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本文主要研究一下AsyncLoadBalancerAutoConfiguration
AsyncLoadBalancerAutoConfiguration
spring-cloud-commons-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/client/loadbalancer/AsyncLoadBalancerAutoConfiguration.java
/**
* Auto configuration for Ribbon (client side load balancing).
*
* @author Rob Worsnop
*/
@Configuration
@ConditionalOnBean(LoadBalancerClient.class)
@ConditionalOnClass(AsyncRestTemplate.class)
public class AsyncLoadBalancerAutoConfiguration {
@Configuration
static class AsyncRestTemplateCustomizerConfig {
@LoadBalanced
@Autowired(required = false)
private List restTemplates = Collections.emptyList();
@Bean
public SmartInitializingSingleton loadBalancedAsyncRestTemplateInitializer(
final List customizers) {
return new SmartInitializingSingleton() {
@Override
public void afterSingletonsInstantiated() {
for (AsyncRestTemplate restTemplate : AsyncRestTemplateCustomizerConfig.this.restTemplates) {
for (AsyncRestTemplateCustomizer customizer : customizers) {
customizer.customize(restTemplate);
}
}
}
};
}
}
@Configuration
static class LoadBalancerInterceptorConfig {
@Bean
public AsyncLoadBalancerInterceptor asyncLoadBalancerInterceptor(LoadBalancerClient loadBalancerClient) {
return new AsyncLoadBalancerInterceptor(loadBalancerClient);
}
@Bean
public AsyncRestTemplateCustomizer asyncRestTemplateCustomizer(
final AsyncLoadBalancerInterceptor loadBalancerInterceptor) {
return new AsyncRestTemplateCustomizer() {
@Override
public void customize(AsyncRestTemplate restTemplate) {
List list = new ArrayList<>(
restTemplate.getInterceptors());
list.add(loadBalancerInterceptor);
restTemplate.setInterceptors(list);
}
};
}
}
} - 这里创建一个AsyncRestTemplateCustomizerConfig，用于加载AsyncRestTemplateCustomizer
- 还有一个LoadBalancerInterceptorConfig，配置了AsyncLoadBalancerInterceptor及AsyncRestTemplateCustomizer
AsyncRestTemplateCustomizer
spring-cloud-commons-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/client/loadbalancer/AsyncRestTemplateCustomizer.java
public interface AsyncRestTemplateCustomizer {
void customize(AsyncRestTemplate restTemplate);
}- 这里采用匿名类实现，主要就是设置AsyncClientHttpRequestInterceptor
AsyncClientHttpRequestInterceptor
spring-cloud-commons-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/client/loadbalancer/AsyncLoadBalancerInterceptor.java
public class AsyncLoadBalancerInterceptor implements AsyncClientHttpRequestInterceptor {
private LoadBalancerClient loadBalancer;
public AsyncLoadBalancerInterceptor(LoadBalancerClient loadBalancer) {
this.loadBalancer = loadBalancer;
}
@Override
public ListenableFuture intercept(final HttpRequest request, final byte[] body,
final AsyncClientHttpRequestExecution execution) throws IOException {
final URI originalUri = request.getURI();
String serviceName = originalUri.getHost();
return this.loadBalancer.execute(serviceName,
new LoadBalancerRequest>() {
@Override
public ListenableFuture apply(final ServiceInstance instance)
throws Exception {
HttpRequest serviceRequest = new ServiceRequestWrapper(request,
instance, loadBalancer);
return execution.executeAsync(serviceRequest, body);
}
});
}
} - 这个拦截器从url获取serviceName，然后调用loadBalancer.execute方法
- 这里构造的LoadBalancerRequest，采用ServiceRequestWrapper，调用的是execution.executeAsync
AbstractAsyncClientHttpRequest
spring-web-5.0.7.RELEASE-sources.jar!/org/springframework/http/client/AbstractAsyncClientHttpRequest.java
/**
* Abstract base for {@link AsyncClientHttpRequest} that makes sure that headers and body
* are not written multiple times.
*
* @author Arjen Poutsma
* @since 4.0
* @deprecated as of Spring 5.0, in favor of {@link org.springframework.http.client.reactive.AbstractClientHttpRequest}
*/
@Deprecated
abstract class AbstractAsyncClientHttpRequest implements AsyncClientHttpRequest {
private final HttpHeaders headers = new HttpHeaders();
private boolean executed = false;
@Override
public final HttpHeaders getHeaders() {
return (this.executed ? HttpHeaders.readOnlyHttpHeaders(this.headers) : this.headers);
}
@Override
public final OutputStream getBody() throws IOException {
assertNotExecuted();
return getBodyInternal(this.headers);
}
@Override
public ListenableFuture executeAsync() throws IOException {
assertNotExecuted();
ListenableFuture result = executeInternal(this.headers);
this.executed = true;
return result;
}
/**
* Asserts that this request has not been {@linkplain #executeAsync() executed} yet.
* @throws IllegalStateException if this request has been executed
*/
protected void assertNotExecuted() {
Assert.state(!this.executed, "ClientHttpRequest already executed");
}
/**
* Abstract template method that returns the body.
* @param headers the HTTP headers
* @return the body output stream
*/
protected abstract OutputStream getBodyInternal(HttpHeaders headers) throws IOException;
/**
* Abstract template method that writes the given headers and content to the HTTP request.
* @param headers the HTTP headers
* @return the response object for the executed request
*/
protected abstract ListenableFuture executeInternal(HttpHeaders headers)
throws IOException;
} - 这个executeAsync的委托给子类的executeInternal实现
- 主要有SimpleStreamingAsyncClientHttpRequest、Netty4ClientHttpRequest两个实现
SimpleStreamingAsyncClientHttpRequest
spring-web-5.0.7.RELEASE-sources.jar!/org/springframework/http/client/SimpleStreamingAsyncClientHttpRequest.java
/**
* {@link org.springframework.http.client.ClientHttpRequest} implementation
* that uses standard Java facilities to execute streaming requests. Created
* via the {@link org.springframework.http.client.SimpleClientHttpRequestFactory}.
*
* @author Arjen Poutsma
* @since 3.0
* @see org.springframework.http.client.SimpleClientHttpRequestFactory#createRequest
* @see org.springframework.http.client.support.AsyncHttpAccessor
* @see org.springframework.web.client.AsyncRestTemplate
* @deprecated as of Spring 5.0, with no direct replacement
*/
@Deprecated
final class SimpleStreamingAsyncClientHttpRequest extends AbstractAsyncClientHttpRequest {
private final HttpURLConnection connection;
private final int chunkSize;
@Nullable
private OutputStream body;
private final boolean outputStreaming;
private final AsyncListenableTaskExecutor taskExecutor;
SimpleStreamingAsyncClientHttpRequest(HttpURLConnection connection, int chunkSize,
boolean outputStreaming, AsyncListenableTaskExecutor taskExecutor) {
this.connection = connection;
this.chunkSize = chunkSize;
this.outputStreaming = outputStreaming;
this.taskExecutor = taskExecutor;
}
@Override
public String getMethodValue() {
return this.connection.getRequestMethod();
}
@Override
public URI getURI() {
try {
return this.connection.getURL().toURI();
}
catch (URISyntaxException ex) {
throw new IllegalStateException(
"Could not get HttpURLConnection URI: " + ex.getMessage(), ex);
}
}
@Override
protected OutputStream getBodyInternal(HttpHeaders headers) throws IOException {
if (this.body == null) {
if (this.outputStreaming) {
long contentLength = headers.getContentLength();
if (contentLength >= 0) {
this.connection.setFixedLengthStreamingMode(contentLength);
}
else {
this.connection.setChunkedStreamingMode(this.chunkSize);
}
}
SimpleBufferingClientHttpRequest.addHeaders(this.connection, headers);
this.connection.connect();
this.body = this.connection.getOutputStream();
}
return StreamUtils.nonClosing(this.body);
}
@Override
protected ListenableFuture executeInternal(final HttpHeaders headers) throws IOException {
return this.taskExecutor.submitListenable(new Callable() {
@Override
public ClientHttpResponse call() throws Exception {
try {
if (body != null) {
body.close();
}
else {
SimpleBufferingClientHttpRequest.addHeaders(connection, headers);
connection.connect();
// Immediately trigger the request in a no-output scenario as well
connection.getResponseCode();
}
}
catch (IOException ex) {
// ignore
}
return new SimpleClientHttpResponse(connection);
}
});
}
} - 主要使用的是jdk的HttpURLConnection来实现
Netty4ClientHttpRequest
spring-web-5.0.7.RELEASE-sources.jar!/org/springframework/http/client/Netty4ClientHttpRequest.java
/**
* {@link ClientHttpRequest} implementation based on Netty 4.
*
* Created via the {@link Netty4ClientHttpRequestFactory}.
*
* @author Arjen Poutsma
* @author Rossen Stoyanchev
* @author Brian Clozel
* @since 4.1.2
* @deprecated as of Spring 5.0, in favor of
* {@link org.springframework.http.client.reactive.ReactorClientHttpConnector}
*/
@Deprecated
class Netty4ClientHttpRequest extends AbstractAsyncClientHttpRequest implements ClientHttpRequest {
private final Bootstrap bootstrap;
private final URI uri;
private final HttpMethod method;
private final ByteBufOutputStream body;
public Netty4ClientHttpRequest(Bootstrap bootstrap, URI uri, HttpMethod method) {
this.bootstrap = bootstrap;
this.uri = uri;
this.method = method;
this.body = new ByteBufOutputStream(Unpooled.buffer(1024));
}
@Override
public HttpMethod getMethod() {
return this.method;
}
@Override
public String getMethodValue() {
return this.method.name();
}
@Override
public URI getURI() {
return this.uri;
}
@Override
public ClientHttpResponse execute() throws IOException {
try {
return executeAsync().get();
}
catch (InterruptedException ex) {
Thread.currentThread().interrupt();
throw new IOException("Interrupted during request execution", ex);
}
catch (ExecutionException ex) {
if (ex.getCause() instanceof IOException) {
throw (IOException) ex.getCause();
}
else {
throw new IOException(ex.getMessage(), ex.getCause());
}
}
}
@Override
protected OutputStream getBodyInternal(HttpHeaders headers) throws IOException {
return this.body;
}
@Override
protected ListenableFuture executeInternal(final HttpHeaders headers) throws IOException {
final SettableListenableFuture responseFuture = new SettableListenableFuture<>();
ChannelFutureListener connectionListener = future -> {
if (future.isSuccess()) {
Channel channel = future.channel();
channel.pipeline().addLast(new RequestExecuteHandler(responseFuture));
FullHttpRequest nettyRequest = createFullHttpRequest(headers);
channel.writeAndFlush(nettyRequest);
}
else {
responseFuture.setException(future.cause());
}
};
this.bootstrap.connect(this.uri.getHost(), getPort(this.uri)).addListener(connectionListener);
return responseFuture;
}
private FullHttpRequest createFullHttpRequest(HttpHeaders headers) {
io.netty.handler.codec.http.HttpMethod nettyMethod =
io.netty.handler.codec.http.HttpMethod.valueOf(this.method.name());
String authority = this.uri.getRawAuthority();
String path = this.uri.toString().substring(this.uri.toString().indexOf(authority) + authority.length());
FullHttpRequest nettyRequest = new DefaultFullHttpRequest(
HttpVersion.HTTP_1_1, nettyMethod, path, this.body.buffer());
nettyRequest.headers().set(HttpHeaders.HOST, this.uri.getHost() + ":" + getPort(uri));
nettyRequest.headers().set(HttpHeaders.CONNECTION, "close");
headers.forEach((headerName, headerValues) -> nettyRequest.headers().add(headerName, headerValues));
if (!nettyRequest.headers().contains(HttpHeaders.CONTENT_LENGTH) && this.body.buffer().readableBytes() > 0) {
nettyRequest.headers().set(HttpHeaders.CONTENT_LENGTH, this.body.buffer().readableBytes());
}
return nettyRequest;
}
private static int getPort(URI uri) {
int port = uri.getPort();
if (port == -1) {
if ("http".equalsIgnoreCase(uri.getScheme())) {
port = 80;
}
else if ("https".equalsIgnoreCase(uri.getScheme())) {
port = 443;
}
}
return port;
}
/**
* A SimpleChannelInboundHandler to update the given SettableListenableFuture.
*/
private static class RequestExecuteHandler extends SimpleChannelInboundHandler {
private final SettableListenableFuture responseFuture;
public RequestExecuteHandler(SettableListenableFuture responseFuture) {
this.responseFuture = responseFuture;
}
@Override
protected void channelRead0(ChannelHandlerContext context, FullHttpResponse response) throws Exception {
this.responseFuture.set(new Netty4ClientHttpResponse(context, response));
}
@Override
public void exceptionCaught(ChannelHandlerContext context, Throwable cause) throws Exception {
this.responseFuture.setException(cause);
}
}
}
- 使用netty的bootstrap.connect进行请求
小结
AsyncLoadBalancerAutoConfiguration使用的AsyncClientHttpRequest及其实现类都被标记为废弃，spring 5之后推荐使用webClient。
doc
- 3.4 Spring WebClient as a Load Balancer Client