英文:
Micronaut generic GRPC proxy
问题
在替换旧的遗留服务为新服务的过程中，我们希望临时将到达新服务的请求转发到旧服务。对于HTTP请求，我们可以通过自定义的HttpFilter来实现这一点：
@Filter("/**/legacy-service/**")
public class LegacyHttpProxyFilter implements HttpFilter {
@Inject
@Named("legacy-http-client")
private ProxyHttpClient httpClient;
@Override
public Publisher<? extends HttpResponse<?>> doFilter(HttpRequest<?> request, FilterChain chain) {
return httpClient.proxy(request);
}
}
对于GRPC的类似方法将是使用ServerInterceptor，如下所示：
@Singleton
public class LegacyGrpcProxyInterceptor implements ServerInterceptor {
@Inject
@Named("legacy-grpc-client")
MyLegacyServiceGrpc.MyLegacyServiceStub legacyServiceStub;
@Override
public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
return null; // 如何以通用方式处理GRPC请求？
}
}
区别在于，使用ProxyHttpClient我们可以转发任何HTTP请求，但似乎不能使用MyLegacyServiceStub GRPC stub 实现相同功能。看起来正确的方法是实现一个自定义的ServerCallHandler，但我并不真正明白如何做，任何示例将不胜感激。
我如何转发任何传入的GRPC请求？
英文:
In the process of replacing an old legacy service by a new one we want to temporarily forward the requests reaching the new service to the legacy one. For HTTP requests we achieve this with a custom HttpFilter:
@Filter("/**/legacy-service/**")
public class LegacyHttpProxyFilter implements HttpFilter {
@Inject
@Named("legacy-http-client")
private ProxyHttpClient httpClient;
@Override
public Publisher<? extends HttpResponse<?>> doFilter(HttpRequest<?> request, FilterChain chain) {
return httpClient.proxy(request);
}
}
The analogous approach for GRPC would be something similar to this with a ServerInterceptor:
@Singleton
public class LegacyGrpcProxyInterceptor implements ServerInterceptor {
@Inject
@Named("legacy-grpc-client")
MyLegacyServiceGrpc.MyLegacyServiceStub legacyServiceStub;
@Override
public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> call, Metadata headers, ServerCallHandler<ReqT, RespT> next) {
return null; // How to handle GRPC requests in a generic way?
}
}
The difference is that with a ProxyHttpClient we can forward any HTTP request, while this doesn't seem to be possible with MyLegacyServiceStub GRPC stub. It looks like the right approach is to implement a custom ServerCallHandler but I don't really see how, any example would be highly appreciated.
How can I forward any incoming GRPC request?
答案1
得分: 1
在grpc-java中有一个示例。
你说得对，它的核心应该是实现一个ServerCallHandler。你还需要一个MethodDescriptor，并将它们打包到一个ServerMethodDefinition中。
该示例使用一个备用的HandlerRegistry来代理所有方法，但如果你只需要静态代理，你可以为要代理的每个服务创建一个ServerServiceDefinition（实质上是一个服务的一组ServerMethodDefinitions），然后将其像平常一样添加到ServerBuilder中：serverBuilder.addService()。
示例的其余部分是将客户端和服务器调用连接在一起，对于流式RPC，还有适当的流量控制。
英文:
There is such an example in grpc-java.
You are right that the core of it should be to implement a ServerCallHandler. You will also need a MethodDescriptor and to package them together into a ServerMethodDefinition.
The example uses a fallback HandlerRegistry to proxy all methods, but if you only need static proxying you could create a ServerServiceDefinition (essentially a set of ServerMethodDefinitions for one service) for each service you want proxied and add it to the ServerBuilder as normal: serverBuilder.addService().
The rest of the example is gluing the client and server calls together, with proper flow control for streaming RPCs.
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