open-consul/command/agent/agent.go

package agent

import (
	"context"
	"crypto/sha512"
	"crypto/tls"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"io/ioutil"
	"log"
	"net"
	"net/http"
	"os"
	"path/filepath"
	"reflect"
	"regexp"
	"strconv"
	"strings"
	"sync"
	"time"

	"github.com/hashicorp/consul/api"
	"github.com/hashicorp/consul/consul"
	"github.com/hashicorp/consul/consul/state"
	"github.com/hashicorp/consul/consul/structs"
	"github.com/hashicorp/consul/ipaddr"
	"github.com/hashicorp/consul/lib"
	"github.com/hashicorp/consul/logger"
	"github.com/hashicorp/consul/types"
	"github.com/hashicorp/go-sockaddr/template"
	"github.com/hashicorp/go-uuid"
	"github.com/hashicorp/raft"
	"github.com/hashicorp/serf/coordinate"
	"github.com/hashicorp/serf/serf"
	"github.com/shirou/gopsutil/host"
)

const (
	// Path to save agent service definitions
	servicesDir = "services"

	// Path to save local agent checks
	checksDir     = "checks"
	checkStateDir = "checks/state"

	// Default reasons for node/service maintenance mode
	defaultNodeMaintReason = "Maintenance mode is enabled for this node, " +
		"but no reason was provided. This is a default message."
	defaultServiceMaintReason = "Maintenance mode is enabled for this " +
		"service, but no reason was provided. This is a default message."
)

// dnsNameRe checks if a name or tag is dns-compatible.
var dnsNameRe = regexp.MustCompile(`^[a-zA-Z0-9\-]+$`)

// clientServer defines the interface shared by both
// consul.Client and consul.Server.
type clientServer interface {
	Encrypted() bool
	GetLANCoordinate() (*coordinate.Coordinate, error)
	Leave() error
	LANMembers() []serf.Member
	LocalMember() serf.Member
	JoinLAN(addrs []string) (n int, err error)
	RemoveFailedNode(node string) error
	RPC(method string, args interface{}, reply interface{}) error
	SnapshotRPC(args *structs.SnapshotRequest, in io.Reader, out io.Writer, replyFn consul.SnapshotReplyFn) error
	Shutdown() error
	Stats() map[string]map[string]string
}

// The agent is the long running process that is run on every machine.
// It exposes an RPC interface that is used by the CLI to control the
// agent. The agent runs the query interfaces like HTTP, DNS, and RPC.
// However, it can run in either a client, or server mode. In server
// mode, it runs a full Consul server. In client-only mode, it only forwards
// requests to other Consul servers.
type Agent struct {
	// config is the agent configuration.
	config *Config

	// Used for writing our logs
	logger *log.Logger

	// Output sink for logs
	LogOutput io.Writer

	// Used for streaming logs to
	LogWriter *logger.LogWriter

	// delegate is either a *consul.Server or *consul.Client
	// depending on the configuration
	delegate clientServer

	// acls is an object that helps manage local ACL enforcement.
	acls *aclManager

	// state stores a local representation of the node,
	// services and checks. Used for anti-entropy.
	state localState

	// checkReapAfter maps the check ID to a timeout after which we should
	// reap its associated service
	checkReapAfter map[types.CheckID]time.Duration

	// checkMonitors maps the check ID to an associated monitor
	checkMonitors map[types.CheckID]*CheckMonitor

	// checkHTTPs maps the check ID to an associated HTTP check
	checkHTTPs map[types.CheckID]*CheckHTTP

	// checkTCPs maps the check ID to an associated TCP check
	checkTCPs map[types.CheckID]*CheckTCP

	// checkTTLs maps the check ID to an associated check TTL
	checkTTLs map[types.CheckID]*CheckTTL

	// checkDockers maps the check ID to an associated Docker Exec based check
	checkDockers map[types.CheckID]*CheckDocker

	// checkLock protects updates to the check* maps
	checkLock sync.Mutex

	// eventCh is used to receive user events
	eventCh chan serf.UserEvent

	// eventBuf stores the most recent events in a ring buffer
	// using eventIndex as the next index to insert into. This
	// is guarded by eventLock. When an insert happens, the
	// eventNotify group is notified.
	eventBuf    []*UserEvent
	eventIndex  int
	eventLock   sync.RWMutex
	eventNotify state.NotifyGroup

	reloadCh chan chan error

	shutdown     bool
	shutdownCh   chan struct{}
	shutdownLock sync.Mutex

	// endpoints lets you override RPC endpoints for testing. Not all
	// agent methods use this, so use with care and never override
	// outside of a unit test.
	endpoints     map[string]string
	endpointsLock sync.RWMutex

	// dnsAddr is the address the DNS server binds to
	dnsAddrs []ProtoAddr

	// dnsServer provides the DNS API
	dnsServers []*DNSServer

	// httpAddrs are the addresses per protocol the HTTP server binds to
	httpAddrs []ProtoAddr

	// httpServers provides the HTTP API on various endpoints
	httpServers []*HTTPServer

	// wgServers is the wait group for all HTTP and DNS servers
	wgServers sync.WaitGroup
}

func NewAgent(c *Config) (*Agent, error) {
	if c.Datacenter == "" {
		return nil, fmt.Errorf("Must configure a Datacenter")
	}
	if c.DataDir == "" && !c.DevMode {
		return nil, fmt.Errorf("Must configure a DataDir")
	}
	dnsAddrs, err := c.DNSAddrs()
	if err != nil {
		return nil, fmt.Errorf("Invalid DNS bind address: %s", err)
	}
	httpAddrs, err := c.HTTPAddrs()
	if err != nil {
		return nil, fmt.Errorf("Invalid HTTP bind address: %s", err)
	}
	acls, err := newACLManager(c)
	if err != nil {
		return nil, err
	}

	a := &Agent{
		config:         c,
		acls:           acls,
		checkReapAfter: make(map[types.CheckID]time.Duration),
		checkMonitors:  make(map[types.CheckID]*CheckMonitor),
		checkTTLs:      make(map[types.CheckID]*CheckTTL),
		checkHTTPs:     make(map[types.CheckID]*CheckHTTP),
		checkTCPs:      make(map[types.CheckID]*CheckTCP),
		checkDockers:   make(map[types.CheckID]*CheckDocker),
		eventCh:        make(chan serf.UserEvent, 1024),
		eventBuf:       make([]*UserEvent, 256),
		reloadCh:       make(chan chan error),
		shutdownCh:     make(chan struct{}),
		endpoints:      make(map[string]string),
		dnsAddrs:       dnsAddrs,
		httpAddrs:      httpAddrs,
	}
	if err := a.resolveTmplAddrs(); err != nil {
		return nil, err
	}
	return a, nil
}

func (a *Agent) Start() error {
	c := a.config

	logOutput := a.LogOutput
	if a.logger == nil {
		if logOutput == nil {
			logOutput = os.Stderr
		}
		a.logger = log.New(logOutput, "", log.LstdFlags)
	}

	// Retrieve or generate the node ID before setting up the rest of the
	// agent, which depends on it.
	if err := a.setupNodeID(c); err != nil {
		return fmt.Errorf("Failed to setup node ID: %v", err)
	}

	// Initialize the local state.
	a.state.Init(c, a.logger)

	// Setup either the client or the server.
	if c.Server {
		server, err := a.makeServer()
		if err != nil {
			return err
		}

		a.delegate = server
		a.state.SetIface(server)

		// Automatically register the "consul" service on server nodes
		consulService := structs.NodeService{
			Service: consul.ConsulServiceName,
			ID:      consul.ConsulServiceID,
			Port:    c.Ports.Server,
			Tags:    []string{},
		}

		a.state.AddService(&consulService, c.GetTokenForAgent())
	} else {
		client, err := a.makeClient()
		if err != nil {
			return err
		}

		a.delegate = client
		a.state.SetIface(client)
	}

	// Load checks/services/metadata.
	if err := a.loadServices(c); err != nil {
		return err
	}
	if err := a.loadChecks(c); err != nil {
		return err
	}
	if err := a.loadMetadata(c); err != nil {
		return err
	}

	// Start watching for critical services to deregister, based on their
	// checks.
	go a.reapServices()

	// Start handling events.
	go a.handleEvents()

	// Start sending network coordinate to the server.
	if !c.DisableCoordinates {
		go a.sendCoordinate()
	}

	// Write out the PID file if necessary.
	if err := a.storePid(); err != nil {
		return err
	}

	// start DNS servers
	if err := a.listenAndServeDNS(); err != nil {
		return err
	}

	// create listeners and unstarted servers
	// see comment on listenHTTP why we are doing this
	httpln, err := a.listenHTTP(a.httpAddrs)
	if err != nil {
		return err
	}

	// start HTTP servers
	for _, l := range httpln {
		srv := NewHTTPServer(l.Addr().String(), a)
		if err := a.serveHTTP(l, srv); err != nil {
			return err
		}
		a.httpServers = append(a.httpServers, srv)
	}
	return nil
}

func (a *Agent) listenAndServeDNS() error {
	notif := make(chan ProtoAddr, len(a.dnsAddrs))
	for _, p := range a.dnsAddrs {
		p := p // capture loop var

		// create server
		s, err := NewDNSServer(a)
		if err != nil {
			return err
		}
		a.dnsServers = append(a.dnsServers, s)

		// start server
		a.wgServers.Add(1)
		go func() {
			defer a.wgServers.Done()

			err := s.ListenAndServe(p.Net, p.Addr, func() { notif <- p })
			if err != nil && !strings.Contains(err.Error(), "accept") {
				a.logger.Printf("[ERR] agent: Error starting DNS server %s (%s): ", p.Addr, p.Net, err)
			}
		}()
	}

	// wait for servers to be up
	timeout := time.After(time.Second)
	for range a.dnsAddrs {
		select {
		case p := <-notif:
			a.logger.Printf("[INFO] agent: Started DNS server %s (%s)", p.Addr, p.Net)
			continue
		case <-timeout:
			return fmt.Errorf("agent: timeout starting DNS servers")
		}
	}
	return nil
}

// listenHTTP binds listeners to the provided addresses and also returns
// pre-configured HTTP servers which are not yet started. The motivation is
// that in the current startup/shutdown setup we de-couple the listener
// creation from the server startup assuming that if any of the listeners
// cannot be bound we fail immediately and later failures do not occur.
// Therefore, starting a server with a running listener is assumed to not
// produce an error.
//
// The second motivation is that an HTTPS server needs to use the same TLSConfig
// on both the listener and the HTTP server. When listeners and servers are
// created at different times this becomes difficult to handle without keeping
// the TLS configuration somewhere or recreating it.
//
// This approach should ultimately be refactored to the point where we just
// start the server and any error should trigger a proper shutdown of the agent.
func (a *Agent) listenHTTP(addrs []ProtoAddr) ([]net.Listener, error) {
	var ln []net.Listener
	for _, p := range addrs {
		var l net.Listener
		var err error

		switch {
		case p.Net == "unix":
			l, err = a.listenSocket(p.Addr, a.config.UnixSockets)

		case p.Net == "tcp" && p.Proto == "http":
			l, err = net.Listen("tcp", p.Addr)
			if err != nil {
				l = &tcpKeepAliveListener{l.(*net.TCPListener)}
			}

		case p.Net == "tcp" && p.Proto == "https":
			var tlscfg *tls.Config
			tlscfg, err = a.config.IncomingHTTPSConfig()
			if err != nil {
				break
			}
			l, err = tls.Listen("tcp", p.Addr, tlscfg)
			if err != nil {
				l = &tcpKeepAliveListener{l.(*net.TCPListener)}
			}

		default:
			return nil, fmt.Errorf("%s:%s listener not supported", p.Net, p.Proto)
		}

		if err != nil {
			for _, l := range ln {
				l.Close()
			}
			return nil, err
		}

		ln = append(ln, l)
	}
	return ln, nil
}

// tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
// connections. It's used by NewHttpServer so dead TCP connections
// eventually go away.
type tcpKeepAliveListener struct {
	*net.TCPListener
}

func (ln tcpKeepAliveListener) Accept() (c net.Conn, err error) {
	tc, err := ln.AcceptTCP()
	if err != nil {
		return
	}
	tc.SetKeepAlive(true)
	tc.SetKeepAlivePeriod(30 * time.Second)
	return tc, nil
}

func (a *Agent) listenSocket(path string, perm FilePermissions) (net.Listener, error) {
	if _, err := os.Stat(path); !os.IsNotExist(err) {
		a.logger.Printf("[WARN] agent: Replacing socket %q", path)
	}
	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
		return nil, fmt.Errorf("error removing socket file: %s", err)
	}
	l, err := net.Listen("unix", path)
	if err != nil {
		return nil, err
	}
	if err := setFilePermissions(path, perm); err != nil {
		return nil, fmt.Errorf("Failed setting up HTTP socket: %s", err)
	}
	return l, nil
}

func (a *Agent) serveHTTP(l net.Listener, srv *HTTPServer) error {
	// https://github.com/golang/go/issues/20239
	//
	// In go.8.1 there is a race between Serve and Shutdown. If
	// Shutdown is called before the Serve go routine was scheduled then
	// the Serve go routine never returns. This deadlocks the agent
	// shutdown for some tests since it will wait forever.
	//
	// Since we need to check for an unexported type (*tls.listener)
	// we cannot just perform a type check since the compiler won't let
	// us. We might be able to use reflection but the fmt.Sprintf() hack
	// works just as well.
	if strings.Contains("*tls.listener", fmt.Sprintf("%T", l)) {
		srv.proto = "https"
	}
	notif := make(chan string)
	a.wgServers.Add(1)
	go func() {
		defer a.wgServers.Done()
		notif <- srv.Addr
		err := srv.Serve(l)
		if err != nil && err != http.ErrServerClosed {
			a.logger.Print(err)
		}
	}()

	select {
	case addr := <-notif:
		if srv.proto == "https" {
			a.logger.Printf("[INFO] agent: Started HTTPS server on %s", addr)
		} else {
			a.logger.Printf("[INFO] agent: Started HTTP server on %s", addr)
		}
		return nil
	case <-time.After(time.Second):
		return fmt.Errorf("agent: timeout starting HTTP servers")
	}
}

// consulConfig is used to return a consul configuration
func (a *Agent) consulConfig() (*consul.Config, error) {
	// Start with the provided config or default config
	base := consul.DefaultConfig()
	if a.config.ConsulConfig != nil {
		base = a.config.ConsulConfig
	}

	// This is set when the agent starts up
	base.NodeID = a.config.NodeID

	// Apply dev mode
	base.DevMode = a.config.DevMode

	// Apply performance factors
	if a.config.Performance.RaftMultiplier > 0 {
		base.ScaleRaft(a.config.Performance.RaftMultiplier)
	}

	// Override with our config
	if a.config.Datacenter != "" {
		base.Datacenter = a.config.Datacenter
	}
	if a.config.DataDir != "" {
		base.DataDir = a.config.DataDir
	}
	if a.config.NodeName != "" {
		base.NodeName = a.config.NodeName
	}
	if a.config.Ports.SerfLan != 0 {
		base.SerfLANConfig.MemberlistConfig.BindPort = a.config.Ports.SerfLan
		base.SerfLANConfig.MemberlistConfig.AdvertisePort = a.config.Ports.SerfLan
	}
	if a.config.Ports.SerfWan != 0 {
		base.SerfWANConfig.MemberlistConfig.BindPort = a.config.Ports.SerfWan
		base.SerfWANConfig.MemberlistConfig.AdvertisePort = a.config.Ports.SerfWan
	}
	if a.config.BindAddr != "" {
		bindAddr := &net.TCPAddr{
			IP:   net.ParseIP(a.config.BindAddr),
			Port: a.config.Ports.Server,
		}
		base.RPCAddr = bindAddr

		// Set the Serf configs using the old default behavior, we may
		// override these in the code right below.
		base.SerfLANConfig.MemberlistConfig.BindAddr = a.config.BindAddr
		base.SerfWANConfig.MemberlistConfig.BindAddr = a.config.BindAddr
	}
	if a.config.SerfLanBindAddr != "" {
		base.SerfLANConfig.MemberlistConfig.BindAddr = a.config.SerfLanBindAddr
	}
	if a.config.SerfWanBindAddr != "" {
		base.SerfWANConfig.MemberlistConfig.BindAddr = a.config.SerfWanBindAddr
	}
	// Try to get an advertise address
	switch {
	case a.config.AdvertiseAddr != "":
		ipStr, err := parseSingleIPTemplate(a.config.AdvertiseAddr)
		if err != nil {
			return nil, fmt.Errorf("Advertise address resolution failed: %v", err)
		}
		if net.ParseIP(ipStr) == nil {
			return nil, fmt.Errorf("Failed to parse advertise address: %v", ipStr)
		}
		a.config.AdvertiseAddr = ipStr

	case a.config.BindAddr != "" && !ipaddr.IsAny(a.config.BindAddr):
		a.config.AdvertiseAddr = a.config.BindAddr

	default:
		ip, err := consul.GetPrivateIP()
		if ipaddr.IsAnyV6(a.config.BindAddr) {
			ip, err = consul.GetPublicIPv6()
		}
		if err != nil {
			return nil, fmt.Errorf("Failed to get advertise address: %v", err)
		}
		a.config.AdvertiseAddr = ip.String()
	}

	// Try to get an advertise address for the wan
	if a.config.AdvertiseAddrWan != "" {
		ipStr, err := parseSingleIPTemplate(a.config.AdvertiseAddrWan)
		if err != nil {
			return nil, fmt.Errorf("Advertise WAN address resolution failed: %v", err)
		}
		if net.ParseIP(ipStr) == nil {
			return nil, fmt.Errorf("Failed to parse advertise address for WAN: %v", ipStr)
		}
		a.config.AdvertiseAddrWan = ipStr
	} else {
		a.config.AdvertiseAddrWan = a.config.AdvertiseAddr
	}

	// Create the default set of tagged addresses.
	a.config.TaggedAddresses = map[string]string{
		"lan": a.config.AdvertiseAddr,
		"wan": a.config.AdvertiseAddrWan,
	}

	if a.config.AdvertiseAddr != "" {
		base.SerfLANConfig.MemberlistConfig.AdvertiseAddr = a.config.AdvertiseAddr
		base.SerfWANConfig.MemberlistConfig.AdvertiseAddr = a.config.AdvertiseAddr
		if a.config.AdvertiseAddrWan != "" {
			base.SerfWANConfig.MemberlistConfig.AdvertiseAddr = a.config.AdvertiseAddrWan
		}
		base.RPCAdvertise = &net.TCPAddr{
			IP:   net.ParseIP(a.config.AdvertiseAddr),
			Port: a.config.Ports.Server,
		}
	}
	if a.config.AdvertiseAddrs.SerfLan != nil {
		base.SerfLANConfig.MemberlistConfig.AdvertiseAddr = a.config.AdvertiseAddrs.SerfLan.IP.String()
		base.SerfLANConfig.MemberlistConfig.AdvertisePort = a.config.AdvertiseAddrs.SerfLan.Port
	}
	if a.config.AdvertiseAddrs.SerfWan != nil {
		base.SerfWANConfig.MemberlistConfig.AdvertiseAddr = a.config.AdvertiseAddrs.SerfWan.IP.String()
		base.SerfWANConfig.MemberlistConfig.AdvertisePort = a.config.AdvertiseAddrs.SerfWan.Port
	}
	if a.config.ReconnectTimeoutLan != 0 {
		base.SerfLANConfig.ReconnectTimeout = a.config.ReconnectTimeoutLan
	}
	if a.config.ReconnectTimeoutWan != 0 {
		base.SerfWANConfig.ReconnectTimeout = a.config.ReconnectTimeoutWan
	}
	if a.config.EncryptVerifyIncoming != nil {
		base.SerfWANConfig.MemberlistConfig.GossipVerifyIncoming = *a.config.EncryptVerifyIncoming
		base.SerfLANConfig.MemberlistConfig.GossipVerifyIncoming = *a.config.EncryptVerifyIncoming
	}
	if a.config.EncryptVerifyOutgoing != nil {
		base.SerfWANConfig.MemberlistConfig.GossipVerifyOutgoing = *a.config.EncryptVerifyOutgoing
		base.SerfLANConfig.MemberlistConfig.GossipVerifyOutgoing = *a.config.EncryptVerifyOutgoing
	}
	if a.config.AdvertiseAddrs.RPC != nil {
		base.RPCAdvertise = a.config.AdvertiseAddrs.RPC
	}
	if a.config.Bootstrap {
		base.Bootstrap = true
	}
	if a.config.RejoinAfterLeave {
		base.RejoinAfterLeave = true
	}
	if a.config.BootstrapExpect != 0 {
		base.BootstrapExpect = a.config.BootstrapExpect
	}
	if a.config.Protocol > 0 {
		base.ProtocolVersion = uint8(a.config.Protocol)
	}
	if a.config.RaftProtocol != 0 {
		base.RaftConfig.ProtocolVersion = raft.ProtocolVersion(a.config.RaftProtocol)
	}
	if a.config.ACLToken != "" {
		base.ACLToken = a.config.ACLToken
	}
	if a.config.ACLAgentToken != "" {
		base.ACLAgentToken = a.config.ACLAgentToken
	}
	if a.config.ACLMasterToken != "" {
		base.ACLMasterToken = a.config.ACLMasterToken
	}
	if a.config.ACLDatacenter != "" {
		base.ACLDatacenter = a.config.ACLDatacenter
	}
	if a.config.ACLTTLRaw != "" {
		base.ACLTTL = a.config.ACLTTL
	}
	if a.config.ACLDefaultPolicy != "" {
		base.ACLDefaultPolicy = a.config.ACLDefaultPolicy
	}
	if a.config.ACLDownPolicy != "" {
		base.ACLDownPolicy = a.config.ACLDownPolicy
	}
	if a.config.ACLReplicationToken != "" {
		base.ACLReplicationToken = a.config.ACLReplicationToken
	}
	if a.config.ACLEnforceVersion8 != nil {
		base.ACLEnforceVersion8 = *a.config.ACLEnforceVersion8
	}
	if a.config.SessionTTLMinRaw != "" {
		base.SessionTTLMin = a.config.SessionTTLMin
	}
	if a.config.Autopilot.CleanupDeadServers != nil {
		base.AutopilotConfig.CleanupDeadServers = *a.config.Autopilot.CleanupDeadServers
	}
	if a.config.Autopilot.LastContactThreshold != nil {
		base.AutopilotConfig.LastContactThreshold = *a.config.Autopilot.LastContactThreshold
	}
	if a.config.Autopilot.MaxTrailingLogs != nil {
		base.AutopilotConfig.MaxTrailingLogs = *a.config.Autopilot.MaxTrailingLogs
	}
	if a.config.Autopilot.ServerStabilizationTime != nil {
		base.AutopilotConfig.ServerStabilizationTime = *a.config.Autopilot.ServerStabilizationTime
	}
	if a.config.NonVotingServer {
		base.NonVoter = a.config.NonVotingServer
	}
	if a.config.Autopilot.RedundancyZoneTag != "" {
		base.AutopilotConfig.RedundancyZoneTag = a.config.Autopilot.RedundancyZoneTag
	}
	if a.config.Autopilot.DisableUpgradeMigration != nil {
		base.AutopilotConfig.DisableUpgradeMigration = *a.config.Autopilot.DisableUpgradeMigration
	}

	// make sure the advertise address is always set
	if base.RPCAdvertise == nil {
		base.RPCAdvertise = base.RPCAddr
	}

	// set the src address for outgoing rpc connections
	// Use port 0 so that outgoing connections use a random port.
	if !ipaddr.IsAny(base.RPCAddr.IP) {
		base.RPCSrcAddr = &net.TCPAddr{IP: base.RPCAddr.IP}
	}

	// Format the build string
	revision := a.config.Revision
	if len(revision) > 8 {
		revision = revision[:8]
	}
	base.Build = fmt.Sprintf("%s%s:%s", a.config.Version, a.config.VersionPrerelease, revision)

	// Copy the TLS configuration
	base.VerifyIncoming = a.config.VerifyIncoming || a.config.VerifyIncomingRPC
	if a.config.CAPath != "" || a.config.CAFile != "" {
		base.UseTLS = true
	}
	base.VerifyOutgoing = a.config.VerifyOutgoing
	base.VerifyServerHostname = a.config.VerifyServerHostname
	base.CAFile = a.config.CAFile
	base.CAPath = a.config.CAPath
	base.CertFile = a.config.CertFile
	base.KeyFile = a.config.KeyFile
	base.ServerName = a.config.ServerName
	base.Domain = a.config.Domain
	base.TLSMinVersion = a.config.TLSMinVersion
	base.TLSCipherSuites = a.config.TLSCipherSuites
	base.TLSPreferServerCipherSuites = a.config.TLSPreferServerCipherSuites

	// Setup the ServerUp callback
	base.ServerUp = a.state.ConsulServerUp

	// Setup the user event callback
	base.UserEventHandler = func(e serf.UserEvent) {
		select {
		case a.eventCh <- e:
		case <-a.shutdownCh:
		}
	}

	// Setup the loggers
	base.LogOutput = a.LogOutput
	return base, nil
}

// parseSingleIPTemplate is used as a helper function to parse out a single IP
// address from a config parameter.
func parseSingleIPTemplate(ipTmpl string) (string, error) {
	out, err := template.Parse(ipTmpl)
	if err != nil {
		return "", fmt.Errorf("Unable to parse address template %q: %v", ipTmpl, err)
	}

	ips := strings.Split(out, " ")
	switch len(ips) {
	case 0:
		return "", errors.New("No addresses found, please configure one.")
	case 1:
		return ips[0], nil
	default:
		return "", fmt.Errorf("Multiple addresses found (%q), please configure one.", out)
	}
}

// resolveTmplAddrs iterates over the myriad of addresses in the agent's config
// and performs go-sockaddr/template Parse on each known address in case the
// user specified a template config for any of their values.
func (a *Agent) resolveTmplAddrs() error {
	if a.config.AdvertiseAddr != "" {
		ipStr, err := parseSingleIPTemplate(a.config.AdvertiseAddr)
		if err != nil {
			return fmt.Errorf("Advertise address resolution failed: %v", err)
		}
		a.config.AdvertiseAddr = ipStr
	}

	if a.config.Addresses.DNS != "" {
		ipStr, err := parseSingleIPTemplate(a.config.Addresses.DNS)
		if err != nil {
			return fmt.Errorf("DNS address resolution failed: %v", err)
		}
		a.config.Addresses.DNS = ipStr
	}

	if a.config.Addresses.HTTP != "" {
		ipStr, err := parseSingleIPTemplate(a.config.Addresses.HTTP)
		if err != nil {
			return fmt.Errorf("HTTP address resolution failed: %v", err)
		}
		a.config.Addresses.HTTP = ipStr
	}

	if a.config.Addresses.HTTPS != "" {
		ipStr, err := parseSingleIPTemplate(a.config.Addresses.HTTPS)
		if err != nil {
			return fmt.Errorf("HTTPS address resolution failed: %v", err)
		}
		a.config.Addresses.HTTPS = ipStr
	}

	if a.config.AdvertiseAddrWan != "" {
		ipStr, err := parseSingleIPTemplate(a.config.AdvertiseAddrWan)
		if err != nil {
			return fmt.Errorf("Advertise WAN address resolution failed: %v", err)
		}
		a.config.AdvertiseAddrWan = ipStr
	}

	if a.config.BindAddr != "" {
		ipStr, err := parseSingleIPTemplate(a.config.BindAddr)
		if err != nil {
			return fmt.Errorf("Bind address resolution failed: %v", err)
		}
		a.config.BindAddr = ipStr
	}

	if a.config.ClientAddr != "" {
		ipStr, err := parseSingleIPTemplate(a.config.ClientAddr)
		if err != nil {
			return fmt.Errorf("Client address resolution failed: %v", err)
		}
		a.config.ClientAddr = ipStr
	}

	if a.config.SerfLanBindAddr != "" {
		ipStr, err := parseSingleIPTemplate(a.config.SerfLanBindAddr)
		if err != nil {
			return fmt.Errorf("Serf LAN Address resolution failed: %v", err)
		}
		a.config.SerfLanBindAddr = ipStr
	}

	if a.config.SerfWanBindAddr != "" {
		ipStr, err := parseSingleIPTemplate(a.config.SerfWanBindAddr)
		if err != nil {
			return fmt.Errorf("Serf WAN Address resolution failed: %v", err)
		}
		a.config.SerfWanBindAddr = ipStr
	}

	// Parse all tagged addresses
	for k, v := range a.config.TaggedAddresses {
		ipStr, err := parseSingleIPTemplate(v)
		if err != nil {
			return fmt.Errorf("%s address resolution failed: %v", k, err)
		}
		a.config.TaggedAddresses[k] = ipStr
	}

	return nil
}

// makeServer creates a new consul server.
func (a *Agent) makeServer() (*consul.Server, error) {
	config, err := a.consulConfig()
	if err != nil {
		return nil, err
	}
	if err := a.setupKeyrings(config); err != nil {
		return nil, fmt.Errorf("Failed to configure keyring: %v", err)
	}
	server, err := consul.NewServerLogger(config, a.logger)
	if err != nil {
		return nil, fmt.Errorf("Failed to start Consul server: %v", err)
	}
	return server, nil
}

// makeClient creates a new consul client.
func (a *Agent) makeClient() (*consul.Client, error) {
	config, err := a.consulConfig()
	if err != nil {
		return nil, err
	}
	if err := a.setupKeyrings(config); err != nil {
		return nil, fmt.Errorf("Failed to configure keyring: %v", err)
	}
	client, err := consul.NewClient(config)
	if err != nil {
		return nil, fmt.Errorf("Failed to start Consul client: %v", err)
	}
	return client, nil
}

// makeRandomID will generate a random UUID for a node.
func (a *Agent) makeRandomID() (string, error) {
	id, err := uuid.GenerateUUID()
	if err != nil {
		return "", err
	}

	a.logger.Printf("[DEBUG] Using random ID %q as node ID", id)
	return id, nil
}

// makeNodeID will try to find a host-specific ID, or else will generate a
// random ID. The returned ID will always be formatted as a GUID. We don't tell
// the caller whether this ID is random or stable since the consequences are
// high for us if this changes, so we will persist it either way. This will let
// gopsutil change implementations without affecting in-place upgrades of nodes.
func (a *Agent) makeNodeID() (string, error) {
	// If they've disabled host-based IDs then just make a random one.
	if a.config.DisableHostNodeID {
		return a.makeRandomID()
	}

	// Try to get a stable ID associated with the host itself.
	info, err := host.Info()
	if err != nil {
		a.logger.Printf("[DEBUG] Couldn't get a unique ID from the host: %v", err)
		return a.makeRandomID()
	}

	// Make sure the host ID parses as a UUID, since we don't have complete
	// control over this process.
	id := strings.ToLower(info.HostID)
	if _, err := uuid.ParseUUID(id); err != nil {
		a.logger.Printf("[DEBUG] Unique ID %q from host isn't formatted as a UUID: %v",
			id, err)
		return a.makeRandomID()
	}

	// Hash the input to make it well distributed. The reported Host UUID may be
	// similar across nodes if they are on a cloud provider or on motherboards
	// created from the same batch.
	buf := sha512.Sum512([]byte(id))
	id = fmt.Sprintf("%08x-%04x-%04x-%04x-%12x",
		buf[0:4],
		buf[4:6],
		buf[6:8],
		buf[8:10],
		buf[10:16])

	a.logger.Printf("[DEBUG] Using unique ID %q from host as node ID", id)
	return id, nil
}

// setupNodeID will pull the persisted node ID, if any, or create a random one
// and persist it.
func (a *Agent) setupNodeID(config *Config) error {
	// If they've configured a node ID manually then just use that, as
	// long as it's valid.
	if config.NodeID != "" {
		config.NodeID = types.NodeID(strings.ToLower(string(config.NodeID)))
		if _, err := uuid.ParseUUID(string(config.NodeID)); err != nil {
			return err
		}

		return nil
	}

	// For dev mode we have no filesystem access so just make one.
	if a.config.DevMode {
		id, err := a.makeNodeID()
		if err != nil {
			return err
		}

		config.NodeID = types.NodeID(id)
		return nil
	}

	// Load saved state, if any. Since a user could edit this, we also
	// validate it.
	fileID := filepath.Join(config.DataDir, "node-id")
	if _, err := os.Stat(fileID); err == nil {
		rawID, err := ioutil.ReadFile(fileID)
		if err != nil {
			return err
		}

		nodeID := strings.TrimSpace(string(rawID))
		nodeID = strings.ToLower(nodeID)
		if _, err := uuid.ParseUUID(nodeID); err != nil {
			return err
		}

		config.NodeID = types.NodeID(nodeID)
	}

	// If we still don't have a valid node ID, make one.
	if config.NodeID == "" {
		id, err := a.makeNodeID()
		if err != nil {
			return err
		}
		if err := lib.EnsurePath(fileID, false); err != nil {
			return err
		}
		if err := ioutil.WriteFile(fileID, []byte(id), 0600); err != nil {
			return err
		}

		config.NodeID = types.NodeID(id)
	}
	return nil
}

// setupKeyrings is used to initialize and load keyrings during agent startup
func (a *Agent) setupKeyrings(config *consul.Config) error {
	fileLAN := filepath.Join(a.config.DataDir, serfLANKeyring)
	fileWAN := filepath.Join(a.config.DataDir, serfWANKeyring)

	if a.config.EncryptKey == "" {
		goto LOAD
	}
	if _, err := os.Stat(fileLAN); err != nil {
		if err := initKeyring(fileLAN, a.config.EncryptKey); err != nil {
			return err
		}
	}
	if a.config.Server {
		if _, err := os.Stat(fileWAN); err != nil {
			if err := initKeyring(fileWAN, a.config.EncryptKey); err != nil {
				return err
			}
		}
	}

LOAD:
	if _, err := os.Stat(fileLAN); err == nil {
		config.SerfLANConfig.KeyringFile = fileLAN
	}
	if err := loadKeyringFile(config.SerfLANConfig); err != nil {
		return err
	}
	if a.config.Server {
		if _, err := os.Stat(fileWAN); err == nil {
			config.SerfWANConfig.KeyringFile = fileWAN
		}
		if err := loadKeyringFile(config.SerfWANConfig); err != nil {
			return err
		}
	}

	// Success!
	return nil
}

// RPC is used to make an RPC call to the Consul servers
// This allows the agent to implement the Consul.Interface
func (a *Agent) RPC(method string, args interface{}, reply interface{}) error {
	return a.delegate.RPC(method, args, reply)
}

// SnapshotRPC performs the requested snapshot RPC against the Consul server in
// a streaming manner. The contents of in will be read and passed along as the
// payload, and the response message will determine the error status, and any
// return payload will be written to out.
func (a *Agent) SnapshotRPC(args *structs.SnapshotRequest, in io.Reader, out io.Writer,
	replyFn consul.SnapshotReplyFn) error {
	return a.delegate.SnapshotRPC(args, in, out, replyFn)
}

// Leave is used to prepare the agent for a graceful shutdown
func (a *Agent) Leave() error {
	return a.delegate.Leave()
}

// Shutdown is used to hard stop the agent. Should be
// preceded by a call to Leave to do it gracefully.
func (a *Agent) Shutdown() error {
	a.shutdownLock.Lock()
	defer a.shutdownLock.Unlock()

	if a.shutdown {
		return nil
	}
	a.logger.Println("[INFO] agent: Requesting shutdown")

	// Stop all API endpoints
	for _, srv := range a.dnsServers {
		a.logger.Printf("[INFO] agent: Stopping DNS server %s (%s)", srv.Server.Addr, srv.Server.Net)
		srv.Shutdown()
	}
	for _, srv := range a.httpServers {
		// http server is HTTPS if TLSConfig is not nil and NextProtos does not only contain "h2"
		// the latter seems to be a side effect of HTTP/2 support in go 1.8. TLSConfig != nil is
		// no longer sufficient to check for an HTTPS server.
		a.logger.Printf("[INFO] agent: Stopping %s server %s",
			strings.ToUpper(srv.proto), srv.Addr)

		// old behavior: just die
		// srv.Close()

		// graceful shutdown
		ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
		defer cancel()

		done := make(chan struct{})
		go func() {
			srv.Shutdown(ctx)
			close(done)
		}()
		select {
		case <-done:
			// server down within timeout
		case <-ctx.Done():
			a.logger.Printf("[WARN] agent: Timeout stopping %s server %s",
				strings.ToUpper(srv.proto), srv.Addr)
		}
	}
	a.logger.Println("[INFO] agent: Waiting for endpoints to shut down")
	a.wgServers.Wait()
	a.logger.Print("[INFO] agent: Endpoints down")

	// Stop all the checks
	a.checkLock.Lock()
	defer a.checkLock.Unlock()
	for _, chk := range a.checkMonitors {
		chk.Stop()
	}
	for _, chk := range a.checkTTLs {
		chk.Stop()
	}

	for _, chk := range a.checkHTTPs {
		chk.Stop()
	}

	for _, chk := range a.checkTCPs {
		chk.Stop()
	}

	var err error
	if a.delegate != nil {
		err = a.delegate.Shutdown()
		if _, ok := a.delegate.(*consul.Server); ok {
			a.logger.Print("[INFO] agent: consul server down")
		} else {
			a.logger.Print("[INFO] agent: consul client down")
		}
	}

	pidErr := a.deletePid()
	if pidErr != nil {
		a.logger.Println("[WARN] agent: could not delete pid file ", pidErr)
	}

	a.logger.Println("[INFO] agent: shutdown complete")
	a.shutdown = true
	close(a.shutdownCh)
	return err
}

// ReloadCh is used to return a channel that can be
// used for triggering reloads and returning a response.
func (a *Agent) ReloadCh() chan chan error {
	return a.reloadCh
}

// ShutdownCh is used to return a channel that can be
// selected to wait for the agent to perform a shutdown.
func (a *Agent) ShutdownCh() <-chan struct{} {
	return a.shutdownCh
}

// JoinLAN is used to have the agent join a LAN cluster
func (a *Agent) JoinLAN(addrs []string) (n int, err error) {
	a.logger.Printf("[INFO] agent: (LAN) joining: %v", addrs)
	n, err = a.delegate.JoinLAN(addrs)
	a.logger.Printf("[INFO] agent: (LAN) joined: %d Err: %v", n, err)
	return
}

// JoinWAN is used to have the agent join a WAN cluster
func (a *Agent) JoinWAN(addrs []string) (n int, err error) {
	a.logger.Printf("[INFO] agent: (WAN) joining: %v", addrs)
	if srv, ok := a.delegate.(*consul.Server); ok {
		n, err = srv.JoinWAN(addrs)
	} else {
		err = fmt.Errorf("Must be a server to join WAN cluster")
	}
	a.logger.Printf("[INFO] agent: (WAN) joined: %d Err: %v", n, err)
	return
}

// ForceLeave is used to remove a failed node from the cluster
func (a *Agent) ForceLeave(node string) (err error) {
	a.logger.Printf("[INFO] Force leaving node: %v", node)
	err = a.delegate.RemoveFailedNode(node)
	if err != nil {
		a.logger.Printf("[WARN] Failed to remove node: %v", err)
	}
	return err
}

// LocalMember is used to return the local node
func (a *Agent) LocalMember() serf.Member {
	return a.delegate.LocalMember()
}

// LANMembers is used to retrieve the LAN members
func (a *Agent) LANMembers() []serf.Member {
	return a.delegate.LANMembers()
}

// WANMembers is used to retrieve the WAN members
func (a *Agent) WANMembers() []serf.Member {
	if srv, ok := a.delegate.(*consul.Server); ok {
		return srv.WANMembers()
	}
	return nil
}

// StartSync is called once Services and Checks are registered.
// This is called to prevent a race between clients and the anti-entropy routines
func (a *Agent) StartSync() {
	// Start the anti entropy routine
	go a.state.antiEntropy(a.shutdownCh)
}

// PauseSync is used to pause anti-entropy while bulk changes are make
func (a *Agent) PauseSync() {
	a.state.Pause()
}

// ResumeSync is used to unpause anti-entropy after bulk changes are make
func (a *Agent) ResumeSync() {
	a.state.Resume()
}

// GetLANCoordinate returns the coordinate of this node in the local pool (assumes coordinates
// are enabled, so check that before calling).
func (a *Agent) GetLANCoordinate() (*coordinate.Coordinate, error) {
	return a.delegate.GetLANCoordinate()
}

// sendCoordinate is a long-running loop that periodically sends our coordinate
// to the server. Closing the agent's shutdownChannel will cause this to exit.
func (a *Agent) sendCoordinate() {
	for {
		rate := a.config.SyncCoordinateRateTarget
		min := a.config.SyncCoordinateIntervalMin
		intv := lib.RateScaledInterval(rate, min, len(a.LANMembers()))
		intv = intv + lib.RandomStagger(intv)

		select {
		case <-time.After(intv):
			members := a.LANMembers()
			grok, err := consul.CanServersUnderstandProtocol(members, 3)
			if err != nil {
				a.logger.Printf("[ERR] agent: failed to check servers: %s", err)
				continue
			}
			if !grok {
				a.logger.Printf("[DEBUG] agent: skipping coordinate updates until servers are upgraded")
				continue
			}

			c, err := a.GetLANCoordinate()
			if err != nil {
				a.logger.Printf("[ERR] agent: failed to get coordinate: %s", err)
				continue
			}

			req := structs.CoordinateUpdateRequest{
				Datacenter:   a.config.Datacenter,
				Node:         a.config.NodeName,
				Coord:        c,
				WriteRequest: structs.WriteRequest{Token: a.config.GetTokenForAgent()},
			}
			var reply struct{}
			if err := a.RPC("Coordinate.Update", &req, &reply); err != nil {
				a.logger.Printf("[ERR] agent: coordinate update error: %s", err)
				continue
			}
		case <-a.shutdownCh:
			return
		}
	}
}

// reapServicesInternal does a single pass, looking for services to reap.
func (a *Agent) reapServicesInternal() {
	reaped := make(map[string]struct{})
	for checkID, check := range a.state.CriticalChecks() {
		// There's nothing to do if there's no service.
		if check.Check.ServiceID == "" {
			continue
		}

		// There might be multiple checks for one service, so
		// we don't need to reap multiple times.
		serviceID := check.Check.ServiceID
		if _, ok := reaped[serviceID]; ok {
			continue
		}

		// See if there's a timeout.
		a.checkLock.Lock()
		timeout, ok := a.checkReapAfter[checkID]
		a.checkLock.Unlock()

		// Reap, if necessary. We keep track of which service
		// this is so that we won't try to remove it again.
		if ok && check.CriticalFor > timeout {
			reaped[serviceID] = struct{}{}
			a.RemoveService(serviceID, true)
			a.logger.Printf("[INFO] agent: Check %q for service %q has been critical for too long; deregistered service",
				checkID, serviceID)
		}
	}
}

// reapServices is a long running goroutine that looks for checks that have been
// critical too long and dregisters their associated services.
func (a *Agent) reapServices() {
	for {
		select {
		case <-time.After(a.config.CheckReapInterval):
			a.reapServicesInternal()

		case <-a.shutdownCh:
			return
		}
	}

}

// persistService saves a service definition to a JSON file in the data dir
func (a *Agent) persistService(service *structs.NodeService) error {
	svcPath := filepath.Join(a.config.DataDir, servicesDir, stringHash(service.ID))

	wrapped := persistedService{
		Token:   a.state.ServiceToken(service.ID),
		Service: service,
	}
	encoded, err := json.Marshal(wrapped)
	if err != nil {
		return err
	}

	return writeFileAtomic(svcPath, encoded)
}

// purgeService removes a persisted service definition file from the data dir
func (a *Agent) purgeService(serviceID string) error {
	svcPath := filepath.Join(a.config.DataDir, servicesDir, stringHash(serviceID))
	if _, err := os.Stat(svcPath); err == nil {
		return os.Remove(svcPath)
	}
	return nil
}

// persistCheck saves a check definition to the local agent's state directory
func (a *Agent) persistCheck(check *structs.HealthCheck, chkType *CheckType) error {
	checkPath := filepath.Join(a.config.DataDir, checksDir, checkIDHash(check.CheckID))

	// Create the persisted check
	wrapped := persistedCheck{
		Check:   check,
		ChkType: chkType,
		Token:   a.state.CheckToken(check.CheckID),
	}

	encoded, err := json.Marshal(wrapped)
	if err != nil {
		return err
	}

	return writeFileAtomic(checkPath, encoded)
}

// purgeCheck removes a persisted check definition file from the data dir
func (a *Agent) purgeCheck(checkID types.CheckID) error {
	checkPath := filepath.Join(a.config.DataDir, checksDir, checkIDHash(checkID))
	if _, err := os.Stat(checkPath); err == nil {
		return os.Remove(checkPath)
	}
	return nil
}

// writeFileAtomic writes the given contents to a temporary file in the same
// directory, does an fsync and then renames the file to its real path
func writeFileAtomic(path string, contents []byte) error {
	uuid, err := uuid.GenerateUUID()
	if err != nil {
		return err
	}
	tempPath := fmt.Sprintf("%s-%s.tmp", path, uuid)

	if err := os.MkdirAll(filepath.Dir(path), 0700); err != nil {
		return err
	}
	fh, err := os.OpenFile(tempPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0600)
	if err != nil {
		return err
	}
	if _, err := fh.Write(contents); err != nil {
		return err
	}
	if err := fh.Sync(); err != nil {
		return err
	}
	if err := fh.Close(); err != nil {
		return err
	}
	return os.Rename(tempPath, path)
}

// AddService is used to add a service entry.
// This entry is persistent and the agent will make a best effort to
// ensure it is registered
func (a *Agent) AddService(service *structs.NodeService, chkTypes CheckTypes, persist bool, token string) error {
	if service.Service == "" {
		return fmt.Errorf("Service name missing")
	}
	if service.ID == "" && service.Service != "" {
		service.ID = service.Service
	}
	for _, check := range chkTypes {
		if !check.Valid() {
			return fmt.Errorf("Check type is not valid")
		}
	}

	// Warn if the service name is incompatible with DNS
	if !dnsNameRe.MatchString(service.Service) {
		a.logger.Printf("[WARN] Service name %q will not be discoverable "+
			"via DNS due to invalid characters. Valid characters include "+
			"all alpha-numerics and dashes.", service.Service)
	}

	// Warn if any tags are incompatible with DNS
	for _, tag := range service.Tags {
		if !dnsNameRe.MatchString(tag) {
			a.logger.Printf("[DEBUG] Service tag %q will not be discoverable "+
				"via DNS due to invalid characters. Valid characters include "+
				"all alpha-numerics and dashes.", tag)
		}
	}

	// Pause the service syncs during modification
	a.PauseSync()
	defer a.ResumeSync()

	// Take a snapshot of the current state of checks (if any), and
	// restore them before resuming anti-entropy.
	snap := a.snapshotCheckState()
	defer a.restoreCheckState(snap)

	// Add the service
	a.state.AddService(service, token)

	// Persist the service to a file
	if persist && !a.config.DevMode {
		if err := a.persistService(service); err != nil {
			return err
		}
	}

	// Create an associated health check
	for i, chkType := range chkTypes {
		checkID := string(chkType.CheckID)
		if checkID == "" {
			checkID = fmt.Sprintf("service:%s", service.ID)
			if len(chkTypes) > 1 {
				checkID += fmt.Sprintf(":%d", i+1)
			}
		}
		name := chkType.Name
		if name == "" {
			name = fmt.Sprintf("Service '%s' check", service.Service)
		}
		check := &structs.HealthCheck{
			Node:        a.config.NodeName,
			CheckID:     types.CheckID(checkID),
			Name:        name,
			Status:      api.HealthCritical,
			Notes:       chkType.Notes,
			ServiceID:   service.ID,
			ServiceName: service.Service,
		}
		if chkType.Status != "" {
			check.Status = chkType.Status
		}
		if err := a.AddCheck(check, chkType, persist, token); err != nil {
			return err
		}
	}
	return nil
}

// RemoveService is used to remove a service entry.
// The agent will make a best effort to ensure it is deregistered
func (a *Agent) RemoveService(serviceID string, persist bool) error {
	// Protect "consul" service from deletion by a user
	if _, ok := a.delegate.(*consul.Server); ok && serviceID == consul.ConsulServiceID {
		return fmt.Errorf(
			"Deregistering the %s service is not allowed",
			consul.ConsulServiceID)
	}

	// Validate ServiceID
	if serviceID == "" {
		return fmt.Errorf("ServiceID missing")
	}

	// Remove service immediately
	if err := a.state.RemoveService(serviceID); err != nil {
		a.logger.Printf("[WARN] agent: Failed to deregister service %q: %s", serviceID, err)
		return nil
	}

	// Remove the service from the data dir
	if persist {
		if err := a.purgeService(serviceID); err != nil {
			return err
		}
	}

	// Deregister any associated health checks
	for checkID, health := range a.state.Checks() {
		if health.ServiceID != serviceID {
			continue
		}
		if err := a.RemoveCheck(checkID, persist); err != nil {
			return err
		}
	}

	log.Printf("[DEBUG] agent: removed service %q", serviceID)
	return nil
}

// AddCheck is used to add a health check to the agent.
// This entry is persistent and the agent will make a best effort to
// ensure it is registered. The Check may include a CheckType which
// is used to automatically update the check status
func (a *Agent) AddCheck(check *structs.HealthCheck, chkType *CheckType, persist bool, token string) error {
	if check.CheckID == "" {
		return fmt.Errorf("CheckID missing")
	}
	if chkType != nil && !chkType.Valid() {
		return fmt.Errorf("Check type is not valid")
	}

	if check.ServiceID != "" {
		svc, ok := a.state.Services()[check.ServiceID]
		if !ok {
			return fmt.Errorf("ServiceID %q does not exist", check.ServiceID)
		}
		check.ServiceName = svc.Service
	}

	a.checkLock.Lock()
	defer a.checkLock.Unlock()

	// Check if already registered
	if chkType != nil {
		if chkType.IsTTL() {
			if existing, ok := a.checkTTLs[check.CheckID]; ok {
				existing.Stop()
			}

			ttl := &CheckTTL{
				Notify:  &a.state,
				CheckID: check.CheckID,
				TTL:     chkType.TTL,
				Logger:  a.logger,
			}

			// Restore persisted state, if any
			if err := a.loadCheckState(check); err != nil {
				a.logger.Printf("[WARN] agent: failed restoring state for check %q: %s",
					check.CheckID, err)
			}

			ttl.Start()
			a.checkTTLs[check.CheckID] = ttl

		} else if chkType.IsHTTP() {
			if existing, ok := a.checkHTTPs[check.CheckID]; ok {
				existing.Stop()
			}
			if chkType.Interval < MinInterval {
				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
					check.CheckID, MinInterval))
				chkType.Interval = MinInterval
			}

			http := &CheckHTTP{
				Notify:        &a.state,
				CheckID:       check.CheckID,
				HTTP:          chkType.HTTP,
				Interval:      chkType.Interval,
				Timeout:       chkType.Timeout,
				Logger:        a.logger,
				TLSSkipVerify: chkType.TLSSkipVerify,
			}
			http.Start()
			a.checkHTTPs[check.CheckID] = http

		} else if chkType.IsTCP() {
			if existing, ok := a.checkTCPs[check.CheckID]; ok {
				existing.Stop()
			}
			if chkType.Interval < MinInterval {
				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
					check.CheckID, MinInterval))
				chkType.Interval = MinInterval
			}

			tcp := &CheckTCP{
				Notify:   &a.state,
				CheckID:  check.CheckID,
				TCP:      chkType.TCP,
				Interval: chkType.Interval,
				Timeout:  chkType.Timeout,
				Logger:   a.logger,
			}
			tcp.Start()
			a.checkTCPs[check.CheckID] = tcp

		} else if chkType.IsDocker() {
			if existing, ok := a.checkDockers[check.CheckID]; ok {
				existing.Stop()
			}
			if chkType.Interval < MinInterval {
				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
					check.CheckID, MinInterval))
				chkType.Interval = MinInterval
			}

			dockerCheck := &CheckDocker{
				Notify:            &a.state,
				CheckID:           check.CheckID,
				DockerContainerID: chkType.DockerContainerID,
				Shell:             chkType.Shell,
				Script:            chkType.Script,
				Interval:          chkType.Interval,
				Logger:            a.logger,
			}
			if err := dockerCheck.Init(); err != nil {
				return err
			}
			dockerCheck.Start()
			a.checkDockers[check.CheckID] = dockerCheck
		} else if chkType.IsMonitor() {
			if existing, ok := a.checkMonitors[check.CheckID]; ok {
				existing.Stop()
			}
			if chkType.Interval < MinInterval {
				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has interval below minimum of %v",
					check.CheckID, MinInterval))
				chkType.Interval = MinInterval
			}

			monitor := &CheckMonitor{
				Notify:   &a.state,
				CheckID:  check.CheckID,
				Script:   chkType.Script,
				Interval: chkType.Interval,
				Timeout:  chkType.Timeout,
				Logger:   a.logger,
			}
			monitor.Start()
			a.checkMonitors[check.CheckID] = monitor
		} else {
			return fmt.Errorf("Check type is not valid")
		}

		if chkType.DeregisterCriticalServiceAfter > 0 {
			timeout := chkType.DeregisterCriticalServiceAfter
			if timeout < a.config.CheckDeregisterIntervalMin {
				timeout = a.config.CheckDeregisterIntervalMin
				a.logger.Println(fmt.Sprintf("[WARN] agent: check '%s' has deregister interval below minimum of %v",
					check.CheckID, a.config.CheckDeregisterIntervalMin))
			}
			a.checkReapAfter[check.CheckID] = timeout
		} else {
			delete(a.checkReapAfter, check.CheckID)
		}
	}

	// Add to the local state for anti-entropy
	a.state.AddCheck(check, token)

	// Persist the check
	if persist && !a.config.DevMode {
		return a.persistCheck(check, chkType)
	}

	return nil
}

// RemoveCheck is used to remove a health check.
// The agent will make a best effort to ensure it is deregistered
func (a *Agent) RemoveCheck(checkID types.CheckID, persist bool) error {
	// Validate CheckID
	if checkID == "" {
		return fmt.Errorf("CheckID missing")
	}

	// Add to the local state for anti-entropy
	a.state.RemoveCheck(checkID)

	a.checkLock.Lock()
	defer a.checkLock.Unlock()

	// Stop any monitors
	delete(a.checkReapAfter, checkID)
	if check, ok := a.checkMonitors[checkID]; ok {
		check.Stop()
		delete(a.checkMonitors, checkID)
	}
	if check, ok := a.checkHTTPs[checkID]; ok {
		check.Stop()
		delete(a.checkHTTPs, checkID)
	}
	if check, ok := a.checkTCPs[checkID]; ok {
		check.Stop()
		delete(a.checkTCPs, checkID)
	}
	if check, ok := a.checkTTLs[checkID]; ok {
		check.Stop()
		delete(a.checkTTLs, checkID)
	}
	if persist {
		if err := a.purgeCheck(checkID); err != nil {
			return err
		}
		if err := a.purgeCheckState(checkID); err != nil {
			return err
		}
	}
	a.logger.Printf("[DEBUG] agent: removed check %q", checkID)
	return nil
}

// updateTTLCheck is used to update the status of a TTL check via the Agent API.
func (a *Agent) updateTTLCheck(checkID types.CheckID, status, output string) error {
	a.checkLock.Lock()
	defer a.checkLock.Unlock()

	// Grab the TTL check.
	check, ok := a.checkTTLs[checkID]
	if !ok {
		return fmt.Errorf("CheckID %q does not have associated TTL", checkID)
	}

	// Set the status through CheckTTL to reset the TTL.
	check.SetStatus(status, output)

	// We don't write any files in dev mode so bail here.
	if a.config.DevMode {
		return nil
	}

	// Persist the state so the TTL check can come up in a good state after
	// an agent restart, especially with long TTL values.
	if err := a.persistCheckState(check, status, output); err != nil {
		return fmt.Errorf("failed persisting state for check %q: %s", checkID, err)
	}

	return nil
}

// persistCheckState is used to record the check status into the data dir.
// This allows the state to be restored on a later agent start. Currently
// only useful for TTL based checks.
func (a *Agent) persistCheckState(check *CheckTTL, status, output string) error {
	// Create the persisted state
	state := persistedCheckState{
		CheckID: check.CheckID,
		Status:  status,
		Output:  output,
		Expires: time.Now().Add(check.TTL).Unix(),
	}

	// Encode the state
	buf, err := json.Marshal(state)
	if err != nil {
		return err
	}

	// Create the state dir if it doesn't exist
	dir := filepath.Join(a.config.DataDir, checkStateDir)
	if err := os.MkdirAll(dir, 0700); err != nil {
		return fmt.Errorf("failed creating check state dir %q: %s", dir, err)
	}

	// Write the state to the file
	file := filepath.Join(dir, checkIDHash(check.CheckID))

	// Create temp file in same dir, to make more likely atomic
	tempFile := file + ".tmp"

	// persistCheckState is called frequently, so don't use writeFileAtomic to avoid calling fsync here
	if err := ioutil.WriteFile(tempFile, buf, 0600); err != nil {
		return fmt.Errorf("failed writing temp file %q: %s", tempFile, err)
	}
	if err := os.Rename(tempFile, file); err != nil {
		return fmt.Errorf("failed to rename temp file from %q to %q: %s", tempFile, file, err)
	}

	return nil
}

// loadCheckState is used to restore the persisted state of a check.
func (a *Agent) loadCheckState(check *structs.HealthCheck) error {
	// Try to read the persisted state for this check
	file := filepath.Join(a.config.DataDir, checkStateDir, checkIDHash(check.CheckID))
	buf, err := ioutil.ReadFile(file)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("failed reading file %q: %s", file, err)
	}

	// Decode the state data
	var p persistedCheckState
	if err := json.Unmarshal(buf, &p); err != nil {
		a.logger.Printf("[ERROR] agent: failed decoding check state: %s", err)
		return a.purgeCheckState(check.CheckID)
	}

	// Check if the state has expired
	if time.Now().Unix() >= p.Expires {
		a.logger.Printf("[DEBUG] agent: check state expired for %q, not restoring", check.CheckID)
		return a.purgeCheckState(check.CheckID)
	}

	// Restore the fields from the state
	check.Output = p.Output
	check.Status = p.Status
	return nil
}

// purgeCheckState is used to purge the state of a check from the data dir
func (a *Agent) purgeCheckState(checkID types.CheckID) error {
	file := filepath.Join(a.config.DataDir, checkStateDir, checkIDHash(checkID))
	err := os.Remove(file)
	if os.IsNotExist(err) {
		return nil
	}
	return err
}

// Stats is used to get various debugging state from the sub-systems
func (a *Agent) Stats() map[string]map[string]string {
	toString := func(v uint64) string {
		return strconv.FormatUint(v, 10)
	}
	stats := a.delegate.Stats()
	stats["agent"] = map[string]string{
		"check_monitors": toString(uint64(len(a.checkMonitors))),
		"check_ttls":     toString(uint64(len(a.checkTTLs))),
		"checks":         toString(uint64(len(a.state.checks))),
		"services":       toString(uint64(len(a.state.services))),
	}

	revision := a.config.Revision
	if len(revision) > 8 {
		revision = revision[:8]
	}
	stats["build"] = map[string]string{
		"revision":   revision,
		"version":    a.config.Version,
		"prerelease": a.config.VersionPrerelease,
	}
	return stats
}

// storePid is used to write out our PID to a file if necessary
func (a *Agent) storePid() error {
	// Quit fast if no pidfile
	pidPath := a.config.PidFile
	if pidPath == "" {
		return nil
	}

	// Open the PID file
	pidFile, err := os.OpenFile(pidPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0666)
	if err != nil {
		return fmt.Errorf("Could not open pid file: %v", err)
	}
	defer pidFile.Close()

	// Write out the PID
	pid := os.Getpid()
	_, err = pidFile.WriteString(fmt.Sprintf("%d", pid))
	if err != nil {
		return fmt.Errorf("Could not write to pid file: %s", err)
	}
	return nil
}

// deletePid is used to delete our PID on exit
func (a *Agent) deletePid() error {
	// Quit fast if no pidfile
	pidPath := a.config.PidFile
	if pidPath == "" {
		return nil
	}

	stat, err := os.Stat(pidPath)
	if err != nil {
		return fmt.Errorf("Could not remove pid file: %s", err)
	}

	if stat.IsDir() {
		return fmt.Errorf("Specified pid file path is directory")
	}

	err = os.Remove(pidPath)
	if err != nil {
		return fmt.Errorf("Could not remove pid file: %s", err)
	}
	return nil
}

// loadServices will load service definitions from configuration and persisted
// definitions on disk, and load them into the local agent.
func (a *Agent) loadServices(conf *Config) error {
	// Register the services from config
	for _, service := range conf.Services {
		ns := service.NodeService()
		chkTypes := service.CheckTypes()
		if err := a.AddService(ns, chkTypes, false, service.Token); err != nil {
			return fmt.Errorf("Failed to register service '%s': %v", service.ID, err)
		}
	}

	// Load any persisted services
	svcDir := filepath.Join(a.config.DataDir, servicesDir)
	files, err := ioutil.ReadDir(svcDir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("Failed reading services dir %q: %s", svcDir, err)
	}
	for _, fi := range files {
		// Skip all dirs
		if fi.IsDir() {
			continue
		}

		// Open the file for reading
		file := filepath.Join(svcDir, fi.Name())
		fh, err := os.Open(file)
		if err != nil {
			return fmt.Errorf("failed opening service file %q: %s", file, err)
		}

		// Read the contents into a buffer
		buf, err := ioutil.ReadAll(fh)
		fh.Close()
		if err != nil {
			return fmt.Errorf("failed reading service file %q: %s", file, err)
		}

		// Try decoding the service definition
		var p persistedService
		if err := json.Unmarshal(buf, &p); err != nil {
			// Backwards-compatibility for pre-0.5.1 persisted services
			if err := json.Unmarshal(buf, &p.Service); err != nil {
				return fmt.Errorf("failed decoding service file %q: %s", file, err)
			}
		}
		serviceID := p.Service.ID

		if _, ok := a.state.services[serviceID]; ok {
			// Purge previously persisted service. This allows config to be
			// preferred over services persisted from the API.
			a.logger.Printf("[DEBUG] agent: service %q exists, not restoring from %q",
				serviceID, file)
			if err := a.purgeService(serviceID); err != nil {
				return fmt.Errorf("failed purging service %q: %s", serviceID, err)
			}
		} else {
			a.logger.Printf("[DEBUG] agent: restored service definition %q from %q",
				serviceID, file)
			if err := a.AddService(p.Service, nil, false, p.Token); err != nil {
				return fmt.Errorf("failed adding service %q: %s", serviceID, err)
			}
		}
	}

	return nil
}

// unloadServices will deregister all services other than the 'consul' service
// known to the local agent.
func (a *Agent) unloadServices() error {
	for _, service := range a.state.Services() {
		if service.ID == consul.ConsulServiceID {
			continue
		}
		if err := a.RemoveService(service.ID, false); err != nil {
			return fmt.Errorf("Failed deregistering service '%s': %v", service.ID, err)
		}
	}

	return nil
}

// loadChecks loads check definitions and/or persisted check definitions from
// disk and re-registers them with the local agent.
func (a *Agent) loadChecks(conf *Config) error {
	// Register the checks from config
	for _, check := range conf.Checks {
		health := check.HealthCheck(conf.NodeName)
		chkType := check.CheckType()
		if err := a.AddCheck(health, chkType, false, check.Token); err != nil {
			return fmt.Errorf("Failed to register check '%s': %v %v", check.Name, err, check)
		}
	}

	// Load any persisted checks
	checkDir := filepath.Join(a.config.DataDir, checksDir)
	files, err := ioutil.ReadDir(checkDir)
	if err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("Failed reading checks dir %q: %s", checkDir, err)
	}
	for _, fi := range files {
		// Ignore dirs - we only care about the check definition files
		if fi.IsDir() {
			continue
		}

		// Open the file for reading
		file := filepath.Join(checkDir, fi.Name())
		fh, err := os.Open(file)
		if err != nil {
			return fmt.Errorf("Failed opening check file %q: %s", file, err)
		}

		// Read the contents into a buffer
		buf, err := ioutil.ReadAll(fh)
		fh.Close()
		if err != nil {
			return fmt.Errorf("failed reading check file %q: %s", file, err)
		}

		// Decode the check
		var p persistedCheck
		if err := json.Unmarshal(buf, &p); err != nil {
			return fmt.Errorf("Failed decoding check file %q: %s", file, err)
		}
		checkID := p.Check.CheckID

		if _, ok := a.state.checks[checkID]; ok {
			// Purge previously persisted check. This allows config to be
			// preferred over persisted checks from the API.
			a.logger.Printf("[DEBUG] agent: check %q exists, not restoring from %q",
				checkID, file)
			if err := a.purgeCheck(checkID); err != nil {
				return fmt.Errorf("Failed purging check %q: %s", checkID, err)
			}
		} else {
			// Default check to critical to avoid placing potentially unhealthy
			// services into the active pool
			p.Check.Status = api.HealthCritical

			if err := a.AddCheck(p.Check, p.ChkType, false, p.Token); err != nil {
				// Purge the check if it is unable to be restored.
				a.logger.Printf("[WARN] agent: Failed to restore check %q: %s",
					checkID, err)
				if err := a.purgeCheck(checkID); err != nil {
					return fmt.Errorf("Failed purging check %q: %s", checkID, err)
				}
			}
			a.logger.Printf("[DEBUG] agent: restored health check %q from %q",
				p.Check.CheckID, file)
		}
	}

	return nil
}

// unloadChecks will deregister all checks known to the local agent.
func (a *Agent) unloadChecks() error {
	for _, check := range a.state.Checks() {
		if err := a.RemoveCheck(check.CheckID, false); err != nil {
			return fmt.Errorf("Failed deregistering check '%s': %s", check.CheckID, err)
		}
	}

	return nil
}

// snapshotCheckState is used to snapshot the current state of the health
// checks. This is done before we reload our checks, so that we can properly
// restore into the same state.
func (a *Agent) snapshotCheckState() map[types.CheckID]*structs.HealthCheck {
	return a.state.Checks()
}

// restoreCheckState is used to reset the health state based on a snapshot.
// This is done after we finish the reload to avoid any unnecessary flaps
// in health state and potential session invalidations.
func (a *Agent) restoreCheckState(snap map[types.CheckID]*structs.HealthCheck) {
	for id, check := range snap {
		a.state.UpdateCheck(id, check.Status, check.Output)
	}
}

// loadMetadata loads node metadata fields from the agent config and
// updates them on the local agent.
func (a *Agent) loadMetadata(conf *Config) error {
	a.state.Lock()
	defer a.state.Unlock()

	for key, value := range conf.Meta {
		a.state.metadata[key] = value
	}

	a.state.changeMade()

	return nil
}

// parseMetaPair parses a key/value pair of the form key:value
func parseMetaPair(raw string) (string, string) {
	pair := strings.SplitN(raw, ":", 2)
	if len(pair) == 2 {
		return pair[0], pair[1]
	}
	return pair[0], ""
}

// unloadMetadata resets the local metadata state
func (a *Agent) unloadMetadata() {
	a.state.Lock()
	defer a.state.Unlock()

	a.state.metadata = make(map[string]string)
}

// serviceMaintCheckID returns the ID of a given service's maintenance check
func serviceMaintCheckID(serviceID string) types.CheckID {
	return types.CheckID(structs.ServiceMaintPrefix + serviceID)
}

// EnableServiceMaintenance will register a false health check against the given
// service ID with critical status. This will exclude the service from queries.
func (a *Agent) EnableServiceMaintenance(serviceID, reason, token string) error {
	service, ok := a.state.Services()[serviceID]
	if !ok {
		return fmt.Errorf("No service registered with ID %q", serviceID)
	}

	// Check if maintenance mode is not already enabled
	checkID := serviceMaintCheckID(serviceID)
	if _, ok := a.state.Checks()[checkID]; ok {
		return nil
	}

	// Use default notes if no reason provided
	if reason == "" {
		reason = defaultServiceMaintReason
	}

	// Create and register the critical health check
	check := &structs.HealthCheck{
		Node:        a.config.NodeName,
		CheckID:     checkID,
		Name:        "Service Maintenance Mode",
		Notes:       reason,
		ServiceID:   service.ID,
		ServiceName: service.Service,
		Status:      api.HealthCritical,
	}
	a.AddCheck(check, nil, true, token)
	a.logger.Printf("[INFO] agent: Service %q entered maintenance mode", serviceID)

	return nil
}

// DisableServiceMaintenance will deregister the fake maintenance mode check
// if the service has been marked as in maintenance.
func (a *Agent) DisableServiceMaintenance(serviceID string) error {
	if _, ok := a.state.Services()[serviceID]; !ok {
		return fmt.Errorf("No service registered with ID %q", serviceID)
	}

	// Check if maintenance mode is enabled
	checkID := serviceMaintCheckID(serviceID)
	if _, ok := a.state.Checks()[checkID]; !ok {
		return nil
	}

	// Deregister the maintenance check
	a.RemoveCheck(checkID, true)
	a.logger.Printf("[INFO] agent: Service %q left maintenance mode", serviceID)

	return nil
}

// EnableNodeMaintenance places a node into maintenance mode.
func (a *Agent) EnableNodeMaintenance(reason, token string) {
	// Ensure node maintenance is not already enabled
	if _, ok := a.state.Checks()[structs.NodeMaint]; ok {
		return
	}

	// Use a default notes value
	if reason == "" {
		reason = defaultNodeMaintReason
	}

	// Create and register the node maintenance check
	check := &structs.HealthCheck{
		Node:    a.config.NodeName,
		CheckID: structs.NodeMaint,
		Name:    "Node Maintenance Mode",
		Notes:   reason,
		Status:  api.HealthCritical,
	}
	a.AddCheck(check, nil, true, token)
	a.logger.Printf("[INFO] agent: Node entered maintenance mode")
}

// DisableNodeMaintenance removes a node from maintenance mode
func (a *Agent) DisableNodeMaintenance() {
	if _, ok := a.state.Checks()[structs.NodeMaint]; !ok {
		return
	}
	a.RemoveCheck(structs.NodeMaint, true)
	a.logger.Printf("[INFO] agent: Node left maintenance mode")
}

// InjectEndpoint overrides the given endpoint with a substitute one. Note
// that not all agent methods use this mechanism, and that is should only
// be used for testing.
func (a *Agent) InjectEndpoint(endpoint string, handler interface{}) error {
	srv, ok := a.delegate.(*consul.Server)
	if !ok {
		return fmt.Errorf("agent must be a server")
	}
	if err := srv.InjectEndpoint(handler); err != nil {
		return err
	}
	name := reflect.Indirect(reflect.ValueOf(handler)).Type().Name()
	a.endpointsLock.Lock()
	a.endpoints[endpoint] = name
	a.endpointsLock.Unlock()

	a.logger.Printf("[WARN] agent: endpoint injected; this should only be used for testing")
	return nil
}

// getEndpoint returns the endpoint name to use for the given endpoint,
// which may be overridden.
func (a *Agent) getEndpoint(endpoint string) string {
	a.endpointsLock.RLock()
	defer a.endpointsLock.RUnlock()
	if override, ok := a.endpoints[endpoint]; ok {
		return override
	}
	return endpoint
}