本文主要是分享Apollo Client客户端使用过程中，遇到的问题、解决问题及分析代码逻辑的过程。其中一个重要问题就是关于apollo.bootstrap.enabled = true的使用及注意事项。

本文是基于Apollo v1.1.1版本，springboot项目客户端引入的是：

<dependency>

<groupId>com.ctrip.framework.apollo</groupId>

<artifactId>apollo-client</artifactId>

<version>1.1.0</version>

</dependency>

<dependency>

<groupId>com.ctrip.framework.apollo</groupId>

<artifactId>apollo-core</artifactId>

<version>1.1.0</version>

</dependency>

Apollo客户端依赖于AppId（项目ID），Apollo Meta Server（配置中心Eureka地址）

1.2.1 AppId

项目application.properties文件内容：

app.id=demo-test

apollo.bootstrap.enabled = true

注：app.id是用来标识应用身份的唯一id，格式为string。

apollo.bootstrap.enabled官方解释为注入默认application namespace的配置示例

1.2.2 Apollo Meta Server

apollo.meta（配置中心Eureka地址） 配置如下：

Apollo默认会读取系统上/opt/settings/server.properties(linux)或

C:\ opt \settings\server.properties(windows)文件（手动新建目录与文件）

apollo.meta=http://localhost:8089

启动类：

package com.test.apollodemo;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.boot.CommandLineRunner;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.stereotype.Component;

import com.test.apollodemo.configbean.MysqlConfig2;

import com.test.apollodemo.configbean.MysqlConfigBean;

@Component

@ComponentScan("com.test")

@SpringBootApplication

public class SpringBootConsoleApplication implements CommandLineRunner {

@Autowired

MysqlConfig2 mysqlConfig2;

public static void main(String[] args) throws Exception {

SpringApplication.run(SpringBootConsoleApplication.class, args);

}

@Override

public void run(String... args) throws Exception {

while(true) {

System.out.println("+++++++++++++++++++++++++");

System.out.println(mysqlConfig2.getMysqlConfigBean().getUrl());

System.out.println(mysqlConfig2.getMysqlConfigBean().getDes());

Thread.sleep(3000);

}

}

}

实体类：

package com.test.apollodemo.configbean;

import org.springframework.beans.factory.annotation.Value;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.Configuration;

import com.ctrip.framework.apollo.model.ConfigChange;

import com.ctrip.framework.apollo.model.ConfigChangeEvent;

import com.ctrip.framework.apollo.spring.annotation.ApolloConfigChangeListener;

import com.ctrip.framework.apollo.spring.annotation.EnableApolloConfig;

@Configuration

@EnableApolloConfig("mysqlcfg")

public class MysqlConfig2 {

@Bean

public MysqlConfigBean getMysqlConfigBean() {

return new MysqlConfigBean();

}

public class MysqlConfigBean{

@Value("${url:}")

private String url;

@Value("${username:}")

private String username;

@Value("${password:}")

private String password;

@Value("${des:我是默认值}")

private String des;

public String getDes() {

return des;

}

public void setDes(String des) {

this.des = des;

}

public String getUrl() {

return url;

}

public void setUrl(String url) {

this.url = url;

}

public String getUsername() {

return username;

}

public void setUsername(String username) {

this.username = username;

}

public String getPassword() {

return password;

}

public void setPassword(String password) {

this.password = password;

}

}

/**

* @ApolloConfigChangeListener用来自动注册ConfigChangeListener

*/

@ApolloConfigChangeListener("mysqlcfg")

private void someOnChange(ConfigChangeEvent changeEvent) {

for(String changeKey:changeEvent.changedKeys()) {

ConfigChange change = changeEvent.getChange(changeKey);

System.out.println(String.format("%%%%%%%%%%Found datasource change - key: %s, oldValue: %s, newValue: %s, changeType: %s", change.getPropertyName(), change.getOldValue(), change.getNewValue(), change.getChangeType()));

}

}

}

1.6.1 代码案例

package com.demo.apollo;

import java.io.IOException;

import com.ctrip.framework.apollo.Config;

import com.ctrip.framework.apollo.ConfigChangeListener;

import com.ctrip.framework.apollo.ConfigService;

import com.ctrip.framework.apollo.model.ConfigChange;

import com.ctrip.framework.apollo.model.ConfigChangeEvent;

public class Apollo {

public static void main(String[] args) throws InterruptedException, IOException {

//src目录下新建：META-INF\app.properties,

//app.id配置如下：app.id=demo-test3//项目ID（唯一）

Config config = ConfigService.getConfig("mysqlcfg");

String someKey = "url";

String someDefaultValue = "我是默认值";

String value = config.getProperty(someKey, someDefaultValue);

System.out.println(value);

config.addChangeListener(new ConfigChangeListener() {

@Override

public void onChange(ConfigChangeEvent changeEvent) {

// TODO Auto-generated method stub

System.out.println("Changes for namespace " + changeEvent.getNamespace());

for (String key : changeEvent.changedKeys()) {

ConfigChange change = changeEvent.getChange(key);

System.out.println(String.format("Found change - key: %s, oldValue: %s, newValue: %s, changeType: %s", change.getPropertyName(), change.getOldValue(), change.getNewValue(), change.getChangeType()));

}

}

});

while(true) {

System.out.println(config.getProperty(someKey, someDefaultValue));

Thread.sleep(3000);

}

}

}

1.6.2 依赖引入

Apollo客户端核心jar包：

apollo-client-1.1.0.jar

apollo-core-1.1.0.jar

只导入核心Jar包报错如下：

Exception in thread "main" java.lang.NoClassDefFoundError: Could not initialize class com.ctrip.framework.apollo.tracer.Tracer

at com.ctrip.framework.apollo.build.ApolloInjector.getInstance(ApolloInjector.java:37)

at com.ctrip.framework.apollo.ConfigService.getManager(ConfigService.java:25)

at com.ctrip.framework.apollo.ConfigService.getConfig(ConfigService.java:61)

 

核心jar包依赖包：

aopalliance-1.0.jar

gson-2.8.5.jar

guava-26.0-jre.jar

guice-4.2.1.jar

javax.inject-1.jar

log4j-api-2.10.0.jar

log4j-core-2.10.0.jar

log4j-slf4j-impl-2.10.0.jar

slf4j-api-1.7.25.jar

1.6.3 日志

引入log4j2.xml日志文件：

<?xml version="1.0" encoding="utf-8"?>

<configuration>

<properties>

<!-- 文件输出格式 -->

<property name="PATTERN">%d{yyyy-MM-dd HH:mm:ss.SSS} |-%-5level [%T-%thread] %c [%L] -| %msg%n</property>

</properties>

<appenders>

<Console name="CONSOLE" target="system_out">

<PatternLayout pattern="${PATTERN}" />

</Console>

</appenders>

<loggers>

<logger name="com.apollo.demo" level="debug" />

<root level="warn">

<appenderref ref="CONSOLE" />

</root>

</loggers>

</configuration>

本来认为执行结果是：

+++++++++++++++++++++++++++++++++++++++++

localhost
application-des

为什么会出现这个情况？（注意：mysqlcfg不管是关联还是私用，des的值本来应该为mysqlcfg-des）

下面将分析出现这个结果的原因及解决办法。

3.3.1 第一步-切入点

首先分析，客户端肯定从服务端，获取了application 和mysqlcfg的配置项，所以从 客户端请求url组装进行分析：

类RemoteConfigLongPollService：

String assembleLongPollRefreshUrl(String uri, String appId, String cluster, String dataCenter,  Map<String, Long> notificationsMap) {

Map<String, String> queryParams = Maps.newHashMap();

queryParams.put("appId", queryParamEscaper.escape(appId));

queryParams.put("cluster", queryParamEscaper.escape(cluster));

//下面这段就是告诉服务器，我要获取application和mysqlcfg的配置项

queryParams

.put("notifications",queryParamEscaper.escape(assembleNotifications(notificationsMap)));

if (!Strings.isNullOrEmpty(dataCenter)) {

queryParams.put("dataCenter", queryParamEscaper.escape(dataCenter));

}

String localIp = m_configUtil.getLocalIp();

if (!Strings.isNullOrEmpty(localIp)) {

queryParams.put("ip", queryParamEscaper.escape(localIp));

}

String params = MAP_JOINER.join(queryParams);

if (!uri.endsWith("/")) {

uri += "/";

}

return uri + "notifications/v2?" + params;

}

方法doLongPollingRefresh会调用：

url =assembleLongPollRefreshUrl(lastServiceDto.getHomepageUrl(), appId, cluster, dataCenter, m_notifications);

doLongPollingRefresh到startLongPolling到submit

3.3.2 第二步-反向追溯

1.类 RemoteConfigRepository：

private void scheduleLongPollingRefresh() {

remoteConfigLongPollService.submit(m_namespace, this);

}

然后：

public RemoteConfigRepository(String namespace) {

m_namespace = namespace;

m_configCache = new AtomicReference<>();

m_configUtil = ApolloInjector.getInstance(ConfigUtil.class);

m_httpUtil = ApolloInjector.getInstance(HttpUtil.class);

m_serviceLocator = ApolloInjector.getInstance(ConfigServiceLocator.class);

remoteConfigLongPollService = ApolloInjector.getInstance(RemoteConfigLongPollService.class);

m_longPollServiceDto = new AtomicReference<>();

m_remoteMessages = new AtomicReference<>();

m_loadConfigRateLimiter = RateLimiter.create(m_configUtil.getLoadConfigQPS());

m_configNeedForceRefresh = new AtomicBoolean(true);

m_loadConfigFailSchedulePolicy = new ExponentialSchedulePolicy(m_configUtil.getOnErrorRetryInterval(),

m_configUtil.getOnErrorRetryInterval() * 8);

gson = new Gson();

this.trySync();

this.schedulePeriodicRefresh();

this.scheduleLongPollingRefresh();

}

2.继续追溯类DefaultConfigFactory：

LocalFileConfigRepository createLocalConfigRepository(String namespace) {

if (m_configUtil.isInLocalMode()) {

logger.warn(

"==== Apollo is in local mode! Won't pull configs from remote server for namespace {} ! ====",

namespace);

return new LocalFileConfigRepository(namespace);

}

return new LocalFileConfigRepository(namespace, createRemoteConfigRepository(namespace));

}

RemoteConfigRepository createRemoteConfigRepository(String namespace) {

return new RemoteConfigRepository(namespace);

}

然后到：

@Override

public Config create(String namespace) {

DefaultConfig defaultConfig =

new DefaultConfig(namespace, createLocalConfigRepository(namespace));

return defaultConfig;

}

3. 类DefaultConfigManager：

@Override

public Config getConfig(String namespace) {

Config config = m_configs.get(namespace);

if (config == null) {

synchronized (this) {

config = m_configs.get(namespace);

if (config == null) {

ConfigFactory factory = m_factoryManager.getFactory(namespace);

config = factory.create(namespace);

m_configs.put(namespace, config);

}

}

}

return config;

}

4. 类ConfigService：

public static Config getConfig(String namespace) {

return s_instance.getManager().getConfig(namespace);

}

5. 类ApolloApplicationContextInitializer：

@Override

public void initialize(ConfigurableApplicationContext context) {

ConfigurableEnvironment environment = context.getEnvironment();

initializeSystemProperty(environment);

String enabled = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED, "false");

if (!Boolean.valueOf(enabled)) {

logger.debug("Apollo bootstrap config is not enabled for context {}, see property: ${{}}", context, PropertySourcesConstants.APOLLO_BOOTSTRAP_ENABLED);

return;

}

logger.debug("Apollo bootstrap config is enabled for context {}", context);

if (environment.getPropertySources().contains(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME)) {

//already initialized

return;

}

String namespaces = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_NAMESPACES, ConfigConsts.NAMESPACE_APPLICATION);

logger.debug("Apollo bootstrap namespaces: {}", namespaces);

List<String> namespaceList = NAMESPACE_SPLITTER.splitToList(namespaces);

CompositePropertySource composite = new CompositePropertySource(PropertySourcesConstants.APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME);

for (String namespace : namespaceList) {

Config config = ConfigService.getConfig(namespace);

composite.addPropertySource(configPropertySourceFactory.getConfigPropertySource(namespace, config));

}

environment.getPropertySources().addFirst(composite);

}

6. 接口PropertySourcesConstants：

package com.ctrip.framework.apollo.spring.config;

public interface PropertySourcesConstants {

String APOLLO_PROPERTY_SOURCE_NAME = "ApolloPropertySources";

String APOLLO_BOOTSTRAP_PROPERTY_SOURCE_NAME = "ApolloBootstrapPropertySources";

String APOLLO_BOOTSTRAP_ENABLED = "apollo.bootstrap.enabled";

String APOLLO_BOOTSTRAP_NAMESPACES = "apollo.bootstrap.namespaces";

}

最终找出原因是跟 APOLLO_BOOTSTRAP_NAMESPACES有关

3.2.1 问题解决

最终找出原因：如果配置文件没有配置apollo.bootstrap.namespaces时，系统默认namespaces为application，所以客户端会去请求application配置项。

String namespaces = environment.getProperty(PropertySourcesConstants.APOLLO_BOOTSTRAP_NAMESPACES, ConfigConsts.NAMESPACE_APPLICATION);

所以在application.properties文件中添加：

apollo.bootstrap.namespaces = mysqlcfg，保证客户端不会去获取application配置项，这样结果输出正常。

 

3.2.2逻辑流程图

关于apollo.meta参数配置优先级

(1) JVM system property 'apollo.meta',

(2) OS env variable 'APOLLO_META'

(3) property 'apollo.meta' from server.properties

(4) property 'apollo.meta' from app.properties

一般项目常用(3)的方式，配置apollo.meta。

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