Function snapshot

BaseServer/concurrentHashMap.go:216–236

Returns a array of channels that contains elements in each shard, which likely takes a snapshot of `m`. It returns once the size of each buffered channel is determined, before all the channels are populated using goroutines. 返回值是SHARD_COUNT个缓冲channel

(m ConcurrentHashMap)

// before all the channels are populated using goroutines.
// 返回值是SHARD_COUNT个缓冲channel
func snapshot(m ConcurrentHashMap) (chans []chan Tuple) {
	chans = make([]chan Tuple, SHARD_COUNT)
	wg := sync.WaitGroup{}
	wg.Add(SHARD_COUNT)
	// Foreach shard.
	for index, shard := range m.ThreadSafeHashMap {
		go func(index int, shard *ConcurrentMapShared) {
			// Foreach key, value pair.
			shard.RLock()
			chans[index] = make(chan Tuple, len(shard.items))
			wg.Done()
			for key, val := range shard.items {
				chans[index] <- Tuple{key, val}
			}
			shard.RUnlock()
			close(chans[index])
		}(index, shard)
	}
	wg.Wait()
	return chans
}

// fanIn reads elements from channels `chans` into channel `out`
func fanIn(chans []chan Tuple, out chan Tuple) {