Handwriting distributed configuration center (1)

1 What is a distributed configuration center

In fact, it is to separate some configuration information from its own system , And these information can be obtained in real time by application . Here we use springboot For example , We all know springboot When it starts , Will load resource Under directory application.properties perhaps application.yml. At this time, we will springboot The configuration file that needs to be loaded when starting Not together with the project , Unified management , This is the core idea of distributed configuration center .

1.1 What are the components of the distributed configuration center

1.1.1, There is an interface to operate and configure

1.1.2, Data can be persistent （ To prevent loss , The service offline configuration still exists at startup ）

1.1.3, There are clients and servers , The client actively pulls data or the server actively pushes data . And refresh the configuration of this machine .（ The core ）

1.1.4, Some operation logs of the management interface , Authority system, etc .

2, Mainstream configuration centers in the market

2.1 Ali's nacos

Nacos Dedicated to helping you discover 、 Configure and manage microservices .Nacos Provides an easy-to-use feature set , Helps you quickly implement dynamic service discovery 、 Service configuration 、 Service metadata and traffic management .

Nacos Helps you build more quickly and easily 、 Deliver and manage microservice platforms . Nacos Is to build in “ service ” Modern application architecture centered ( For example, the microservices paradigm 、 Cloud native paradigm ) Service infrastructure . Please refer to the official website for specific use

2.2 nacos Principle , Namely service Monitor whether the configuration changes , Send it to the client through a long link

The schematic diagram of the architecture is as follows , This is push mode , But it is based on long links

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2.3 Ctrip's Apollo

Apollo It is a production level configuration center product developed and open-source by Ctrip framework department , It can centrally manage applications in different environments 、 Configuration of different clusters , After configuration modification, it can be pushed to the application end in real time , And have standard authority 、 Process governance and other features , Applicable to microservice configuration management scenarios . Please refer to the official website for specific use

The schematic diagram of Ctrip's architecture is also similar to Nacos It's the same , Also long link polling , Server push mode .

2.3 spirgcloud config

springCloudConfig, It supports the configuration service to be placed in the memory of the configuration service （ Namely local ）, It also supports remote Git/svn Warehouse .

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When the service starts config Service It will be remotely git Pull configuration file , And save it locally git library , When remote git Is not available , From the local git The file library pulls configuration information . Please refer to the official website for specific use .

2.4 Baidu disconf

Disconf Baidu is an open source product based on Zookeeper Distributed configuration management software . At present, many companies are using , Including drops 、 Baidu 、 NetEase 、 Shunfeng and other companies . The configuration properties can be dynamically modified through simple interface operation , It's very convenient . Use Disconf One of the great benefits found after is that it saves a lot of configuration , And the configuration can be automatically load, In real time .

Basic schematic diagram ： Of course, the concrete must be more complicated than this , This is just the main process .

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3 How to implement your own distributed configuration center

3.1 Dynamically modify local @Value Configuration of annotations

3.2 In different bean in , same value How to modify at the same time .

4 Specific ideas

How to dynamically modify @Value annotation Configuration of , We need to know springboot How to load application.ym perhaps application.properties Of documents .

I use it here. springboot2.1.1 Code for demonstration .

Start by opening

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find spring.factors Configuration file for

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We can see that the above three are the loaders of configuration files , It also shows why properties The priority ratio yaml High priority . He is arranged from top to bottom . But the real configuration file executes the following

Let's click to see the implementation class

ConfigFileApplicationListene

@Override

public void postProcessEnvironment(ConfigurableEnvironment environment,

      SpringApplication application) {

      // How to load resources 

   addPropertySources(environment, application.getResourceLoader());

}

protected void addPropertySources(ConfigurableEnvironment environment,

      ResourceLoader resourceLoader) {

   RandomValuePropertySource.addToEnvironment(environment);

   //  Give resources to load  To the environment variable 

   new Loader(environment, resourceLoader).load();

}

//  Reuse  propertySource  The parser parses 

Loader(ConfigurableEnvironment environment, ResourceLoader resourceLoader) {

   this.environment = environment;

   this.placeholdersResolver = new PropertySourcesPlaceholdersResolver(

         this.environment);

   this.resourceLoader = (resourceLoader != null) ? resourceLoade

         : new DefaultResourceLoader();

   this.propertySourceLoaders = SpringFactoriesLoader.loadFactories(

         PropertySourceLoader.class, getClass().getClassLoader());

}

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Then we will know , That is, if we can EnvironmentPostProcessor , The method in the rewrite can also dynamically load the configuration file . Now let's start the code implementation .

4.1 Code implementation

In that case, we can achieve EnvironmentPostProcessor This class dynamically loads the configuration file through the interface .

The following is the specific code implementation

@Autowired
ConfigurableEnvironment configurableEnvironment;


@Autowired
Environment environment;



@Test
public void test() {

    String name = environment.getProperty("name");

    System.out.printf(" Before dynamic loading " +name);

    Map<String,String> map = new HashMap<>();

    map.put("name"," toot toot ");

    configurableEnvironment.getPropertySources().addLast(

            new OriginTrackedMapPropertySource("xxxx.xml", map)

    );

    String property = environment.getProperty("name");

    System.out.printf(" After dynamic loading " +property);

}

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4.1.2 unit testing

The end result is

image.png

We have now solved the first problem , How to dynamically add environment variables

The second question is @value How to dynamically refresh the annotation .

Then we need ConfigurablePropertyResolver This class , To parse this key , stay find @value Corresponding bean Refresh through reflection

Specific code

4.2 Code implementation

public static void refreshBean(Object bean, ConfigurablePropertyResolver propertyResolver) {

    //  Definition EL Expression interpreter 

    SpelExpressionParser spelExpressionParser = new SpelExpressionParser();

    TemplateParserContext templateParserContext= new TemplateParserContext();



    String keyResolver, valueResolver = null;

    Object parserValue;

    //  Get real object properties 



    Field[] declaredFields = bean.getClass().getDeclaredFields();

    boolean cglib = Arrays.stream(declaredFields).anyMatch(x -> x.getName().contains("CGLIB"));

    //  If it is cglib  The proxy finds its parent 

    if(cglib){

        declaredFields = bean.getClass().getSuperclass().getDeclaredFields();

    }



    //  Traverse Bean All attributes of the instance 

    for (Field field : declaredFields) {

        //  Judge field Does it contain @Value annotation 

        if (field.isAnnotationPresent(Value.class)) {

            //  Read Value Annotation placeholder 

            keyResolver = field.getAnnotation(Value.class).value();

            try {

                //  Read property values 

                valueResolver = propertyResolver.resolveRequiredPlaceholders(keyResolver);

                // EL Expression parsing 

                //  Compatible form as ：@Value("#{'${codest.five.url}'.split(',')}") contain EL In the case of expressions 

                Expression expression = spelExpressionParser.parseExpression(valueResolver, templateParserContext);

                if(field.getType() == Boolean.class){

                    parserValue =Boolean.valueOf(expression.getValue().toString());

                }

                else if(field.getType() == Integer.class){

                    parserValue =Integer.valueOf(expression.getValue().toString());

                }

                else if(field.getType() == Long.class){

                    parserValue =Long.valueOf(expression.getValue().toString());

                }else {

                    parserValue = expression.getValue(field.getType());



                }



            } catch (IllegalArgumentException e) {

                continue;

            }

            //  Determine whether the configuration item exists 

            if (Objects.nonNull(valueResolver)) {

                field.setAccessible(true);

                try {

                    field.set(bean, parserValue);

                    continue;

                } catch (IllegalAccessException e) {

                    e.printStackTrace();

                }

            }

        }

    }

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We are writing a unit test test

4.2.1 unit testing

image.png

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@Autowired

ConfigurableEnvironment configurableEnvironment;

@Autowired

ConfigurablePropertyResolver configurablePropertyResolver;


@Autowired
Person person;


@Test
public void test() {

    System.out.printf(" Before dynamic loading " +person.getName());

    Map<String,Object> map = new HashMap<>();

    map.put("name"," toot toot ");

    configurableEnvironment.getPropertySources().forEach( x->{

        if (x instanceof OriginTrackedMapPropertySource ) {

            Map<String,Object>  map1 = (Map<String, Object>) x.getSource();

            map1.putAll(map);

        }

    }

    );

    refreshBean(person,configurablePropertyResolver);

    System.out.printf(" After dynamic loading " +person.getName());

}

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The final results ：

image.png

perfect , In the next issue, we will solve Multiple bean, @value How to refresh at the same time .

Specific documents will be sent to Nuggets first , Please pay attention to Nuggets https://juejin.cn/post/7121327906269200421