New Relic Java Agent 6.2.0 is broken with SpringBoot 2.3.5 if there is no response body.

[northyg]

Filing this on behalf of Lawrence Ong regarding Support ticket #435916 and Community post.

Description

The NewRelic Java agent with SpringBoot 2.3.5 hangs if there is no response body. Tried this with HTTP OK response with zero body and HTTP NoContent response (where we cannot add any body at all).

Sample Code - Hangs with Agent 6.2.0, works with Agent 6.1.0

@Configuration
class Routes {
    @Bean
    fun route() = router {
        ("/api" and accept(MediaType.APPLICATION_JSON)).nest {
            GET("/test") {
                ServerResponse.ok().build()
            }
            GET("/test204") {
                ServerResponse.noContent().build()
            }
        }
    }
}

Expected Behavior

Java agent should work as it did in 6.1.0 and not hang.

Troubleshooting or NR Diag results

Logs and further details are in the support ticket linked below.

Steps to Reproduce

Sample application in support ticket.

Additional context

Internal support ticket with details: https://support.newrelic.com/tickets/435916
https://discuss.newrelic.com/t/new-relic-java-agent-6-2-0-is-broken-with-springboot/121470