open-consul/agent/structs/structs.go

package structs

import (
	"bytes"
	"fmt"
	"math/rand"
	"reflect"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/hashicorp/consul/agent/cache"
	"github.com/hashicorp/consul/api"
	"github.com/hashicorp/consul/types"
	"github.com/hashicorp/go-msgpack/codec"
	"github.com/hashicorp/go-multierror"
	"github.com/hashicorp/serf/coordinate"
	"github.com/mitchellh/hashstructure"
)

type MessageType uint8

// RaftIndex is used to track the index used while creating
// or modifying a given struct type.
type RaftIndex struct {
	CreateIndex uint64
	ModifyIndex uint64
}

// These are serialized between Consul servers and stored in Consul snapshots,
// so entries must only ever be added.
const (
	RegisterRequestType        MessageType = 0
	DeregisterRequestType                  = 1
	KVSRequestType                         = 2
	SessionRequestType                     = 3
	ACLRequestType                         = 4 // DEPRECATED (ACL-Legacy-Compat)
	TombstoneRequestType                   = 5
	CoordinateBatchUpdateType              = 6
	PreparedQueryRequestType               = 7
	TxnRequestType                         = 8
	AutopilotRequestType                   = 9
	AreaRequestType                        = 10
	ACLBootstrapRequestType                = 11
	IntentionRequestType                   = 12
	ConnectCARequestType                   = 13
	ConnectCAProviderStateType             = 14
	ConnectCAConfigType                    = 15 // FSM snapshots only.
	IndexRequestType                       = 16 // FSM snapshots only.
	ACLTokenUpsertRequestType              = 17
	ACLTokenDeleteRequestType              = 18
	ACLPolicyUpsertRequestType             = 19
	ACLPolicyDeleteRequestType             = 20
)

const (
	// IgnoreUnknownTypeFlag is set along with a MessageType
	// to indicate that the message type can be safely ignored
	// if it is not recognized. This is for future proofing, so
	// that new commands can be added in a way that won't cause
	// old servers to crash when the FSM attempts to process them.
	IgnoreUnknownTypeFlag MessageType = 128

	// NodeMaint is the special key set by a node in maintenance mode.
	NodeMaint = "_node_maintenance"

	// ServiceMaintPrefix is the prefix for a service in maintenance mode.
	ServiceMaintPrefix = "_service_maintenance:"

	// The meta key prefix reserved for Consul's internal use
	metaKeyReservedPrefix = "consul-"

	// metaMaxKeyPairs is maximum number of metadata key pairs allowed to be registered
	metaMaxKeyPairs = 64

	// metaKeyMaxLength is the maximum allowed length of a metadata key
	metaKeyMaxLength = 128

	// metaValueMaxLength is the maximum allowed length of a metadata value
	metaValueMaxLength = 512

	// MetaSegmentKey is the node metadata key used to store the node's network segment
	MetaSegmentKey = "consul-network-segment"

	// MaxLockDelay provides a maximum LockDelay value for
	// a session. Any value above this will not be respected.
	MaxLockDelay = 60 * time.Second
)

// metaKeyFormat checks if a metadata key string is valid
var metaKeyFormat = regexp.MustCompile(`^[a-zA-Z0-9_-]+$`).MatchString

func ValidStatus(s string) bool {
	return s == api.HealthPassing || s == api.HealthWarning || s == api.HealthCritical
}

// RPCInfo is used to describe common information about query
type RPCInfo interface {
	RequestDatacenter() string
	IsRead() bool
	AllowStaleRead() bool
	TokenSecret() string
}

// QueryOptions is used to specify various flags for read queries
type QueryOptions struct {
	// Token is the ACL token ID. If not provided, the 'anonymous'
	// token is assumed for backwards compatibility.
	Token string

	// If set, wait until query exceeds given index. Must be provided
	// with MaxQueryTime.
	MinQueryIndex uint64

	// Provided with MinQueryIndex to wait for change.
	MaxQueryTime time.Duration

	// If set, any follower can service the request. Results
	// may be arbitrarily stale.
	AllowStale bool

	// If set, the leader must verify leadership prior to
	// servicing the request. Prevents a stale read.
	RequireConsistent bool

	// If set, the local agent may respond with an arbitrarily stale locally
	// cached response. The semantics differ from AllowStale since the agent may
	// be entirely partitioned from the servers and still considered "healthy" by
	// operators. Stale responses from Servers are also arbitrarily stale, but can
	// provide additional bounds on the last contact time from the leader. It's
	// expected that servers that are partitioned are noticed and replaced in a
	// timely way by operators while the same may not be true for client agents.
	UseCache bool

	// If set and AllowStale is true, will try first a stale
	// read, and then will perform a consistent read if stale
	// read is older than value.
	MaxStaleDuration time.Duration

	// MaxAge limits how old a cached value will be returned if UseCache is true.
	// If there is a cached response that is older than the MaxAge, it is treated
	// as a cache miss and a new fetch invoked. If the fetch fails, the error is
	// returned. Clients that wish to allow for stale results on error can set
	// StaleIfError to a longer duration to change this behaviour. It is ignored
	// if the endpoint supports background refresh caching. See
	// https://www.consul.io/api/index.html#agent-caching for more details.
	MaxAge time.Duration

	// MustRevalidate forces the agent to fetch a fresh version of a cached
	// resource or at least validate that the cached version is still fresh. It is
	// implied by either max-age=0 or must-revalidate Cache-Control headers. It
	// only makes sense when UseCache is true. We store it since MaxAge = 0 is the
	// default unset value.
	MustRevalidate bool

	// StaleIfError specifies how stale the client will accept a cached response
	// if the servers are unavailable to fetch a fresh one. Only makes sense when
	// UseCache is true and MaxAge is set to a lower, non-zero value. It is
	// ignored if the endpoint supports background refresh caching. See
	// https://www.consul.io/api/index.html#agent-caching for more details.
	StaleIfError time.Duration
}

// IsRead is always true for QueryOption.
func (q QueryOptions) IsRead() bool {
	return true
}

// ConsistencyLevel display the consistency required by a request
func (q QueryOptions) ConsistencyLevel() string {
	if q.RequireConsistent {
		return "consistent"
	} else if q.AllowStale {
		return "stale"
	} else {
		return "leader"
	}
}

func (q QueryOptions) AllowStaleRead() bool {
	return q.AllowStale
}

func (q QueryOptions) TokenSecret() string {
	return q.Token
}

type WriteRequest struct {
	// Token is the ACL token ID. If not provided, the 'anonymous'
	// token is assumed for backwards compatibility.
	Token string
}

// WriteRequest only applies to writes, always false
func (w WriteRequest) IsRead() bool {
	return false
}

func (w WriteRequest) AllowStaleRead() bool {
	return false
}

func (w WriteRequest) TokenSecret() string {
	return w.Token
}

// QueryMeta allows a query response to include potentially
// useful metadata about a query
type QueryMeta struct {
	// This is the index associated with the read
	Index uint64

	// If AllowStale is used, this is time elapsed since
	// last contact between the follower and leader. This
	// can be used to gauge staleness.
	LastContact time.Duration

	// Used to indicate if there is a known leader node
	KnownLeader bool

	// Consistencylevel returns the consistency used to serve the query
	// Having `discovery_max_stale` on the agent can affect whether
	// the request was served by a leader.
	ConsistencyLevel string
}

// RegisterRequest is used for the Catalog.Register endpoint
// to register a node as providing a service. If no service
// is provided, the node is registered.
type RegisterRequest struct {
	Datacenter      string
	ID              types.NodeID
	Node            string
	Address         string
	TaggedAddresses map[string]string
	NodeMeta        map[string]string
	Service         *NodeService
	Check           *HealthCheck
	Checks          HealthChecks

	// SkipNodeUpdate can be used when a register request is intended for
	// updating a service and/or checks, but doesn't want to overwrite any
	// node information if the node is already registered. If the node
	// doesn't exist, it will still be created, but if the node exists, any
	// node portion of this update will not apply.
	SkipNodeUpdate bool

	WriteRequest
}

func (r *RegisterRequest) RequestDatacenter() string {
	return r.Datacenter
}

// ChangesNode returns true if the given register request changes the given
// node, which can be nil. This only looks for changes to the node record itself,
// not any of the health checks.
func (r *RegisterRequest) ChangesNode(node *Node) bool {
	// This means it's creating the node.
	if node == nil {
		return true
	}

	// If we've been asked to skip the node update, then say there are no
	// changes.
	if r.SkipNodeUpdate {
		return false
	}

	// Check if any of the node-level fields are being changed.
	if r.ID != node.ID ||
		r.Node != node.Node ||
		r.Address != node.Address ||
		r.Datacenter != node.Datacenter ||
		!reflect.DeepEqual(r.TaggedAddresses, node.TaggedAddresses) ||
		!reflect.DeepEqual(r.NodeMeta, node.Meta) {
		return true
	}

	return false
}

// DeregisterRequest is used for the Catalog.Deregister endpoint
// to deregister a node as providing a service. If no service is
// provided the entire node is deregistered.
type DeregisterRequest struct {
	Datacenter string
	Node       string
	ServiceID  string
	CheckID    types.CheckID
	WriteRequest
}

func (r *DeregisterRequest) RequestDatacenter() string {
	return r.Datacenter
}

// QuerySource is used to pass along information about the source node
// in queries so that we can adjust the response based on its network
// coordinates.
type QuerySource struct {
	Datacenter string
	Segment    string
	Node       string
	Ip         string
}

// DCSpecificRequest is used to query about a specific DC
type DCSpecificRequest struct {
	Datacenter      string
	NodeMetaFilters map[string]string
	Source          QuerySource
	QueryOptions
}

func (r *DCSpecificRequest) RequestDatacenter() string {
	return r.Datacenter
}

func (r *DCSpecificRequest) CacheInfo() cache.RequestInfo {
	info := cache.RequestInfo{
		Token:          r.Token,
		Datacenter:     r.Datacenter,
		MinIndex:       r.MinQueryIndex,
		Timeout:        r.MaxQueryTime,
		MaxAge:         r.MaxAge,
		MustRevalidate: r.MustRevalidate,
	}

	// To calculate the cache key we only hash the node filters. The
	// datacenter is handled by the cache framework. The other fields are
	// not, but should not be used in any cache types.
	v, err := hashstructure.Hash(r.NodeMetaFilters, nil)
	if err == nil {
		// If there is an error, we don't set the key. A blank key forces
		// no cache for this request so the request is forwarded directly
		// to the server.
		info.Key = strconv.FormatUint(v, 10)
	}

	return info
}

func (r *DCSpecificRequest) CacheMinIndex() uint64 {
	return r.QueryOptions.MinQueryIndex
}

// ServiceSpecificRequest is used to query about a specific service
type ServiceSpecificRequest struct {
	Datacenter      string
	NodeMetaFilters map[string]string
	ServiceName     string
	ServiceTag      string
	ServiceTags     []string
	ServiceAddress  string
	TagFilter       bool // Controls tag filtering
	Source          QuerySource

	// Connect if true will only search for Connect-compatible services.
	Connect bool

	QueryOptions
}

func (r *ServiceSpecificRequest) RequestDatacenter() string {
	return r.Datacenter
}

func (r *ServiceSpecificRequest) CacheInfo() cache.RequestInfo {
	info := cache.RequestInfo{
		Token:          r.Token,
		Datacenter:     r.Datacenter,
		MinIndex:       r.MinQueryIndex,
		Timeout:        r.MaxQueryTime,
		MaxAge:         r.MaxAge,
		MustRevalidate: r.MustRevalidate,
	}

	// To calculate the cache key we hash over all the fields that affect the
	// output other than Datacenter and Token which are dealt with in the cache
	// framework already. Note the order here is important for the outcome - if we
	// ever care about cache-invalidation on updates e.g. because we persist
	// cached results, we need to be careful we maintain the same order of fields
	// here. We could alternatively use `hash:set` struct tag on an anonymous
	// struct to make it more robust if it becomes significant.
	v, err := hashstructure.Hash([]interface{}{
		r.NodeMetaFilters,
		r.ServiceName,
		r.ServiceTag,
		r.ServiceAddress,
		r.TagFilter,
		r.Connect,
	}, nil)
	if err == nil {
		// If there is an error, we don't set the key. A blank key forces
		// no cache for this request so the request is forwarded directly
		// to the server.
		info.Key = strconv.FormatUint(v, 10)
	}

	return info
}

func (r *ServiceSpecificRequest) CacheMinIndex() uint64 {
	return r.QueryOptions.MinQueryIndex
}

// NodeSpecificRequest is used to request the information about a single node
type NodeSpecificRequest struct {
	Datacenter string
	Node       string
	QueryOptions
}

func (r *NodeSpecificRequest) RequestDatacenter() string {
	return r.Datacenter
}

// ChecksInStateRequest is used to query for nodes in a state
type ChecksInStateRequest struct {
	Datacenter      string
	NodeMetaFilters map[string]string
	State           string
	Source          QuerySource
	QueryOptions
}

func (r *ChecksInStateRequest) RequestDatacenter() string {
	return r.Datacenter
}

// Used to return information about a node
type Node struct {
	ID              types.NodeID
	Node            string
	Address         string
	Datacenter      string
	TaggedAddresses map[string]string
	Meta            map[string]string

	RaftIndex
}
type Nodes []*Node

// IsSame return whether nodes are similar without taking into account
// RaftIndex fields.
func (n *Node) IsSame(other *Node) bool {
	return n.ID == other.ID &&
		n.Node == other.Node &&
		n.Address == other.Address &&
		n.Datacenter == other.Datacenter &&
		reflect.DeepEqual(n.TaggedAddresses, other.TaggedAddresses) &&
		reflect.DeepEqual(n.Meta, other.Meta)
}

// ValidateMeta validates a set of key/value pairs from the agent config
func ValidateMetadata(meta map[string]string, allowConsulPrefix bool) error {
	if len(meta) > metaMaxKeyPairs {
		return fmt.Errorf("Node metadata cannot contain more than %d key/value pairs", metaMaxKeyPairs)
	}

	for key, value := range meta {
		if err := validateMetaPair(key, value, allowConsulPrefix); err != nil {
			return fmt.Errorf("Couldn't load metadata pair ('%s', '%s'): %s", key, value, err)
		}
	}

	return nil
}

// ValidateWeights checks the definition of DNS weight is valid
func ValidateWeights(weights *Weights) error {
	if weights == nil {
		return nil
	}
	if weights.Passing < 1 {
		return fmt.Errorf("Passing must be greater than 0")
	}
	if weights.Warning < 0 {
		return fmt.Errorf("Warning must be greater or equal than 0")
	}
	if weights.Passing > 65535 || weights.Warning > 65535 {
		return fmt.Errorf("DNS Weight must be between 0 and 65535")
	}
	return nil
}

// validateMetaPair checks that the given key/value pair is in a valid format
func validateMetaPair(key, value string, allowConsulPrefix bool) error {
	if key == "" {
		return fmt.Errorf("Key cannot be blank")
	}
	if !metaKeyFormat(key) {
		return fmt.Errorf("Key contains invalid characters")
	}
	if len(key) > metaKeyMaxLength {
		return fmt.Errorf("Key is too long (limit: %d characters)", metaKeyMaxLength)
	}
	if strings.HasPrefix(key, metaKeyReservedPrefix) && !allowConsulPrefix {
		return fmt.Errorf("Key prefix '%s' is reserved for internal use", metaKeyReservedPrefix)
	}
	if len(value) > metaValueMaxLength {
		return fmt.Errorf("Value is too long (limit: %d characters)", metaValueMaxLength)
	}
	return nil
}

// SatisfiesMetaFilters returns true if the metadata map contains the given filters
func SatisfiesMetaFilters(meta map[string]string, filters map[string]string) bool {
	for key, value := range filters {
		if v, ok := meta[key]; !ok || v != value {
			return false
		}
	}
	return true
}

// Used to return information about a provided services.
// Maps service name to available tags
type Services map[string][]string

// ServiceNode represents a node that is part of a service. ID, Address,
// TaggedAddresses, and NodeMeta are node-related fields that are always empty
// in the state store and are filled in on the way out by parseServiceNodes().
// This is also why PartialClone() skips them, because we know they are blank
// already so it would be a waste of time to copy them.
type ServiceNode struct {
	ID                       types.NodeID
	Node                     string
	Address                  string
	Datacenter               string
	TaggedAddresses          map[string]string
	NodeMeta                 map[string]string
	ServiceKind              ServiceKind
	ServiceID                string
	ServiceName              string
	ServiceTags              []string
	ServiceAddress           string
	ServiceWeights           Weights
	ServiceMeta              map[string]string
	ServicePort              int
	ServiceEnableTagOverride bool
	// DEPRECATED (ProxyDestination) - remove this when removing ProxyDestination
	ServiceProxyDestination string
	ServiceProxy            ConnectProxyConfig
	ServiceConnect          ServiceConnect

	RaftIndex
}

// PartialClone() returns a clone of the given service node, minus the node-
// related fields that get filled in later, Address and TaggedAddresses.
func (s *ServiceNode) PartialClone() *ServiceNode {
	tags := make([]string, len(s.ServiceTags))
	copy(tags, s.ServiceTags)
	nsmeta := make(map[string]string)
	for k, v := range s.ServiceMeta {
		nsmeta[k] = v
	}

	return &ServiceNode{
		// Skip ID, see above.
		Node: s.Node,
		// Skip Address, see above.
		// Skip TaggedAddresses, see above.
		ServiceKind:              s.ServiceKind,
		ServiceID:                s.ServiceID,
		ServiceName:              s.ServiceName,
		ServiceTags:              tags,
		ServiceAddress:           s.ServiceAddress,
		ServicePort:              s.ServicePort,
		ServiceMeta:              nsmeta,
		ServiceWeights:           s.ServiceWeights,
		ServiceEnableTagOverride: s.ServiceEnableTagOverride,
		// DEPRECATED (ProxyDestination) - remove this when removing ProxyDestination
		ServiceProxyDestination: s.ServiceProxyDestination,
		ServiceProxy:            s.ServiceProxy,
		ServiceConnect:          s.ServiceConnect,
		RaftIndex: RaftIndex{
			CreateIndex: s.CreateIndex,
			ModifyIndex: s.ModifyIndex,
		},
	}
}

// ToNodeService converts the given service node to a node service.
func (s *ServiceNode) ToNodeService() *NodeService {
	return &NodeService{
		Kind:              s.ServiceKind,
		ID:                s.ServiceID,
		Service:           s.ServiceName,
		Tags:              s.ServiceTags,
		Address:           s.ServiceAddress,
		Port:              s.ServicePort,
		Meta:              s.ServiceMeta,
		Weights:           &s.ServiceWeights,
		EnableTagOverride: s.ServiceEnableTagOverride,
		Proxy:             s.ServiceProxy,
		Connect:           s.ServiceConnect,
		RaftIndex: RaftIndex{
			CreateIndex: s.CreateIndex,
			ModifyIndex: s.ModifyIndex,
		},
	}
}

// Weights represent the weight used by DNS for a given status
type Weights struct {
	Passing int
	Warning int
}

type ServiceNodes []*ServiceNode

// ServiceKind is the kind of service being registered.
type ServiceKind string

const (
	// ServiceKindTypical is a typical, classic Consul service. This is
	// represented by the absence of a value. This was chosen for ease of
	// backwards compatibility: existing services in the catalog would
	// default to the typical service.
	ServiceKindTypical ServiceKind = ""

	// ServiceKindConnectProxy is a proxy for the Connect feature. This
	// service proxies another service within Consul and speaks the connect
	// protocol.
	ServiceKindConnectProxy ServiceKind = "connect-proxy"
)

// NodeService is a service provided by a node
type NodeService struct {
	// Kind is the kind of service this is. Different kinds of services may
	// have differing validation, DNS behavior, etc. An empty kind will default
	// to the Default kind. See ServiceKind for the full list of kinds.
	Kind ServiceKind `json:",omitempty"`

	ID                string
	Service           string
	Tags              []string
	Address           string
	Meta              map[string]string
	Port              int
	Weights           *Weights
	EnableTagOverride bool

	// ProxyDestination is DEPRECATED in favor of Proxy.DestinationServiceName.
	// It's retained since this struct is used to parse input for
	// /catalog/register but nothing else internal should use it - once
	// request/config definitions are passes all internal uses of NodeService
	// should have this empty and use the Proxy.DestinationServiceNames field
	// below.
	//
	// It used to store the name of the service that this service is a Connect
	// proxy for. This is only valid if Kind is "connect-proxy". The destination
	// may be a service that isn't present in the catalog. This is expected and
	// allowed to allow for proxies to come up earlier than their target services.
	// DEPRECATED (ProxyDestination) - remove this when removing ProxyDestination
	ProxyDestination string

	// Proxy is the configuration set for Kind = connect-proxy. It is mandatory in
	// that case and an error to be set for any other kind. This config is part of
	// a proxy service definition and is distinct from but shares some fields with
	// the Connect.Proxy which configures a managed proxy as part of the actual
	// service's definition. This duplication is ugly but seemed better than the
	// alternative which was to re-use the same struct fields for both cases even
	// though the semantics are different and the non-shred fields make no sense
	// in the other case. ProxyConfig may be a more natural name here, but it's
	// confusing for the UX because one of the fields in ConnectProxyConfig is
	// also called just "Config"
	Proxy ConnectProxyConfig

	// Connect are the Connect settings for a service. This is purposely NOT
	// a pointer so that we never have to nil-check this.
	Connect ServiceConnect

	// LocallyRegisteredAsSidecar is private as it is only used by a local agent
	// state to track if the service was registered from a nested sidecar_service
	// block. We need to track that so we can know whether we need to deregister
	// it automatically too if it's removed from the service definition or if the
	// parent service is deregistered. Relying only on ID would cause us to
	// deregister regular services if they happen to be registered using the same
	// ID scheme as our sidecars do by default. We could use meta but that gets
	// unpleasant because we can't use the consul- prefix from an agent (reserved
	// for use internally but in practice that means within the state store or in
	// responses only), and it leaks the detail publicly which people might rely
	// on which is a bit unpleasant for something that is meant to be config-file
	// syntax sugar. Note this is not translated to ServiceNode and friends and
	// may not be set on a NodeService that isn't the one the agent registered and
	// keeps in it's local state. We never want this rendered in JSON as it's
	// internal only. Right now our agent endpoints return api structs which don't
	// include it but this is a safety net incase we change that or there is
	// somewhere this is used in API output.
	LocallyRegisteredAsSidecar bool `json:"-"`

	RaftIndex
}

// ServiceConnect are the shared Connect settings between all service
// definitions from the agent to the state store.
type ServiceConnect struct {
	// Native is true when this service can natively understand Connect.
	Native bool `json:",omitempty"`

	// Proxy configures a connect proxy instance for the service. This is
	// only used for agent service definitions and is invalid for non-agent
	// (catalog API) definitions.
	Proxy *ServiceDefinitionConnectProxy `json:",omitempty"`

	// SidecarService is a nested Service Definition to register at the same time.
	// It's purely a convenience mechanism to allow specifying a sidecar service
	// along with the application service definition. It's nested nature allows
	// all of the fields to be defaulted which can reduce the amount of
	// boilerplate needed to register a sidecar service separately, but the end
	// result is identical to just making a second service registration via any
	// other means.
	SidecarService *ServiceDefinition `json:",omitempty"`
}

// Validate validates the node service configuration.
//
// NOTE(mitchellh): This currently only validates fields for a ConnectProxy.
// Historically validation has been directly in the Catalog.Register RPC.
// ConnectProxy validation was moved here for easier table testing, but
// other validation still exists in Catalog.Register.
func (s *NodeService) Validate() error {
	var result error

	// ConnectProxy validation
	if s.Kind == ServiceKindConnectProxy {
		// DEPRECATED (ProxyDestination) - remove this when removing ProxyDestination
		// Fixup legacy requests that specify the ProxyDestination still
		if s.ProxyDestination != "" && s.Proxy.DestinationServiceName == "" {
			s.Proxy.DestinationServiceName = s.ProxyDestination
			s.ProxyDestination = ""
		}

		if strings.TrimSpace(s.Proxy.DestinationServiceName) == "" {
			result = multierror.Append(result, fmt.Errorf(
				"Proxy.DestinationServiceName must be non-empty for Connect proxy "+
					"services"))
		}

		if s.Port == 0 {
			result = multierror.Append(result, fmt.Errorf(
				"Port must be set for a Connect proxy"))
		}

		if s.Connect.Native {
			result = multierror.Append(result, fmt.Errorf(
				"A Proxy cannot also be Connect Native, only typical services"))
		}
	}

	// Nested sidecar validation
	if s.Connect.SidecarService != nil {
		if s.Connect.SidecarService.ID != "" {
			result = multierror.Append(result, fmt.Errorf(
				"A SidecarService cannot specify an ID as this is managed by the "+
					"agent"))
		}
		if s.Connect.SidecarService.Connect != nil {
			if s.Connect.SidecarService.Connect.SidecarService != nil {
				result = multierror.Append(result, fmt.Errorf(
					"A SidecarService cannot have a nested SidecarService"))
			}
			if s.Connect.SidecarService.Connect.Proxy != nil {
				result = multierror.Append(result, fmt.Errorf(
					"A SidecarService cannot have a managed proxy"))
			}
		}
	}

	return result
}

// IsSame checks if one NodeService is the same as another, without looking
// at the Raft information (that's why we didn't call it IsEqual). This is
// useful for seeing if an update would be idempotent for all the functional
// parts of the structure.
func (s *NodeService) IsSame(other *NodeService) bool {
	if s.ID != other.ID ||
		s.Service != other.Service ||
		!reflect.DeepEqual(s.Tags, other.Tags) ||
		s.Address != other.Address ||
		s.Port != other.Port ||
		!reflect.DeepEqual(s.Weights, other.Weights) ||
		!reflect.DeepEqual(s.Meta, other.Meta) ||
		s.EnableTagOverride != other.EnableTagOverride ||
		s.Kind != other.Kind ||
		!reflect.DeepEqual(s.Proxy, other.Proxy) ||
		s.Connect != other.Connect {
		return false
	}

	return true
}

// IsSameService checks if one Service of a ServiceNode is the same as another,
// without looking at the Raft information or Node information (that's why we
// didn't call it IsEqual).
// This is useful for seeing if an update would be idempotent for all the functional
// parts of the structure.
// In a similar fashion as ToNodeService(), fields related to Node are ignored
// see ServiceNode for more information.
func (s *ServiceNode) IsSameService(other *ServiceNode) bool {
	// Skip the following fields, see ServiceNode definition
	// Address                  string
	// Datacenter               string
	// TaggedAddresses          map[string]string
	// NodeMeta                 map[string]string
	if s.ID != other.ID ||
		s.Node != other.Node ||
		s.ServiceKind != other.ServiceKind ||
		s.ServiceID != other.ServiceID ||
		s.ServiceName != other.ServiceName ||
		!reflect.DeepEqual(s.ServiceTags, other.ServiceTags) ||
		s.ServiceAddress != other.ServiceAddress ||
		s.ServicePort != other.ServicePort ||
		!reflect.DeepEqual(s.ServiceMeta, other.ServiceMeta) ||
		!reflect.DeepEqual(s.ServiceWeights, other.ServiceWeights) ||
		s.ServiceEnableTagOverride != other.ServiceEnableTagOverride ||
		s.ServiceProxyDestination != other.ServiceProxyDestination ||
		!reflect.DeepEqual(s.ServiceProxy, other.ServiceProxy) ||
		!reflect.DeepEqual(s.ServiceConnect, other.ServiceConnect) {
		return false
	}

	return true
}

// ToServiceNode converts the given node service to a service node.
func (s *NodeService) ToServiceNode(node string) *ServiceNode {
	theWeights := Weights{
		Passing: 1,
		Warning: 1,
	}
	if s.Weights != nil {
		if err := ValidateWeights(s.Weights); err == nil {
			theWeights = *s.Weights
		}
	}
	// DEPRECATED (ProxyDestination) - remove this when removing ProxyDestination
	legacyProxyDest := s.Proxy.DestinationServiceName
	if legacyProxyDest == "" {
		legacyProxyDest = s.ProxyDestination
	}
	return &ServiceNode{
		// Skip ID, see ServiceNode definition.
		Node: node,
		// Skip Address, see ServiceNode definition.
		// Skip TaggedAddresses, see ServiceNode definition.
		ServiceKind:              s.Kind,
		ServiceID:                s.ID,
		ServiceName:              s.Service,
		ServiceTags:              s.Tags,
		ServiceAddress:           s.Address,
		ServicePort:              s.Port,
		ServiceMeta:              s.Meta,
		ServiceWeights:           theWeights,
		ServiceEnableTagOverride: s.EnableTagOverride,
		ServiceProxy:             s.Proxy,
		ServiceProxyDestination:  legacyProxyDest,
		ServiceConnect:           s.Connect,
		RaftIndex: RaftIndex{
			CreateIndex: s.CreateIndex,
			ModifyIndex: s.ModifyIndex,
		},
	}
}

type NodeServices struct {
	Node     *Node
	Services map[string]*NodeService
}

// HealthCheck represents a single check on a given node
type HealthCheck struct {
	Node        string
	CheckID     types.CheckID // Unique per-node ID
	Name        string        // Check name
	Status      string        // The current check status
	Notes       string        // Additional notes with the status
	Output      string        // Holds output of script runs
	ServiceID   string        // optional associated service
	ServiceName string        // optional service name
	ServiceTags []string      // optional service tags

	Definition HealthCheckDefinition

	RaftIndex
}

type HealthCheckDefinition struct {
	HTTP                           string               `json:",omitempty"`
	TLSSkipVerify                  bool                 `json:",omitempty"`
	Header                         map[string][]string  `json:",omitempty"`
	Method                         string               `json:",omitempty"`
	TCP                            string               `json:",omitempty"`
	Interval                       api.ReadableDuration `json:",omitempty"`
	Timeout                        api.ReadableDuration `json:",omitempty"`
	DeregisterCriticalServiceAfter api.ReadableDuration `json:",omitempty"`
}

// IsSame checks if one HealthCheck is the same as another, without looking
// at the Raft information (that's why we didn't call it IsEqual). This is
// useful for seeing if an update would be idempotent for all the functional
// parts of the structure.
func (c *HealthCheck) IsSame(other *HealthCheck) bool {
	if c.Node != other.Node ||
		c.CheckID != other.CheckID ||
		c.Name != other.Name ||
		c.Status != other.Status ||
		c.Notes != other.Notes ||
		c.Output != other.Output ||
		c.ServiceID != other.ServiceID ||
		c.ServiceName != other.ServiceName ||
		!reflect.DeepEqual(c.ServiceTags, other.ServiceTags) {
		return false
	}

	return true
}

// Clone returns a distinct clone of the HealthCheck.
func (c *HealthCheck) Clone() *HealthCheck {
	clone := new(HealthCheck)
	*clone = *c
	return clone
}

// HealthChecks is a collection of HealthCheck structs.
type HealthChecks []*HealthCheck

// CheckServiceNode is used to provide the node, its service
// definition, as well as a HealthCheck that is associated.
type CheckServiceNode struct {
	Node    *Node
	Service *NodeService
	Checks  HealthChecks
}
type CheckServiceNodes []CheckServiceNode

// Shuffle does an in-place random shuffle using the Fisher-Yates algorithm.
func (nodes CheckServiceNodes) Shuffle() {
	for i := len(nodes) - 1; i > 0; i-- {
		j := rand.Int31n(int32(i + 1))
		nodes[i], nodes[j] = nodes[j], nodes[i]
	}
}

// Filter removes nodes that are failing health checks (and any non-passing
// check if that option is selected). Note that this returns the filtered
// results AND modifies the receiver for performance.
func (nodes CheckServiceNodes) Filter(onlyPassing bool) CheckServiceNodes {
	return nodes.FilterIgnore(onlyPassing, nil)
}

// FilterIgnore removes nodes that are failing health checks just like Filter.
// It also ignores the status of any check with an ID present in ignoreCheckIDs
// as if that check didn't exist. Note that this returns the filtered results
// AND modifies the receiver for performance.
func (nodes CheckServiceNodes) FilterIgnore(onlyPassing bool,
	ignoreCheckIDs []types.CheckID) CheckServiceNodes {
	n := len(nodes)
OUTER:
	for i := 0; i < n; i++ {
		node := nodes[i]
	INNER:
		for _, check := range node.Checks {
			for _, ignore := range ignoreCheckIDs {
				if check.CheckID == ignore {
					// Skip this _check_ but keep looking at other checks for this node.
					continue INNER
				}
			}
			if check.Status == api.HealthCritical ||
				(onlyPassing && check.Status != api.HealthPassing) {
				nodes[i], nodes[n-1] = nodes[n-1], CheckServiceNode{}
				n--
				i--
				// Skip this _node_ now we've swapped it off the end of the list.
				continue OUTER
			}
		}
	}
	return nodes[:n]
}

// NodeInfo is used to dump all associated information about
// a node. This is currently used for the UI only, as it is
// rather expensive to generate.
type NodeInfo struct {
	ID              types.NodeID
	Node            string
	Address         string
	TaggedAddresses map[string]string
	Meta            map[string]string
	Services        []*NodeService
	Checks          HealthChecks
}

// NodeDump is used to dump all the nodes with all their
// associated data. This is currently used for the UI only,
// as it is rather expensive to generate.
type NodeDump []*NodeInfo

type IndexedNodes struct {
	Nodes Nodes
	QueryMeta
}

type IndexedServices struct {
	Services Services
	QueryMeta
}

type IndexedServiceNodes struct {
	ServiceNodes ServiceNodes
	QueryMeta
}

type IndexedNodeServices struct {
	// TODO: This should not be a pointer, see comments in
	// agent/catalog_endpoint.go.
	NodeServices *NodeServices
	QueryMeta
}

type IndexedHealthChecks struct {
	HealthChecks HealthChecks
	QueryMeta
}

type IndexedCheckServiceNodes struct {
	Nodes CheckServiceNodes
	QueryMeta
}

type IndexedNodeDump struct {
	Dump NodeDump
	QueryMeta
}

// DirEntry is used to represent a directory entry. This is
// used for values in our Key-Value store.
type DirEntry struct {
	LockIndex uint64
	Key       string
	Flags     uint64
	Value     []byte
	Session   string `json:",omitempty"`

	RaftIndex
}

// Returns a clone of the given directory entry.
func (d *DirEntry) Clone() *DirEntry {
	return &DirEntry{
		LockIndex: d.LockIndex,
		Key:       d.Key,
		Flags:     d.Flags,
		Value:     d.Value,
		Session:   d.Session,
		RaftIndex: RaftIndex{
			CreateIndex: d.CreateIndex,
			ModifyIndex: d.ModifyIndex,
		},
	}
}

type DirEntries []*DirEntry

// KVSRequest is used to operate on the Key-Value store
type KVSRequest struct {
	Datacenter string
	Op         api.KVOp // Which operation are we performing
	DirEnt     DirEntry // Which directory entry
	WriteRequest
}

func (r *KVSRequest) RequestDatacenter() string {
	return r.Datacenter
}

// KeyRequest is used to request a key, or key prefix
type KeyRequest struct {
	Datacenter string
	Key        string
	QueryOptions
}

func (r *KeyRequest) RequestDatacenter() string {
	return r.Datacenter
}

// KeyListRequest is used to list keys
type KeyListRequest struct {
	Datacenter string
	Prefix     string
	Seperator  string
	QueryOptions
}

func (r *KeyListRequest) RequestDatacenter() string {
	return r.Datacenter
}

type IndexedDirEntries struct {
	Entries DirEntries
	QueryMeta
}

type IndexedKeyList struct {
	Keys []string
	QueryMeta
}

type SessionBehavior string

const (
	SessionKeysRelease SessionBehavior = "release"
	SessionKeysDelete                  = "delete"
)

const (
	SessionTTLMax        = 24 * time.Hour
	SessionTTLMultiplier = 2
)

// Session is used to represent an open session in the KV store.
// This issued to associate node checks with acquired locks.
type Session struct {
	ID        string
	Name      string
	Node      string
	Checks    []types.CheckID
	LockDelay time.Duration
	Behavior  SessionBehavior // What to do when session is invalidated
	TTL       string

	RaftIndex
}
type Sessions []*Session

type SessionOp string

const (
	SessionCreate  SessionOp = "create"
	SessionDestroy           = "destroy"
)

// SessionRequest is used to operate on sessions
type SessionRequest struct {
	Datacenter string
	Op         SessionOp // Which operation are we performing
	Session    Session   // Which session
	WriteRequest
}

func (r *SessionRequest) RequestDatacenter() string {
	return r.Datacenter
}

// SessionSpecificRequest is used to request a session by ID
type SessionSpecificRequest struct {
	Datacenter string
	Session    string
	QueryOptions
}

func (r *SessionSpecificRequest) RequestDatacenter() string {
	return r.Datacenter
}

type IndexedSessions struct {
	Sessions Sessions
	QueryMeta
}

// Coordinate stores a node name with its associated network coordinate.
type Coordinate struct {
	Node    string
	Segment string
	Coord   *coordinate.Coordinate
}

type Coordinates []*Coordinate

// IndexedCoordinate is used to represent a single node's coordinate from the state
// store.
type IndexedCoordinate struct {
	Coord *coordinate.Coordinate
	QueryMeta
}

// IndexedCoordinates is used to represent a list of nodes and their
// corresponding raw coordinates.
type IndexedCoordinates struct {
	Coordinates Coordinates
	QueryMeta
}

// DatacenterMap is used to represent a list of nodes with their raw coordinates,
// associated with a datacenter. Coordinates are only compatible between nodes in
// the same area.
type DatacenterMap struct {
	Datacenter  string
	AreaID      types.AreaID
	Coordinates Coordinates
}

// CoordinateUpdateRequest is used to update the network coordinate of a given
// node.
type CoordinateUpdateRequest struct {
	Datacenter string
	Node       string
	Segment    string
	Coord      *coordinate.Coordinate
	WriteRequest
}

// RequestDatacenter returns the datacenter for a given update request.
func (c *CoordinateUpdateRequest) RequestDatacenter() string {
	return c.Datacenter
}

// EventFireRequest is used to ask a server to fire
// a Serf event. It is a bit odd, since it doesn't depend on
// the catalog or leader. Any node can respond, so it's not quite
// like a standard write request. This is used only internally.
type EventFireRequest struct {
	Datacenter string
	Name       string
	Payload    []byte

	// Not using WriteRequest so that any server can process
	// the request. It is a bit unusual...
	QueryOptions
}

func (r *EventFireRequest) RequestDatacenter() string {
	return r.Datacenter
}

// EventFireResponse is used to respond to a fire request.
type EventFireResponse struct {
	QueryMeta
}

type TombstoneOp string

const (
	TombstoneReap TombstoneOp = "reap"
)

// TombstoneRequest is used to trigger a reaping of the tombstones
type TombstoneRequest struct {
	Datacenter string
	Op         TombstoneOp
	ReapIndex  uint64
	WriteRequest
}

func (r *TombstoneRequest) RequestDatacenter() string {
	return r.Datacenter
}

// msgpackHandle is a shared handle for encoding/decoding of structs
var msgpackHandle = &codec.MsgpackHandle{}

// Decode is used to decode a MsgPack encoded object
func Decode(buf []byte, out interface{}) error {
	return codec.NewDecoder(bytes.NewReader(buf), msgpackHandle).Decode(out)
}

// Encode is used to encode a MsgPack object with type prefix
func Encode(t MessageType, msg interface{}) ([]byte, error) {
	var buf bytes.Buffer
	buf.WriteByte(uint8(t))
	err := codec.NewEncoder(&buf, msgpackHandle).Encode(msg)
	return buf.Bytes(), err
}

// CompoundResponse is an interface for gathering multiple responses. It is
// used in cross-datacenter RPC calls where more than 1 datacenter is
// expected to reply.
type CompoundResponse interface {
	// Add adds a new response to the compound response
	Add(interface{})

	// New returns an empty response object which can be passed around by
	// reference, and then passed to Add() later on.
	New() interface{}
}

type KeyringOp string

const (
	KeyringList    KeyringOp = "list"
	KeyringInstall           = "install"
	KeyringUse               = "use"
	KeyringRemove            = "remove"
)

// KeyringRequest encapsulates a request to modify an encryption keyring.
// It can be used for install, remove, or use key type operations.
type KeyringRequest struct {
	Operation   KeyringOp
	Key         string
	Datacenter  string
	Forwarded   bool
	RelayFactor uint8
	QueryOptions
}

func (r *KeyringRequest) RequestDatacenter() string {
	return r.Datacenter
}

// KeyringResponse is a unified key response and can be used for install,
// remove, use, as well as listing key queries.
type KeyringResponse struct {
	WAN        bool
	Datacenter string
	Segment    string
	Messages   map[string]string `json:",omitempty"`
	Keys       map[string]int
	NumNodes   int
	Error      string `json:",omitempty"`
}

// KeyringResponses holds multiple responses to keyring queries. Each
// datacenter replies independently, and KeyringResponses is used as a
// container for the set of all responses.
type KeyringResponses struct {
	Responses []*KeyringResponse
	QueryMeta
}

func (r *KeyringResponses) Add(v interface{}) {
	val := v.(*KeyringResponses)
	r.Responses = append(r.Responses, val.Responses...)
}

func (r *KeyringResponses) New() interface{} {
	return new(KeyringResponses)
}