nacos版本
<dependency>
<groupId>com.alibaba.cloud</groupId>
<artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId>
<version>2.0.0.RELEASE</version>
</dependency>
bootstrap.yaml
spring:
application:
name: service1
profiles:
active: dev
cloud:
nacos:
config:
namespace: 14d29622-bf23-4d4a-b86d-cdedc18ff83b
file-extension: yaml
server-addr: 127.0.0.1:8848
ext-config[0]:
data-id: common-${spring.profiles.active}.yaml
refresh: true
nacos是Alibaba 开源的微服务发现、管理、配置的组件，它提供了server端和客户端的能力，这里我们将来分析下nacos与spring cloud服务集成，作为微服务的配置中心的nacos的底层源码
nacos读取配置分析
// springboot服务的统一入口
public static void main(String[] args) {
SpringApplication.run(MyApplication.class, args);
}
启动微服务，从SpringApplication.run()方法进入，到达SpringApplication#run(java.lang.String...) 进行spring容器的启动的各项工作：
1、准备上下文
2、应用初始化设定（配置刷新）
3、加载各种初始化配置，其中包括属性配置初始化
4、PropertySourceBootstrapConfiguration#initialize方法中加载到nacos配置源
public void initialize(ConfigurableApplicationContext applicationContext) {
List<PropertySource<?>> composite = new ArrayList<>();
AnnotationAwareOrderComparator.sort(this.propertySourceLocators);
boolean empty = true;
ConfigurableEnvironment environment = applicationContext.getEnvironment();
for (PropertySourceLocator locator : this.propertySourceLocators) {
// 配置源
Collection<PropertySource<?>> source = locator.locateCollection(environment);
if (source == null || source.size() == 0) {
continue;
}
List<PropertySource<?>> sourceList = new ArrayList<>();
for (PropertySource<?> p : source) {
if (p instanceof EnumerablePropertySource) {
EnumerablePropertySource<?> enumerable = (EnumerablePropertySource<?>) p;
sourceList.add(new BootstrapPropertySource<>(enumerable));
}
else {
sourceList.add(new SimpleBootstrapPropertySource(p));
}
}
logger.info("Located property source: " + sourceList);
composite.addAll(sourceList);
empty = false;
}
if (!empty) {
MutablePropertySources propertySources = environment.getPropertySources();
String logConfig = environment.resolvePlaceholders("${logging.config:}");
LogFile logFile = LogFile.get(environment);
for (PropertySource<?> p : environment.getPropertySources()) {
if (p.getName().startsWith(BOOTSTRAP_PROPERTY_SOURCE_NAME)) {
propertySources.remove(p.getName());
}
}
insertPropertySources(propertySources, composite);
reinitializeLoggingSystem(environment, logConfig, logFile);
setLogLevels(applicationContext, environment);
handleIncludedProfiles(environment);
}
}
5、然后到达此方法NacosPropertySourceLocator#locate 进行bootstrap.yaml配置的nacos相关配置获取与加载
public PropertySource<?> locate(Environment env) {
ConfigService configService = nacosConfigProperties.configServiceInstance();
if (null == configService) {
log.warn("no instance of config service found, can't load config from nacos");
return null;
}
long timeout = nacosConfigProperties.getTimeout();
nacosPropertySourceBuilder = new NacosPropertySourceBuilder(configService,
timeout);
String name = nacosConfigProperties.getName();
String dataIdPrefix = nacosConfigProperties.getPrefix();
if (StringUtils.isEmpty(dataIdPrefix)) {
dataIdPrefix = name;
}
if (StringUtils.isEmpty(dataIdPrefix)) {
dataIdPrefix = env.getProperty("spring.application.name");
}
CompositePropertySource composite = new CompositePropertySource(
NACOS_PROPERTY_SOURCE_NAME);
// 加载共享配置 对应 shared-dataids 配置项
loadSharedConfiguration(composite);
// 加载额外配置 对应 ext-config[n] 配置项
loadExtConfiguration(composite);
// 加载微服务对应配置
loadApplicationConfiguration(composite, dataIdPrefix, nacosConfigProperties, env);
return composite;
}
6、主要看NacosPropertySourceLocator#loadApplicationConfiguration 加载微服务配置，另外两个加载方法雷同。加载顺序，按照
${prefix}.${file-extension} => ${prefix}-${spring.profiles.active}.${file-extension}
7、第一次启动从远程获取数据进行加载
8、然后在NacosConfigService#getConfigInner方法进行加载配置，首先加载本地配置：nacos从远程读取配置文件成功，会将配置文件快照备份在磁盘上，当无法连接服务端时，使用本地快照的配置。如果存在本地备份，则不会从远程获取配置。那如果配置发生更新怎么办？这就涉及到nacos动态配置功能，将在下一篇进行分析。
private String getConfigInner(String tenant, String dataId, String group, long timeoutMs) throws NacosException {
group = null2defaultGroup(group);
ParamUtils.checkKeyParam(dataId, group);
ConfigResponse cr = new ConfigResponse();
cr.setDataId(dataId);
cr.setTenant(tenant);
cr.setGroup(group);
// 优先使用本地配置
String content = LocalConfigInfoProcessor.getFailover(agent.getName(), dataId, group, tenant);
if (content != null) {
LOGGER.warn("[{}] [get-config] get failover ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
dataId, group, tenant, ContentUtils.truncateContent(content));
cr.setContent(content);
configFilterChainManager.doFilter(null, cr);
content = cr.getContent();
return content;
}
try { // 没有磁盘快照，从配置中心加载服务配置
content = worker.getServerConfig(dataId, group, tenant, timeoutMs);
cr.setContent(content);
configFilterChainManager.doFilter(null, cr);
content = cr.getContent();
return content;
} catch (NacosException ioe) {
if (NacosException.NO_RIGHT == ioe.getErrCode()) {
throw ioe;
}
LOGGER.warn("[{}] [get-config] get from server error, dataId={}, group={}, tenant={}, msg={}",
agent.getName(), dataId, group, tenant, ioe.toString());
}
LOGGER.warn("[{}] [get-config] get snapshot ok, dataId={}, group={}, tenant={}, config={}", agent.getName(),
dataId, group, tenant, ContentUtils.truncateContent(content));
content = LocalConfigInfoProcessor.getSnapshot(agent.getName(), dataId, group, tenant);
cr.setContent(content);
configFilterChainManager.doFilter(null, cr);
content = cr.getContent();
return content;
}
9、ClientWorker#getServerConfig方法
public String getServerConfig(String dataId, String group, String tenant, long readTimeout)
throws NacosException {
if (StringUtils.isBlank(group)) {
group = Constants.DEFAULT_GROUP;
}
HttpResult result = null;
try {
List<String> params = null;
if (StringUtils.isBlank(tenant)) {
params = Arrays.asList("dataId", dataId, "group", group);
} else {
params = Arrays.asList("dataId", dataId, "group", group, "tenant", tenant);
}
// get方法获取配置文件内容
result = agent.httpGet(Constants.CONFIG_CONTROLLER_PATH, null, params, agent.getEncode(), readTimeout);
} catch (IOException e) {
String message = String.format(
"[%s] [sub-server] get server config exception, dataId=%s, group=%s, tenant=%s", agent.getName(),
dataId, group, tenant);
LOGGER.error(message, e);
throw new NacosException(NacosException.SERVER_ERROR, e);
}
switch (result.code) {
case HttpURLConnection.HTTP_OK:
// 备份快照至磁盘
LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, result.content);
return result.content;
case HttpURLConnection.HTTP_NOT_FOUND:
LocalConfigInfoProcessor.saveSnapshot(agent.getName(), dataId, group, tenant, null);
return null;
case HttpURLConnection.HTTP_CONFLICT: {
LOGGER.error(
"[{}] [sub-server-error] get server config being modified concurrently, dataId={}, group={}, "
+ "tenant={}", agent.getName(), dataId, group, tenant);
throw new NacosException(NacosException.CONFLICT,
"data being modified, dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
}
case HttpURLConnection.HTTP_FORBIDDEN: {
LOGGER.error("[{}] [sub-server-error] no right, dataId={}, group={}, tenant={}", agent.getName(), dataId,
group, tenant);
throw new NacosException(result.code, result.content);
}
default: {
LOGGER.error("[{}] [sub-server-error] dataId={}, group={}, tenant={}, code={}", agent.getName(), dataId,
group, tenant, result.code);
throw new NacosException(result.code,
"http error, code=" + result.code + ",dataId=" + dataId + ",group=" + group + ",tenant=" + tenant);
}
}
}
10、具体http请求方法，请求失败时，重试3次，从服务端配置地址获取下一个服务地址进行新的请求。如果请求成功nacos服务端返回的字符串内容。
public HttpResult httpGet(String path, List<String> headers, List<String> paramValues, String encoding,
long readTimeoutMs) throws IOException {
final long endTime = System.currentTimeMillis() + readTimeoutMs;
final boolean isSSL = false;
String currentServerAddr = serverListMgr.getCurrentServerAddr();
// 默认 3
int maxRetry = this.maxRetry;
do {
try {
List<String> newHeaders = getSpasHeaders(paramValues);
if (headers != null) {
newHeaders.addAll(headers);
}
HttpResult result = HttpSimpleClient.httpGet(
getUrl(currentServerAddr, path), newHeaders, paramValues, encoding,
readTimeoutMs, isSSL);
if (result.code == HttpURLConnection.HTTP_INTERNAL_ERROR
|| result.code == HttpURLConnection.HTTP_BAD_GATEWAY
|| result.code == HttpURLConnection.HTTP_UNAVAILABLE) {
LOGGER.error("[NACOS ConnectException] currentServerAddr: {}, httpCode: {}",
serverListMgr.getCurrentServerAddr(), result.code);
} else {
// Update the currently available server addr
serverListMgr.updateCurrentServerAddr(currentServerAddr);
return result;
}
} catch (ConnectException ce) {
LOGGER.error("[NACOS ConnectException httpGet] currentServerAddr:{}, err : {}", serverListMgr.getCurrentServerAddr(), ce.getMessage());
} catch (SocketTimeoutException stoe) {
LOGGER.error("[NACOS SocketTimeoutException httpGet] currentServerAddr:{}， err : {}", serverListMgr.getCurrentServerAddr(), stoe.getMessage());
} catch (IOException ioe) {
LOGGER.error("[NACOS IOException httpGet] currentServerAddr: " + serverListMgr.getCurrentServerAddr(), ioe);
throw ioe;
}
if (serverListMgr.getIterator().hasNext()) {
// 下一个nacos服务地址
currentServerAddr = serverListMgr.getIterator().next();
} else {
maxRetry --;
if (maxRetry < 0) {
throw new ConnectException("[NACOS HTTP-GET] The maximum number of tolerable server reconnection errors has been reached");
}
serverListMgr.refreshCurrentServerAddr();
}
} while (System.currentTimeMillis() <= endTime);
LOGGER.error("no available server");
throw new ConnectException("no available server");
}
至此，nacos从配置中心加载配置的源码就分析完了。
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