Memcached架构与工作原理：深入理解高性能缓存系统的核心机制
2025/8/30大约 13 分钟
Memcached作为一个高性能的分布式内存对象缓存系统，自2003年由Brad Fitzpatrick开发以来，一直以其简单性、高性能和可扩展性在互联网应用中得到广泛应用。理解Memcached的架构与工作原理对于正确使用和优化这一缓存系统至关重要。本节将深入探讨Memcached的系统架构、核心组件、工作流程以及性能优化机制。
Memcached概述
Memcached是一个自由开源的高性能分布式内存对象缓存系统，主要用于动态Web应用以减轻数据库负载。它通过在内存中缓存数据和对象来减少读取数据库的次数，从而提高Web应用的速度。Memcached基于一个存储键值对的哈希表，其守护进程运行在服务器上，通过简单的协议处理客户端的请求。
核心特性
- 简单性：采用简单的键值存储模型，API简洁易用
- 高性能：基于libevent事件驱动，支持高并发访问
- 分布式：支持多台服务器协同工作
- 内存管理：高效的内存分配和回收机制
- 协议简单：使用简单的文本协议进行通信
- 跨平台：支持多种操作系统和编程语言
Memcached系统架构
1. 整体架构
Memcached采用客户端-服务器架构，其核心组件包括：
// Memcached架构示意图
/*
客户端应用
↓
Memcached客户端库
↓
网络通信
↓
Memcached服务器集群
↓
内存存储层
*/2. 服务器端架构
// Memcached服务器端架构
public class MemcachedServerArchitecture {
/*
Memcached服务器端核心组件：
1. 网络层：处理客户端连接和请求
2. 协议解析层：解析文本协议命令
3. 内存管理层：管理内存分配和回收
4. 存储引擎：存储键值对数据
5. 淘汰策略：LRU算法淘汰过期数据
6. 统计监控：收集运行时统计信息
*/
// 核心组件接口
public interface MemcachedComponent {
void initialize();
void shutdown();
}
// 网络处理组件
public static class NetworkHandler implements MemcachedComponent {
private EventBase eventBase;
private int port;
private ServerSocket serverSocket;
@Override
public void initialize() {
try {
// 初始化libevent事件循环
eventBase = new EventBase();
serverSocket = new ServerSocket(port);
// 注册监听事件
eventBase.registerListener(serverSocket, this::handleNewConnection);
} catch (IOException e) {
throw new RuntimeException("Failed to initialize network handler", e);
}
}
private void handleNewConnection(Socket clientSocket) {
// 处理新连接
ConnectionHandler handler = new ConnectionHandler(clientSocket);
eventBase.registerListener(clientSocket, handler::handleData);
}
@Override
public void shutdown() {
try {
if (serverSocket != null) {
serverSocket.close();
}
if (eventBase != null) {
eventBase.shutdown();
}
} catch (IOException e) {
log.warn("Error shutting down network handler", e);
}
}
}
// 连接处理组件
public static class ConnectionHandler {
private Socket socket;
private ByteBuffer inputBuffer;
private ByteBuffer outputBuffer;
public ConnectionHandler(Socket socket) {
this.socket = socket;
this.inputBuffer = ByteBuffer.allocate(8192);
this.outputBuffer = ByteBuffer.allocate(8192);
}
public void handleData() {
try {
// 读取客户端数据
int bytesRead = socket.getInputStream().read(inputBuffer.array());
if (bytesRead > 0) {
inputBuffer.position(bytesRead);
inputBuffer.flip();
// 解析协议命令
Command command = parseCommand(inputBuffer);
if (command != null) {
// 处理命令
processCommand(command);
}
}
} catch (IOException e) {
log.warn("Error handling client data", e);
closeConnection();
}
}
private Command parseCommand(ByteBuffer buffer) {
// 解析Memcached文本协议命令
// SET key flags exptime bytes [noreply]\r\n
// VALUE key flags bytes\r\n
// END\r\n
return null; // 简化实现
}
private void processCommand(Command command) {
// 根据命令类型处理
switch (command.getType()) {
case SET:
handleSetCommand(command);
break;
case GET:
handleGetCommand(command);
break;
case DELETE:
handleDeleteCommand(command);
break;
// 其他命令...
}
}
private void handleSetCommand(Command command) {
// 处理SET命令
StorageEngine.getInstance().set(command.getKey(),
command.getValue(),
command.getExpiryTime());
// 发送响应
sendResponse("STORED\r\n");
}
private void handleGetCommand(Command command) {
// 处理GET命令
Object value = StorageEngine.getInstance().get(command.getKey());
if (value != null) {
// 发送VALUE响应
sendValueResponse(command.getKey(), value);
} else {
// 发送END响应
sendResponse("END\r\n");
}
}
private void handleDeleteCommand(Command command) {
// 处理DELETE命令
boolean deleted = StorageEngine.getInstance().delete(command.getKey());
if (deleted) {
sendResponse("DELETED\r\n");
} else {
sendResponse("NOT_FOUND\r\n");
}
}
private void sendValueResponse(String key, Object value) {
// 发送VALUE响应
String response = String.format("VALUE %s 0 %d\r\n%s\r\nEND\r\n",
key, value.toString().length(), value);
sendResponse(response);
}
private void sendResponse(String response) {
try {
socket.getOutputStream().write(response.getBytes());
} catch (IOException e) {
log.warn("Error sending response", e);
}
}
private void closeConnection() {
try {
socket.close();
} catch (IOException e) {
log.warn("Error closing connection", e);
}
}
}
// 协议命令类
public static class Command {
private CommandType type;
private String key;
private Object value;
private int flags;
private int expiryTime;
private boolean noReply;
// 构造函数、getter、setter...
}
public enum CommandType {
SET, GET, DELETE, ADD, REPLACE, APPEND, PREPEND, INCR, DECR, STATS, VERSION, QUIT
}
}3. 客户端架构
// Memcached客户端架构
public class MemcachedClientArchitecture {
/*
Memcached客户端核心组件：
1. 连接池：管理与服务器的连接
2. 负载均衡：分发请求到不同服务器
3. 协议编码：将操作编码为文本协议
4. 结果解码：解析服务器响应
5. 故障处理：处理服务器故障和重试
6. 统计收集：收集客户端性能数据
*/
// 客户端配置
public static class ClientConfig {
private List<InetSocketAddress> servers;
private int connectionPoolSize;
private int timeoutMillis;
private int retryAttempts;
private HashAlgorithm hashAlgorithm;
// 构造函数、getter、setter...
}
// 哈希算法枚举
public enum HashAlgorithm {
NATIVE_HASH, // 原生哈希
CRC_HASH, // CRC哈希
FNV1_64_HASH, // FNV1 64位哈希
FNV1A_64_HASH, // FNV1A 64位哈希
FNV1_32_HASH, // FNV1 32位哈希
FNV1A_32_HASH, // FNV1A 32位哈希
KETAMA_HASH // Ketama一致性哈希
}
// 连接池管理
public static class ConnectionPool {
private final List<InetSocketAddress> servers;
private final Map<InetSocketAddress, Queue<MemcachedConnection>> connectionPools;
private final int poolSize;
public ConnectionPool(List<InetSocketAddress> servers, int poolSize) {
this.servers = servers;
this.poolSize = poolSize;
this.connectionPools = new ConcurrentHashMap<>();
initializeConnectionPools();
}
private void initializeConnectionPools() {
for (InetSocketAddress server : servers) {
Queue<MemcachedConnection> pool = new ConcurrentLinkedQueue<>();
for (int i = 0; i < poolSize; i++) {
try {
MemcachedConnection connection = new MemcachedConnection(server);
pool.offer(connection);
} catch (IOException e) {
log.warn("Failed to create connection to " + server, e);
}
}
connectionPools.put(server, pool);
}
}
public MemcachedConnection getConnection(String key) {
// 根据键选择服务器
InetSocketAddress server = selectServer(key);
Queue<MemcachedConnection> pool = connectionPools.get(server);
if (pool != null && !pool.isEmpty()) {
return pool.poll();
}
// 如果连接池为空，创建新连接
try {
return new MemcachedConnection(server);
} catch (IOException e) {
throw new RuntimeException("Failed to create connection to " + server, e);
}
}
public void returnConnection(MemcachedConnection connection) {
InetSocketAddress server = connection.getServerAddress();
Queue<MemcachedConnection> pool = connectionPools.get(server);
if (pool != null) {
pool.offer(connection);
} else {
// 关闭连接
connection.close();
}
}
private InetSocketAddress selectServer(String key) {
// 使用一致性哈希选择服务器
return KetamaNodeLocator.getInstance().getPrimary(key, servers);
}
}
// Ketama一致性哈希实现
public static class KetamaNodeLocator {
private static final KetamaNodeLocator INSTANCE = new KetamaNodeLocator();
public static KetamaNodeLocator getInstance() {
return INSTANCE;
}
public InetSocketAddress getPrimary(String key, List<InetSocketAddress> nodes) {
if (nodes.isEmpty()) {
return null;
}
if (nodes.size() == 1) {
return nodes.get(0);
}
// 计算键的哈希值
long hash = hashKey(key);
// 使用TreeMap存储节点哈希值，便于查找
TreeMap<Long, InetSocketAddress> ketamaNodes = new TreeMap<>();
for (InetSocketAddress node : nodes) {
// 为每个节点生成多个虚拟节点
for (int i = 0; i < 160; i++) {
long nodeHash = hashNode(node.toString() + "-" + i);
ketamaNodes.put(nodeHash, node);
}
}
// 查找最近的节点
if (!ketamaNodes.containsKey(hash)) {
// 获取大于等于hash的第一个节点
SortedMap<Long, InetSocketAddress> tailMap = ketamaNodes.tailMap(hash);
hash = tailMap.isEmpty() ? ketamaNodes.firstKey() : tailMap.firstKey();
}
return ketamaNodes.get(hash);
}
private long hashKey(String key) {
// 使用MD5哈希算法
MessageDigest md5;
try {
md5 = MessageDigest.getInstance("MD5");
} catch (NoSuchAlgorithmException e) {
throw new RuntimeException("MD5 not supported", e);
}
md5.update(key.getBytes());
byte[] digest = md5.digest();
// 将16字节的MD5摘要转换为4个long值，然后求和
long hash = 0;
for (int i = 0; i < 4; i++) {
hash += ((long) (digest[i * 4] & 0xFF) << 24)
| ((long) (digest[i * 4 + 1] & 0xFF) << 16)
| ((long) (digest[i * 4 + 2] & 0xFF) << 8)
| ((long) (digest[i * 4 + 3] & 0xFF));
}
return hash;
}
private long hashNode(String nodeInfo) {
return hashKey(nodeInfo);
}
}
// Memcached连接类
public static class MemcachedConnection {
private final InetSocketAddress serverAddress;
private final Socket socket;
private final BufferedReader reader;
private final BufferedWriter writer;
public MemcachedConnection(InetSocketAddress serverAddress) throws IOException {
this.serverAddress = serverAddress;
this.socket = new Socket(serverAddress.getAddress(), serverAddress.getPort());
this.socket.setSoTimeout(5000); // 5秒超时
this.reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
this.writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
}
public void sendCommand(String command) throws IOException {
writer.write(command);
writer.flush();
}
public String readResponse() throws IOException {
StringBuilder response = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
response.append(line).append("\r\n");
if (line.equals("END") || line.equals("STORED") ||
line.equals("DELETED") || line.equals("NOT_FOUND")) {
break;
}
}
return response.toString();
}
public InetSocketAddress getServerAddress() {
return serverAddress;
}
public void close() {
try {
if (socket != null && !socket.isClosed()) {
socket.close();
}
} catch (IOException e) {
log.warn("Error closing connection", e);
}
}
}
}Memcached工作流程
1. 数据存储流程
// Memcached数据存储流程
public class MemcachedStorageWorkflow {
/*
SET命令处理流程：
1. 客户端发送SET命令
2. 客户端库编码命令并发送到服务器
3. 服务器接收命令并解析
4. 服务器检查内存是否足够
5. 服务器分配内存存储数据
6. 服务器返回响应给客户端
*/
// SET命令处理示例
public static class SetCommandHandler {
public void handleSet(String key, Object value, int expiryTime, int flags) {
// 1. 计算键的哈希值
int hash = key.hashCode();
// 2. 检查键是否已存在
Item existingItem = StorageEngine.getInstance().getItem(key);
if (existingItem != null) {
// 3. 如果存在，更新数据
existingItem.setValue(value);
existingItem.setExpiryTime(System.currentTimeMillis() + expiryTime * 1000L);
existingItem.setFlags(flags);
} else {
// 4. 如果不存在，创建新项
Item newItem = new Item(key, value, flags, expiryTime);
// 5. 检查内存是否足够
if (!MemoryManager.getInstance().hasEnoughSpace(newItem.getSize())) {
// 6. 内存不足时执行LRU淘汰
evictItemsIfNeeded(newItem.getSize());
}
// 7. 分配内存并存储数据
MemoryManager.getInstance().allocateItem(newItem);
StorageEngine.getInstance().storeItem(newItem);
}
// 8. 返回成功响应
sendResponse("STORED\r\n");
}
private void evictItemsIfNeeded(int requiredSpace) {
// 执行LRU淘汰算法
LRUManager.getInstance().evictItems(requiredSpace);
}
private void sendResponse(String response) {
// 发送响应给客户端
}
}
// 数据项类
public static class Item {
private String key;
private Object value;
private int flags;
private long expiryTime;
private int size;
private long lastAccessTime;
public Item(String key, Object value, int flags, int expiryTime) {
this.key = key;
this.value = value;
this.flags = flags;
this.expiryTime = System.currentTimeMillis() + expiryTime * 1000L;
this.size = calculateSize();
this.lastAccessTime = System.currentTimeMillis();
}
private int calculateSize() {
// 计算项的大小
int size = 0;
size += key != null ? key.length() : 0;
size += value != null ? value.toString().length() : 0;
size += 32; // 对象头和其他元数据
return size;
}
// getter和setter方法...
}
}2. 数据获取流程
// Memcached数据获取流程
public class MemcachedRetrievalWorkflow {
/*
GET命令处理流程：
1. 客户端发送GET命令
2. 客户端库编码命令并发送到服务器
3. 服务器接收命令并解析
4. 服务器查找键对应的项
5. 检查项是否过期
6. 如果未过期，返回数据给客户端
7. 如果过期，删除项并返回NOT_FOUND
*/
// GET命令处理示例
public static class GetCommandHandler {
public void handleGet(String key) {
// 1. 查找键对应的项
Item item = StorageEngine.getInstance().getItem(key);
if (item != null) {
// 2. 检查项是否过期
if (isExpired(item)) {
// 3. 如果过期，删除项
StorageEngine.getInstance().deleteItem(key);
sendNotFoundResponse();
} else {
// 4. 更新最后访问时间
item.setLastAccessTime(System.currentTimeMillis());
// 5. 返回数据给客户端
sendValueResponse(item);
}
} else {
// 6. 键不存在，返回NOT_FOUND
sendNotFoundResponse();
}
}
private boolean isExpired(Item item) {
return System.currentTimeMillis() > item.getExpiryTime();
}
private void sendValueResponse(Item item) {
// 构造VALUE响应
String response = String.format("VALUE %s %d %d\r\n%s\r\nEND\r\n",
item.getKey(), item.getFlags(),
item.getValue().toString().length(),
item.getValue());
sendResponse(response);
}
private void sendNotFoundResponse() {
sendResponse("END\r\n");
}
private void sendResponse(String response) {
// 发送响应给客户端
}
}
}Memcached性能优化机制
1. 事件驱动架构
// Memcached事件驱动架构
public class EventDrivenArchitecture {
/*
Memcached使用libevent库实现事件驱动架构：
1. 单线程事件循环
2. 非阻塞I/O操作
3. 事件回调机制
4. 高效的事件处理
*/
// 事件基础类
public static class EventBase {
private Selector selector;
private Map<SelectableChannel, EventHandler> handlers;
private volatile boolean running;
public EventBase() throws IOException {
this.selector = Selector.open();
this.handlers = new ConcurrentHashMap<>();
this.running = false;
}
public void registerListener(SelectableChannel channel, EventHandler handler)
throws IOException {
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_READ);
handlers.put(channel, handler);
}
public void start() {
running = true;
while (running) {
try {
// 等待事件
selector.select(1000); // 1秒超时
// 处理事件
Set<SelectionKey> selectedKeys = selector.selectedKeys();
Iterator<SelectionKey> iterator = selectedKeys.iterator();
while (iterator.hasNext()) {
SelectionKey key = iterator.next();
iterator.remove();
if (key.isReadable()) {
SelectableChannel channel = key.channel();
EventHandler handler = handlers.get(channel);
if (handler != null) {
handler.handleEvent();
}
}
}
} catch (IOException e) {
log.error("Error in event loop", e);
}
}
}
public void shutdown() {
running = false;
try {
selector.close();
} catch (IOException e) {
log.warn("Error closing selector", e);
}
}
}
// 事件处理器接口
public interface EventHandler {
void handleEvent();
}
// 连接事件处理器
public static class ConnectionEventHandler implements EventHandler {
private SocketChannel channel;
public ConnectionEventHandler(SocketChannel channel) {
this.channel = channel;
}
@Override
public void handleEvent() {
try {
// 处理连接事件
if (channel.isOpen()) {
// 读取数据
ByteBuffer buffer = ByteBuffer.allocate(8192);
int bytesRead = channel.read(buffer);
if (bytesRead > 0) {
// 处理读取到的数据
processData(buffer);
} else if (bytesRead == -1) {
// 连接关闭
channel.close();
}
}
} catch (IOException e) {
log.warn("Error handling connection event", e);
try {
channel.close();
} catch (IOException ce) {
log.warn("Error closing channel", ce);
}
}
}
private void processData(ByteBuffer buffer) {
// 处理数据的逻辑
}
}
}2. 内存预分配
// Memcached内存预分配机制
public class MemoryPreallocation {
/*
Memcached内存预分配特点：
1. 启动时预分配指定大小的内存
2. 使用Slab Allocation管理内存
3. 避免运行时内存分配开销
4. 减少内存碎片
*/
// 内存管理器
public static class MemoryManager {
private static final MemoryManager INSTANCE = new MemoryManager();
private long totalMemory;
private long usedMemory;
private Map<Integer, SlabClass> slabClasses;
public static MemoryManager getInstance() {
return INSTANCE;
}
private MemoryManager() {
this.slabClasses = new ConcurrentHashMap<>();
initializeSlabClasses();
}
private void initializeSlabClasses() {
// 初始化不同大小的Slab类
int[] sizes = {96, 120, 152, 192, 240, 304, 384, 480, 600, 752,
944, 1184, 1480, 1856, 2320, 2904, 3632, 4544, 5680, 7104};
for (int i = 0; i < sizes.length; i++) {
slabClasses.put(i, new SlabClass(i, sizes[i]));
}
}
public boolean hasEnoughSpace(int size) {
// 查找合适的Slab类
SlabClass slabClass = findSlabClass(size);
return slabClass != null && slabClass.hasAvailableChunks();
}
public void allocateItem(Item item) {
int size = item.getSize();
SlabClass slabClass = findSlabClass(size);
if (slabClass != null) {
slabClass.allocateChunk(item);
usedMemory += slabClass.getChunkSize();
}
}
private SlabClass findSlabClass(int size) {
for (SlabClass slabClass : slabClasses.values()) {
if (slabClass.getChunkSize() >= size) {
return slabClass;
}
}
return null;
}
public long getTotalMemory() {
return totalMemory;
}
public long getUsedMemory() {
return usedMemory;
}
public double getMemoryUsagePercentage() {
return totalMemory > 0 ? (double) usedMemory / totalMemory * 100 : 0;
}
}
// Slab类
public static class SlabClass {
private int id;
private int chunkSize;
private int chunksPerSlab;
private Queue<Chunk> freeChunks;
private List<Slab> slabs;
public SlabClass(int id, int chunkSize) {
this.id = id;
this.chunkSize = chunkSize;
this.chunksPerSlab = (1024 * 1024 - Slab.SLAB_HEADER_SIZE) / chunkSize; // 1MB slab
this.freeChunks = new ConcurrentLinkedQueue<>();
this.slabs = new ArrayList<>();
}
public boolean hasAvailableChunks() {
return !freeChunks.isEmpty() || createNewSlab();
}
public void allocateChunk(Item item) {
Chunk chunk = freeChunks.poll();
if (chunk == null) {
// 创建新的Slab
createNewSlab();
chunk = freeChunks.poll();
}
if (chunk != null) {
chunk.setItem(item);
}
}
private boolean createNewSlab() {
try {
Slab slab = new Slab(chunkSize, chunksPerSlab);
slabs.add(slab);
// 将新Slab中的所有Chunk加入空闲队列
for (Chunk chunk : slab.getChunks()) {
freeChunks.offer(chunk);
}
return true;
} catch (OutOfMemoryError e) {
log.warn("Failed to create new slab due to memory limit");
return false;
}
}
public int getChunkSize() {
return chunkSize;
}
public int getId() {
return id;
}
}
// Slab类
public static class Slab {
public static final int SLAB_HEADER_SIZE = 80;
private int chunkSize;
private int chunksPerSlab;
private List<Chunk> chunks;
private byte[] memory;
public Slab(int chunkSize, int chunksPerSlab) {
this.chunkSize = chunkSize;
this.chunksPerSlab = chunksPerSlab;
this.chunks = new ArrayList<>(chunksPerSlab);
// 分配内存
int totalSize = SLAB_HEADER_SIZE + chunkSize * chunksPerSlab;
this.memory = new byte[totalSize];
// 创建Chunk
for (int i = 0; i < chunksPerSlab; i++) {
int offset = SLAB_HEADER_SIZE + i * chunkSize;
chunks.add(new Chunk(this, offset, chunkSize));
}
}
public List<Chunk> getChunks() {
return chunks;
}
}
// Chunk类
public static class Chunk {
private Slab slab;
private int offset;
private int size;
private Item item;
public Chunk(Slab slab, int offset, int size) {
this.slab = slab;
this.offset = offset;
this.size = size;
}
public void setItem(Item item) {
this.item = item;
}
public Item getItem() {
return item;
}
public int getSize() {
return size;
}
}
}Memcached协议详解
1. 存储命令
// Memcached存储命令协议
public class StorageCommands {
/*
SET命令：
SET <key> <flags> <exptime> <bytes> [noreply]\r\n
<data block>\r\n
ADD命令：
ADD <key> <flags> <exptime> <bytes> [noreply]\r\n
<data block>\r\n
REPLACE命令：
REPLACE <key> <flags> <exptime> <bytes> [noreply]\r\n
<data block>\r\n
*/
// SET命令解析器
public static class SetCommandParser {
public static SetCommand parse(String commandLine, String dataBlock) {
// SET key flags exptime bytes [noreply]
String[] parts = commandLine.split(" ");
if (parts.length < 5 || !parts[0].equals("SET")) {
throw new IllegalArgumentException("Invalid SET command");
}
String key = parts[1];
int flags = Integer.parseInt(parts[2]);
int exptime = Integer.parseInt(parts[3]);
int bytes = Integer.parseInt(parts[4]);
boolean noreply = parts.length > 5 && parts[5].equals("noreply");
// 验证数据块大小
if (dataBlock.length() != bytes) {
throw new IllegalArgumentException("Data block size mismatch");
}
return new SetCommand(key, flags, exptime, dataBlock, noreply);
}
}
// SET命令类
public static class SetCommand {
private String key;
private int flags;
private int exptime;
private String data;
private boolean noreply;
public SetCommand(String key, int flags, int exptime, String data, boolean noreply) {
this.key = key;
this.flags = flags;
this.exptime = exptime;
this.data = data;
this.noreply = noreply;
}
// getter方法...
}
}2. 检索命令
// Memcached检索命令协议
public class RetrievalCommands {
/*
GET命令：
GET <key>*\r\n
GETS命令：
GETS <key>*\r\n
*/
// GET命令解析器
public static class GetCommandParser {
public static GetCommand parse(String commandLine) {
// GET key1 key2 key3...
String[] parts = commandLine.split(" ");
if (parts.length < 2 || !parts[0].equals("GET")) {
throw new IllegalArgumentException("Invalid GET command");
}
String[] keys = new String[parts.length - 1];
System.arraycopy(parts, 1, keys, 0, keys.length);
return new GetCommand(keys);
}
}
// GET命令类
public static class GetCommand {
private String[] keys;
public GetCommand(String[] keys) {
this.keys = keys;
}
public String[] getKeys() {
return keys;
}
}
}总结
Memcached的架构与工作原理体现了其作为高性能缓存系统的设计哲学：
- 简单性设计：采用简单的键值存储模型和文本协议，降低了使用复杂度
- 高性能架构：基于事件驱动和预分配内存机制，实现了高并发处理能力
- 分布式特性：通过客户端分片实现水平扩展
- 内存管理优化：使用Slab Allocation避免内存碎片，提高内存利用率
关键要点：
- 理解Memcached的客户端-服务器架构和工作流程
- 掌握Memcached的内存管理机制和Slab Allocation原理
- 熟悉Memcached的协议格式和命令处理流程
- 了解Memcached的性能优化机制和事件驱动架构
在下一节中，我们将深入探讨Memcached的内存管理与LRU淘汰策略，这是其高性能的关键所在。