Welcome to mszhe's blog

Markdown Beginner

2018-12-18

mszhe

工具

Markdown

Markdown: Syntax
- 目录
- 标题
- 列表
- 引用
- 图片
- 链接
- 索引链接
- 本身就是链接
- 分割线
- 表格
- 代码块
- 转义
- Others
Reference

Markdown语法

标题

# content
## content
### content
......

一共可以设置六级标题

列表

无序

* 1
* 2
* 3 * 1 * 2 * 3

有序

1
2
3 1. 1 2. 2 3. 3

嵌套列表

- AAA
  + A
    - a
      1. contentA
      2. contentB

AAA
- A
  - a
    1. contentA
    2. contentB

引用

> contentA
  >> contentB

contentA

contentB

之后的文本内容需要插入空行

图片

！[icon](link to the picture)

链接

[content](link to the content)

索引链接

[content][1]
[1]:Url [content][1] [1]:Url

本身就是链接

<url>

https://mszhe.github.io/

分割线

***
---

表格

| Tables        | Are           | Cool  |
| ------------- |:-------------:| -----:|
| col 3 is      | right-aligned | $1600 |
| col 2 is      | centered      |   $12 |
| zebra stripes | are neat      |    $1 |

Tables	Are	Cool
col 3 is	right-aligned	$1600
col 2 is	centered	$12
zebra stripes	are neat	$1

代码块

``` [python]
@requires_authorization
def add(a, b): # add a and b
    return a+b
class TA:
```

@requires_authorization
def add(a, b): # add a and b
	return a+b
class TA:

or 每行文字前加4个空格或者1个Tab

转义

Others

粗体

**content** **content**

__content__ __content__

斜体

*content* *content*

_content_ _content_

字体, 字号, 和颜色

<font face="黑体">我是黑体字</font>
<font face="微软雅黑">我是微软雅黑</font>
<font face="Verdana">I like Verdana format</font>

我是黑体字我是微软雅黑 I like Verdana format

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mysql高低排名

2018-01-05

数据库

mysql 排名 mysql变量

数据准备

CREATE TABLE `user_score` (
  `id` bigint(64) NOT NULL AUTO_INCREMENT,
  `userId` bigint(64) DEFAULT NULL,
  `score` double DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;
insert into `user_score` (`id`, `userId`, `score`) values('1','1','1');
insert into `user_score` (`id`, `userId`, `score`) values('2','2','20');
insert into `user_score` (`id`, `userId`, `score`) values('3','3','20');
insert into `user_score` (`id`, `userId`, `score`) values('4','4','60');
insert into `user_score` (`id`, `userId`, `score`) values('5','5','90');
insert into `user_score` (`id`, `userId`, `score`) values('6','6','100');
insert into `user_score` (`id`, `userId`, `score`) values('7','7',NULL);

A相同分数排名不一样

SELECT 
  t1.*,
  @rank := @rank + 1 rank 
FROM
  (SELECT 
    a.`userId`,
    a.`score` 
  FROM
    `user_score` a 
  ORDER BY a.`score` DESC) t1,
  (SELECT 
    @rank := 0) t2 

B相同分数排名一样

SELECT 
  t1.*,
  (
    CASE
      WHEN @score  = t1.score THEN @rank 
      WHEN @score := t1.score THEN @rank := @rank + 1 
      WHEN @score  = 0 OR @score IS NULL THEN @rank := @rank + 1 
    END
  ) rank 
FROM
  (SELECT 
    userId,
    score 
  FROM
    user_score a 
  ORDER BY a.`score` DESC) t1,
  (SELECT 
    @rank := 0,
    @score := NULL) t2 ;

C相同分数占用排名位

SELECT 
  b.userId,
  b.score,
  b.rank 
FROM
  (SELECT 
    a.*,
    @index := @index + 1,
    @rank := (
      CASE
        WHEN @temp_view_count = a.score THEN @rank 
        WHEN @temp_view_count := a.score THEN @index 
        WHEN @temp_view_count = 0  OR @temp_view_count IS NULL THEN @index 
      END
    ) rank 
  FROM
    (SELECT 
      userId,
      score 
    FROM
      user_score 
    ORDER BY score DESC) a,
    (SELECT 
      @rank := 0,
      @rowtotal := NULL,
      @index := 0) r) b 

Read All

selinux开启导致docker无法启动

2017-12-26

docker linux

selinux centos
现象：docker突然无法启动，错误如下

解决：禁用selinux
- 经查selinux处于启动状态
- 禁用selinuxvim /etc/selinux/config
- 重启机器,reboot, 再看selinux状态selinux -v
- 再次启动docker, 正常启动!
Read All

java异步非阻塞示例

2017-12-26

java

Future Callable ExecutorService CompletionService

java中执行耗时任务，有时需要线程池、Callable、Future结合使用

Callable类

import java.util.Random;
import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

public class MyCallable implements Callable<Boolean> {
    private int no;

    public MyCallable(int no) {
        this.no = no;
    }

    @Override
    public Boolean call() throws Exception {
        int sleep = new Random().nextInt(15);
        TimeUnit.SECONDS.sleep(sleep);
        System.out.printf("task #%02d, sleep %ds, ok!\n", no, sleep);
        return Boolean.TRUE;
    }
}

Main方法

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.*;

public class Main {
    public static void main(String[] args) {
        ExecutorService pool = Executors.newCachedThreadPool();
//        List<Future<Boolean>> list = new ArrayList<>();
        CompletionService<Boolean> cs = new ExecutorCompletionService<>(pool);

        for (int i = 0; i < 15; i++) {
            final int j = i;
//            list.add(pool.submit(new MyCallable(j)));
            cs.submit(new MyCallable(j));
        }

//        for (Future<Boolean> future : list) {
//            try {
//                future.get();
//            } catch (Exception e) {
//                e.printStackTrace();
//            }
//        }
        for (int i = 0; i < 15; i++) {
            try {
                cs.take().get();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }

        pool.shutdown();
    }
}

执行结果如下

结论：future.get();为非阻塞，不会阻塞其它线程执行

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nginx配置说明一

2017-12-12

nginx

反向代理

nginx反向代理之后获取request真实ip

nginx.conf

location /xx {
    proxy_set_header   realurl $request_uri;
    proxy_set_header   Host $http_host;
    proxy_set_header   Referer $http_referer;

    proxy_set_header   X-Real-IP   $remote_addr;
    proxy_set_header   X-Forwarded-For $proxy_add_x_forwarded_for;

    proxy_redirect     off;
    proxy_pass         http://xx-server;
}

code

ip := c.Ctx.Request.Header.Get("X-Forwarded-For")

nginx.conf

http {
    include       mime.types;
    default_type  application/octet-stream;
    ...
    underscores_in_headers on;
    ...
}

code

accessToken := c.Ctx.Request.Header.Get("access_token") // 从header中获取

nginx修改上传文件大小限制

nginx.conf

http {
    ...
    client_max_body_size 20m;
    ...

参考 nginx官方文档

Read All

redis数据丢失

2017-12-09

数据库

redis nosql

现象

redis出现数据短暂丢失问题（测试环境和生产环境）

解决

Read All

2/6

Welcome to mszhe's blog

Markdown Beginner

Markdown语法

目录

标题

列表

无序

有序

嵌套列表

引用

图片

链接

索引链接

本身就是链接

分割线

表格

代码块

转义

Others

粗体

斜体

字体, 字号, 和颜色

mysql高低排名

selinux开启导致docker无法启动

现象：docker突然无法启动，错误如下

解决：禁用selinux

java异步非阻塞示例

nginx配置说明一

nginx反向代理之后获取request真实ip

开启nginx支持小写、带下划线的header(默认不支持)

nginx修改上传文件大小限制

redis数据丢失

现象

解决