github.com/inspektor-gadget/inspektor-gadget@v0.28.1/pkg/container-collection/pubsub.go (about)

     1  // Copyright 2019-2022 The Inspektor Gadget authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package containercollection
    16  
    17  import (
    18  	"sync"
    19  	"time"
    20  )
    21  
    22  type EventType int
    23  
    24  type FuncNotify func(event PubSubEvent)
    25  
    26  const (
    27  	EventTypeAddContainer EventType = iota
    28  	EventTypeRemoveContainer
    29  )
    30  
    31  func (e *EventType) String() string {
    32  	switch *e {
    33  	case EventTypeRemoveContainer:
    34  		return "DELETED"
    35  	case EventTypeAddContainer:
    36  		fallthrough
    37  	default:
    38  		return "CREATED"
    39  	}
    40  }
    41  
    42  func EventTypeFromString(s string) EventType {
    43  	switch s {
    44  	case "DELETED":
    45  		return EventTypeRemoveContainer
    46  	case "CREATED":
    47  		fallthrough
    48  	default:
    49  		return EventTypeAddContainer
    50  	}
    51  }
    52  
    53  func (e *EventType) MarshalText() (text []byte, err error) {
    54  	return []byte(e.String()), nil
    55  }
    56  
    57  func (e *EventType) UnmarshalText(bytes []byte) error {
    58  	*e = EventTypeFromString(string(bytes))
    59  	return nil
    60  }
    61  
    62  type PubSubEvent struct {
    63  	Timestamp string     `json:"timestamp,omitempty" column:"timestamp,maxWidth:30" columnTags:"runtime"`
    64  	Type      EventType  `json:"event" column:"event,maxWidth:10" columnTags:"runtime"`
    65  	Container *Container `json:"container"`
    66  }
    67  
    68  // GadgetPubSub provides a synchronous publish subscribe mechanism for gadgets
    69  // to be informed of container creation and deletion. It needs to be
    70  // synchronous so that gadgets have time to attach their tracer before the
    71  // container is started.
    72  type GadgetPubSub struct {
    73  	mu sync.RWMutex
    74  
    75  	// subs is the set of subscribers
    76  	subs map[interface{}]FuncNotify
    77  }
    78  
    79  func NewGadgetPubSub() *GadgetPubSub {
    80  	return &GadgetPubSub{
    81  		subs: make(map[interface{}]FuncNotify),
    82  	}
    83  }
    84  
    85  // Subscribe registers the callback to be called for every container event
    86  // published with Publish(). Optionally, the caller can pass an initializer()
    87  // function that is guaranteed to be called before any new container events are
    88  // published.
    89  func (g *GadgetPubSub) Subscribe(key interface{}, callback FuncNotify, initializer func()) {
    90  	g.mu.Lock()
    91  	defer g.mu.Unlock()
    92  
    93  	g.subs[key] = callback
    94  
    95  	if initializer != nil {
    96  		initializer()
    97  	}
    98  }
    99  
   100  func (g *GadgetPubSub) Unsubscribe(key interface{}) {
   101  	g.mu.Lock()
   102  	defer g.mu.Unlock()
   103  
   104  	delete(g.subs, key)
   105  }
   106  
   107  func (g *GadgetPubSub) Publish(eventType EventType, container *Container) {
   108  	// Make a copy so we don't keep the lock while actually publishing
   109  	g.mu.RLock()
   110  	copiedSubs := []FuncNotify{}
   111  	for _, callback := range g.subs {
   112  		copiedSubs = append(copiedSubs, callback)
   113  	}
   114  	g.mu.RUnlock()
   115  
   116  	var wg sync.WaitGroup
   117  	for _, callback := range copiedSubs {
   118  		wg.Add(1)
   119  		go func(callback FuncNotify) {
   120  			event := PubSubEvent{
   121  				Timestamp: time.Now().Format(time.RFC3339),
   122  				Type:      eventType,
   123  				Container: container,
   124  			}
   125  			callback(event)
   126  			wg.Done()
   127  		}(callback)
   128  	}
   129  
   130  	wg.Wait()
   131  }