github.com/inspektor-gadget/inspektor-gadget@v0.28.1/pkg/snapshotcombiner/snapshotcombiner.go (about)

     1  // Copyright 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 snapshotcombiner
    16  
    17  import (
    18  	"sync"
    19  	"time"
    20  )
    21  
    22  // Stats contains the status of the SnapshotCombiner when calling GetSnapshots()
    23  type Stats struct {
    24  	Epochs           int // Number of calls to GetSnapshots()
    25  	CurrentSnapshots int // Number of wrappedSnapshots that have been updated since the previous call to GetSnapshots()
    26  	ExpiredSnapshots int // Number of wrappedSnapshots that have a ttl of 0
    27  	TotalSnapshots   int // Number of wrappedSnapshots known
    28  }
    29  
    30  type snapshotWrapper[T any] struct {
    31  	snapshot   []*T
    32  	ttl        int
    33  	count      int
    34  	lastUpdate time.Time
    35  }
    36  
    37  type SnapshotCombiner[T any] struct {
    38  	lock             sync.Mutex
    39  	defaultTTL       int
    40  	wrappedSnapshots map[string]*snapshotWrapper[T]
    41  	epoch            int
    42  }
    43  
    44  // NewSnapshotCombiner creates a new wrappedSnapshots combiner that stores structs of type T using a key. Each key is
    45  // given a time-to-live (ttl) and only valid for ttl calls of GetSnapshots(). Whenever a key is refreshed using
    46  // AddSnapshot(), the ttl will be reset to the initial value.
    47  func NewSnapshotCombiner[T any](ttl int) *SnapshotCombiner[T] {
    48  	return &SnapshotCombiner[T]{
    49  		defaultTTL:       ttl,
    50  		wrappedSnapshots: make(map[string]*snapshotWrapper[T]),
    51  	}
    52  }
    53  
    54  // AddSnapshot adds the given snapshot to the given key (e.g. a node name) and set its ttl to the defaultTTL of the
    55  // SnapshotCombiner
    56  func (sc *SnapshotCombiner[T]) AddSnapshot(key string, snapshot []*T) {
    57  	now := time.Now()
    58  
    59  	sc.lock.Lock()
    60  	defer sc.lock.Unlock()
    61  
    62  	if entry, ok := sc.wrappedSnapshots[key]; ok {
    63  		entry.snapshot = snapshot
    64  		entry.ttl = sc.defaultTTL
    65  		entry.count++
    66  		entry.lastUpdate = now
    67  		return
    68  	}
    69  	sc.wrappedSnapshots[key] = &snapshotWrapper[T]{
    70  		snapshot:   snapshot,
    71  		ttl:        sc.defaultTTL,
    72  		count:      1,
    73  		lastUpdate: now,
    74  	}
    75  }
    76  
    77  // GetSnapshots combines all stored wrappedSnapshots from all keys and decreases each keys defaultTTL by one.
    78  // If the ttl of an entry is less than zero, it will not be returned anymore.
    79  func (sc *SnapshotCombiner[T]) GetSnapshots() ([]*T, Stats) {
    80  	sc.lock.Lock()
    81  	defer sc.lock.Unlock()
    82  
    83  	// increase epoch
    84  	sc.epoch++
    85  
    86  	stats := Stats{
    87  		Epochs: sc.epoch,
    88  	}
    89  
    90  	result := make([]*T, 0, len(sc.wrappedSnapshots))
    91  	for _, wrapper := range sc.wrappedSnapshots {
    92  		if wrapper.ttl == sc.defaultTTL {
    93  			stats.CurrentSnapshots++
    94  		}
    95  		if wrapper.ttl > 0 {
    96  			result = append(result, wrapper.snapshot...)
    97  			wrapper.ttl--
    98  		} else {
    99  			stats.ExpiredSnapshots++
   100  		}
   101  	}
   102  
   103  	stats.TotalSnapshots = len(sc.wrappedSnapshots)
   104  
   105  	return result, stats
   106  }