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Monitor the cache update of Eureka client

2022-06-23 13:38:00 【51CTO】

Welcome to visit mine GitHub

Here we classify and summarize all the original works of Xinchen ( Including supporting source code )： https://github.com/zq2599/blog_demos

from Eureka server Get a list of services

Spring cloud Application in environment , If you register to Eureka server, It will start from Eureka server Get the registration information of all apps （ Also called service list ）, And save it locally , This operation is periodic , Once every 30 seconds by default ;
Here's the official structure , You can see Application Service towards Eureka Server Yes Get Registry Request ：

Live monitoring Eureka client Cache update for _spring cloud

Reference article

If you are interested , Want to know more about spring Broadcast mechanism perhaps Eureka client Update service list , I recommend you to refer to the following two articles ：

《spring4.1.8 The third expansion of actual combat ： Broadcasting and monitoring 》
《Spring Cloud Source code analysis Eureka Chapter five ： Update service list 》

Actual combat content

This article is a practical article , The actual combat content is as follows ：

start-up Eureka server;
Develop an application springcloudcustomizelistener, After startup, it will be registered to Eureka server;
At this time, the application identity is Eureka client, Will periodically from Eureka server Get a list of services （ There is logic ）;
Each time the successfully obtained service list is successfully stored in the local cache （ There is logic ）;
After being stored in the cache , Will be in spring Send broadcast in container （ There is logic ）;
The focus of this actual battle is to customize a listener to receive the above broadcast , After receiving the broadcast, print out the details in the log ;
Start another application springclouddeepprovider, Will also register with Eureka server;
And then observe springcloudcustomizelistener Broadcast monitoring log of , Will find springclouddeepprovider Registration information ;

Eureka client Introduction to the source code of cache service list

Before actual combat , First pair Eureka client The implementation source code of cache service list is introduced , In this way, a matching listener can be made ;
Application as Eureka Client Start time of , stay com.netflix.discovery.DiscoveryClient Class initScheduledTasks In the method , Will start a recurring task , every other 30 Seconds from Eureka server Get service list information , Here's the picture , The red box TimedSupervisorTask Responsible for periodic execution , In the green box CacheRefreshThread Responsible for specific update logic ：

Live monitoring Eureka client Cache update for _eureka_02

stay CacheRefreshThread Class through layers of calls , The logic to get the service list and update the local cache is in fetchRegistry Method implementation , Here's the picture , The red box getAndStoreFullRegistry Be responsible for updating the whole method , In the green box getAndUpdateDelta Method is responsible for incremental updates , In the Yellow frame onCacheRefreshed Method is the focus of today ： Send a broadcast , The broadcast type is The local cache of the service list has been updated

Live monitoring Eureka client Cache update for _spring_03

onCacheRefreshed Method in subclass CloudEurekaClient It's rewritten in , It can be seen that a normal spring In vessel broadcast , The type is HeartbeatEvent, We can customize the listening class to receive broadcasts , And only... Is accepted by generic specification HeartbeatEvent type ：

    @Override
    protected void onCacheRefreshed() {
        if (this.cacheRefreshedCount != null) { //might be called during construction and will be null
            long newCount = this.cacheRefreshedCount.incrementAndGet();
            log.trace("onCacheRefreshed called with count: " + newCount);
            //spring In vessel broadcast ,HeartbeatEvent The instance receives two parameters when it is created ：CloudEurekaClient Instance and cache refresh times 
            this.publisher.publishEvent(new HeartbeatEvent(this, newCount));
        }
    }

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Actual application settings

This actual battle will build a small Spring Cloud Environmental Science , The following applications are included ：

apply name	identity	effect	port	Startup sequence
springclouddeepeureka	Eureka server	Registry Center	8081	First of all
springcloudcustomizelistener	Eureka client	There is a custom broadcast listener , Listen to the broadcast of service list cache updates	8085	second
springclouddeepprovider	Eureka client	Ordinary web application	8082	Third

Source download

springclouddeepeureka and springclouddeepprovider These two applications , In the article 《Spring Cloud Source code analysis Eureka Chapter one ： preparation 》 This is described in detail in , I won't say much in this article , You can refer to the article , It can also be in github Download the source code of these two applications , The address and link information is shown in the following table ：

name	link	remarks
Project home page	https://github.com/zq2599/blog_demos	The project is in progress. GitHub Home page on
git Warehouse address (https)	https://github.com/zq2599/blog_demos.git	The warehouse address of the source code of the project ,https agreement
git Warehouse address (ssh)	[email protected]:zq2599/blog_demos.git	The warehouse address of the source code of the project ,ssh agreement

This git Multiple folders in project , The source code of this chapter is in springclouddeepeureka、springclouddeepprovider Under these two folders , As shown in the red box below ：

Live monitoring Eureka client Cache update for _eureka_04

start-up springclouddeepeureka

application springclouddeepeureka Start immediately after development , Access the address in the browser ： http://localhost:8081, so Eureka server Has been launched , But no apps have been registered yet , Here's the picture ：

Live monitoring Eureka client Cache update for _spring cloud_05

Development springcloudcustomizelistener

Next, we will develop applications together springcloudcustomizelistener, Add custom... In this app spring Radio monitor , If you don't want to type the code , You can also get it from github Download the source code directly from , The address and link information is shown in the following table ：

name	link	remarks
Project home page	https://github.com/zq2599/blog_demos	The project is in progress. GitHub Home page on
git Warehouse address (https)	https://github.com/zq2599/blog_demos.git	The warehouse address of the source code of the project ,https agreement
git Warehouse address (ssh)	[email protected]:zq2599/blog_demos.git	The warehouse address of the source code of the project ,ssh agreement

This git Multiple folders in project , The source code of this chapter is in springcloudcustomizelistener Under the folder , As shown in the red box below ：

Live monitoring Eureka client Cache update for _eureka_06

Let's develop together ：
Create a springboot Of web application ,pom.xml The contents are as follows , Note that in order to show more details in the log , Rely on fastjson library ：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.bolingcavalry</groupId>
    <artifactId>springcloudcustomizelistener</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>springcloudcustomizelistener</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.9.RELEASE</version>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.28</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Edgware.RELEASE</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

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Application profile application.yml Is as follows ：

server:
  port: 8085
spring:
  application:
    name: springcloud-customize-listener
eureka:
  client:
    serviceUrl:
      defaultZone: http://localhost:8081/eureka/
  instance:
    prefer-ip-address: true

     
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Create a listener EurekaCacheRefreshListener.java, I've analyzed HeartbeatEvent Two member variables of the instance , The values are the number of cache flushes and CloudEurekaClient example , On receiving the broadcast , Print both member variables in the log ：

@Component
public class EurekaCacheRefreshListener implements ApplicationListener<HeartbeatEvent> {

    private static final Logger logger = LoggerFactory.getLogger(EurekaCacheRefreshListener.class);

    @Override
    public void onApplicationEvent(HeartbeatEvent event) {
        Object count = event.getValue();
        Object source = event.getSource();

        logger.info("start onApplicationEvent, count [{}], source :\n{}", count, JSON.toJSON(source));
    }
}

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Start the application , Wait for about 30 About seconds ,EurekaCacheRefreshListener The log in will be output on the console , Rich content , It is recommended that you copy these contents to format them online JSON Format your website to see it again , Some key information is listed below , Other contents have been omitted ：

{
    "instanceRemoteStatus": "UP",
    "lastSuccessfulHeartbeatTimePeriod": 316,
    "allKnownRegions": [
        "us-east-1"
    ],
    ...
     Some contents are omitted here 
    ...
    "applications": {
        "appsHashCode": "UP_1_",
        "registeredApplications": [
            {
                "instances": [
                    {
                        "hostName": "192.168.31.104",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "64656",
                            "management.port": "8085"
                        },
                        "statusPageUrl": "http://192.168.31.104:8085/info",
                        "secureVipAddress": "springcloud-customize-listener",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537827838033,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537827987419,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537827837461
                        },
                        "homePageUrl": "http://192.168.31.104:8085/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "DESKTOP-82CCEBN:springcloud-customize-listener:8085",
                        "coordinatingDiscoveryServer": false,
                        "id": "DESKTOP-82CCEBN:springcloud-customize-listener:8085",
                        "vIPAddress": "springcloud-customize-listener",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537827838033,
                        "healthCheckUrl": "http://192.168.31.104:8085/health",
                        "appName": "SPRINGCLOUD-CUSTOMIZE-LISTENER",
                        "lastDirtyTimestamp": 1537827837401,
                        "iPAddr": "192.168.31.104",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8085,
                        "healthCheckUrls": [
                            "http://192.168.31.104:8085/health"
                        ],
                        "status": "UP"
                    }
                ]

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As shown above , The instance information of the current application has been cached locally ;

start-up springclouddeepprovider

application springclouddeepprovider Is the last application to launch , After starting the application , And then observe springcloudcustomizelistener Log , Discover applications springclouddeepprovider The registration information of has been obtained ：

{
                "instances": [
                    {
                        "hostName": "192.168.119.1",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "58420",
                            "management.port": "8082"
                        },
                        "statusPageUrl": "http://192.168.119.1:8082/info",
                        "secureVipAddress": "springcloud-deep-provider",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537840715486,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537840715486,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537840715486
                        },
                        "homePageUrl": "http://192.168.119.1:8082/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "localhost:springcloud-deep-provider:8082",
                        "coordinatingDiscoveryServer": false,
                        "id": "localhost:springcloud-deep-provider:8082",
                        "vIPAddress": "springcloud-deep-provider",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537840715486,
                        "healthCheckUrl": "http://192.168.119.1:8082/health",
                        "appName": "SPRINGCLOUD-DEEP-PROVIDER",
                        "lastDirtyTimestamp": 1537840715451,
                        "iPAddr": "192.168.119.1",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8082,
                        "healthCheckUrls": [
                            "http://192.168.119.1:8082/health"
                        ],
                        "status": "UP"
                    }
                ],
                "name": "SPRINGCLOUD-DEEP-PROVIDER",
                "instancesAsIsFromEureka": [
                    {
                        "hostName": "192.168.119.1",
                        "overriddenStatus": "UNKNOWN",
                        "metadata": {
                            "jmx.port": "58420",
                            "management.port": "8082"
                        },
                        "statusPageUrl": "http://192.168.119.1:8082/info",
                        "secureVipAddress": "springcloud-deep-provider",
                        "leaseInfo": {
                            "renewalIntervalInSecs": 30,
                            "registrationTimestamp": 1537840715486,
                            "evictionTimestamp": 0,
                            "renewalTimestamp": 1537840715486,
                            "durationInSecs": 90,
                            "serviceUpTimestamp": 1537840715486
                        },
                        "homePageUrl": "http://192.168.119.1:8082/",
                        "countryId": 1,
                        "sID": "na",
                        "securePort": 443,
                        "dataCenterInfo": {
                            "name": "MyOwn"
                        },
                        "instanceId": "localhost:springcloud-deep-provider:8082",
                        "coordinatingDiscoveryServer": false,
                        "id": "localhost:springcloud-deep-provider:8082",
                        "vIPAddress": "springcloud-deep-provider",
                        "dirty": false,
                        "lastUpdatedTimestamp": 1537840715486,
                        "healthCheckUrl": "http://192.168.119.1:8082/health",
                        "appName": "SPRINGCLOUD-DEEP-PROVIDER",
                        "lastDirtyTimestamp": 1537840715451,
                        "iPAddr": "192.168.119.1",
                        "version": "unknown",
                        "actionType": "ADDED",
                        "port": 8082,
                        "healthCheckUrls": [
                            "http://192.168.119.1:8082/health"
                        ],
                        "status": "UP"
                    }
                ]
            }

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thus , This actual battle has been completed , By developing a custom broadcast listener , We are right. Eureka We have a better understanding of the registration discovery mechanism of , In your Spring Cloud Learning process , I hope this article can help you ;