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validation.go
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validation.go
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package pubsub
import (
"context"
"fmt"
"runtime"
"time"
"github.com/libp2p/go-libp2p-core/peer"
)
const (
defaultValidateQueueSize = 32
defaultValidateConcurrency = 1024
defaultValidateThrottle = 8192
)
// Validator is a function that validates a message.
type Validator func(context.Context, peer.ID, *Message) bool
// ValidatorOpt is an option for RegisterTopicValidator.
type ValidatorOpt func(addVal *addValReq) error
// validation represents the validator pipeline.
// The validator pipeline performs signature validation and runs a
// sequence of user-configured validators per-topic. It is possible to
// adjust various concurrency parameters, such as the number of
// workers and the max number of simultaneous validations. The user
// can also attach inline validators that will be executed
// synchronously; this may be useful to prevent superfluous
// context-switching for lightweight tasks.
type validation struct {
p *PubSub
tracer *pubsubTracer
// topicVals tracks per topic validators
topicVals map[string]*topicVal
// validateQ is the front-end to the validation pipeline
validateQ chan *validateReq
// validateThrottle limits the number of active validation goroutines
validateThrottle chan struct{}
// this is the number of synchronous validation workers
validateWorkers int
}
// validation requests
type validateReq struct {
vals []*topicVal
src peer.ID
msg *Message
}
// representation of topic validators
type topicVal struct {
topic string
validate Validator
validateTimeout time.Duration
validateThrottle chan struct{}
validateInline bool
}
// async request to add a topic validators
type addValReq struct {
topic string
validate Validator
timeout time.Duration
throttle int
inline bool
resp chan error
}
// async request to remove a topic validator
type rmValReq struct {
topic string
resp chan error
}
// newValidation creates a new validation pipeline
func newValidation() *validation {
return &validation{
topicVals: make(map[string]*topicVal),
validateQ: make(chan *validateReq, defaultValidateQueueSize),
validateThrottle: make(chan struct{}, defaultValidateThrottle),
validateWorkers: runtime.NumCPU(),
}
}
// Start attaches the validation pipeline to a pubsub instance and starts background
// workers
func (v *validation) Start(p *PubSub) {
v.p = p
v.tracer = p.tracer
for i := 0; i < v.validateWorkers; i++ {
go v.validateWorker()
}
}
// AddValidator adds a new validator
func (v *validation) AddValidator(req *addValReq) {
topic := req.topic
_, ok := v.topicVals[topic]
if ok {
req.resp <- fmt.Errorf("Duplicate validator for topic %s", topic)
return
}
val := &topicVal{
topic: topic,
validate: req.validate,
validateTimeout: 0,
validateThrottle: make(chan struct{}, defaultValidateConcurrency),
validateInline: req.inline,
}
if req.timeout > 0 {
val.validateTimeout = req.timeout
}
if req.throttle > 0 {
val.validateThrottle = make(chan struct{}, req.throttle)
}
v.topicVals[topic] = val
req.resp <- nil
}
// RemoveValidator removes an existing validator
func (v *validation) RemoveValidator(req *rmValReq) {
topic := req.topic
_, ok := v.topicVals[topic]
if ok {
delete(v.topicVals, topic)
req.resp <- nil
} else {
req.resp <- fmt.Errorf("No validator for topic %s", topic)
}
}
// Push pushes a message into the validation pipeline.
// It returns true if the message can be forwarded immediately without validation.
func (v *validation) Push(src peer.ID, msg *Message) bool {
vals := v.getValidators(msg)
if len(vals) > 0 || msg.Signature != nil {
select {
case v.validateQ <- &validateReq{vals, src, msg}:
default:
log.Warningf("message validation throttled; dropping message from %s", src)
v.tracer.RejectMessage(msg, "validation throttled")
}
return false
}
return true
}
// getValidators returns all validators that apply to a given message
func (v *validation) getValidators(msg *Message) []*topicVal {
var vals []*topicVal
for _, topic := range msg.GetTopicIDs() {
val, ok := v.topicVals[topic]
if !ok {
continue
}
vals = append(vals, val)
}
return vals
}
// validateWorker is an active goroutine performing inline validation
func (v *validation) validateWorker() {
for {
select {
case req := <-v.validateQ:
v.validate(req.vals, req.src, req.msg)
case <-v.p.ctx.Done():
return
}
}
}
// validate performs validation and only sends the message if all validators succeed
// signature validation is performed synchronously, while user validators are invoked
// asynchronously, throttled by the global validation throttle.
func (v *validation) validate(vals []*topicVal, src peer.ID, msg *Message) {
if msg.Signature != nil {
if !v.validateSignature(msg) {
log.Warningf("message signature validation failed; dropping message from %s", src)
v.tracer.RejectMessage(msg, "invalid signature")
return
}
}
// we can mark the message as seen now that we have verified the signature
// and avoid invoking user validators more than once
id := v.p.msgID(msg.Message)
if !v.p.markSeen(id) {
v.tracer.DuplicateMessage(msg)
return
}
var inline, async []*topicVal
for _, val := range vals {
if val.validateInline {
inline = append(inline, val)
} else {
async = append(async, val)
}
}
// apply inline (synchronous) validators
for _, val := range inline {
if !val.validateMsg(v.p.ctx, src, msg) {
log.Debugf("message validation failed; dropping message from %s", src)
v.tracer.RejectMessage(msg, "validation failed")
return
}
}
// apply async validators
if len(async) > 0 {
select {
case v.validateThrottle <- struct{}{}:
go func() {
v.doValidateTopic(async, src, msg)
<-v.validateThrottle
}()
default:
log.Warningf("message validation throttled; dropping message from %s", src)
v.tracer.RejectMessage(msg, "validation throttled")
}
return
}
// no async validators, send the message
v.p.sendMsg <- msg
}
func (v *validation) validateSignature(msg *Message) bool {
err := verifyMessageSignature(msg.Message)
if err != nil {
log.Debugf("signature verification error: %s", err.Error())
return false
}
return true
}
func (v *validation) doValidateTopic(vals []*topicVal, src peer.ID, msg *Message) {
if !v.validateTopic(vals, src, msg) {
log.Warningf("message validation failed; dropping message from %s", src)
v.tracer.RejectMessage(msg, "validation failed")
return
}
v.p.sendMsg <- msg
}
func (v *validation) validateTopic(vals []*topicVal, src peer.ID, msg *Message) bool {
if len(vals) == 1 {
return v.validateSingleTopic(vals[0], src, msg)
}
ctx, cancel := context.WithCancel(v.p.ctx)
defer cancel()
rch := make(chan bool, len(vals))
rcount := 0
throttle := false
loop:
for _, val := range vals {
rcount++
select {
case val.validateThrottle <- struct{}{}:
go func(val *topicVal) {
rch <- val.validateMsg(ctx, src, msg)
<-val.validateThrottle
}(val)
default:
log.Debugf("validation throttled for topic %s", val.topic)
throttle = true
break loop
}
}
if throttle {
v.tracer.RejectMessage(msg, "validation throttled")
return false
}
for i := 0; i < rcount; i++ {
valid := <-rch
if !valid {
return false
}
}
return true
}
// fast path for single topic validation that avoids the extra goroutine
func (v *validation) validateSingleTopic(val *topicVal, src peer.ID, msg *Message) bool {
select {
case val.validateThrottle <- struct{}{}:
res := val.validateMsg(v.p.ctx, src, msg)
<-val.validateThrottle
return res
default:
log.Debugf("validation throttled for topic %s", val.topic)
v.tracer.RejectMessage(msg, "validation throttled")
return false
}
}
func (val *topicVal) validateMsg(ctx context.Context, src peer.ID, msg *Message) bool {
if val.validateTimeout > 0 {
var cancel func()
ctx, cancel = context.WithTimeout(ctx, val.validateTimeout)
defer cancel()
}
valid := val.validate(ctx, src, msg)
if !valid {
log.Debugf("validation failed for topic %s", val.topic)
}
return valid
}
/// Options
// WithValidateQueueSize sets the buffer of validate queue. Defaults to 32.
// When queue is full, validation is throttled and new messages are dropped.
func WithValidateQueueSize(n int) Option {
return func(ps *PubSub) error {
if n > 0 {
ps.val.validateQ = make(chan *validateReq, n)
return nil
}
return fmt.Errorf("validate queue size must be > 0")
}
}
// WithValidateThrottle sets the upper bound on the number of active validation
// goroutines across all topics. The default is 8192.
func WithValidateThrottle(n int) Option {
return func(ps *PubSub) error {
ps.val.validateThrottle = make(chan struct{}, n)
return nil
}
}
// WithValidateWorkers sets the number of synchronous validation worker goroutines.
// Defaults to NumCPU.
//
// The synchronous validation workers perform signature validation, apply inline
// user validators, and schedule asynchronous user validators.
// You can adjust this parameter to devote less cpu time to synchronous validation.
func WithValidateWorkers(n int) Option {
return func(ps *PubSub) error {
if n > 0 {
ps.val.validateWorkers = n
return nil
}
return fmt.Errorf("number of validation workers must be > 0")
}
}
// WithValidatorTimeout is an option that sets a timeout for an (asynchronous) topic validator.
// By default there is no timeout in asynchronous validators.
func WithValidatorTimeout(timeout time.Duration) ValidatorOpt {
return func(addVal *addValReq) error {
addVal.timeout = timeout
return nil
}
}
// WithValidatorConcurrency is an option that sets the topic validator throttle.
// This controls the number of active validation goroutines for the topic; the default is 1024.
func WithValidatorConcurrency(n int) ValidatorOpt {
return func(addVal *addValReq) error {
addVal.throttle = n
return nil
}
}
// WithValidatorInline is an option that sets the validation disposition to synchronous:
// it will be executed inline in validation front-end, without spawning a new goroutine.
// This is suitable for simple or cpu-bound validators that do not block.
func WithValidatorInline(inline bool) ValidatorOpt {
return func(addVal *addValReq) error {
addVal.inline = inline
return nil
}
}