css复制代码var values []string
for(i:=0;i<num;i++){
  values=append(values,redis.rpop())
}

scss复制代码var values []string
locker:=new(sync.mutux)
wg:=new(sync.WaitGroup)
for(i:=0;i<n;i++){
  wg.Add(1)
  go func(){
    locker.Lock()
    values=append(values,redis.rpop())
    locker.Unlock()
    wg.Done()
  }
}
wg.Wait()

css复制代码p:=redis.txpipeline()
// 查询 0~n-1 之间的元素
p.lrange(key, 0, n - 1) 
// 保留 n~最后（-1）之间的元素，换言之删除 0~n-1 之间的元素
p.ltrim(key, n, -1) 
values:=p.execute()

css复制代码p:=redis.txpipeline()
for(i:=0;i<n;i++){
  p.rpop()
}
values:=p.execute()

txt复制代码    NameNode内存计算

    每个文件块大概占用150byte，一台服务器128G内存为例，能存储多少文件块呢？

    128 * 1024 * 1024 * 1024  / 150Byte ≈  9.1亿

    G     MB     KB     Byte

sh复制代码HADOOP_NAMENODE_OPTS=-Xmx3072m

sh复制代码# The maximum amount of heap to use (Java -Xmx).  If no unit
# is provided, it will be converted to MB.  Daemons will
# prefer any Xmx setting in their respective _OPT variable.
# There is no default; the JVM will autoscale based upon machine
# memory size.
# export HADOOP_HEAPSIZE_MAX=

# The minimum amount of heap to use (Java -Xms).  If no unit
# is provided, it will be converted to MB.  Daemons will
# prefer any Xms setting in their respective _OPT variable.
# There is no default; the JVM will autoscale based upon machine
# memory size.
# export HADOOP_HEAPSIZE_MIN=
HADOOP_NAMENODE_OPTS=-Xmx102400m

shell复制代码[moe@hadoop102 bin]$ jps
6816 NameNode
7558 Jps
6951 DataNode
7289 NodeManager
7471 JobHistoryServer
[moe@hadoop102 bin]$ jmap -heap 6816
MaxHeapSize              = 1031798784 (984.0MB)

shell复制代码[moe@hadoop102 bin]$  jps
6816 NameNode
7654 Jps
6951 DataNode
7289 NodeManager
7471 JobHistoryServer
[moe@hadoop102 bin]$ jmap -heap 6951
MaxHeapSize              = 1031798784 (984.0MB)

sh复制代码export HDFS_NAMENODE_OPTS="-Dhadoop.security.logger=INFO,RFAS -Xmx1024m"

export HDFS_DATANODE_OPTS="-Dhadoop.security.logger=ERROR,RFAS -Xmx1024m"

xml复制代码The number of Namenode RPC server threads that listen to requests from clients. If dfs.namenode.servicerpc-address is not configured then Namenode RPC server threads listen to requests from all nodes.
NameNode有一个工作线程池，用来处理不同DataNode的并发心跳以及客户端并发的元数据操作。
对于大集群或者有大量客户端的集群来说，通常需要增大该参数。默认值是10。
<property>
    <name>dfs.namenode.handler.count</name>
    <value>21</value>
</property>

shell复制代码[moe@hadoop102 ~]$ sudo yum install -y python

[moe@hadoop102 ~]$ python
Python 2.7.5 (default, Nov 16 2020, 22:23:17) 
[GCC 4.8.5 20150623 (Red Hat 4.8.5-44)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> print int(20*math.log(3))
21
>>>

xml复制代码<property>
    <name>fs.trash.interval</name>
    <value>1</value>
</property>

java复制代码Trash trash = New Trash(conf);
trash.moveToTrash(path);

shell复制代码[moe@hadoop102 hadoop]$ hadoop fs -rm -r /input
2021-11-17 23:16:50,135 INFO fs.TrashPolicyDefault: Moved: 'hdfs://hadoop102:8020/input' to trash at: hdfs://hadoop102:8020/user/moe/.Trash/Current/input

shell复制代码[moe@hadoop102 hadoop]$ hadoop fs -mv /user/moe/.Trash/Current/input /input

shell复制代码[moe@hadoop102 ~]$ cd /opt/module/
[moe@hadoop102 module]$ python -m SimpleHTTPServer

shell复制代码[moe@hadoop102 mapreduce]$ hadoop jar /opt/module/hadoop-3.1.3/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.1.3-tests.jar TestDFSIO -write -nrFiles 10 -fileSize 128MB

xml复制代码<!--是否启动一个线程检查每个任务正使用的虚拟内存量，如果任务超出分配值，则直接将其杀掉，默认是true -->
<property>
     <name>yarn.nodemanager.vmem-check-enabled</name>
     <value>false</value>
</property>

shell复制代码[moe@hadoop102 mapreduce]$ hadoop jar /opt/module/hadoop-3.1.3/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.1.3-tests.jar TestDFSIO -read -nrFiles 10 -fileSize 128MB

shell复制代码[moe@hadoop102 mapreduce]$ hadoop jar /opt/module/hadoop-3.1.3/share/hadoop/mapreduce/hadoop-mapreduce-client-jobclient-3.1.3-tests.jar TestDFSIO -clean

java复制代码//默认不是新增
boolean insert = false;

//先查询用户
User user = UserMapper.selectUserInfoById(id);
if (null == user){
    //如果为空 则新建
    user = new User();
    insert = true;
}
user.setName(name);
user.setAge(age);
if(insert){
  return userDao.insert(user);
}
return userDao.update(user)

java复制代码INSERT INTO t_user(id,name,age) VALUES (1,'张三',25) 
ON DUPLICATE KEY UPDATE name='张小三',age=30;

java复制代码INSERT INTO t_user(name,age) VALUES ('张三',25) 
ON DUPLICATE KEY UPDATE name='张小三',age=30;

java复制代码CREATE UNIQUE INDEX IDX_NAME ON t_user(name);

java复制代码INSERT INTO t_user(name,age) VALUES ('张三',25) 
ON DUPLICATE KEY UPDATE name='张小三',age=30;

java复制代码RTopic<SomeObject> topic = redisson.getTopic("anyTopic");
topic.addListener(new MessageListener<SomeObject>() {
    @Override
    public void onMessage(String channel, SomeObject message) {
    //..
    .}
});
// in other thread or JVM
RTopic<SomeObject> topic = redisson.getTopic("anyTopic");
long clientsReceivedMessage = topic.publish(new SomeObject());

java复制代码@Component
public class ProjectMessageRedisListener implements MessageListener<ContractPassedEvent> {
    public static final String TOPIC = "ContractPassedEvent";
    @Autowired
    RedissonClient redissonClient;

    @Override
    public void onMessage(CharSequence channel, ContractPassedEvent msg) {
        System.out.println("收到事件：" + msg);
    }
}


//必须实现序列化接口
@Data
public class ContractPassedEvent  implements Serializable {
    private static final long serialVersionUID = -1L;
    private String name;
}

less复制代码@Configuration
@EnableAsyncpublic 
class WebMvcConfigure implements WebMvcConfigurer {
@Autowired
RedissonClient redissonClient;

@Bean("contractPassedTopic")
public RTopic contractPassedTopic(){
    //注册监听
    RTopic topic = redissonClient.getTopic(ProjectMessageRedisListener.TOPIC);
    topic.addListener(ContractPassedEvent.class, projectMessageRedisListener);
    return topic;
}

less复制代码@RunWith(SpringRunner.class)
@SpringBootTest(classes = WebSpringBootTestApplication.class)
public class ProjectMessageRedisListenerTest{
    @Autowired
    RTopic topic;

    @Test
    public void testRedisTopic(){
        topic.publish(new ContractPassedEvent("A00-Nj-2021-01-289-002932"));
    }
}

typescript复制代码// subscribe to all topics by `topic1.*` pattern
RPatternTopic<Message> topic1 = redisson.getPatternTopic("topic1.*");
int listenerId = topic1.addListener(new PatternMessageListener<Message>() {
    @Override
    public void onMessage(String pattern, String channel, Message msg) {
        Assert.fail();
        }
});

bash复制代码· 横幅广告
· 视频广告
· Facebook 广告
· 弹出窗口广告
· 所有其他显眼的广告

css复制代码header.payload.signature

json复制代码{
  "type": "JWT",
  "sign": "HS256"
}

ini复制代码JSONObject headerJson = JSONUtil.createObj();
String headerStr = base64UrlEncode(headerJson);

json复制代码{
    "sub": 1,
    "name": "John",
    "admin": true
}

ini复制代码 JSONObject payloadJson = JSONUtil.createObj();
 String payloadStr = base64UrlEncode(payloadJson);

ini复制代码String headerStr = base64UrlEncode(header);
String payloadStr = base64UrlEncode(payload);
String secret = "xxxxx";
String headerPayload = headerStr + "." + payloadStr;


// 生成签名
String signature = HMACSHA256(headerPayload, secret);

xml复制代码<!-- jwt -->
<dependency>
    <groupId>io.jsonwebtoken</groupId>
    <artifactId>jjwt</artifactId>
    <version>0.7.0</version>
</dependency>

javascript复制代码# 声明
Map<String, Object> claims = new HashMap<>(2);
claims.put("authId", activityUser.getId());
claims.put("authRole", "user");


String jwt = Jwts.builder()
          .setClaims(claims)
          .setSubject("api")
          .setIssuedAt(new Date())
          .setExpiration(expirationAt)
          .signWith(SignatureAlgorithm.HS512, signingKey)
          .compact();

java复制代码public class TokenInterceptor implements HandlerInterceptor {
  @Override
  public boolean preHandler(HttpServletRequest request,
                            HttpServletResponse response,
                            Object handler) throws Exception {
    // 方便演示，硬编码
    String tokenKey = "Bearer";
    String tokenSecret = "xxx";
    // 1、从 request 头部获取 token
    String token = request.getHeader(tokenKey);
    // 方便演示，去掉了 null 等判断
    // 2、调用 Jwts 开源工具提供的方法，获取声明
    Claims claims = Jwts.parser().setSigningKey(signingKey).parseClaimsJws(tokenKey).getBody();
    // 判断是否过期等，硬编码
    boolean judgeResult = this.isNullOrExpired(claims);
    
    // 后续业务逻辑
  }
}


/**
 * 判断令牌是否过期
 *
 * @param claims 令牌解密后的Map对象。
 * @return true 过期，否则false。
 */
public boolean isNullOrExpired(Claims claims) {
    return ObjectUtil.isNull(claims) || DateUtil.date().after(claims.getExpiration());
}

typescript复制代码@Component
public class InterceptorConfig implements WebMvcConfigurer {


    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new TokenInterceptor ())
                .addPathPatterns("/api/**")
                .excludePathPatterns("/api/oauth/login");
    }
}

json复制代码{
    "message": "用户会话已过期，请重新登录！",
    "statusCode": 401
}

java复制代码//示例一
//创建， 并赋初始值
ThreadLocal<String> threadLocal = ThreadLocal.withInitial(() -> "baseStr");

//线程1
new Thread(() -> {
    //打印默认值
    System.out.println(threadLocal.get());
    //赋值
    threadLocal.set(Thread.currentThread().getName());
    //打印值
    System.out.println(threadLocal.get());
}).start();

//线程2
new Thread(() -> {
    //打印默认值
    System.out.println(threadLocal.get());
    //赋值
    threadLocal.set(Thread.currentThread().getName());
    //打印值
    System.out.println(threadLocal.get());
}).start();

arduino复制代码此类提供线程局部变量。 
这些变量不同于它们的普通对应物，
因为每个访问一个（通过其get或set方法）的线程都有自己的、独立初始化的变量副本。 
ThreadLocal实例通常是希望绑定与线程相关的类中的私有静态字段（例如，用户 ID 或事务 ID）。

java复制代码//示例二
ThreadLocal<HashMap<String, Object>> threadLocal = ThreadLocal.withInitial(() -> new HashMap<>());

new Thread(() -> {
    HashMap<String, Object> map = threadLocal.get();
    map = map == null ? new HashMap<>() : map;
    map.put("current1", Thread.currentThread().getName());
    threadLocal.set(map);
    System.out.println("t1:" + JSONObject.toJSONString(threadLocal.get()));
}).start();

new Thread(() -> {
    HashMap<String, Object> map = threadLocal.get();
    map = map == null ? new HashMap<>() : map;
    map.put("current2", Thread.currentThread().getName());
    threadLocal.set(map);
    System.out.println("t2:" + JSONObject.toJSONString(threadLocal.get()));
}).start();

System.out.println("main:" + JSONObject.toJSONString(threadLocal.get()));

Java复制代码public void set(T value) {
    //获取当前线程
    Thread t = Thread.currentThread();
    //获取存储值的对象
    ThreadLocalMap map = getMap(t);
    if (map != null)
        //不为空则set值
        map.set(this, value);
    else
        //未初始化则初始化
        createMap(t, value);
}

java复制代码ThreadLocalMap getMap(Thread t) {
    return t.threadLocals;
}

java复制代码void createMap(Thread t, T firstValue) {
    t.threadLocals = new ThreadLocalMap(this, firstValue);
}

java复制代码ThreadLocalMap(ThreadLocal<?> firstKey, Object firstValue) {
    //创建条目* table是一个数组
    table = new Entry[INITIAL_CAPACITY];
    //计算下标, 并赋值
    int i = firstKey.threadLocalHashCode & (INITIAL_CAPACITY - 1);
    table[i] = new Entry(firstKey, firstValue);
    //记录条数
    size = 1;
    //调整容量阀值
    setThreshold(INITIAL_CAPACITY);
}

scala复制代码    static class Entry extends WeakReference<ThreadLocal<?>> {
    
          Object value;

          Entry(ThreadLocal<?> k, Object v) {
              super(k);
              value = v;
          }
      }

java复制代码public T get() {
    //获取当前线程
    Thread t = Thread.currentThread();
    //获取ThreadLocalMap对象
    ThreadLocalMap map = getMap(t);
    if (map != null) {
        //不为空, 则获取值
        ThreadLocalMap.Entry e = map.getEntry(this);
        if (e != null) {
            //值不为空, 则返回关联的值
            @SuppressWarnings("unchecked")
            T result = (T)e.value;
            return result;
        }
    }
    //如果ThreadLocalMap为空, 或对应Entity为空, 则进行初始化
    return setInitialValue();
}

Java复制代码private T setInitialValue() {
    T value = initialValue();
    Thread t = Thread.currentThread();
    ThreadLocalMap map = getMap(t);
    if (map != null)
        map.set(this, value);
    else
        createMap(t, value);
    return value;
}

Java复制代码public void remove() {
    ThreadLocalMap m = getMap(Thread.currentThread());
    if (m != null)
        m.remove(this);
}

Java复制代码ThreadLocal<String> threadLocal = new ThreadLocal<String>(){
    @Override
    protected String initialValue() {
        return "base";
    }
};

Java复制代码ThreadLocal<String> threadLocal = ThreadLocal.withInitial(() -> "baseStr");

Java复制代码public static <S> ThreadLocal<S> withInitial(Supplier<? extends S> supplier) {
    return new SuppliedThreadLocal<>(supplier);
}

Java复制代码//扩展了ThreadLocal
static final class SuppliedThreadLocal<T> extends ThreadLocal<T> {

    private final Supplier<? extends T> supplier;

    SuppliedThreadLocal(Supplier<? extends T> supplier) {
        this.supplier = Objects.requireNonNull(supplier);
    }

    //覆盖了ThreadLocal的initialValue方法
    @Override
    protected T initialValue() {
        return supplier.get();
    }
}

csharp复制代码@FunctionalInterface
public interface Supplier<T> {
    T get();
}

ini复制代码ThreadLocal<String> threadLocal = ThreadLocal.withInitial(() -> "baseStr");

typescript复制代码ThreadLocal<String> threadLocal = ThreadLocal.withInitial(new Supplier<String>() {
    @Override
    public String get() {
        return "baseStr";
    }
});

go复制代码type ShardCtrler struct {
	configs []Config
}

type Config struct {
	Num    int              // config number
	Shards [NShards]int     // shard -> gid
	Groups map[int][]string // gid -> servers[]
}

go复制代码func (sc *ShardCtrler) Join(servers map[int][]string) {
	config := sc.GetConfig()
	for gid, group := range servers {
		config.Groups[gid] = append([]string(nil), group...)
	}
	sc.configs = append(sc.configs, config)
}

go复制代码func (sc *ShardCtrler) Leave(gids []int) {
	config := sc.GetConfig()
	for _, gid := range gids {
		delete(config.Groups, gid)
	}
	sc.configs = append(sc.configs, config)
}

go复制代码func (sc *ShardCtrler) Move(shard int, gid int) {
	config := sc.GetConfig()
	config.Shards[shard] = gid
	sc.configs = append(sc.configs, config)
}

go复制代码func (sc *ShardCtrler) Balance() {
	config := sc.configs[len(sc.configs)-1]
	if len(config.Groups) == 0 {
		return
	}
	m_gid_shardnum := make(map[int]int)
	unassigned := make([]int, 0)
	avgShardNum := NShards / len(config.Groups)

	for gid := range config.Groups {
		m_gid_shardnum[gid] = 0
	}
	for shard, gid := range config.Shards {
		if _, ok := config.Groups[gid]; !ok {
			unassigned = append(unassigned, shard)
			continue
		}
		if m_gid_shardnum[gid] < avgShardNum {
			m_gid_shardnum[gid]++
		} else {
			unassigned = append(unassigned, shard)
		}
	}

	s_gid_shardnum := make([][2]int, 0)
	for gid, shardnum := range m_gid_shardnum {
		s_gid_shardnum = append(s_gid_shardnum, [2]int{gid, shardnum})
	}

	sort.Slice(s_gid_shardnum, func(i, j int) bool {
		if s_gid_shardnum[i][1] == s_gid_shardnum[j][1] {
			return s_gid_shardnum[i][0] < s_gid_shardnum[j][0]
		}
		return s_gid_shardnum[i][1] < s_gid_shardnum[j][1]
	})

	base := 0
	for _, v := range s_gid_shardnum {
		gid := v[0]
		shardnum := v[1]
		for i := 0; i < avgShardNum-shardnum; i++ {
			config.Shards[unassigned[base+i]] = gid
		}
		if avgShardNum-shardnum > 0 {
			base += avgShardNum - shardnum
		}
	}

	for _, v := range s_gid_shardnum {
		if base >= len(unassigned) {
			break
		}
		gid := v[0]
		config.Shards[unassigned[base]] = gid
		base++
	}
	sc.configs[len(sc.configs)-1].Shards = config.Shards
}

python复制代码#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time : 2021/11/15 11:58 下午
# @Author : LeiXueWei
# @CSDN/Juejin/Wechat: 雷学委
# @XueWeiTag: CodingDemo
# @File : __init__.py.py
# @Project : hello

"""
下面是一个程序员类定义
"""


class Programmer():
    def code(self):
        print("life is short, why not python?")

"""
下面是一个学生类定义
"""


class Student(object):
    """这里是一个学生类定义"""

    def __init__(self, name):
        self.name = name

    def get_name(self):
        return self.name

    def set_name(self, name):
        self.name = name

    def study(self):
        print(f"{self.name} : 好好学习，天天向上！")


# 多继承（父类1，父类2）可以更多父类
class PrimarySchoolStudent(Student, Programmer):
    pass


print("*" * 16)
xiaopengyou = PrimarySchoolStudent("一个小学生（学委的一个粉丝）")
xiaopengyou.study()
xiaopengyou.code()

print("类的基类:", PrimarySchoolStudent.__bases__)

kotlin复制代码class PrimarySchoolStudent(Student, Programmer)

python复制代码# 判断对象是由哪个类衍的子类吗
print("PrimarySchoolStudent 是 Programmer 的子类吗 ？", issubclass(PrimarySchoolStudent, Programmer))
print("PrimarySchoolStudent 是 Student 的子类吗 ？", issubclass(PrimarySchoolStudent, Student))
print("Student 是 Programmer 的子类吗 ？", issubclass(Student, Programmer))

# 判断对象是由哪个类创建出来的实例
print("xiaopengyou 是 PrimarySchoolStudent 的实例 ？", isinstance(xiaopengyou, PrimarySchoolStudent))
print("xiaopengyou 是 Programmer 的实例吗 ？", isinstance(xiaopengyou, Programmer))
print("xiaopengyou 是 Student 的实例吗 ？", isinstance(xiaopengyou, Student))
print("xiaopengyou 是 dict 的实例吗 ？", isinstance(xiaopengyou, dict))

python复制代码#!/usr/bin/env python
# -*- coding: utf-8 -*-
# @Time : 2021/11/15 11:58 下午
# @Author : LeiXueWei
# @CSDN/Juejin/Wechat: 雷学委
# @XueWeiTag: CodingDemo
# @File : __init__.py.py
# @Project : hello
"""
下面是一个程序员类定义
"""


class Programmer():
    def code(self):
        print("life is short, why not python?")


"""
下面是一个学生类定义
"""


class Student(object):
    """这里是一个学生类定义"""

    def __init__(self, name):
        self.name = name

    def get_name(self):
        return self.name

    def set_name(self, name):
        self.name = name

    def study(self):
        print(f"{self.name} : 好好学习，天天向上！")


class PrimarySchoolStudent(Student, Programmer):
    def study(self):
        print(f"{self.name} ：开开心心玩游戏！")


print("*" * 16)
xiaopengyou = PrimarySchoolStudent("一个小学生（学委的一个粉丝）")
xiaopengyou.study() 
xiaopengyou.code()