I'm trying to connect to a grpc-service from a Java client. The problem is that this service is currently supporting only grpc-web over http1.1, this is because of a limitation of supporting http2 in Azure App service where the service is deployed.
The grpc-java client liberary from io.grpc only supports grpc over http2 protocol, which maskes sense, and unfortenatly is not working for me.
I managed to consume a service using HTTP client from apache and okhttp3 but this works for unary calls and it didn't work for a server-side streaming service.
Is any one aware of a grpc-web java client liberary that I could use or a work arround using convenienal Http for reading grpc-web server-side streaming service.
If I understand your question correctly, you want a Java client for gRPC-Web so that your client can talk HTTP/1.1 through a gRPC-Web proxy (e.g. Envoy gRPC-Web) because you're unable to talk HTTP/2 directly to your service because of the Azure networking limitation?
In theory this should be possible. The JavaScript implementation is because, in-browser, there's no alternative except JSON transcoding. The JavaScript implementation does implement server-side streaming, which is another requirement and confirms that this should be possible over HTTP/1.1.
However, in a quick search I found no other (i.e non-JavaScript) client implementations of gRPC-Web.
Related
I have an application running behind a Load Balancer in Google Cloud Platform.
When I use the HTTPS protocol in the backend, I'm able to connect with WebSockets and all WebSocket connections work fine. However, when I change the backend protocol to HTTP/2, I'm unable to connect from the application, and it returns a response of 502 Bad Gateway.
Can I use WebSockets with HTTP/2, or do I need to perform some configuration in order to use WebSockets with an HTTP2 backend?
As others have commented, WebSockets are not supported in HTTP/2 and this is the reason why you receive the 5XX error.
Having said that, the WebSocket functionality is achievable (and improved) with HTTP/2 ref.
If you have existing code working with WebSocket it might not be great to rewrite both backend and frontend.
However, if you are developing a new asynchronous service, it is a good idea to take a look at the HTTP/2 + Server Sent Event (SSE) scheme.
I'm newbie of grpc and have played with simple grpc clients of java, go, and python. I know basic http and https but not familiar with protocal details. So this question may be rediculous to you but I didn't find any explaination online.
I know grpc has insecure(go: grpc.WithInsecure(), python: grpc.insecure_channel, java: usePlaintext()) and secure mode(TLS). and grpc is based on httpv2, and http has security mode(https).
So what if use insecure grpc with https? Is the overall data transfer safe?
And what if use TLS grpc with https? Is there performance overhead(becuase I think the messages are encrypted twice)?
Thank you for any answer, any exsiting webpages explaining such topic that will be best!
Insecure implies http. And TLS implies https. So there's no way "to use insecure grpc with https", as at that point it is then http.
There is no double-encryption. The gRPC security mode is the same as the HTTP security mode.
Using gRPC over TLS is highly recommended if you gRPC server is serving requests coming from outside(external network). For example you're creating front end app in javascript serving user requests. Your javascript app make call to your gRPC server for APIs your server provide. Your javascript communicate to your gRPC server through stub created in javascript end. At the end of your gRPC server, you need to set tls mechanism to secure communication between your javascript app and your gRPC server(because requests coming from outside).
gRPC somehow mostly used for internal services communication inside internal network in microservice architecture. You don't need to set tls for internal network usage since requests coming from your own environment from within your watch.
If you want to apply something like "gRPC over HTTPS", then you need something like gateway to map your http call to your gRPC server. Check this out.
You need to compile your proto file as gateway service definitions as well using provided tools. Now you can create your normal http server with tls enabled through something like http.ListenAndServeTLS(...). Dont forget to register your grpc server to the http server using the service definitions compiled from the proto file. With this all your requests to are encrypted with tls to your http server like normal rest apis do, but get proxied to gRPC server you defined. There's no need to enable tls at your gRPC server since it has been enabled in your http server.
I am a little bit confused about grpc and http/2. From what I learned, grpc is a RPC framework and can use different types of transports and http/2 is just one of the transports.
In golang, grpc.Dial() will create a connection to the server and the grpc server is created by grpc#Server.Serve(). So what is this connection? Is that a http/2 connection?
Thank you very much for your help.
When you connect to a server with gRPC, that does establish a single HTTP/2 connection that can be shared between many gRPC requests (the channel concept).
gRPC is indeed an RPC framework, built on HTTP/2. By default, it uses Protobufs as the serialization protocol, but that can be customised.
Think of gRPC as an RPC application layer over HTTP/2. To quote the FAQ:
"... gRPC is also a set of libraries that will provide higher-level features consistently across platforms that common HTTP libraries typically do not. Examples of such features include:
interaction with flow-control at the application layer
cascading call-cancellation
load balancing & failover
"
gRPC is based on HTTP/2, which (assumption) is widely supported by browsers. Therefore, I feel there should be no problem with gRPC from a browser.
However, it is clear that there is a problem. The protocol, grpc web, is different, as exists "due to browser limitation". There are also numerous blog post describing complicated tech stacks deployed to get gRPC to work from a browser.
I'm missing the actual problem - why does gRPC not simply work from browsers?
I now understand that browsers only supports HTTP/2 in the sense that they use it to fetch resources from the server on behalf of your application (javascript) code.
Javascipt application code can still only use HTTP/1 (which may be handled under the hood by the browser in an HTTP/2 connection). Therefore it is not possible for application code to use grpc.
If anyone should find where this is explained in the docs, it would be good to add a link to it here.
Most browsers use HTTP1.1 whereas GRPC only works with HTTP2. You can use nginx, envoy or traefic to run it behind a reverse proxy, very similar to how web sockets are often used behind a reverse proxy(in that case the http1 is upgraded to a websockets connection). The reverse proxy will send the grpc request sent over http1 to an http2 backend and vice versa. You can use Envoy(suggested/currently used by grpc-web), traefik(am using this personally) and nginx.
Web-servers work in response to incoming HTTP requests... process the request and return an HTTP response. Are there any common ways that a server can PUSH data to clients in this architecture... e.g a request comes in from client1 and the server wants to notify client2? It can obviously be done by a non-web server, using sockets, but what about a web-server app which has to support page requests AND allow PUSHing data..?
what about a web-server app which has to support page requests AND allow PUSHing data..?
Servlet 3.0 introduces Async support allowing to write Comet style applications (i.e. applications using Long-lived HTTP connections and either long polling or streaming).
If you can't wait for Servlet 3.0 Async support and don't want to use proprietary Comet or WebSocket support from containers (like GlassFish, Jetty), then have a look at Atmosphere.
See also
JavaOne 2008: Comet (AJAX, Grizzly and Cometd)
Asynchronous processing support in Servlet 3.0
Servlet 3.0 Async API or Atmosphere? A Simple Comparison
You can use web app containers like Jetty which support Web Sockets if you don't mind waiting for the web world to catch up to this up-and-coming standard. Then you'll have real bi-directional communications instead of HTTP + Polling or special plug-ins or the like.
No, not without some client side tech (Flash, Silverlight, Applets, etc.)
You could have the page poll the server with AJAX though.
Another possibility would be to abuse HTTP Keep Alive to achieve this. See http://en.wikipedia.org/wiki/HTTP_persistent_connection for some background. In your scenario you would have client2 initiate a connection to the server that then would stay open listening for notifications.
This is not a great solution, first off you need to keep lots of long lived TCP connections around, and if a connection is lost there is no way for the server to reconnect. It must wait for the client to come back.