When a websocket request is initiated, the response header type is ReadOnlyHttpHeaders

[bojiangzhou]

Dependent version

• spring-cloud-dependencies: 2020.0.3
• spring-boot-starter-parent: 2.4.6

1. application.yml

Add one of SetResponseHeader or DedupeResponseHeader under "default-filters"

spring:
  cloud:
    gateway:
      default-filters:
        - SetResponseHeader=Access-Control-Expose-Headers, Content-Disposition
        - DedupeResponseHeader=Access-Control-Allow-Credentials Access-Control-Allow-Origin Vary, RETAIN_UNIQUE

2. a websocket request

ws://localhost:8080/hpfm/websocket?access_token=0d261199-b39e-4424-82f9-9055b92119fd

3. exception

2021-06-04 14:41:48.161 ERROR 20152 --- [ctor-http-nio-7] o.s.w.s.adapter.HttpWebHandlerAdapter    : [ee2db0e7-1] Error [java.lang.UnsupportedOperationException] for HTTP GET "/hpfm/websocket?access_token=0d261199-b39e-4424-82f9-9055b92119fd", but ServerHttpResponse already committed (200 OK)
2021-06-04 14:41:48.164 ERROR 20152 --- [ctor-http-nio-7] r.n.http.server.HttpServerOperations     : [id:ee2db0e7-1, L:/10.215.0.89:8080 - R:bojiangzhou/10.215.0.89:53965] Error finishing response. Closing connection

java.lang.UnsupportedOperationException: null
    at org.springframework.http.ReadOnlyHttpHeaders.put(ReadOnlyHttpHeaders.java:126) ~[spring-web-5.3.7.jar:5.3.7]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Error has been observed at the following site(s):
    |_ checkpoint ⇢ org.springframework.boot.actuate.web.trace.reactive.HttpTraceWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.springframework.cloud.gateway.filter.WeightCalculatorWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.hzero.gateway.filter.GateWayHelperFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.springframework.boot.actuate.metrics.web.reactive.server.MetricsWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.springframework.web.cors.reactive.CorsWebFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ org.hzero.gateway.filter.IpCheckedFilter [DefaultWebFilterChain]
    |_ checkpoint ⇢ HTTP GET "/hpfm/websocket?access_token=0d261199-b39e-4424-82f9-9055b92119fd" [ExceptionHandlingWebHandler]
Stack trace:
        at org.springframework.http.ReadOnlyHttpHeaders.put(ReadOnlyHttpHeaders.java:126) ~[spring-web-5.3.7.jar:5.3.7]
        at org.springframework.cloud.gateway.filter.factory.DedupeResponseHeaderGatewayFilterFactory.dedupe(DedupeResponseHeaderGatewayFilterFactory.java:147) ~[spring-cloud-gateway-server-3.0.3.jar:3.0.3]
        at org.springframework.cloud.gateway.filter.factory.DedupeResponseHeaderGatewayFilterFactory.dedupe(DedupeResponseHeaderGatewayFilterFactory.java:130) ~[spring-cloud-gateway-server-3.0.3.jar:3.0.3]
        at org.springframework.cloud.gateway.filter.factory.DedupeResponseHeaderGatewayFilterFactory$1.lambda$filter$0(DedupeResponseHeaderGatewayFilterFactory.java:93) ~[spring-cloud-gateway-server-3.0.3.jar:3.0.3]
        at reactor.core.publisher.MonoRunnable.call(MonoRunnable.java:73) ~[reactor-core-3.4.6.jar:3.4.6]
        at reactor.core.publisher.MonoRunnable.call(MonoRunnable.java:32) ~[reactor-core-3.4.6.jar:3.4.6]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.subscribeNext(MonoIgnoreThen.java:224) [reactor-core-3.4.6.jar:3.4.6]
..............

4. the reason

When the websocket request is completed, the request will be completed ahead of time.

Then the status of ServerHttpResponse will be changed to COMMITTED.

When finally entering DedupeResponseHeaderGatewayFilterFactory to get HttpHeaders, since the status of ServerHttpResponse is COMMITTED, it returns ReadOnlyHttpHeaders.

Is this a bug, or how to solve it ?

[fengzheng0571]

I have the same problem

[ChampionRoy]

same problem here

[spencergibb]

There's nothing at that point that the DedupeResponseHeaderGatewayFilterFactory or any that modify response headers can do. Maybe log a warning and move on?

[MonDeveloper]

Actually I do not understand your point @spencergibb, the question seems reasonable to me. I had the same problem and I solved putting the responseHeaders' update within the exchange.getResponse().beforeCommit(...); instead of the classic chain.filter(exchange).then(...);

I'm not sure I haven't broken any "very well hidden secret rule of reactor usage in spring" but it works.

Could you please tell me if I done it right?