rpc: implement websockets with github.com/gorilla/websocket

[fjl]

This change makes package rpc use the github.com/gorilla/websocket package
for WebSockets instead of golang.org/x/net/websocket. The new library is more robust
and supports all WebSocket features including continuation frames.

There are new tests for two issues with the previously-used library:

• TestWebsocketClientPing checks handling of Ping frames.
• TestWebsocketLargeCall checks whether the request size limit is
  applied correctly.

DialWebsocket's handling of the default Origin header has changed. It used to set the
local machine's hostname as the origin, but that's weird and won't work with any
Internet-facing service. The new behavior is creating connections without an Origin
header unless one is provided explicitly.

This change also raises the request size limit for HTTP and WebSocket connections
to 5 MB. Quite a few people have reported issues where geth fails to deploy contracts
when they're too large, and retesteth needs a larger limit to upload the pre-state of large
tests.

Fixes #19798
Fixes #16846
Updates #19640
Updates #19001

[karalabe]

We need to use req.Header.Get here, otherwise the code won't ignore the case.

[fjl]

That's actually not true. net/http canonicalizes header keys, i.e. the keys in the map are assumed to be in the form returned by http.CanonicalHeaderKey.

[fjl]

Using req.Header.Get is not great because it doesn't distinguish between absent and empty headers.

[karalabe]

SGTM, can't say I'm confident nothing's borked, but I guess we'd find out soon enough if anything obvious went haywire.

[Deviad]

I have connection issues via websocket with web3j. Is it related to these changes?

[karalabe]

Possibly. Please provide more information and a repro.

[Deviad]

I started having problems with Infura (same websocket connection issue) and for this reason I gave the go-ethereum client a shot (in order to have more debugging info possibly).
Here is where I establish the connection:

• Connection - service
  Here is where I use this service:
• Controller

I know I had to use Websocket in the controller along with stomp probably, but before complicating things and get into an unexplored territory I wanted to be sure to be able to establish a connection and get some kind of result.

[Deviad]

EDIT
It finally works like this:

@Configuration
@Slf4j
public class InfuraSocketConfiguration {

    @Autowired
    private Web3jService web3jService;

    @SneakyThrows
    @Bean("webSocketSubscription")
    Flux<String> wsConnectNetty() {
//        Map<String, Object> config = Stream.of(
//                new AbstractMap.SimpleEntry<>("includeTransactions", true)
//        ).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

        Map<String, Object> map = Stream.of(
                new AbstractMap.SimpleEntry<>("id", 1),
                new AbstractMap.SimpleEntry<>("method", "eth_subscribe"),
                new AbstractMap.SimpleEntry<>("params", new Object[]{"newHeads"})
        ).collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));


        ObjectMapper objectMapper = new ObjectMapper();

        String json = objectMapper.writeValueAsString(map);

        Flux<String> input = Flux.generate(sink -> sink.next(json));

        ReactorNettyWebSocketClient client = new ReactorNettyWebSocketClient();
        EmitterProcessor<String> output = EmitterProcessor.create();

        Mono<Void> sessionMono = client.execute(URI.create(web3jService.getInfuraWsEndpoint()), session -> session.send(input.map(session::textMessage))
                .thenMany(session.receive().map(WebSocketMessage::getPayloadAsText).subscribeWith(output).then()).then());

        return output.doOnSubscribe(s -> {
            sessionMono.subscribe();
        }).doOnError(x -> log.info(x.getMessage()));
    }

    @Bean
    public ApplicationRunner applicationRunner(final @Qualifier("webSocketSubscription") Flux<String> ws) {
        return applicationArguments -> ws.subscribe(log::info);
    }

}

I would like to know why it doesn't work with Web3j though.
Basically now I have to create a class that is a wrapper over this lower level implementation with the operations that I need to perform.