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engine_subscribers.go
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engine_subscribers.go
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// Copyright (c) 2022 Gobalsky Labs Limited
//
// Use of this software is governed by the Business Source License included
// in the LICENSE.VEGA file and at https://www.mariadb.com/bsl11.
//
// Change Date: 18 months from the later of the date of the first publicly
// available Distribution of this version of the repository, and 25 June 2022.
//
// On the date above, in accordance with the Business Source License, use
// of this software will be governed by version 3 or later of the GNU General
// Public License.
package oracles
import (
"context"
"fmt"
"sync"
"time"
"code.vegaprotocol.io/vega/core/types"
)
// OnMatchedOracleData describes the callback function used when an oracle data matches the spec.
type OnMatchedOracleData func(ctx context.Context, data OracleData) error
// OracleSpecPredicate describes the predicate used to filter the subscribers.
// When returning true, all the subscribers associated to the matching
// OracleSpec are collected.
// The order between specs and subscribers is preserved.
type OracleSpecPredicate func(spec OracleSpec) (bool, error)
// OracleSubscriptionPredicate describes the predicate used to check if any
// of the currently existing subscriptions expects the public keys inside
// the incoming OracleSpec object.
type OracleSubscriptionPredicate func(spec OracleSpec) bool
// SubscriptionID is a unique identifier referencing the subscription of an
// OnMatchedOracleData to an OracleSpec.
type SubscriptionID uint64
// Unsubscriber is a closure that is created at subscription step in order to
// provide the ability to unsubscribe at any conveninent moment.
type Unsubscriber func(context.Context, SubscriptionID)
// updatedSubscription wraps all useful information about an updated
// subscription.
type updatedSubscription struct {
subscriptionID SubscriptionID
spec types.OracleSpec
specActivatedAt time.Time
}
// filterResult describes the result of the filter operation.
type filterResult struct {
// oracleSpecIDs lists all the OracleSpec ID that matched the filter
// predicate.
oracleSpecIDs []OracleSpecID
// subscribers list all the subscribers associated to the matched
// OracleSpec.
subscribers []OnMatchedOracleData
}
// hasMatched returns true if filter has matched the predicated.
func (r filterResult) hasMatched() bool {
return len(r.oracleSpecIDs) > 0
}
// specSubscriptions wraps the subscribers (in form of OnMatchedOracleData) to
// the OracleSpec.
type specSubscriptions struct {
mu sync.RWMutex
lastSubscriptionID SubscriptionID
subscriptions []*specSubscription
// subscriptionsMatrix maps a SubscriptionID to an OracleSpecID to speed up
// the retrieval of the OnMatchedOracleData into the subscriptions.
subscriptionsMatrix map[SubscriptionID]OracleSpecID
}
// newSpecSubscriptions initialises the subscription handler.
func newSpecSubscriptions() *specSubscriptions {
return &specSubscriptions{
subscriptions: []*specSubscription{},
subscriptionsMatrix: map[SubscriptionID]OracleSpecID{},
}
}
// hasAnySubscribers checks if any of the subscriptions contains public keys that
// match the given ones by the predicate.
// Returns fast on the first match.
func (s *specSubscriptions) hasAnySubscribers(predicate OracleSubscriptionPredicate) bool {
s.mu.RLock()
defer s.mu.RUnlock()
for _, subscription := range s.subscriptions {
if predicate(subscription.spec) {
return true
}
}
return false
}
// filterSubscribers collects the subscribers that match the predicate on the
// OracleSpec.
// The order between specs and subscribers is preserved.
func (s *specSubscriptions) filterSubscribers(predicate OracleSpecPredicate) (*filterResult, error) {
s.mu.RLock()
defer s.mu.RUnlock()
result := &filterResult{
oracleSpecIDs: []OracleSpecID{},
subscribers: []OnMatchedOracleData{},
}
for _, subscription := range s.subscriptions {
matched, err := predicate(subscription.spec)
if err != nil {
return nil, err
}
if !matched {
continue
}
result.oracleSpecIDs = append(result.oracleSpecIDs, subscription.spec.id)
for _, subscriber := range subscription.subscribers {
result.subscribers = append(result.subscribers, subscriber.cb)
}
}
return result, nil
}
func (s *specSubscriptions) addSubscriber(spec OracleSpec, cb OnMatchedOracleData, tm time.Time) updatedSubscription {
s.mu.Lock()
defer s.mu.Unlock()
_, subscription := s.getSubscription(spec.id)
if subscription == nil {
subscription = s.createSubscription(spec, tm)
}
subscriptionID := s.nextSubscriptionID()
subscription.addSubscriber(subscriptionID, cb)
s.subscriptionsMatrix[subscriptionID] = spec.id
return updatedSubscription{
subscriptionID: subscriptionID,
specActivatedAt: subscription.specActivatedAt,
spec: *spec.OriginalSpec,
}
}
func (s *specSubscriptions) removeSubscriber(subscriptionID SubscriptionID) (updatedSubscription, bool) {
s.mu.Lock()
defer s.mu.Unlock()
specID, ok := s.subscriptionsMatrix[subscriptionID]
if !ok {
panic(fmt.Sprintf("unknown subscriber ID %d", subscriptionID))
}
index, subscription := s.getSubscription(specID)
subscription.removeSubscriber(subscriptionID)
delete(s.subscriptionsMatrix, subscriptionID)
hasNoMoreSubscriber := subscription.hasNoMoreSubscriber()
if hasNoMoreSubscriber {
s.removeSubscriptionFromIndex(index)
}
return updatedSubscription{
subscriptionID: subscriptionID,
specActivatedAt: subscription.specActivatedAt,
spec: *subscription.spec.OriginalSpec,
}, hasNoMoreSubscriber
}
// Internal usage.
func (s *specSubscriptions) removeSubscriptionFromIndex(index int) {
copy(s.subscriptions[index:], s.subscriptions[index+1:])
lastIndex := len(s.subscriptions) - 1
s.subscriptions[lastIndex] = nil
s.subscriptions = s.subscriptions[:lastIndex]
}
// Internal usage.
func (s *specSubscriptions) createSubscription(spec OracleSpec, tm time.Time) *specSubscription {
subscription := newOracleSpecSubscription(spec, tm)
s.subscriptions = append(s.subscriptions, subscription)
return subscription
}
// Internal usage.
func (s *specSubscriptions) getSubscription(id OracleSpecID) (int, *specSubscription) {
for i, subscription := range s.subscriptions {
if subscription.spec.id == id {
return i, subscription
}
}
return -1, nil
}
// nextSubscriptionID computes the next SubscriptionID
// Internal usage.
func (s *specSubscriptions) nextSubscriptionID() SubscriptionID {
s.lastSubscriptionID++
return s.lastSubscriptionID
}
// specSubscription groups all OnMatchedOracleData callbacks by
// OracleSpec.
type specSubscription struct {
spec OracleSpec
specActivatedAt time.Time
subscribers []*specSubscriber
}
type specSubscriber struct {
id SubscriptionID
cb OnMatchedOracleData
}
// Internal usage.
func newOracleSpecSubscription(spec OracleSpec, activationTime time.Time) *specSubscription {
return &specSubscription{
spec: spec,
specActivatedAt: activationTime,
subscribers: []*specSubscriber{},
}
}
// Internal usage.
func (s *specSubscription) addSubscriber(id SubscriptionID, cb OnMatchedOracleData) {
s.subscribers = append(s.subscribers, &specSubscriber{
id: id,
cb: cb,
})
}
// Internal usage.
func (s *specSubscription) removeSubscriber(id SubscriptionID) {
index, _ := s.getSubscriber(id)
s.removeSubscriberFromIndex(index)
}
// hasNoMoreSubscriber returns true if there is no subscriber for the associated
// OracleSpec, false otherwise.
// Internal usage.
func (s *specSubscription) hasNoMoreSubscriber() bool {
return len(s.subscribers) == 0
}
// Internal usage.
func (s *specSubscription) getSubscriber(id SubscriptionID) (int, *specSubscriber) {
for i, subscriber := range s.subscribers {
if subscriber.id == id {
return i, subscriber
}
}
return -1, nil
}
// Internal usage.
func (s *specSubscription) removeSubscriberFromIndex(index int) {
copy(s.subscribers[index:], s.subscribers[index+1:])
lastIndex := len(s.subscribers) - 1
s.subscribers[lastIndex] = nil
s.subscribers = s.subscribers[:lastIndex]
}