Use workerpools to enforce FIFO without blocking other topics
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parent
53bd0d57ad
commit
d02e37620d
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@ -2,8 +2,9 @@ package events
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import (
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import (
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"encoding/json"
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"encoding/json"
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"fmt"
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"github.com/gammazero/workerpool"
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"github.com/pkg/errors"
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"github.com/pkg/errors"
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"reflect"
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"strings"
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"strings"
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"sync"
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"sync"
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)
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)
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@ -14,13 +15,13 @@ type Event struct {
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}
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}
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type EventBus struct {
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type EventBus struct {
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mu sync.RWMutex
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mu sync.RWMutex
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callbacks map[string][]*func(Event)
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pools map[string]*CallbackPool
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}
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}
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func New() *EventBus {
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func New() *EventBus {
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return &EventBus{
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return &EventBus{
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callbacks: make(map[string][]*func(Event)),
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pools: make(map[string]*CallbackPool),
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}
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}
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}
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}
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@ -46,12 +47,25 @@ func (e *EventBus) Publish(topic string, data string) {
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// Acquire a read lock and loop over all of the channels registered for the topic. This
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// Acquire a read lock and loop over all of the channels registered for the topic. This
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// avoids a panic crash if the process tries to unregister the channel while this routine
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// avoids a panic crash if the process tries to unregister the channel while this routine
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// is running.
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// is running.
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if _, ok := e.callbacks[t]; ok {
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if cp, ok := e.pools[t]; ok {
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evt := Event{Data: data, Topic: topic}
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evt := Event{Data: data, Topic: topic}
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for _, callback := range e.callbacks[t] {
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go func(evt Event, callback func(Event)) {
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for _, callback := range cp.callbacks {
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callback(evt)
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c := *callback
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}(evt, *callback)
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evt := evt
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// Using the workerpool with one worker allows us to execute events in a FIFO manner. Running
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// this using goroutines would cause things such as console output to just output in random order
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// if more than one event is fired at the same time.
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//
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// However, the pool submission does not block the execution of this function itself, allowing
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// us to call publish without blocking any of the other pathways.
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//
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// @see https://github.com/pterodactyl/panel/issues/2303
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fmt.Println("pre-submit for topic:", evt.Topic)
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cp.pool.Submit(func() {
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fmt.Println("executing callback for event:", evt.Topic)
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c(evt)
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})
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}
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}
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}
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}
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}
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}
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@ -76,15 +90,17 @@ func (e *EventBus) On(topic string, callback *func(Event)) {
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// Check if this topic has been registered at least once for the event listener, and if
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// Check if this topic has been registered at least once for the event listener, and if
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// not create an empty struct for the topic.
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// not create an empty struct for the topic.
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if _, exists := e.callbacks[topic]; !exists {
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if _, exists := e.pools[topic]; !exists {
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e.callbacks[topic] = make([]*func(Event), 0)
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fmt.Println("no pool for topic, creating:", topic)
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e.pools[topic] = &CallbackPool{
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callbacks: make([]*func(Event), 0),
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pool: workerpool.New(1),
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}
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}
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}
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// If this callback is not already registered as an event listener, go ahead and append
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// If this callback is not already registered as an event listener, go ahead and append
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// it to the array of callbacks for this topic.
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// it to the array of callbacks for this topic.
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if e.index(topic, reflect.ValueOf(callback)) < 0 {
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e.pools[topic].Add(callback)
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e.callbacks[topic] = append(e.callbacks[topic], callback)
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}
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}
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}
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// Removes an event listener from the bus.
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// Removes an event listener from the bus.
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@ -92,41 +108,22 @@ func (e *EventBus) Off(topic string, callback *func(Event)) {
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e.mu.Lock()
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e.mu.Lock()
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defer e.mu.Unlock()
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defer e.mu.Unlock()
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i := e.index(topic, reflect.ValueOf(callback))
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if cp, ok := e.pools[topic]; ok {
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cp.Remove(callback)
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// If i < 0 it means there was no index found for the given callback, meaning it was
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// never registered or was already unregistered from the listeners. Also double check
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// that we didn't somehow escape the length of the topic callback (not sure how that
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// would happen, but lets avoid a panic condition).
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if i < 0 || i >= len(e.callbacks[topic]) {
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return
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}
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}
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// We can assume that the topic still exists at this point since we acquire an exclusive
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// lock on the process, and the "e.index" function cannot return a value >= 0 if there is
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// no topic already existing.
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e.callbacks[topic] = append(e.callbacks[topic][:i], e.callbacks[topic][i+1:]...)
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}
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}
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// Removes all of the event listeners that have been registered for any topic.
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// Removes all of the event listeners that have been registered for any topic. Also stops the worker
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func (e *EventBus) RemoveAll() {
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// pool to close that routine.
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func (e *EventBus) Destroy() {
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e.mu.Lock()
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e.mu.Lock()
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defer e.mu.Unlock()
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defer e.mu.Unlock()
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e.callbacks = make(map[string][]*func(Event))
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fmt.Println("destroying pool for event bus")
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}
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// Stop every pool that exists for a given callback topic.
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for _, cp := range e.pools {
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// Finds the index of a given callback in the topic by comparing all of the registered callback
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cp.pool.Stop()
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// pointers to the passed function. This function does not aquire a lock as it should only be called
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// within the confines of a function that has already acquired a lock for the duration of the lookup.
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func (e *EventBus) index(topic string, v reflect.Value) int {
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if _, ok := e.callbacks[topic]; ok {
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for i, handler := range e.callbacks[topic] {
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if reflect.ValueOf(handler).Pointer() == v.Pointer() {
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return i
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}
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}
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}
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}
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return -1
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e.pools = make(map[string]*CallbackPool)
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}
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}
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49
events/pool.go
Normal file
49
events/pool.go
Normal file
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@ -0,0 +1,49 @@
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package events
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import (
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"github.com/gammazero/workerpool"
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"reflect"
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)
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type CallbackPool struct {
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callbacks []*func(Event)
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pool *workerpool.WorkerPool
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}
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// Pushes a new callback into the array of listeners for the pool.
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func (cp *CallbackPool) Add(callback *func(Event)) {
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if cp.index(reflect.ValueOf(callback)) < 0 {
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cp.callbacks = append(cp.callbacks, callback)
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}
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}
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// Removes a callback from the array of registered callbacks if it exists.
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func (cp *CallbackPool) Remove(callback *func(Event)) {
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i := cp.index(reflect.ValueOf(callback))
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// If i < 0 it means there was no index found for the given callback, meaning it was
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// never registered or was already unregistered from the listeners. Also double check
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// that we didn't somehow escape the length of the topic callback (not sure how that
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// would happen, but lets avoid a panic condition).
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if i < 0 || i >= len(cp.callbacks) {
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return
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}
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// We can assume that the topic still exists at this point since we acquire an exclusive
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// lock on the process, and the "e.index" function cannot return a value >= 0 if there is
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// no topic already existing.
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cp.callbacks = append(cp.callbacks[:i], cp.callbacks[i+1:]...)
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}
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// Finds the index of a given callback in the topic by comparing all of the registered callback
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// pointers to the passed function. This function does not aquire a lock as it should only be called
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// within the confines of a function that has already acquired a lock for the duration of the lookup.
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func (cp *CallbackPool) index(v reflect.Value) int {
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for i, handler := range cp.callbacks {
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if reflect.ValueOf(handler).Pointer() == v.Pointer() {
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return i
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}
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}
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return -1
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}
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@ -198,7 +198,7 @@ func deleteServer(c *gin.Context) {
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}
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}
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// Unsubscribe all of the event listeners.
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// Unsubscribe all of the event listeners.
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s.Events().RemoveAll()
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s.Events().Destroy()
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// Destroy the environment; in Docker this will handle a running container and
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// Destroy the environment; in Docker this will handle a running container and
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// forcibly terminate it before removing the container, so we do not need to handle
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// forcibly terminate it before removing the container, so we do not need to handle
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