回答我自己的问题：
在我进入细节之前，一个警示故事：
在我的本地机器上测试故障转移时，Eureka 的自我保护模式让我陷入了困境。我建议在进行测试时关闭自我保护模式。因为我以固定速率删除节点然后重新启动（使用随机值使用不同的实例 ID），所以我触发了 Eureka 的自我保存模式。我最终在 Eureka 中找到了许多指向同一台机器、同一端口的实例。故障转移实际上正在工作，但选择的下一个节点恰好是另一个死实例。一开始很困惑！
我能够使用修改后的 RibbonClientHttpRequestFactory 版本进行故障转移。因为 RibbonAutoConfiguration 使用这个工厂创建了一个负载平衡的 RestTemplate，而不是注入这个 rest 模板，所以我用我修改过的请求工厂版本创建了一个新模板：
protected RestTemplate restTemplate;
@Autowired
public void customizeRestTemplate(SpringClientFactory springClientFactory, LoadBalancerClient loadBalancerClient) {
restTemplate = new RestTemplate();
// Use a modified version of the http request factory that leverages the load balacing in netflix's RestClient.
RibbonRetryHttpRequestFactory lFactory = new RibbonRetryHttpRequestFactory(springClientFactory, loadBalancerClient);
restTemplate.setRequestFactory(lFactory);
}
修改后的 Request Factory 只是 RibbonClientHttpRequestFactory 的一个副本，有两个小改动：
1) 在 createRequest 中，我删除了从负载均衡器中选择服务器的代码，因为 RestClient 会为我们执行此操作。
2) 在内部类 RibbonHttpRequest 中，我将 executeInternal 更改为调用“executeWithLoadBalancer”。
全班：
@SuppressWarnings("deprecation")
public class RibbonRetryHttpRequestFactory implements ClientHttpRequestFactory {
private final SpringClientFactory clientFactory;
private LoadBalancerClient loadBalancer;
public RibbonRetryHttpRequestFactory(SpringClientFactory clientFactory, LoadBalancerClient loadBalancer) {
this.clientFactory = clientFactory;
this.loadBalancer = loadBalancer;
}
@Override
public ClientHttpRequest createRequest(URI originalUri, HttpMethod httpMethod) throws IOException {
String serviceId = originalUri.getHost();
IClientConfig clientConfig = clientFactory.getClientConfig(serviceId);
RestClient client = clientFactory.getClient(serviceId, RestClient.class);
HttpRequest.Verb verb = HttpRequest.Verb.valueOf(httpMethod.name());
return new RibbonHttpRequest(originalUri, verb, client, clientConfig);
}
public class RibbonHttpRequest extends AbstractClientHttpRequest {
private HttpRequest.Builder builder;
private URI uri;
private HttpRequest.Verb verb;
private RestClient client;
private IClientConfig config;
private ByteArrayOutputStream outputStream = null;
public RibbonHttpRequest(URI uri, HttpRequest.Verb verb, RestClient client, IClientConfig config) {
this.uri = uri;
this.verb = verb;
this.client = client;
this.config = config;
this.builder = HttpRequest.newBuilder().uri(uri).verb(verb);
}
@Override
public HttpMethod getMethod() {
return HttpMethod.valueOf(verb.name());
}
@Override
public URI getURI() {
return uri;
}
@Override
protected OutputStream getBodyInternal(HttpHeaders headers) throws IOException {
if (outputStream == null) {
outputStream = new ByteArrayOutputStream();
}
return outputStream;
}
@Override
protected ClientHttpResponse executeInternal(HttpHeaders headers) throws IOException {
try {
addHeaders(headers);
if (outputStream != null) {
outputStream.close();
builder.entity(outputStream.toByteArray());
}
HttpRequest request = builder.build();
HttpResponse response = client.executeWithLoadBalancer(request, config);
return new RibbonHttpResponse(response);
}
catch (Exception e) {
throw new IOException(e);
}
//TODO: fix stats, now that execute is not called
// use execute here so stats are collected
/*
return loadBalancer.execute(this.config.getClientName(), new LoadBalancerRequest<ClientHttpResponse>() {
@Override
public ClientHttpResponse apply(ServiceInstance instance) throws Exception {}
});
*/
}
private void addHeaders(HttpHeaders headers) {
for (String name : headers.keySet()) {
// apache http RequestContent pukes if there is a body and
// the dynamic headers are already present
if (!isDynamic(name) || outputStream == null) {
List<String> values = headers.get(name);
for (String value : values) {
builder.header(name, value);
}
}
}
}
private boolean isDynamic(String name) {
return name.equals("Content-Length") || name.equals("Transfer-Encoding");
}
}
public class RibbonHttpResponse extends AbstractClientHttpResponse {
private HttpResponse response;
private HttpHeaders httpHeaders;
public RibbonHttpResponse(HttpResponse response) {
this.response = response;
this.httpHeaders = new HttpHeaders();
List<Map.Entry<String, String>> headers = response.getHttpHeaders().getAllHeaders();
for (Map.Entry<String, String> header : headers) {
this.httpHeaders.add(header.getKey(), header.getValue());
}
}
@Override
public InputStream getBody() throws IOException {
return response.getInputStream();
}
@Override
public HttpHeaders getHeaders() {
return this.httpHeaders;
}
@Override
public int getRawStatusCode() throws IOException {
return response.getStatus();
}
@Override
public String getStatusText() throws IOException {
return HttpStatus.valueOf(response.getStatus()).name();
}
@Override
public void close() {
response.close();
}
}
}