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本文主要研究一下spring cloud gateway的LoadBalancerClientFilter
GatewayLoadBalancerClientAutoConfiguration
spring-cloud-gateway-core-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/gateway/config/GatewayLoadBalancerClientAutoConfiguration.java
@Configuration
@ConditionalOnClass({LoadBalancerClient.class, RibbonAutoConfiguration.class, DispatcherHandler.class})
@AutoConfigureAfter(RibbonAutoConfiguration.class)
public class GatewayLoadBalancerClientAutoConfiguration {
// GlobalFilter beans
@Bean
@ConditionalOnBean(LoadBalancerClient.class)
public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client) {
return new LoadBalancerClientFilter(client);
}
}
如果检测到有ribbon，则开启LoadBalancerClientFilter
LoadBalancerClientFilter
spring-cloud-gateway-core-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/gateway/filter/LoadBalancerClientFilter.java
public class LoadBalancerClientFilter implements GlobalFilter, Ordered {
private static final Log log = LogFactory.getLog(LoadBalancerClientFilter.class);
public static final int LOAD_BALANCER_CLIENT_FILTER_ORDER = 10100;
private final LoadBalancerClient loadBalancer;
public LoadBalancerClientFilter(LoadBalancerClient loadBalancer) {
this.loadBalancer = loadBalancer;
}
@Override
public int getOrder() {
return LOAD_BALANCER_CLIENT_FILTER_ORDER;
}
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
URI url = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
String schemePrefix = exchange.getAttribute(GATEWAY_SCHEME_PREFIX_ATTR);
if (url == null || (!"lb".equals(url.getScheme()) && !"lb".equals(schemePrefix))) {
return chain.filter(exchange);
}
//preserve the original url
addOriginalRequestUrl(exchange, url);
log.trace("LoadBalancerClientFilter url before: " + url);
final ServiceInstance instance = loadBalancer.choose(url.getHost());
if (instance == null) {
throw new NotFoundException("Unable to find instance for " + url.getHost());
}
URI uri = exchange.getRequest().getURI();
// if the `lb:<scheme>` mechanism was used, use `<scheme>` as the default,
// if the loadbalancer doesn't provide one.
String overrideScheme = null;
if (schemePrefix != null) {
overrideScheme = url.getScheme();
}
URI requestUrl = loadBalancer.reconstructURI(new DelegatingServiceInstance(instance, overrideScheme), uri);
log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
return chain.filter(exchange);
}
//......
}
- 这里首先获取scheme，如果不是lb，则直接往下一个filter传递
- 之后通过loadBalancer.choose(url.getHost())来选取服务实例
- 最后构造好requestUrl，设置到GATEWAY_REQUEST_URL_ATTR属性中
GATEWAY_SCHEME_PREFIX_ATTR
spring-cloud-gateway-core-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/gateway/filter/RouteToRequestUrlFilter.java
GATEWAY_SCHEME_PREFIX_ATTR这个属性是在RouteToRequestUrlFilter里头设置进去的。
public class RouteToRequestUrlFilter implements GlobalFilter, Ordered {
private static final Log log = LogFactory.getLog(RouteToRequestUrlFilter.class);
public static final int ROUTE_TO_URL_FILTER_ORDER = 10000;
private static final String SCHEME_REGEX = "[a-zA-Z]([a-zA-Z]|\\d|\\+|\\.|-)*:.*";
static final Pattern schemePattern = Pattern.compile(SCHEME_REGEX);
@Override
public int getOrder() {
return ROUTE_TO_URL_FILTER_ORDER;
}
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
if (route == null) {
return chain.filter(exchange);
}
log.trace("RouteToRequestUrlFilter start");
URI uri = exchange.getRequest().getURI();
boolean encoded = containsEncodedParts(uri);
URI routeUri = route.getUri();
if (hasAnotherScheme(routeUri)) {
// this is a special url, save scheme to special attribute
// replace routeUri with schemeSpecificPart
exchange.getAttributes().put(GATEWAY_SCHEME_PREFIX_ATTR, routeUri.getScheme());
routeUri = URI.create(routeUri.getSchemeSpecificPart());
}
URI requestUrl = UriComponentsBuilder.fromUri(uri)
.uri(routeUri)
.build(encoded)
.toUri();
exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
return chain.filter(exchange);
}
/* for testing */ static boolean hasAnotherScheme(URI uri) {
return schemePattern.matcher(uri.getSchemeSpecificPart()).matches() && uri.getHost() == null
&& uri.getRawPath() == null;
}
}
GATEWAY_REQUEST_URL_ATTR
spring-cloud-gateway-core-2.0.0.RELEASE-sources.jar!/org/springframework/cloud/gateway/filter/NettyRoutingFilter.java
public class NettyRoutingFilter implements GlobalFilter, Ordered {
private final HttpClient httpClient;
private final ObjectProvider<List<HttpHeadersFilter>> headersFilters;
public NettyRoutingFilter(HttpClient httpClient,
ObjectProvider<List<HttpHeadersFilter>> headersFilters) {
this.httpClient = httpClient;
this.headersFilters = headersFilters;
}
@Override
public int getOrder() {
return Ordered.LOWEST_PRECEDENCE;
}
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);
String scheme = requestUrl.getScheme();
if (isAlreadyRouted(exchange) || (!"http".equals(scheme) && !"https".equals(scheme))) {
return chain.filter(exchange);
}
setAlreadyRouted(exchange);
ServerHttpRequest request = exchange.getRequest();
final HttpMethod method = HttpMethod.valueOf(request.getMethod().toString());
final String url = requestUrl.toString();
HttpHeaders filtered = filterRequest(this.headersFilters.getIfAvailable(),
exchange);
final DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
filtered.forEach(httpHeaders::set);
String transferEncoding = request.getHeaders().getFirst(HttpHeaders.TRANSFER_ENCODING);
boolean chunkedTransfer = "chunked".equalsIgnoreCase(transferEncoding);
boolean preserveHost = exchange.getAttributeOrDefault(PRESERVE_HOST_HEADER_ATTRIBUTE, false);
return this.httpClient.request(method, url, req -> {
final HttpClientRequest proxyRequest = req.options(NettyPipeline.SendOptions::flushOnEach)
.headers(httpHeaders)
.chunkedTransfer(chunkedTransfer)
.failOnServerError(false)
.failOnClientError(false);
if (preserveHost) {
String host = request.getHeaders().getFirst(HttpHeaders.HOST);
proxyRequest.header(HttpHeaders.HOST, host);
}
return proxyRequest.sendHeaders() //I shouldn't need this
.send(request.getBody().map(dataBuffer ->
((NettyDataBuffer)dataBuffer).getNativeBuffer()));
}).doOnNext(res -> {
ServerHttpResponse response = exchange.getResponse();
// put headers and status so filters can modify the response
HttpHeaders headers = new HttpHeaders();
res.responseHeaders().forEach(entry -> headers.add(entry.getKey(), entry.getValue()));
exchange.getAttributes().put("original_response_content_type", headers.getContentType());
HttpHeaders filteredResponseHeaders = HttpHeadersFilter.filter(
this.headersFilters.getIfAvailable(), headers, exchange, Type.RESPONSE);
response.getHeaders().putAll(filteredResponseHeaders);
HttpStatus status = HttpStatus.resolve(res.status().code());
if (status != null) {
response.setStatusCode(status);
} else if (response instanceof AbstractServerHttpResponse) {
// https://jira.spring.io/browse/SPR-16748
((AbstractServerHttpResponse) response).setStatusCodeValue(res.status().code());
} else {
throw new IllegalStateException("Unable to set status code on response: " +res.status().code()+", "+response.getClass());
}
// Defer committing the response until all route filters have run
// Put client response as ServerWebExchange attribute and write response later NettyWriteResponseFilter
exchange.getAttributes().put(CLIENT_RESPONSE_ATTR, res);
}).then(chain.filter(exchange));
}
}
在NettyRoutingFilter中根据GATEWAY_REQUEST_URL_ATTR属性读取requestUrl，然后进行相应请求。
小结
LoadBalancerClientFilter会作用在url以lb开头的路由，然后利用loadBalancer来获取服务实例，构造目标requestUrl，设置到GATEWAY_REQUEST_URL_ATTR属性中，供NettyRoutingFilter使用。
