if err != nil {
return fmt.Errorf("failed to create anonymous token: %v", err)
}
}
// Check for configured master token
master := s.config.ACLMasterToken
if len(master) == 0 {
return nil
}
// Look for the master token
_, acl, err = state.ACLGet(master)
if err != nil {
return fmt.Errorf("failed to get master token: %v", err)
}
if acl == nil {
req := structs.ACLRequest{
Datacenter: authDC,
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Op: structs.ACLSet,
ACL: structs.ACL{
ID: master,
Name: "Master Token",
Type: structs.ACLTypeManagement,
},
}
_, err := s.raftApply(structs.ACLRequestType, &req)
if err != nil {
return fmt.Errorf("failed to create master token: %v", err)
}
}
return nil
}
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// 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) {
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defer metrics.MeasureSince([]string{"consul", "leader", "reconcile"}, time.Now())
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members := s.serfLAN.Members()
knownMembers := make(map[string]struct{})
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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
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// in a critical 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()
_, checks, err := state.ChecksInState(structs.HealthAny)
if err != nil {
return err
}
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for _, check := range checks {
// 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, err := state.NodeServices(check.Node)
if err != nil {
return err
}
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
}
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}
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) {
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s.logger.Printf("[WARN] consul: skipping reconcile of node %v", member)
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return nil
}
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defer metrics.MeasureSince([]string{"consul", "leader", "reconcileMember"}, time.Now())
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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)
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case StatusReap:
err = s.handleReapMember(member)
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}
if err != nil {
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s.logger.Printf("[ERR] consul: failed to reconcile member: %v: %v",
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member, err)
// Permission denied should not bubble up
if strings.Contains(err.Error(), permissionDenied) {
return nil
}
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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
}
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if valid, parts := agent.IsConsulServer(member); valid && parts.Datacenter == s.config.Datacenter {
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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 {
// Register consul service if a server
var service *structs.NodeService
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if valid, parts := agent.IsConsulServer(member); valid {
service = &structs.NodeService{
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ID: ConsulServiceID,
Service: ConsulServiceName,
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Port: parts.Port,
}
// Attempt to join the consul server
if err := s.joinConsulServer(member, parts); err != nil {
return err
}
}
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// Check if the node exists
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node != nil && node.Address == member.Addr.String() {
// Check if the associated service is available
if service != nil {
match := false
_, services, err := state.NodeServices(member.Name)
if err != nil {
return err
}
if services != nil {
for id, _ := range services.Services {
if id == service.ID {
match = true
}
}
}
if !match {
goto AFTER_CHECK
}
}
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// Check if the serfCheck is in the passing state
_, checks, err := state.NodeChecks(member.Name)
if err != nil {
return err
}
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for _, check := range checks {
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if check.CheckID == SerfCheckID && check.Status == structs.HealthPassing {
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return nil
}
}
}
AFTER_CHECK:
s.logger.Printf("[INFO] consul: member '%s' joined, marking health alive", member.Name)
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// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
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Service: service,
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Check: &structs.HealthCheck{
Node: member.Name,
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CheckID: SerfCheckID,
Name: SerfCheckName,
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Status: structs.HealthPassing,
Output: SerfCheckAliveOutput,
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},
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
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}
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 {
// Check if the node exists
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node != nil && node.Address == member.Addr.String() {
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// Check if the serfCheck is in the critical state
_, checks, err := state.NodeChecks(member.Name)
if err != nil {
return err
}
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for _, check := range checks {
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if check.CheckID == SerfCheckID && check.Status == structs.HealthCritical {
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return nil
}
}
}
s.logger.Printf("[INFO] consul: member '%s' failed, marking health critical", member.Name)
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// Register with the catalog
req := structs.RegisterRequest{
Datacenter: s.config.Datacenter,
Node: member.Name,
Address: member.Addr.String(),
Check: &structs.HealthCheck{
Node: member.Name,
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CheckID: SerfCheckID,
Name: SerfCheckName,
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Status: structs.HealthCritical,
Output: SerfCheckFailedOutput,
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},
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
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}
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 {
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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 {
// Do not deregister ourself. This can only happen if the current leader
// is leaving. Instead, we should allow a follower to take-over and
// deregister us later.
if member.Name == s.config.NodeName {
s.logger.Printf("[WARN] consul: deregistering self (%s) should be done by follower", s.config.NodeName)
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return nil
}
// Remove from Raft peers if this was a server
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if valid, parts := agent.IsConsulServer(member); valid {
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if err := s.removeConsulServer(member, parts.Port); err != nil {
return err
}
}
// Check if the node does not exist
state := s.fsm.State()
_, node, err := state.GetNode(member.Name)
if err != nil {
return err
}
if node == nil {
return nil
}
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// Deregister the node
s.logger.Printf("[INFO] consul: member '%s' %s, deregistering", member.Name, reason)
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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
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func (s *Server) joinConsulServer(m serf.Member, parts *agent.Server) error {
// Do not join ourself
if m.Name == s.config.NodeName {
return nil
}
// Check for possibility of multiple bootstrap nodes
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if parts.Bootstrap {
members := s.serfLAN.Members()
for _, member := range members {
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valid, p := agent.IsConsulServer(member)
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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}
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future := s.raft.AddPeer(addr.String())
if err := future.Error(); err != nil && err != raft.ErrKnownPeer {
s.logger.Printf("[ERR] consul: failed to add raft peer: %v", err)
return err
}
return nil
}
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// removeConsulServer is used to try to remove a consul server that has left
func (s *Server) removeConsulServer(m serf.Member, port int) error {
// Attempt to remove as peer
peer := &net.TCPAddr{IP: m.Addr, Port: port}
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future := s.raft.RemovePeer(peer.String())
if err := future.Error(); err != nil && err != raft.ErrUnknownPeer {
s.logger.Printf("[ERR] consul: failed to remove raft peer '%v': %v",
peer, err)
return err
} else if err == nil {
s.logger.Printf("[INFO] consul: removed server '%s' as peer", m.Name)
}
return nil
}
// reapTombstones is invoked by the current leader to manage garbage
// collection of tombstones. When a key is deleted, we trigger a tombstone
// GC clock. Once the expiration is reached, this routine is invoked
// to clear all tombstones before this index. This must be replicated
// through Raft to ensure consistency. We do this outside the leader loop
// to avoid blocking.
func (s *Server) reapTombstones(index uint64) {
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defer metrics.MeasureSince([]string{"consul", "leader", "reapTombstones"}, time.Now())
req := structs.TombstoneRequest{
Datacenter: s.config.Datacenter,
Op: structs.TombstoneReap,
ReapIndex: index,
WriteRequest: structs.WriteRequest{Token: s.config.ACLToken},
}
_, err := s.raftApply(structs.TombstoneRequestType, &req)
if err != nil {
s.logger.Printf("[ERR] consul: failed to reap tombstones up to %d: %v",
index, err)
}
}