1. EurekaTransport
EurekaTransport 持有了用于 http 通讯的组件，用于向 eureka server 发送服务注册等信息的有 registrationClient，用于向 eureka server 查询服务信息的有 queryClient。bootstrapResolver 这个是用于对 service-url.defaultZone 这个配置或者其他的 zone 进行解析。
1
2
3
4
5
6
7
8
9
10
private static final class EurekaTransport {
private ClosableResolver bootstrapResolver;
private TransportClientFactory transportClientFactory;
private EurekaHttpClient registrationClient;
private EurekaHttpClientFactory registrationClientFactory;
private EurekaHttpClient queryClient;
private EurekaHttpClientFactory queryClientFactory;
}
2. ClosableResolver
ClosableResolver 的实现类为 ConfigClusterResolver，在 getClusterEndpoints -> getClusterEndpointsFromConfig -> EndpointUtils.getServiceUrlsMapFromConfig -> EurekaClientConfig.getEurekaServerServiceUrls 从配置文件中获取到了 eureka 集群信息。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
public List<String> getEurekaServerServiceUrls(String myZone) {
String serviceUrls = configInstance.getStringProperty(
namespace + CONFIG_EUREKA_SERVER_SERVICE_URL_PREFIX + "." + myZone, null).get();
if (serviceUrls == null || serviceUrls.isEmpty()) {
serviceUrls = configInstance.getStringProperty(
namespace + CONFIG_EUREKA_SERVER_SERVICE_URL_PREFIX + ".default", null).get();
}
if (serviceUrls != null) {
return Arrays.asList(serviceUrls.split(","));
}
return new ArrayList<String>();
}
3. registrationClient
如果registration.enabled = true则需要向 eureka server 进行注册，那么就会创建 registrationClient。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
if (clientConfig.shouldRegisterWithEureka()) {
EurekaHttpClientFactory newRegistrationClientFactory = null;
EurekaHttpClient newRegistrationClient = null;
try {
newRegistrationClientFactory = EurekaHttpClients.registrationClientFactory(
eurekaTransport.bootstrapResolver,
eurekaTransport.transportClientFactory,
transportConfig
);
newRegistrationClient = newRegistrationClientFactory.newClient();
} catch (Exception e) {
logger.warn("Transport initialization failure", e);
}
eurekaTransport.registrationClientFactory = newRegistrationClientFactory;
eurekaTransport.registrationClient = newRegistrationClient;
}
newRegistrationClientFactory 用于创建 newRegistrationClient。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
static EurekaHttpClientFactory canonicalClientFactory(final String name,
final EurekaTransportConfig transportConfig,
final ClusterResolver<EurekaEndpoint> clusterResolver,
final TransportClientFactory transportClientFactory) {
return new EurekaHttpClientFactory() {
@Override
public EurekaHttpClient newClient() {
return new SessionedEurekaHttpClient(
name,
RetryableEurekaHttpClient.createFactory(
name,
transportConfig,
clusterResolver,
RedirectingEurekaHttpClient.createFactory(transportClientFactory),
ServerStatusEvaluators.legacyEvaluator()),
transportConfig.getSessionedClientReconnectIntervalSeconds() * 1000
);
}
@Override
public void shutdown() {
wrapClosable(clusterResolver).shutdown();
}
};
}
我们可以看到当调用 factory.newClient 函数时，最终创建的是一个 SessionedEurekaHttpClient。至于 RetryableEurekaHttpClient 和 RedirectingEurekaHttpClient 则是在执行 execute 函数时创建的。
现在我们看到了三种代理的 EurekaHttpClient，但是 MetricsCollectingEurekaHttpClient 是在哪里创建的呢？
在创建 RedirectingEurekaHttpClient 的时候，最终会使用到 eurekaTransport.transportClientFactory，也就是 Jersey1TransportClientFactories。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
public TransportClientFactory newTransportClientFactory(final Collection<ClientFilter> additionalFilters,
final EurekaJerseyClient providedJerseyClient) {
ApacheHttpClient4 apacheHttpClient = providedJerseyClient.getClient();
if (additionalFilters != null) {
for (ClientFilter filter : additionalFilters) {
if (filter != null) {
apacheHttpClient.addFilter(filter);
}
}
}
final TransportClientFactory jerseyFactory = new JerseyEurekaHttpClientFactory(providedJerseyClient, false);
final TransportClientFactory metricsFactory = MetricsCollectingEurekaHttpClient.createFactory(jerseyFactory);
return new TransportClientFactory() {
@Override
public EurekaHttpClient newClient(EurekaEndpoint serviceUrl) {
return metricsFactory.newClient(serviceUrl);
}
@Override
public void shutdown() {
metricsFactory.shutdown();
jerseyFactory.shutdown();
}
};
}
至此，我们可以得到 EurekaHttpClient 的调用顺序，SessionedEurekaHttpClient -> RetryableEurekaHttpClient -> RedirectingEurekaHttpClient -> MetricsCollectingEurekaHttpClient -> JerseyApplicationClient
4. EurekaHttpClientDecorator
就以从实现 EurekaHttpClient 接口的 register 函数举例，将 register 的行为下放到了实现类。在子类中，当调用 RequestExecutor#execute 时， 会委托给代理进行 register，这样的话装饰器可以在实际调用函数前后做一些装饰操作。
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
protected abstract <R> EurekaHttpResponse<R> execute(RequestExecutor<R> requestExecutor);
@Override
public EurekaHttpResponse<Void> register(final InstanceInfo info) {
return execute(new RequestExecutor<Void>() {
@Override
public EurekaHttpResponse<Void> execute(EurekaHttpClient delegate) {
return delegate.register(info);
}
@Override
public RequestType getRequestType() {
return RequestType.Register;
}
});
}
5. EurekaHttpClientDecorator实现类的作用
- MetricsCollectingEurekaHttpClient： 对不同的请求结果进行统计。
- RedirectingEurekaHttpClient：在创建 client 的时候，会进行一次请求，如果返回结果需要进行重定向，就会根据重新重定向地址重新生成一个client
- RetryableEurekaHttpClient：如果请求失败，则会换一个 eureka server 进行重试
- SessionedEurekaHttpClient： 超过一定时间没有使用过这个 client，就会重新创建一个新的 client。防止一直使用相同的 client。