connection_heap.go

// Copyright 2013-2017 Aerospike, Inc.
//
// 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 aerospike

import (
	"runtime"
	"sync"
)

// singleConnectionHeap is a non-blocking LIFO heap.
// If the heap is empty, nil is returned.
// if the heap is full, offer will return false
type singleConnectionHeap struct {
	head, tail uint32
	data       []*Connection
	size       uint32
	full       bool
	mutex      sync.Mutex
}

// newSingleConnectionHeap creates a new heap with initial size.
func newSingleConnectionHeap(size int) *singleConnectionHeap {
	if size <= 0 {
		panic("Heap size cannot be less than 1")
	}

	return &singleConnectionHeap{
		full: false,
		data: make([]*Connection, uint32(size)),
		size: uint32(size),
	}
}

// Offer adds an item to the heap unless the heap is full.
// In case the heap is full, the item will not be added to the heap
// and false will be returned
func (h *singleConnectionHeap) Offer(conn *Connection) bool {
	h.mutex.Lock()
	// make sure heap is not full
	if h.full {
		h.mutex.Unlock()
		return false
	}

	h.head = (h.head + 1) % h.size
	h.full = (h.head == h.tail)
	h.data[h.head] = conn
	h.mutex.Unlock()
	return true
}

// Poll removes and returns an item from the heap.
// If the heap is empty, nil will be returned.
func (h *singleConnectionHeap) Poll() (res *Connection) {
	h.mutex.Lock()
	// if heap is not empty
	if (h.tail != h.head) || h.full {
		res = h.data[h.head]
		h.data[h.head] = nil

		h.full = false
		if h.head == 0 {
			h.head = h.size - 1
		} else {
			h.head--
		}
	}

	h.mutex.Unlock()
	return res
}

// DropIdleTail closes idle connection in tail.
// It will return true if tail connection was idle and dropped
func (h *singleConnectionHeap) DropIdleTail() bool {
	h.mutex.Lock()
	defer h.mutex.Unlock()

	// if heap is not empty
	if h.full || (h.tail != h.head) {
		conn := h.data[(h.tail+1)%h.size]

		if conn.IsConnected() && !conn.isIdle() {
			return false
		}

		h.tail = (h.tail + 1) % h.size
		h.data[h.tail] = nil
		h.full = false
		conn.Close()

		return true
	}

	return false
}

// Len returns the number of connections in the heap
func (h *singleConnectionHeap) Len() int {
	cnt := 0
	h.mutex.Lock()

	if !h.full {
		if h.head >= h.tail {
			cnt = int(h.head) - int(h.tail)
		} else {
			cnt = int(h.size) - (int(h.tail) - int(h.head))
		}
	} else {
		cnt = int(h.size)
	}
	h.mutex.Unlock()
	return cnt
}

// connectionHeap is a non-blocking FIFO heap.
// If the heap is empty, nil is returned.
// if the heap is full, offer will return false
type connectionHeap struct {
	heaps []singleConnectionHeap
}

func newConnectionHeap(size int) *connectionHeap {
	heapCount := runtime.NumCPU()
	if heapCount > size {
		heapCount = size
	}

	// will be >= 1
	perHeapSize := size / heapCount

	heaps := make([]singleConnectionHeap, heapCount)
	for i := range heaps {
		heaps[i] = *newSingleConnectionHeap(perHeapSize)
	}

	// add a heap for the remainder
	if (perHeapSize*heapCount)-size > 0 {
		heaps = append(heaps, *newSingleConnectionHeap(size - heapCount*perHeapSize))
	}

	return &connectionHeap{
		heaps: heaps,
	}
}

// Offer adds an item to the heap unless the heap is full.
// In case the heap is full, the item will not be added to the heap
// and false will be returned
func (h *connectionHeap) Offer(conn *Connection, hint byte) bool {
	idx := int(hint) % len(h.heaps)
	end := idx + len(h.heaps)
	for i := idx; i < end; i++ {
		if h.heaps[i%len(h.heaps)].Offer(conn) {
			// success
			return true
		}
	}
	return false
}

// Poll removes and returns an item from the heap.
// If the heap is empty, nil will be returned.
func (h *connectionHeap) Poll(hint byte) (res *Connection) {
	idx := int(hint)

	end := idx + len(h.heaps)
	for i := idx; i < end; i++ {
		if conn := h.heaps[i%len(h.heaps)].Poll(); conn != nil {
			return conn
		}
	}
	return nil
}

// DropIdle closes all idle connections.
func (h *connectionHeap) DropIdle() {
	for i := 0; i < len(h.heaps); i++ {
		for h.heaps[i].DropIdleTail() {
		}
	}
}

// Len returns the number of connections in all or a specific sub-heap.
// If hint is < 0 or invalid, then the total number of connections will be returned.
func (h *connectionHeap) Len(hint byte) (cnt int) {
	if hint >= 0 && int(hint) < len(h.heaps) {
		cnt = h.heaps[hint].Len()
	} else {
		for i := range h.heaps {
			cnt += h.heaps[i].Len()
		}
	}

	return cnt
}