用Java写一个分布式缓存——RESP服务端
前言
本篇我们将完成一个RESP的socket的服务端，初步完成一个单机版缓存。
另外在其中我们还需要完成命令的动态路由
源码：https://github.com/weloe/Java-Distributed-Cache
本篇代码：
https://github.com/weloe/Java-Distributed-Cache/tree/master/src/main/java/com/weloe/cache/server
上篇：缓存管理 https://www.cnblogs.com/weloe/p/17068891.html
RESP协议
RESP协议支持5种数据类型：字符串，异常，整数，多行字符串，数组
数据类型由第一个字节进行区分，不同部分使用\r\n来分开
'+': 简单字符串'-': 异常':': 整数'$': 多行字符串'*': 数组
简单字符串一般用来返回该操作无误，操作成功，例如返回+ok\r\n
异常： -error msg\r\n
整数：: 1\r\n
多行字符串：
$4\r\n
test
这里的4是实际数据的长度
实际信息为 test
数组：
*2\r\n
$2\r\n
ab\r\n
$3\r\n
cde\r\n
信息为字符串数组[ab][cde]
实现
根据协议我们就能编写出对请求信息的解析类了，我们把它抽象为一个工具类
对返回内容解析的代码
/**
* 读取RESP协议的字节，转为String
*
* @return String
*/
public static String parseRESPBytes(InputStream inputStream) {
byte[] bytes;
String result = null;
try {
while (inputStream.available() == 0) {
}
bytes = new byte[inputStream.available()];
inputStream.read(bytes);
result = new String(bytes);
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
/**
* 解析RESP协议的String
*
* @param raw
* @return
*/
public static Object parseRESPString(String raw) {
byte type = raw.getBytes()[0];
String result = raw.substring(1);
switch (type) {
case '+':
// +ok\r\n
// 读单行
return result.replace("\r\n", "");
case '-':
// 异常
// -Error msg\r\n
throw new RuntimeException(result.replace("\r\n", ""));
case ':':
// 数字
return result.replace("\r\n", "");
case '$':
return result.split("\r\n")[1];
case '*':
// 多行字符串
String[] strList = result.substring(result.indexOf("$")).split("\r\n");
System.out.print("多条批量请求：");
List<String> list = new LinkedList<>();
for (int i = 1; i < strList.length; i += 2) {
System.out.print(strList[i] + " ");
list.add(strList[i]);
}
System.out.println();
return list;
default:
throw new RuntimeException("错误的数据格式");
}
}
发送请求的代码
/**
* 发送RESP请求
* @param host
* @param port
* @param args
* @return
* @throws IOException
*/
public static byte[] sendRequest(String host,Integer port, String ... args) throws IOException {
Socket socket = new Socket(host,port);
RESPRequest request = new RESPRequest(socket);
PrintWriter writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.UTF_8));
sendRequest(writer,args);
byte[] param = request.getBytes();
request.close();
writer.close();
socket.close();
return param;
}
/**
* 发送RESP请求
* @param writer
* @param args
* @throws IOException
*/
public static void sendRequest(PrintWriter writer, String ... args) throws IOException {
writer.println("*"+args.length);
for (String arg : args) {
writer.println("$"+arg.getBytes(StandardCharsets.UTF_8).length);
writer.println(arg);
}
writer.flush();
}
命令的解析
通过RESP协议的实现，我们就能做到对我们的缓存发送命令，那么我们又该怎么对命令进行解析，然后做出对应的操作呢？
这里我们使用前缀树结构来进行动态路由
Node
首先要构建树的节点
需要注意的是只有叶子节点才有pattern
isWild来判断是否有通配符则是为了来匹配用户输入的参数，我们设置路由的时候用:作为通配符
例如设置路由set :group :k :v
命令为：set g1 k1 v1
把 :group和g1匹配，:k和k1匹配，:v和v1匹配
最后我们要解析出 group = g1 , k = k1, v = v1
/**
* @author weloe
*/
public class Node {
/**
* 待匹配的命令参数，只有最后一层才有 例如 set :group :key :value
*/
private String pattern;
/**
* 命令参数的一部分例如 set :group :key :value 中的 :group
*/
private String part;
/**
* 子节点
*/
private List<Node> children;
/**
* 是否是通配符节点
*/
private boolean isWild;
public Node() {
this.children = new LinkedList<>();
this.part = "";
this.pattern = "";
}
public Node(String part, boolean isWild) {
this.part = part;
this.isWild = isWild;
this.children = new LinkedList<>();
}
}
注册节点的方法
/**
* 注册节点
*
* @param pattern
* @param parts
* @param height
*/
public void insert(String pattern, String[] parts, int height) {
// 终止条件,height匹配完，到了最下层
if (parts.length == height) {
this.pattern = pattern;
return;
}
String part = parts[height];
// 匹配出一个子节点
Node child = matchChild(part);
if (child == null) {
// 如果当前part的第一个字符是":"或者"*"就为模糊匹配
child = new Node(part, part.startsWith(":") || part.startsWith("*"));
// 增加当前节点的子节点
children.add(child);
}
child.insert(pattern, parts, height + 1);
}
注册节点方法中调用的machChild()为 根据part部分匹配子节点的方法
/**
* 根据part匹配子节点
*
* @param part
* @return 第一个匹配节点
*/
public Node matchChild(String part) {
for (Node child : children) {
if (child.part.equals(part) || child.isWild) {
return child;
}
}
return null;
}
根据字符串数组(输入命令)来递归匹配出对应叶子节点的方法
/**
* 根据parts[]匹配出节点
* @param parts
* @param height
* @return
*/
public Node search(String[] parts, int height) {
// 匹配到末端
if(parts.length == height || part.startsWith("*")){
if(pattern == null){
return null;
}
// 匹配到节点
return this;
}
String part = parts[height];
// 根据part找到匹配的子节点
List<Node> children = matchChildren(part);
for (Node child : children) {
Node node = child.search(parts, height + 1);
if(node != null){
return node;
}
}
return null;
}
search方法中调用的matchChildren为 根据part来匹配出所有符合的子节点的方法
/**
* 根据part匹配子节点
* @param part
* @return 所有匹配的节点
*/
public List<Node> matchChildren(String part) {
ArrayList<Node> nodes = new ArrayList<>();
for (Node child : children) {
if (child.part.equals(part) || child.isWild) {
nodes.add(child);
}
}
return nodes;
}
Router
Router提供了添加路由和根据用户命令匹配路由的方法
这里的HandlerFunc是需要我们在添加路由addRoute时进行设置的命令对应的处理函数
这里的Route类是我们在getRoute时返回的，node就是匹配到的树的叶子节点，map为匹配到的通配符参数
例如设置路由set :group :k :v
命令为：set g1 k1 v1
把 :group和g1匹配，:k和k1匹配，:v和v1匹配
map即为 group = g1 , k = k1, v = v1
/**
* @author weloe
*/
public class Router {
@FunctionalInterface
public interface HandlerFunc {
Object handle(RESPContext context);
}
public class Route{
private Node node;
private Map<String,String> map;
public Route(Node node, Map<String, String> map) {
this.node = node;
this.map = map;
}
public Object handle(RESPContext context){
context.setParamMap(map);
String key = "command"+"-"+node.getPattern();
return handlers.get(key).handle(context);
}
public Map<String, String> getMap() {
return map;
}
public Node getNode() {
return node;
}
}
/**
* 根节点
*/
private Map<String,Node> roots;
private Map<String,HandlerFunc> handlers;
public Router() {
this.roots = new LinkedHashMap<>();
this.handlers = new LinkedHashMap<>();
}
/**
* 解析pattern
* @param pattern
* @return
*/
public String[] parsePattern(String pattern){
String[] patterns = pattern.split(" ");
String[] parts = new String[patterns.length];
for (int i = 0; i < patterns.length; i++) {
parts[i] = patterns[i];
if(patterns[i].charAt(0) == '*'){
break;
}
}
return parts;
}
public void addRoute(String method,String pattern,HandlerFunc handler){
String[] parts = parsePattern(pattern);
String key = method + "-" + pattern;
Node node = roots.get(method);
// 判断有没有该method对应的根节点，没有就建一个
if (node == null) {
roots.put(method,new Node());
}
roots.get(method).insert(pattern,parts,0);
handlers.put(key,handler);
}
public Route getRoute(String path){
return getRoute("command",path);
}
public Route getRoute(String method,String path){
String[] patterns = parsePattern(path);
Map<String, String> params = new LinkedHashMap<>();
Node root = roots.get(method);
if(root == null){
return null;
}
Node res = root.search(patterns, 0);
if (res == null) {
return null;
}
String[] parts = parsePattern(res.getPattern());
for (int i = 0; i < parts.length; i++) {
String part = parts[i];
if (part.charAt(0) == ':') {
params.put(part.substring(1),patterns[i]);
}
if(part.charAt(0) == '*' && part.length() > 1){
String collect = Arrays.stream(patterns).skip(i).collect(Collectors.joining(" "));
params.put(part.substring(1),collect);
break;
}
}
return new Route(res,params);
}
}
测试
这里相当于我们输入delete g1 k1 v1
匹配到命令为 delete
匹配到的参数为key:k1
@Test
void getRoute() {
Router router = new Router();
router.addRoute("command","set :group :key :v",null);
router.addRoute("command","delete :group :key :v",null);
router.addRoute("command","expire :group :key :v",null);
router.addRoute("command","get :group :key :v",null);
router.addRoute("command","hget :key :field",null);
router.addRoute("command","config set maxsize :size",null);
router.addRoute("command","config set maxnum :num",null);
router.addRoute("command","config set cachestrategy :strategy",null);
Router.Route route = router.getRoute("command", "delete g1 k1 v1");
Assertions.assertEquals(route.getNode().getPattern(),"delete :group :key :v");
Assertions.assertEquals(route.getMap().get("key"),"k1");
}
服务端
根据以上内容我们可以封装出RESPContext，RESPRqeuest，以及RESPReqspnse类
RESPContext
作为一个服务端自然有上下文信息，我们将它封装为一个Context类
/**
* @author weloe
*/
public class RESPContext {
private LocalDateTime startTime;
private Socket socket;
private RESPRequest request;
private RESPResponse response;
private Router.Route route;
private Map<String,String> paramMap;
private Group group;
public void initServer(Socket socket, RESPRequest request, RESPResponse response) throws IOException {
this.socket = socket;
this.request = request;
this.response = response;
this.startTime = LocalDateTime.now();
}
/**
* 解析RESP协议的字节
*
* @return
*/
public String parseRESPBytes() {
String result = request.parseRESPBytes();
return result;
}
/**
* 解析RESP协议的String
*
* @param raw
* @return
*/
public Object parseRESPString(String raw) {
Object obj = request.parseRESPString(raw);
return obj;
}
public void ok() {
response.ok();
}
public void ok(byte[] bytes){
response.ok(String.valueOf(bytes));
}
public void ok(String arg) {
response.ok(arg);
}
public void ok(String... args) {
response.ok(args);
}
public void error(String msg) {
response.error(msg);
}
public void close() {
if (request != null) {
try {
request.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (response != null) {
response.close();
}
if (socket != null) {
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public Socket getSocket() {
return socket;
}
public RESPRequest getRequest() {
return request;
}
public RESPResponse getResponse() {
return response;
}
public LocalDateTime getStartTime() {
return startTime;
}
public void setStartTime(LocalDateTime startTime) {
this.startTime = startTime;
}
public void setParamMap(Map<String, String> paramMap) {
this.paramMap = paramMap;
}
public Map<String, String> getParamMap() {
return paramMap;
}
public void setRoute(Router.Route route) {
this.route = route;
}
public Router.Route getRoute() {
return route;
}
public void setGroup(Group group) {
this.group = group;
}
public Group getGroup() {
return group;
}
public String getParam(String key){
return paramMap.get(key);
}
}
RESPRequest
/**
* @author weloe
*/
public class RESPRequest {
private InputStream inputStream;
private Map<String,String> params;
public RESPRequest(Socket socket) throws IOException {
this.inputStream = socket.getInputStream();
}
public String getParam(String key) {
return params.get(key);
}
/**
* 解析RESP协议的字节
*
* @return
*/
public byte[] getBytes() {
byte[] bytes = null;
try {
while (inputStream.available() == 0) {
}
bytes = new byte[inputStream.available()];
inputStream.read(bytes);
} catch (IOException e) {
e.printStackTrace();
}
return bytes;
}
/**
* 解析RESP协议的字节
*
* @return
*/
public String parseRESPBytes() {
byte[] bytes;
byte[] buf = new byte[1];
String result = null;
try {
System.out.println("等待数据传输");
// try {
// // 读不到阻塞
// inputStream.read(buf);
// } catch (IOException e) {
// return null;
// }
// result = new String(buf) + new String(bytes);
while (inputStream.available() == 0) {
}
bytes = new byte[inputStream.available()];
inputStream.read(bytes);
result = new String(bytes);
} catch (IOException e) {
e.printStackTrace();
}
return result;
}
/**
* 解析RESP协议的String
*
* @param raw
* @return
*/
public Object parseRESPString(String raw) {
byte type = raw.getBytes()[0];
String result = raw.substring(1);
switch (type) {
case '+':
// +ok\r\n
// 读单行
return result.replace("\r\n", "");
case '-':
// 异常
// -Error msg\r\n
throw new RuntimeException(result.replace("\r\n", ""));
case ':':
// 数字
return result.replace("\r\n", "");
case '$':
return result.substring(1).replace("\r\n", "");
case '*':
// 多行字符串
String[] strList = result.substring(result.indexOf("$")).split("\r\n");
System.out.print("多条批量请求：");
List<String> list = new LinkedList<>();
for (int i = 1; i < strList.length; i += 2) {
System.out.print(strList[i] + " ");
list.add(strList[i]);
}
System.out.println();
return list;
default:
throw new RuntimeException("错误的数据格式");
}
}
public void close() throws IOException {
if (inputStream != null) {
inputStream.close();
}
}
public InputStream getInputStream() {
return inputStream;
}
}
RESPResponse
/**
* @author weloe
*/
public class RESPResponse {
private PrintWriter writer;
public RESPResponse(Socket socket) throws IOException {
// 字符输出流，可以直接按行输出
writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.UTF_8));
}
public void ok() {
writer.println(RESPStatus.OK.getMsg());
writer.flush();
}
public void ok(Integer arg) {
writer.println(":" + arg);
writer.flush();
}
public void ok(String arg) {
writer.println("$" + arg.getBytes(StandardCharsets.UTF_8).length);
writer.println(arg);
writer.flush();
}
public void ok(String... args) {
writer.println("*" + args.length);
for (String arg : args) {
writer.println("$" + arg.getBytes(StandardCharsets.UTF_8).length);
writer.println(arg);
}
writer.flush();
}
public void error(String msg) {
writer.println(RESPStatus.ERROR.getMsg() + " " + msg);
writer.flush();
}
public void close() {
if (writer != null) {
writer.close();
}
}
public PrintWriter getWriter() {
return writer;
}
}
Service
命令有对应的HandlerFunc函数，我们就需要在函数中调用我们的相应的service，因此需要抽象出对应的service
这里的service为对前篇缓存管理中的类的简单调用，就不再一一赘述
ConfigService
/**
* config操作
* @author weloe
*/
public class ConfigService {
public Object getNormalSize(Group group){
return group.getNormalSize();
}
public Object getMaxSize(Group group){
return group.getMaxSize();
}
public Object setMaxSize(Group group,String size) {
group.setMaxSize(Integer.parseInt(size));
return "";
}
public Object setMaxNum(Group group,String num) {
return null;
}
}
DeleteService
/**
* 删除key相关操作
* @author weloe
*/
public class DeleteService {
public Object delete(Group group,String key) {
CacheObj delete = group.delete(key);
if(delete == null){
return null;
}
return "";
}
public Object clear(Group group) {
group.clear();
return "";
}
}
ExpireService
/**
* 设置,获取key的过期时间，单位秒
* @author weloe
*/
public class ExpireService {
public Object expire(Group group,String key,String value) {
LocalDateTime time = group.expire(key, Long.parseLong(value), ChronoUnit.SECONDS);
return time;
}
public Object ttl(Group group,String key) {
long ttl = group.ttl(key);
return ttl;
}
}
GroupService
/**
* group操作
* @author weloe
*/
public class GroupService {
private GroupManager groupManager = GroupManager.getInstance();
public Object add(String groupName) {
Group group = new Group();
group.setName(groupName);
group.setCache(new Cache());
group.setGetter(k -> null);
groupManager.put(group);
return "";
}
}
StringService
/**
* 缓存set，get操作
* @author weloe
*/
public class StringService {
public String get(Group group,String key) {
CacheObj cacheObj = group.get(key);
if(cacheObj != null){
return new String(cacheObj.getData());
}
return null;
}
public Object set(Group group,String key,String value) {
group.putCacheObj(key, new CacheObj(value.getBytes(StandardCharsets.UTF_8)));
return "";
}
}
ServiceFactory
为了方便管理，另外写了管理service的类
public class ServiceFactory {
Map<String,Object> map;
public ServiceFactory() {
map = new LinkedHashMap<>();
map.put("str",new StringService());
map.put("group",new GroupService());
map.put("config",new ConfigService());
map.put("delete",new DeleteService());
map.put("expire",new ExpireService());
}
public<T> T getBean(String name){
return (T) map.get(name);
}
}
CommandQueue
这里我们使用多线程io解析命令，单线程执行命令的模型，多线程解析完命令得到Route后把Context加入到阻塞队列中，再消费阻塞队列的Context执行命令
public class CommandQueue {
private static PriorityBlockingQueue<RESPContext> commandQueue = new PriorityBlockingQueue<>(5, (o1, o2) -> {
if (o1.getStartTime().isBefore(o2.getStartTime())) {
return -1;
}
return 1;
});
public boolean add(RESPContext context){
return commandQueue.add(context);
}
public void consume() {
new Thread(() -> {
System.out.println("服务端等待接收命令...");
while (true) {
RESPContext respContext = null;
try {
respContext = commandQueue.take();
} catch (InterruptedException e) {
respContext.error(e.getMessage());
e.printStackTrace();
continue;
}
System.out.println("执行命令"+respContext.getRoute().getNode().getPattern());
// 执行命令
Object handle = respContext.getRoute().handle(respContext);
System.out.println(handle);
if(handle == null){
respContext.ok("nil");
}else if(handle.equals("")){
respContext.ok();
}else {
respContext.ok(handle.toString());
}
}
}).start();
}
public PriorityBlockingQueue<RESPContext> getCommandQueue() {
return commandQueue;
}
}
Launch服务端启动类
public class Launch {
private static final ExecutorService poolExecutor = new ThreadPoolExecutor(2, 5,
30L, TimeUnit.SECONDS,
new ArrayBlockingQueue(10));
private static final GroupManager groupManager = GroupManager.getInstance();
private static final ServiceFactory factory = new ServiceFactory();
private static final Router router = new Router();
static {
// 注册路由信息
ConfigService config = factory.getBean("config");
StringService str = factory.getBean("str");
DeleteService delete = factory.getBean("delete");
ExpireService expire = factory.getBean("expire");
GroupService groupService = factory.getBean("group");
router.addRoute("group add :name", c -> groupService.add(c.getParam("name")));
router.addRoute("config set maxByteSize :group :size", c -> config.setMaxSize(c.getGroup(),c.getParam("size")))
.addRoute("config get maxByteSize :group", c -> config.getMaxSize(c.getGroup()))
.addRoute("config get normalSize :group", c -> config.getNormalSize(c.getGroup()))
.addRoute("config set maxNum :group :num", c -> config.setMaxNum(c.getGroup(),c.getParam("num")));
router.addRoute("expire :group :k :n", c -> expire.expire(c.getGroup(),c.getParam("k"),c.getParam("n")))
.addRoute("ttl :group :k", c -> expire.ttl(c.getGroup(),c.getParam("k")));
router.addRoute("delete :group :k", c -> delete.delete(c.getGroup(),c.getParam("size")))
.addRoute("clear :group", c -> delete.clear(c.getGroup()));
router.addRoute("set :group :k :v", c -> str.set(c.getGroup(),c.getParam("k"),c.getParam("v")))
.addRoute("get :group :k", c -> str.get(c.getGroup(),c.getParam("k")));
}
public static void main(String[] args) throws IOException {
CommandQueue commandQueue = new CommandQueue();
commandQueue.consume();
ServerSocket serverSocket = new ServerSocket(8081);
while (true) {
// 初始化server
Socket socket = serverSocket.accept();
System.out.println(socket.getInetAddress() + ":" + socket.getPort() + "连接");
poolExecutor.submit(() -> task(commandQueue, socket));
}
}
private static void task(CommandQueue commandQueue, Socket socket) {
RESPContext context = null;
System.out.println("线程"+Thread.currentThread().getId()+" 执行");
try {
while (true) {
context = new RESPContext();
context.initServer(socket,new RESPRequest(socket),new RESPResponse(socket));
Object requestData = null;
try {
// 处理请求
String res = context.parseRESPBytes();
if(res == null){
return;
}
System.out.printf("%s => %s%n", "原始格式", res.replace("\r\n", "\\r\\n"));
requestData = context.parseRESPString(res);
} catch (Exception e) {
System.out.println(e.getMessage());
context.error(e.getMessage());
continue;
}
List<String> commandStr = (List<String>) requestData;
System.out.println("接收到" + socket.getInetAddress() + ":" + socket.getPort() +"的命令");
// 解析命令
Router.Route route = router.getRoute(String.join(" ",commandStr));
if (route == null) {
context.ok("请检查你的命令参数");
continue;
}
Map<String, String> paramMap = route.getMap();
String name = paramMap.get("group");
if(name != null){
if(groupManager.getGroup(name) == null){
context.ok("该group不存在");
continue;
}
context.setGroup(groupManager.getGroup(name));
}
context.setRoute(route);
// 命令加入阻塞队列
commandQueue.add(context);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
context.close();
}
}
}
Client
public class ClientLaunch {
static Socket socket;
static PrintWriter writer;
static BufferedReader reader;
static InputStream inputStream;
static String host = "127.0.0.1";
static int port = 8081;
public static void main(String[] args) {
try {
// 建立连接
socket = new Socket(host,port);
// 获取输出输入流
// 字符输出流，可以直接按行输出
writer = new PrintWriter(new OutputStreamWriter(socket.getOutputStream(), StandardCharsets.UTF_8));
inputStream = socket.getInputStream();
while (true) {
Scanner reader = new Scanner(System.in);
if (reader.hasNextLine()) {
String s = reader.nextLine();
if("exit".equals(s)){
System.out.println("exit cli");
return;
}
if (!s.isEmpty()) {
Object obj;
// 操作命令
sendRequest(s.split(" "));
// 响应
obj = inputStreamHandleByteResponse();
System.out.println(obj);
}
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
// 释放连接
try {
if(reader != null) {
reader.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(inputStream != null) {
inputStream.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(writer != null) {
writer.close();
}
} catch (Exception e) {
e.printStackTrace();
}
try {
if(socket != null) {
socket.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
private static void sendRequest(String ... args) {
writer.println("*"+args.length);
for (String arg : args) {
writer.println("$"+arg.getBytes(StandardCharsets.UTF_8).length);
writer.println(arg);
}
writer.flush();
}
public static Object inputStreamHandleByteResponse() {
String result = RESPUtil.parseRESPBytes(inputStream);
return RESPUtil.parseRESPString(result);
}
}
测试
最后我们就可以启动Launch和Client来进行一下使用了
服务端启动
服务端等待接收命令...
/127.0.0.1:53779连接
线程13 执行
等待数据传输
客户端发送请求group add test
服务端返回
ok
服务端输出
原始格式 => *3\r\n$5\r\ngroup\r\n$3\r\nadd\r\n$4\r\ntest\r\n
多条批量请求：group add test
接收到/127.0.0.1:53779的命令
执行命令group add :name
客户端设置缓存set test testKey testV
服务端返回
ok
服务端输出
原始格式 => *4\r\n$3\r\nset\r\n$4\r\ntest\r\n$7\r\ntestKey\r\n$5\r\ntestV\r\n
多条批量请求：set test testKey testV
接收到/127.0.0.1:53779的命令
执行命令set :group :k :v
客户端get操作get test testKey
服务端返回
testV
至此，单机的缓存就基本完成~
