package consul

import (
	"context"
	"fmt"
	"net"
	"net/url"
	"reflect"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
	"time"

	metrics "github.com/armon/go-metrics"
	log "github.com/hashicorp/go-hclog"

	"github.com/hashicorp/consul/api"
	"github.com/hashicorp/nomad/helper"
	"github.com/hashicorp/nomad/nomad/structs"
	"github.com/hashicorp/nomad/plugins/drivers"
)

const (
	// nomadServicePrefix is the prefix that scopes all Nomad registered
	// services (both agent and task entries).
	nomadServicePrefix = "_nomad"

	// nomadTaskPrefix is the prefix that scopes Nomad registered services
	// for tasks.
	nomadTaskPrefix = nomadServicePrefix + "-task-"

	// nomadCheckPrefix is the prefix that scopes Nomad registered checks for
	// services.
	nomadCheckPrefix = nomadServicePrefix + "-check-"

	// defaultRetryInterval is how quickly to retry syncing services and
	// checks to Consul when an error occurs. Will backoff up to a max.
	defaultRetryInterval = time.Second

	// defaultMaxRetryInterval is the default max retry interval.
	defaultMaxRetryInterval = 30 * time.Second

	// defaultPeriodicalInterval is the interval at which the service
	// client reconciles state between the desired services and checks and
	// what's actually registered in Consul. This is done at an interval,
	// rather than being purely edge triggered, to handle the case that the
	// Consul agent's state may change underneath us
	defaultPeriodicInterval = 30 * time.Second

	// ttlCheckBuffer is the time interval that Nomad can take to report Consul
	// the check result
	ttlCheckBuffer = 31 * time.Second

	// defaultShutdownWait is how long Shutdown() should block waiting for
	// enqueued operations to sync to Consul by default.
	defaultShutdownWait = time.Minute

	// DefaultQueryWaitDuration is the max duration the Consul Agent will
	// spend waiting for a response from a Consul Query.
	DefaultQueryWaitDuration = 2 * time.Second

	// ServiceTagHTTP is the tag assigned to HTTP services
	ServiceTagHTTP = "http"

	// ServiceTagRPC is the tag assigned to RPC services
	ServiceTagRPC = "rpc"

	// ServiceTagSerf is the tag assigned to Serf services
	ServiceTagSerf = "serf"

	// deregisterProbationPeriod is the initialization period where
	// services registered in Consul but not in Nomad don't get deregistered,
	// to allow for nomad restoring tasks
	deregisterProbationPeriod = time.Minute
)

// CatalogAPI is the consul/api.Catalog API used by Nomad.
type CatalogAPI interface {
	Datacenters() ([]string, error)
	Service(service, tag string, q *api.QueryOptions) ([]*api.CatalogService, *api.QueryMeta, error)
}

// AgentAPI is the consul/api.Agent API used by Nomad.
type AgentAPI interface {
	Services() (map[string]*api.AgentService, error)
	Checks() (map[string]*api.AgentCheck, error)
	CheckRegister(check *api.AgentCheckRegistration) error
	CheckDeregister(checkID string) error
	Self() (map[string]map[string]interface{}, error)
	ServiceRegister(service *api.AgentServiceRegistration) error
	ServiceDeregister(serviceID string) error
	UpdateTTL(id, output, status string) error
}

func agentServiceUpdateRequired(reg *api.AgentServiceRegistration, svc *api.AgentService) bool {
	return !(reg.Kind == svc.Kind &&
		reg.ID == svc.ID &&
		reg.Port == svc.Port &&
		reg.Address == svc.Address &&
		reg.Name == svc.Service &&
		reflect.DeepEqual(reg.Tags, svc.Tags))
}

// operations are submitted to the main loop via commit() for synchronizing
// with Consul.
type operations struct {
	regServices   []*api.AgentServiceRegistration
	regChecks     []*api.AgentCheckRegistration
	deregServices []string
	deregChecks   []string
}

// AllocRegistration holds the status of services registered for a particular
// allocations by task.
type AllocRegistration struct {
	// Tasks maps the name of a task to its registered services and checks
	Tasks map[string]*ServiceRegistrations
}

func (a *AllocRegistration) copy() *AllocRegistration {
	c := &AllocRegistration{
		Tasks: make(map[string]*ServiceRegistrations, len(a.Tasks)),
	}

	for k, v := range a.Tasks {
		c.Tasks[k] = v.copy()
	}

	return c
}

// NumServices returns the number of registered services
func (a *AllocRegistration) NumServices() int {
	if a == nil {
		return 0
	}

	total := 0
	for _, treg := range a.Tasks {
		for _, sreg := range treg.Services {
			if sreg.Service != nil {
				total++
			}
		}
	}

	return total
}

// NumChecks returns the number of registered checks
func (a *AllocRegistration) NumChecks() int {
	if a == nil {
		return 0
	}

	total := 0
	for _, treg := range a.Tasks {
		for _, sreg := range treg.Services {
			total += len(sreg.Checks)
		}
	}

	return total
}

// ServiceRegistrations holds the status of services registered for a particular
// task or task group.
type ServiceRegistrations struct {
	Services map[string]*ServiceRegistration
}

func (t *ServiceRegistrations) copy() *ServiceRegistrations {
	c := &ServiceRegistrations{
		Services: make(map[string]*ServiceRegistration, len(t.Services)),
	}

	for k, v := range t.Services {
		c.Services[k] = v.copy()
	}

	return c
}

// ServiceRegistration holds the status of a registered Consul Service and its
// Checks.
type ServiceRegistration struct {
	// serviceID and checkIDs are internal fields that track just the IDs of the
	// services/checks registered in Consul. It is used to materialize the other
	// fields when queried.
	serviceID string
	checkIDs  map[string]struct{}

	// Service is the AgentService registered in Consul.
	Service *api.AgentService

	// Checks is the status of the registered checks.
	Checks []*api.AgentCheck
}

func (s *ServiceRegistration) copy() *ServiceRegistration {
	// Copy does not copy the external fields but only the internal fields. This
	// is so that the caller of AllocRegistrations can not access the internal
	// fields and that method uses these fields to populate the external fields.
	return &ServiceRegistration{
		serviceID: s.serviceID,
		checkIDs:  helper.CopyMapStringStruct(s.checkIDs),
	}
}

// ServiceClient handles task and agent service registration with Consul.
type ServiceClient struct {
	client           AgentAPI
	logger           log.Logger
	retryInterval    time.Duration
	maxRetryInterval time.Duration
	periodicInterval time.Duration

	// exitCh is closed when the main Run loop exits
	exitCh chan struct{}

	// shutdownCh is closed when the client should shutdown
	shutdownCh chan struct{}

	// shutdownWait is how long Shutdown() blocks waiting for the final
	// sync() to finish. Defaults to defaultShutdownWait
	shutdownWait time.Duration

	opCh chan *operations

	services map[string]*api.AgentServiceRegistration
	checks   map[string]*api.AgentCheckRegistration

	explicitlyDeregisteredServices map[string]bool
	explicitlyDeregisteredChecks   map[string]bool

	// allocRegistrations stores the services and checks that are registered
	// with Consul by allocation ID.
	allocRegistrations     map[string]*AllocRegistration
	allocRegistrationsLock sync.RWMutex

	// agent services and checks record entries for the agent itself which
	// should be removed on shutdown
	agentServices map[string]struct{}
	agentChecks   map[string]struct{}
	agentLock     sync.Mutex

	// seen is 1 if Consul has ever been seen; otherwise 0. Accessed with
	// atomics.
	seen int32

	// deregisterProbationExpiry is the time before which consul sync shouldn't deregister
	// unknown services.
	// Used to mitigate risk of deleting restored services upon client restart.
	deregisterProbationExpiry time.Time

	// checkWatcher restarts checks that are unhealthy.
	checkWatcher *checkWatcher

	// isClientAgent specifies whether this Consul client is being used
	// by a Nomad client.
	isClientAgent bool
}

// NewServiceClient creates a new Consul ServiceClient from an existing Consul API
// Client, logger and takes whether the client is being used by a Nomad Client agent.
// When being used by a Nomad client, this Consul client reconciles all services and
// checks created by Nomad on behalf of running tasks.
func NewServiceClient(consulClient AgentAPI, logger log.Logger, isNomadClient bool) *ServiceClient {
	logger = logger.ResetNamed("consul.sync")
	return &ServiceClient{
		client:                         consulClient,
		logger:                         logger,
		retryInterval:                  defaultRetryInterval,
		maxRetryInterval:               defaultMaxRetryInterval,
		periodicInterval:               defaultPeriodicInterval,
		exitCh:                         make(chan struct{}),
		shutdownCh:                     make(chan struct{}),
		shutdownWait:                   defaultShutdownWait,
		opCh:                           make(chan *operations, 8),
		services:                       make(map[string]*api.AgentServiceRegistration),
		checks:                         make(map[string]*api.AgentCheckRegistration),
		explicitlyDeregisteredServices: make(map[string]bool),
		explicitlyDeregisteredChecks:   make(map[string]bool),
		allocRegistrations:             make(map[string]*AllocRegistration),
		agentServices:                  make(map[string]struct{}),
		agentChecks:                    make(map[string]struct{}),
		checkWatcher:                   newCheckWatcher(logger, consulClient),
		isClientAgent:                  isNomadClient,
		deregisterProbationExpiry:      time.Now().Add(deregisterProbationPeriod),
	}
}

// seen is used by markSeen and hasSeen
const seen = 1

// markSeen marks Consul as having been seen (meaning at least one operation
// has succeeded).
func (c *ServiceClient) markSeen() {
	atomic.StoreInt32(&c.seen, seen)
}

// hasSeen returns true if any Consul operation has ever succeeded. Useful to
// squelch errors if Consul isn't running.
func (c *ServiceClient) hasSeen() bool {
	return atomic.LoadInt32(&c.seen) == seen
}

// Run the Consul main loop which retries operations against Consul. It should
// be called exactly once.
func (c *ServiceClient) Run() {
	defer close(c.exitCh)

	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()

	// init will be closed when Consul has been contacted
	init := make(chan struct{})
	go checkConsulTLSSkipVerify(ctx, c.logger, c.client, init)

	// Process operations while waiting for initial contact with Consul but
	// do not sync until contact has been made.
INIT:
	for {
		select {
		case <-init:
			c.markSeen()
			break INIT
		case <-c.shutdownCh:
			return
		case ops := <-c.opCh:
			c.merge(ops)
		}
	}
	c.logger.Trace("able to contact Consul")

	// Block until contact with Consul has been established
	// Start checkWatcher
	go c.checkWatcher.Run(ctx)

	// Always immediately sync to reconcile Nomad and Consul's state
	retryTimer := time.NewTimer(0)

	failures := 0
	for {
		select {
		case <-retryTimer.C:
		case <-c.shutdownCh:
			// Cancel check watcher but sync one last time
			cancel()
		case ops := <-c.opCh:
			c.merge(ops)
		}

		if err := c.sync(); err != nil {
			if failures == 0 {
				// Log on the first failure
				c.logger.Warn("failed to update services in Consul", "error", err)
			} else if failures%10 == 0 {
				// Log every 10th consecutive failure
				c.logger.Error("still unable to update services in Consul", "failures", failures, "error", err)
			}

			failures++
			if !retryTimer.Stop() {
				// Timer already expired, since the timer may
				// or may not have been read in the select{}
				// above, conditionally receive on it
				select {
				case <-retryTimer.C:
				default:
				}
			}
			backoff := c.retryInterval * time.Duration(failures)
			if backoff > c.maxRetryInterval {
				backoff = c.maxRetryInterval
			}
			retryTimer.Reset(backoff)
		} else {
			if failures > 0 {
				c.logger.Info("successfully updated services in Consul")
				failures = 0
			}

			// on successful sync, clear deregistered consul entities
			c.clearExplicitlyDeregistered()

			// Reset timer to periodic interval to periodically
			// reconile with Consul
			if !retryTimer.Stop() {
				select {
				case <-retryTimer.C:
				default:
				}
			}
			retryTimer.Reset(c.periodicInterval)
		}

		select {
		case <-c.shutdownCh:
			// Exit only after sync'ing all outstanding operations
			if len(c.opCh) > 0 {
				for len(c.opCh) > 0 {
					c.merge(<-c.opCh)
				}
				continue
			}
			return
		default:
		}

	}
}

// commit operations unless already shutting down.
func (c *ServiceClient) commit(ops *operations) {
	select {
	case c.opCh <- ops:
	case <-c.shutdownCh:
	}
}

func (c *ServiceClient) clearExplicitlyDeregistered() {
	c.explicitlyDeregisteredServices = map[string]bool{}
	c.explicitlyDeregisteredChecks = map[string]bool{}
}

// merge registrations into state map prior to sync'ing with Consul
func (c *ServiceClient) merge(ops *operations) {
	for _, s := range ops.regServices {
		c.services[s.ID] = s
	}
	for _, check := range ops.regChecks {
		c.checks[check.ID] = check
	}
	for _, sid := range ops.deregServices {
		delete(c.services, sid)
		c.explicitlyDeregisteredServices[sid] = true
	}
	for _, cid := range ops.deregChecks {
		delete(c.checks, cid)
		c.explicitlyDeregisteredChecks[cid] = true
	}
	metrics.SetGauge([]string{"client", "consul", "services"}, float32(len(c.services)))
	metrics.SetGauge([]string{"client", "consul", "checks"}, float32(len(c.checks)))
}

// sync enqueued operations.
func (c *ServiceClient) sync() error {
	sreg, creg, sdereg, cdereg := 0, 0, 0, 0

	consulServices, err := c.client.Services()
	if err != nil {
		metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
		return fmt.Errorf("error querying Consul services: %v", err)
	}

	consulChecks, err := c.client.Checks()
	if err != nil {
		metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
		return fmt.Errorf("error querying Consul checks: %v", err)
	}

	inProbation := time.Now().Before(c.deregisterProbationExpiry)

	// Remove Nomad services in Consul but unknown locally
	for id := range consulServices {
		if _, ok := c.services[id]; ok {
			// Known service, skip
			continue
		}

		// Ignore if this is not a Nomad managed service. Also ignore
		// Nomad managed services if this is not a client agent.
		// This is to prevent server agents from removing services
		// registered by client agents
		if !isNomadService(id) || !c.isClientAgent {
			// Not managed by Nomad, skip
			continue
		}

		// Ignore unknown services during probation
		if inProbation && !c.explicitlyDeregisteredServices[id] {
			continue
		}

		// Ignore if this is a service for a Nomad managed sidecar proxy.
		if isNomadSidecar(id, c.services) {
			continue
		}

		// Unknown Nomad managed service; kill
		if err := c.client.ServiceDeregister(id); err != nil {
			if isOldNomadService(id) {
				// Don't hard-fail on old entries. See #3620
				continue
			}

			metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
			return err
		}
		sdereg++
		metrics.IncrCounter([]string{"client", "consul", "service_deregistrations"}, 1)
	}

	// Add Nomad services missing from Consul, or where the service has been updated.
	for id, locals := range c.services {
		existingSvc, ok := consulServices[id]

		if ok {
			// There is an existing registration of this service in Consul, so here
			// we validate to see if the service has been invalidated to see if it
			// should be updated.
			if !agentServiceUpdateRequired(locals, existingSvc) {
				// No Need to update services that have not changed
				continue
			}
		}

		if err = c.client.ServiceRegister(locals); err != nil {
			metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
			return err
		}
		sreg++
		metrics.IncrCounter([]string{"client", "consul", "service_registrations"}, 1)
	}

	// Remove Nomad checks in Consul but unknown locally
	for id, check := range consulChecks {
		if _, ok := c.checks[id]; ok {
			// Known check, leave it
			continue
		}

		// Ignore if this is not a Nomad managed check. Also ignore
		// Nomad managed checks if this is not a client agent.
		// This is to prevent server agents from removing checks
		// registered by client agents
		if !isNomadService(check.ServiceID) || !c.isClientAgent || !isNomadCheck(check.CheckID) {
			// Service not managed by Nomad, skip
			continue
		}

		// Ignore unknown services during probation
		if inProbation && !c.explicitlyDeregisteredChecks[id] {
			continue
		}

		// Ignore if this is a check for a Nomad managed sidecar proxy.
		if isNomadSidecar(check.ServiceID, c.services) {
			continue
		}

		// Unknown Nomad managed check; remove
		if err := c.client.CheckDeregister(id); err != nil {
			if isOldNomadService(check.ServiceID) {
				// Don't hard-fail on old entries.
				continue
			}

			metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
			return err
		}
		cdereg++
		metrics.IncrCounter([]string{"client", "consul", "check_deregistrations"}, 1)
	}

	// Add Nomad checks missing from Consul
	for id, check := range c.checks {
		if _, ok := consulChecks[id]; ok {
			// Already in Consul; skipping
			continue
		}

		if err := c.client.CheckRegister(check); err != nil {
			metrics.IncrCounter([]string{"client", "consul", "sync_failure"}, 1)
			return err
		}
		creg++
		metrics.IncrCounter([]string{"client", "consul", "check_registrations"}, 1)
	}

	// Only log if something was actually synced
	if sreg > 0 || sdereg > 0 || creg > 0 || cdereg > 0 {
		c.logger.Debug("sync complete", "registered_services", sreg, "deregistered_services", sdereg,
			"registered_checks", creg, "deregistered_checks", cdereg)
	}
	return nil
}

// RegisterAgent registers Nomad agents (client or server). The
// Service.PortLabel should be a literal port to be parsed with SplitHostPort.
// Script checks are not supported and will return an error. Registration is
// asynchronous.
//
// Agents will be deregistered when Shutdown is called.
func (c *ServiceClient) RegisterAgent(role string, services []*structs.Service) error {
	ops := operations{}

	for _, service := range services {
		id := makeAgentServiceID(role, service)

		// Unlike tasks, agents don't use port labels. Agent ports are
		// stored directly in the PortLabel.
		host, rawport, err := net.SplitHostPort(service.PortLabel)
		if err != nil {
			return fmt.Errorf("error parsing port label %q from service %q: %v", service.PortLabel, service.Name, err)
		}
		port, err := strconv.Atoi(rawport)
		if err != nil {
			return fmt.Errorf("error parsing port %q from service %q: %v", rawport, service.Name, err)
		}
		serviceReg := &api.AgentServiceRegistration{
			ID:      id,
			Name:    service.Name,
			Tags:    service.Tags,
			Address: host,
			Port:    port,
			// This enables the consul UI to show that Nomad registered this service
			Meta: map[string]string{
				"external-source": "nomad",
			},
		}
		ops.regServices = append(ops.regServices, serviceReg)

		for _, check := range service.Checks {
			checkID := MakeCheckID(id, check)
			if check.Type == structs.ServiceCheckScript {
				return fmt.Errorf("service %q contains invalid check: agent checks do not support scripts", service.Name)
			}
			checkHost, checkPort := serviceReg.Address, serviceReg.Port
			if check.PortLabel != "" {
				// Unlike tasks, agents don't use port labels. Agent ports are
				// stored directly in the PortLabel.
				host, rawport, err := net.SplitHostPort(check.PortLabel)
				if err != nil {
					return fmt.Errorf("error parsing port label %q from check %q: %v", service.PortLabel, check.Name, err)
				}
				port, err := strconv.Atoi(rawport)
				if err != nil {
					return fmt.Errorf("error parsing port %q from check %q: %v", rawport, check.Name, err)
				}
				checkHost, checkPort = host, port
			}
			checkReg, err := createCheckReg(id, checkID, check, checkHost, checkPort)
			if err != nil {
				return fmt.Errorf("failed to add check %q: %v", check.Name, err)
			}
			ops.regChecks = append(ops.regChecks, checkReg)
		}
	}

	// Don't bother committing agent checks if we're already shutting down
	c.agentLock.Lock()
	defer c.agentLock.Unlock()
	select {
	case <-c.shutdownCh:
		return nil
	default:
	}

	// Now add them to the registration queue
	c.commit(&ops)

	// Record IDs for deregistering on shutdown
	for _, id := range ops.regServices {
		c.agentServices[id.ID] = struct{}{}
	}
	for _, id := range ops.regChecks {
		c.agentChecks[id.ID] = struct{}{}
	}
	return nil
}

// serviceRegs creates service registrations, check registrations, and script
// checks from a service. It returns a service registration object with the
// service and check IDs populated.
func (c *ServiceClient) serviceRegs(ops *operations, service *structs.Service, workload *WorkloadServices) (
	*ServiceRegistration, error) {

	// Get the services ID
	id := MakeAllocServiceID(workload.AllocID, workload.Name(), service)
	sreg := &ServiceRegistration{
		serviceID: id,
		checkIDs:  make(map[string]struct{}, len(service.Checks)),
	}

	// Service address modes default to auto
	addrMode := service.AddressMode
	if addrMode == "" {
		addrMode = structs.AddressModeAuto
	}

	// Determine the address to advertise based on the mode
	ip, port, err := getAddress(addrMode, service.PortLabel, workload.Networks, workload.DriverNetwork)
	if err != nil {
		return nil, fmt.Errorf("unable to get address for service %q: %v", service.Name, err)
	}

	// Determine whether to use tags or canary_tags
	var tags []string
	if workload.Canary && len(service.CanaryTags) > 0 {
		tags = make([]string, len(service.CanaryTags))
		copy(tags, service.CanaryTags)
	} else {
		tags = make([]string, len(service.Tags))
		copy(tags, service.Tags)
	}

	// newConnect returns (nil, nil) if there's no Connect-enabled service.
	connect, err := newConnect(service.Name, service.Connect, workload.Networks)
	if err != nil {
		return nil, fmt.Errorf("invalid Consul Connect configuration for service %q: %v", service.Name, err)
	}

	meta := make(map[string]string, len(service.Meta))
	for k, v := range service.Meta {
		meta[k] = v
	}

	// This enables the consul UI to show that Nomad registered this service
	meta["external-source"] = "nomad"

	// Build the Consul Service registration request
	serviceReg := &api.AgentServiceRegistration{
		ID:      id,
		Name:    service.Name,
		Tags:    tags,
		Address: ip,
		Port:    port,
		Meta:    meta,
		Connect: connect, // will be nil if no Connect stanza
	}
	ops.regServices = append(ops.regServices, serviceReg)

	// Build the check registrations
	checkIDs, err := c.checkRegs(ops, id, service, workload)
	if err != nil {
		return nil, err
	}
	for _, cid := range checkIDs {
		sreg.checkIDs[cid] = struct{}{}
	}
	return sreg, nil
}

// checkRegs registers the checks for the given service and returns the
// registered check ids.
func (c *ServiceClient) checkRegs(ops *operations, serviceID string, service *structs.Service,
	workload *WorkloadServices) ([]string, error) {

	// Fast path
	numChecks := len(service.Checks)
	if numChecks == 0 {
		return nil, nil
	}

	checkIDs := make([]string, 0, numChecks)
	for _, check := range service.Checks {
		checkID := MakeCheckID(serviceID, check)
		checkIDs = append(checkIDs, checkID)
		if check.Type == structs.ServiceCheckScript {
			// Skip getAddress for script checks
			checkReg, err := createCheckReg(serviceID, checkID, check, "", 0)
			if err != nil {
				return nil, fmt.Errorf("failed to add script check %q: %v", check.Name, err)
			}
			ops.regChecks = append(ops.regChecks, checkReg)
			continue
		}

		// Default to the service's port but allow check to override
		portLabel := check.PortLabel
		if portLabel == "" {
			// Default to the service's port label
			portLabel = service.PortLabel
		}

		// Checks address mode defaults to host for pre-#3380 backward compat
		addrMode := check.AddressMode
		if addrMode == "" {
			addrMode = structs.AddressModeHost
		}

		ip, port, err := getAddress(addrMode, portLabel, workload.Networks, workload.DriverNetwork)
		if err != nil {
			return nil, fmt.Errorf("error getting address for check %q: %v", check.Name, err)
		}

		checkReg, err := createCheckReg(serviceID, checkID, check, ip, port)
		if err != nil {
			return nil, fmt.Errorf("failed to add check %q: %v", check.Name, err)
		}
		ops.regChecks = append(ops.regChecks, checkReg)
	}
	return checkIDs, nil
}

// RegisterWorkload with Consul. Adds all service entries and checks to Consul.
//
// If the service IP is set it used as the address in the service registration.
// Checks will always use the IP from the Task struct (host's IP).
//
// Actual communication with Consul is done asynchronously (see Run).
func (c *ServiceClient) RegisterWorkload(workload *WorkloadServices) error {
	// Fast path
	numServices := len(workload.Services)
	if numServices == 0 {
		return nil
	}

	t := new(ServiceRegistrations)
	t.Services = make(map[string]*ServiceRegistration, numServices)

	ops := &operations{}
	for _, service := range workload.Services {
		sreg, err := c.serviceRegs(ops, service, workload)
		if err != nil {
			return err
		}
		t.Services[sreg.serviceID] = sreg
	}

	// Add the workload to the allocation's registration
	c.addRegistrations(workload.AllocID, workload.Name(), t)

	c.commit(ops)

	// Start watching checks. Done after service registrations are built
	// since an error building them could leak watches.
	for _, service := range workload.Services {
		serviceID := MakeAllocServiceID(workload.AllocID, workload.Name(), service)
		for _, check := range service.Checks {
			if check.TriggersRestarts() {
				checkID := MakeCheckID(serviceID, check)
				c.checkWatcher.Watch(workload.AllocID, workload.Name(), checkID, check, workload.Restarter)
			}
		}
	}
	return nil
}

// UpdateWorkload in Consul. Does not alter the service if only checks have
// changed.
//
// DriverNetwork must not change between invocations for the same allocation.
func (c *ServiceClient) UpdateWorkload(old, newWorkload *WorkloadServices) error {
	ops := &operations{}

	regs := new(ServiceRegistrations)
	regs.Services = make(map[string]*ServiceRegistration, len(newWorkload.Services))

	existingIDs := make(map[string]*structs.Service, len(old.Services))
	for _, s := range old.Services {
		existingIDs[MakeAllocServiceID(old.AllocID, old.Name(), s)] = s
	}
	newIDs := make(map[string]*structs.Service, len(newWorkload.Services))
	for _, s := range newWorkload.Services {
		newIDs[MakeAllocServiceID(newWorkload.AllocID, newWorkload.Name(), s)] = s
	}

	// Loop over existing Service IDs to see if they have been removed
	for existingID, existingSvc := range existingIDs {
		newSvc, ok := newIDs[existingID]

		if !ok {
			// Existing service entry removed
			ops.deregServices = append(ops.deregServices, existingID)
			for _, check := range existingSvc.Checks {
				cid := MakeCheckID(existingID, check)
				ops.deregChecks = append(ops.deregChecks, cid)

				// Unwatch watched checks
				if check.TriggersRestarts() {
					c.checkWatcher.Unwatch(cid)
				}
			}
			continue
		}

		oldHash := existingSvc.Hash(old.AllocID, old.Name(), old.Canary)
		newHash := newSvc.Hash(newWorkload.AllocID, newWorkload.Name(), newWorkload.Canary)
		if oldHash == newHash {
			// Service exists and hasn't changed, don't re-add it later
			delete(newIDs, existingID)
		}

		// Service still exists so add it to the task's registration
		sreg := &ServiceRegistration{
			serviceID: existingID,
			checkIDs:  make(map[string]struct{}, len(newSvc.Checks)),
		}
		regs.Services[existingID] = sreg

		// See if any checks were updated
		existingChecks := make(map[string]*structs.ServiceCheck, len(existingSvc.Checks))
		for _, check := range existingSvc.Checks {
			existingChecks[MakeCheckID(existingID, check)] = check
		}

		// Register new checks
		for _, check := range newSvc.Checks {
			checkID := MakeCheckID(existingID, check)
			if _, exists := existingChecks[checkID]; exists {
				// Check is still required. Remove it from the map so it doesn't get
				// deleted later.
				delete(existingChecks, checkID)
				sreg.checkIDs[checkID] = struct{}{}
			}

			// New check on an unchanged service; add them now
			newCheckIDs, err := c.checkRegs(ops, existingID, newSvc, newWorkload)
			if err != nil {
				return err
			}

			for _, checkID := range newCheckIDs {
				sreg.checkIDs[checkID] = struct{}{}
			}

			// Update all watched checks as CheckRestart fields aren't part of ID
			if check.TriggersRestarts() {
				c.checkWatcher.Watch(newWorkload.AllocID, newWorkload.Name(), checkID, check, newWorkload.Restarter)
			}
		}

		// Remove existing checks not in updated service
		for cid, check := range existingChecks {
			ops.deregChecks = append(ops.deregChecks, cid)

			// Unwatch checks
			if check.TriggersRestarts() {
				c.checkWatcher.Unwatch(cid)
			}
		}
	}

	// Any remaining services should just be enqueued directly
	for _, newSvc := range newIDs {
		sreg, err := c.serviceRegs(ops, newSvc, newWorkload)
		if err != nil {
			return err
		}

		regs.Services[sreg.serviceID] = sreg
	}

	// Add the task to the allocation's registration
	c.addRegistrations(newWorkload.AllocID, newWorkload.Name(), regs)

	c.commit(ops)

	// Start watching checks. Done after service registrations are built
	// since an error building them could leak watches.
	for _, service := range newIDs {
		serviceID := MakeAllocServiceID(newWorkload.AllocID, newWorkload.Name(), service)
		for _, check := range service.Checks {
			if check.TriggersRestarts() {
				checkID := MakeCheckID(serviceID, check)
				c.checkWatcher.Watch(newWorkload.AllocID, newWorkload.Name(), checkID, check, newWorkload.Restarter)
			}
		}
	}
	return nil
}

// RemoveWorkload from Consul. Removes all service entries and checks.
//
// Actual communication with Consul is done asynchronously (see Run).
func (c *ServiceClient) RemoveWorkload(workload *WorkloadServices) {
	ops := operations{}

	for _, service := range workload.Services {
		id := MakeAllocServiceID(workload.AllocID, workload.Name(), service)
		ops.deregServices = append(ops.deregServices, id)

		for _, check := range service.Checks {
			cid := MakeCheckID(id, check)
			ops.deregChecks = append(ops.deregChecks, cid)

			if check.TriggersRestarts() {
				c.checkWatcher.Unwatch(cid)
			}
		}
	}

	// Remove the workload from the alloc's registrations
	c.removeRegistration(workload.AllocID, workload.Name())

	// Now add them to the deregistration fields; main Run loop will update
	c.commit(&ops)
}

// AllocRegistrations returns the registrations for the given allocation. If the
// allocation has no reservations, the response is a nil object.
func (c *ServiceClient) AllocRegistrations(allocID string) (*AllocRegistration, error) {
	// Get the internal struct using the lock
	c.allocRegistrationsLock.RLock()
	regInternal, ok := c.allocRegistrations[allocID]
	if !ok {
		c.allocRegistrationsLock.RUnlock()
		return nil, nil
	}

	// Copy so we don't expose internal structs
	reg := regInternal.copy()
	c.allocRegistrationsLock.RUnlock()

	// Query the services and checks to populate the allocation registrations.
	services, err := c.client.Services()
	if err != nil {
		return nil, err
	}

	checks, err := c.client.Checks()
	if err != nil {
		return nil, err
	}

	// Populate the object
	for _, treg := range reg.Tasks {
		for serviceID, sreg := range treg.Services {
			sreg.Service = services[serviceID]
			for checkID := range sreg.checkIDs {
				if check, ok := checks[checkID]; ok {
					sreg.Checks = append(sreg.Checks, check)
				}
			}
		}
	}

	return reg, nil
}

// UpdateTTL is used to update the TTL of a check. Typically this will only be
// called to heartbeat script checks.
func (c *ServiceClient) UpdateTTL(id, output, status string) error {
	return c.client.UpdateTTL(id, output, status)
}

// Shutdown the Consul client. Update running task registrations and deregister
// agent from Consul. On first call blocks up to shutdownWait before giving up
// on syncing operations.
func (c *ServiceClient) Shutdown() error {
	// Serialize Shutdown calls with RegisterAgent to prevent leaking agent
	// entries.
	c.agentLock.Lock()
	defer c.agentLock.Unlock()
	select {
	case <-c.shutdownCh:
		return nil
	default:
		close(c.shutdownCh)
	}

	// Give run loop time to sync, but don't block indefinitely
	deadline := time.After(c.shutdownWait)

	// Wait for Run to finish any outstanding operations and exit
	select {
	case <-c.exitCh:
	case <-deadline:
		// Don't wait forever though
	}

	// If Consul was never seen nothing could be written so exit early
	if !c.hasSeen() {
		return nil
	}

	// Always attempt to deregister Nomad agent Consul entries, even if
	// deadline was reached
	for id := range c.agentServices {
		if err := c.client.ServiceDeregister(id); err != nil {
			c.logger.Error("failed deregistering agent service", "service_id", id, "error", err)
		}
	}
	for id := range c.agentChecks {
		if err := c.client.CheckDeregister(id); err != nil {
			c.logger.Error("failed deregistering agent check", "check_id", id, "error", err)
		}
	}

	return nil
}

// addRegistration adds the service registrations for the given allocation.
func (c *ServiceClient) addRegistrations(allocID, taskName string, reg *ServiceRegistrations) {
	c.allocRegistrationsLock.Lock()
	defer c.allocRegistrationsLock.Unlock()

	alloc, ok := c.allocRegistrations[allocID]
	if !ok {
		alloc = &AllocRegistration{
			Tasks: make(map[string]*ServiceRegistrations),
		}
		c.allocRegistrations[allocID] = alloc
	}
	alloc.Tasks[taskName] = reg
}

// removeRegistrations removes the registration for the given allocation.
func (c *ServiceClient) removeRegistration(allocID, taskName string) {
	c.allocRegistrationsLock.Lock()
	defer c.allocRegistrationsLock.Unlock()

	alloc, ok := c.allocRegistrations[allocID]
	if !ok {
		return
	}

	// Delete the task and if it is the last one also delete the alloc's
	// registration
	delete(alloc.Tasks, taskName)
	if len(alloc.Tasks) == 0 {
		delete(c.allocRegistrations, allocID)
	}
}

// makeAgentServiceID creates a unique ID for identifying an agent service in
// Consul.
//
// Agent service IDs are of the form:
//
//	{nomadServicePrefix}-{ROLE}-b32(sha1({Service.Name}-{Service.Tags...})
//	Example Server ID: _nomad-server-fbbk265qn4tmt25nd4ep42tjvmyj3hr4
//	Example Client ID: _nomad-client-ggnjpgl7yn7rgmvxzilmpvrzzvrszc7l
//
func makeAgentServiceID(role string, service *structs.Service) string {
	return fmt.Sprintf("%s-%s-%s", nomadServicePrefix, role, service.Hash(role, "", false))
}

// MakeAllocServiceID creates a unique ID for identifying an alloc service in
// Consul.
//
//	Example Service ID: _nomad-task-b4e61df9-b095-d64e-f241-23860da1375f-redis-http-http
func MakeAllocServiceID(allocID, taskName string, service *structs.Service) string {
	return fmt.Sprintf("%s%s-%s-%s-%s", nomadTaskPrefix, allocID, taskName, service.Name, service.PortLabel)
}

// MakeCheckID creates a unique ID for a check.
//
//  Example Check ID: _nomad-check-434ae42f9a57c5705344974ac38de2aee0ee089d
func MakeCheckID(serviceID string, check *structs.ServiceCheck) string {
	return fmt.Sprintf("%s%s", nomadCheckPrefix, check.Hash(serviceID))
}

// createCheckReg creates a Check that can be registered with Consul.
//
// Script checks simply have a TTL set and the caller is responsible for
// running the script and heartbeating.
func createCheckReg(serviceID, checkID string, check *structs.ServiceCheck, host string, port int) (*api.AgentCheckRegistration, error) {
	chkReg := api.AgentCheckRegistration{
		ID:        checkID,
		Name:      check.Name,
		ServiceID: serviceID,
	}
	chkReg.Status = check.InitialStatus
	chkReg.Timeout = check.Timeout.String()
	chkReg.Interval = check.Interval.String()

	// Require an address for http or tcp checks
	if port == 0 && check.RequiresPort() {
		return nil, fmt.Errorf("%s checks require an address", check.Type)
	}

	switch check.Type {
	case structs.ServiceCheckHTTP:
		proto := check.Protocol
		if proto == "" {
			proto = "http"
		}
		if check.TLSSkipVerify {
			chkReg.TLSSkipVerify = true
		}
		base := url.URL{
			Scheme: proto,
			Host:   net.JoinHostPort(host, strconv.Itoa(port)),
		}
		relative, err := url.Parse(check.Path)
		if err != nil {
			return nil, err
		}
		url := base.ResolveReference(relative)
		chkReg.HTTP = url.String()
		chkReg.Method = check.Method
		chkReg.Header = check.Header

	case structs.ServiceCheckTCP:
		chkReg.TCP = net.JoinHostPort(host, strconv.Itoa(port))

	case structs.ServiceCheckScript:
		chkReg.TTL = (check.Interval + ttlCheckBuffer).String()
		// As of Consul 1.0.0 setting TTL and Interval is a 400
		chkReg.Interval = ""

	case structs.ServiceCheckGRPC:
		chkReg.GRPC = fmt.Sprintf("%s/%s", net.JoinHostPort(host, strconv.Itoa(port)), check.GRPCService)
		chkReg.GRPCUseTLS = check.GRPCUseTLS
		if check.TLSSkipVerify {
			chkReg.TLSSkipVerify = true
		}

	default:
		return nil, fmt.Errorf("check type %+q not valid", check.Type)
	}
	return &chkReg, nil
}

// isNomadCheck returns true if the ID matches the pattern of a Nomad managed
// check.
func isNomadCheck(id string) bool {
	return strings.HasPrefix(id, nomadCheckPrefix)
}

// isNomadService returns true if the ID matches the pattern of a Nomad managed
// service (new or old formats). Agent services return false as independent
// client and server agents may be running on the same machine. #2827
func isNomadService(id string) bool {
	return strings.HasPrefix(id, nomadTaskPrefix) || isOldNomadService(id)
}

// isOldNomadService returns true if the ID matches an old pattern managed by
// Nomad.
//
// Pre-0.7.1 task service IDs are of the form:
//
//	{nomadServicePrefix}-executor-{ALLOC_ID}-{Service.Name}-{Service.Tags...}
//	Example Service ID: _nomad-executor-1234-echo-http-tag1-tag2-tag3
//
func isOldNomadService(id string) bool {
	const prefix = nomadServicePrefix + "-executor"
	return strings.HasPrefix(id, prefix)
}

// isNomadSidecar returns true if the ID matches a sidecar proxy for a Nomad
// managed service.
//
// For example if you have a Connect enabled service with the ID:
//
//	_nomad-task-5229c7f8-376b-3ccc-edd9-981e238f7033-cache-redis-cache-db
//
// Consul will create a service for the sidecar proxy with the ID:
//
//	_nomad-task-5229c7f8-376b-3ccc-edd9-981e238f7033-cache-redis-cache-db-sidecar-proxy
//
func isNomadSidecar(id string, services map[string]*api.AgentServiceRegistration) bool {
	const suffix = "-sidecar-proxy"
	if !strings.HasSuffix(id, suffix) {
		return false
	}

	// Make sure the Nomad managed service for this proxy still exists.
	_, ok := services[id[:len(id)-len(suffix)]]
	return ok
}

// getAddress returns the IP and port to use for a service or check. If no port
// label is specified (an empty value), zero values are returned because no
// address could be resolved.
func getAddress(addrMode, portLabel string, networks structs.Networks, driverNet *drivers.DriverNetwork) (string, int, error) {
	switch addrMode {
	case structs.AddressModeAuto:
		if driverNet.Advertise() {
			addrMode = structs.AddressModeDriver
		} else {
			addrMode = structs.AddressModeHost
		}
		return getAddress(addrMode, portLabel, networks, driverNet)
	case structs.AddressModeHost:
		if portLabel == "" {
			if len(networks) != 1 {
				// If no networks are specified return zero
				// values. Consul will advertise the host IP
				// with no port. This is the pre-0.7.1 behavior
				// some people rely on.
				return "", 0, nil
			}

			return networks[0].IP, 0, nil
		}

		// Default path: use host ip:port
		ip, port := networks.Port(portLabel)
		if ip == "" && port <= 0 {
			return "", 0, fmt.Errorf("invalid port %q: port label not found", portLabel)
		}
		return ip, port, nil

	case structs.AddressModeDriver:
		// Require a driver network if driver address mode is used
		if driverNet == nil {
			return "", 0, fmt.Errorf(`cannot use address_mode="driver": no driver network exists`)
		}

		// If no port label is specified just return the IP
		if portLabel == "" {
			return driverNet.IP, 0, nil
		}

		// If the port is a label, use the driver's port (not the host's)
		if port, ok := driverNet.PortMap[portLabel]; ok {
			return driverNet.IP, port, nil
		}

		// If port isn't a label, try to parse it as a literal port number
		port, err := strconv.Atoi(portLabel)
		if err != nil {
			// Don't include Atoi error message as user likely
			// never intended it to be a numeric and it creates a
			// confusing error message
			return "", 0, fmt.Errorf("invalid port label %q: port labels in driver address_mode must be numeric or in the driver's port map", portLabel)
		}
		if port <= 0 {
			return "", 0, fmt.Errorf("invalid port: %q: port must be >0", portLabel)
		}

		return driverNet.IP, port, nil

	default:
		// Shouldn't happen due to validation, but enforce invariants
		return "", 0, fmt.Errorf("invalid address mode %q", addrMode)
	}
}

// newConnect creates a new Consul AgentServiceConnect struct based on a Nomad
// Connect struct. If the nomad Connect struct is nil, nil will be returned to
// disable Connect for this service.
func newConnect(serviceName string, nc *structs.ConsulConnect, networks structs.Networks) (*api.AgentServiceConnect, error) {
	if nc == nil {
		// No Connect stanza, returning nil is fine
		return nil, nil
	}

	cc := &api.AgentServiceConnect{
		Native: nc.Native,
	}

	if nc.SidecarService == nil {
		return cc, nil
	}

	net, port, err := getConnectPort(serviceName, networks)
	if err != nil {
		return nil, err
	}

	// Bind to netns IP(s):port
	proxyConfig := map[string]interface{}{}
	localServiceAddress := ""
	localServicePort := 0
	if nc.SidecarService.Proxy != nil {
		localServiceAddress = nc.SidecarService.Proxy.LocalServiceAddress
		localServicePort = nc.SidecarService.Proxy.LocalServicePort
		if nc.SidecarService.Proxy.Config != nil {
			proxyConfig = nc.SidecarService.Proxy.Config
		}
	}
	proxyConfig["bind_address"] = "0.0.0.0"
	proxyConfig["bind_port"] = port.To

	// Advertise host IP:port
	cc.SidecarService = &api.AgentServiceRegistration{
		Tags:    helper.CopySliceString(nc.SidecarService.Tags),
		Address: net.IP,
		Port:    port.Value,

		// Automatically configure the proxy to bind to all addresses
		// within the netns.
		Proxy: &api.AgentServiceConnectProxyConfig{
			LocalServiceAddress: localServiceAddress,
			LocalServicePort:    localServicePort,
			Config:              proxyConfig,
		},
	}

	// If no further proxy settings were explicitly configured, exit early
	if nc.SidecarService.Proxy == nil {
		return cc, nil
	}

	numUpstreams := len(nc.SidecarService.Proxy.Upstreams)
	if numUpstreams == 0 {
		return cc, nil
	}

	upstreams := make([]api.Upstream, numUpstreams)
	for i, nu := range nc.SidecarService.Proxy.Upstreams {
		upstreams[i].DestinationName = nu.DestinationName
		upstreams[i].LocalBindPort = nu.LocalBindPort
	}
	cc.SidecarService.Proxy.Upstreams = upstreams

	return cc, nil
}

// getConnectPort returns the network and port for the Connect proxy sidecar
// defined for this service. An error is returned if the network and port
// cannot be determined.
func getConnectPort(serviceName string, networks structs.Networks) (*structs.NetworkResource, structs.Port, error) {
	if n := len(networks); n != 1 {
		return nil, structs.Port{}, fmt.Errorf("Connect only supported with exactly 1 network (found %d)", n)
	}

	port, ok := networks[0].PortForService(serviceName)
	if !ok {
		return nil, structs.Port{}, fmt.Errorf("No Connect port defined for service %q", serviceName)
	}

	return networks[0], port, nil
}