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pubsub.go
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pubsub.go
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// Copyright 2019-2022 The Inspektor Gadget authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package containercollection
import (
"sync"
"time"
)
type EventType int
type FuncNotify func(event PubSubEvent)
const (
EventTypeAddContainer EventType = iota
EventTypeRemoveContainer
)
func (e *EventType) String() string {
switch *e {
case EventTypeRemoveContainer:
return "DELETED"
case EventTypeAddContainer:
fallthrough
default:
return "CREATED"
}
}
func EventTypeFromString(s string) EventType {
switch s {
case "DELETED":
return EventTypeRemoveContainer
case "CREATED":
fallthrough
default:
return EventTypeAddContainer
}
}
func (e *EventType) MarshalText() (text []byte, err error) {
return []byte(e.String()), nil
}
func (e *EventType) UnmarshalText(bytes []byte) error {
*e = EventTypeFromString(string(bytes))
return nil
}
type PubSubEvent struct {
Timestamp string `json:"timestamp,omitempty" column:"timestamp,maxWidth:30" columnTags:"runtime"`
Type EventType `json:"event" column:"event,maxWidth:10" columnTags:"runtime"`
Container *Container `json:"container"`
}
// GadgetPubSub provides a synchronous publish subscribe mechanism for gadgets
// to be informed of container creation and deletion. It needs to be
// synchronous so that gadgets have time to attach their tracer before the
// container is started.
type GadgetPubSub struct {
mu sync.RWMutex
// subs is the set of subscribers
subs map[interface{}]FuncNotify
}
func NewGadgetPubSub() *GadgetPubSub {
return &GadgetPubSub{
subs: make(map[interface{}]FuncNotify),
}
}
// Subscribe registers the callback to be called for every container event
// published with Publish(). Optionally, the caller can pass an initializer()
// function that is guaranteed to be called before any new container events are
// published.
func (g *GadgetPubSub) Subscribe(key interface{}, callback FuncNotify, initializer func()) {
g.mu.Lock()
defer g.mu.Unlock()
g.subs[key] = callback
if initializer != nil {
initializer()
}
}
func (g *GadgetPubSub) Unsubscribe(key interface{}) {
g.mu.Lock()
defer g.mu.Unlock()
delete(g.subs, key)
}
func (g *GadgetPubSub) Publish(eventType EventType, container *Container) {
// Make a copy so we don't keep the lock while actually publishing
g.mu.RLock()
copiedSubs := []FuncNotify{}
for _, callback := range g.subs {
copiedSubs = append(copiedSubs, callback)
}
g.mu.RUnlock()
var wg sync.WaitGroup
for _, callback := range copiedSubs {
wg.Add(1)
go func(callback FuncNotify) {
event := PubSubEvent{
Timestamp: time.Now().Format(time.RFC3339),
Type: eventType,
Container: container,
}
callback(event)
wg.Done()
}(callback)
}
wg.Wait()
}