remove default async validation timeout and increase default topic validation throttle.

and some better documentation.

pubsub.go

@@ -22,8 +22,7 @@ import (
 )
 
 const (
-	defaultValidateTimeout     = 150 * time.Millisecond
+	defaultValidateConcurrency = 1024
-	defaultValidateConcurrency = 100
 	defaultValidateThrottle    = 8192
 )
 
@@ -227,7 +226,7 @@ func NewPubSub(ctx context.Context, h host.Host, rt PubSubRouter, opts ...Option
 }
 
 // WithValidateThrottle sets the upper bound on the number of active validation
-// goroutines.
+// goroutines across all topics. The default is 8192.
 func WithValidateThrottle(n int) Option {
 	return func(ps *PubSub) error {
 		ps.validateThrottle = make(chan struct{}, n)
@@ -966,7 +965,8 @@ type Validator func(context.Context, peer.ID, *Message) bool
 // ValidatorOpt is an option for RegisterTopicValidator.
 type ValidatorOpt func(addVal *addValReq) error
 
-// WithValidatorTimeout is an option that sets the topic validator timeout.
+// 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
@@ -974,7 +974,8 @@ func WithValidatorTimeout(timeout time.Duration) ValidatorOpt {
 	}
 }
 
-// WithValidatorConcurrency is an option that sets topic validator throttle.
+// 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
@@ -983,6 +984,9 @@ func WithValidatorConcurrency(n int) ValidatorOpt {
 }
 
 // RegisterTopicValidator registers a validator for topic.
+// By default validators are asynchronous, which means they will run in a separate goroutine.
+// The number of active goroutines is controlled by global and per topic validator
+// throttles; if it exceeds the throttle threshold, messages will be dropped.
 func (p *PubSub) RegisterTopicValidator(topic string, val Validator, opts ...ValidatorOpt) error {
 	addVal := &addValReq{
 		topic:    topic,
@@ -1013,7 +1017,7 @@ func (ps *PubSub) addValidator(req *addValReq) {
 	val := &topicVal{
 		topic:            topic,
 		validate:         req.validate,
-		validateTimeout:  defaultValidateTimeout,
+		validateTimeout:  0,
 		validateThrottle: make(chan struct{}, defaultValidateConcurrency),
 	}
 
@@ -1054,10 +1058,13 @@ func (ps *PubSub) rmValidator(req *rmValReq) {
 }
 
 func (val *topicVal) validateMsg(ctx context.Context, src peer.ID, msg *Message) bool {
-	vctx, cancel := context.WithTimeout(ctx, val.validateTimeout)
+	if val.validateTimeout > 0 {
-	defer cancel()
+		var cancel func()
+		ctx, cancel = context.WithTimeout(ctx, val.validateTimeout)
+		defer cancel()
+	}
 
-	valid := val.validate(vctx, src, msg)
+	valid := val.validate(ctx, src, msg)
 	if !valid {
 		log.Debugf("validation failed for topic %s", val.topic)
 	}