IllegalStateException thrown when reading the vert.x http client response body - vert.x

Question

I am getting the following error when I attempt to read the body from the http client response object. I don't get the exception all the time so I guess it's a threading issue related to the CompletableFuture. Any idea of what I am doing wrong? I use vert.x 3.8.1
java.lang.IllegalStateException
at io.vertx.core.http.impl.HttpClientResponseImpl.checkEnded(HttpClientResponseImpl.java:134)
at io.vertx.core.http.impl.HttpClientResponseImpl.endHandler(HttpClientResponseImpl.java:153)
at io.vertx.core.http.impl.HttpClientResponseImpl.bodyHandler(HttpClientResponseImpl.java:193)
at com.diagnostics.Response.body(Web.kt:116)
at com.diagnostics.Response.bodyNow(Web.kt:111)
at com.diagnostics.Response.bodyNow$default(Web.kt:110)
at com.diagnostics.Main.postVerificationTest(Main.kt:73)
at com.diagnostics.Main.main(Main.kt:52)
at com.diagnostics.Main.main(Main.kt)
Code that throws the exception:
val response = client.get(requestUri = "/api/info").get(3, TimeUnit.SECONDS)
val expectedStatus = 200
assertConditionOrExit(pvtLog, response.status == expectedStatus, "response status is ${response.status} expecting $expectedStatus")
val body = response.bodyNow()
assertConditionOrExit(pvtLog, body.isNotEmpty(), "body is empty expecting a non empty value")
The http client response object is created from the following code:
private fun request(
method: HttpMethod,
port: Int,
host: String,
requestUri: String
): CompletableFuture<Response> {
val future = CompletableFuture<Response>()
httpClient.request(method, port, host, requestUri)
.exceptionHandler { future.completeExceptionally(it) }
.handler { resp -> future.complete(Response(resp)) }
.end()
return future
}
And the body is retrieved...
fun bodyNow(timeout: Long = 10, unit: TimeUnit = SECONDS): String {
return body().get(30000, SECONDS)
}
fun body(): CompletableFuture<String> {
val future = CompletableFuture<String>()
resp.bodyHandler { buff -> future.complete(buff.toString())}
return future
}

Answer 1

The body() function sets a bodyHandler after the HttpClientRequest handler has been invoked in the request() method.
So there is a chance that, while your main thread proceeds, the eventloop receives content and drops it. If content is small, the request could even end before the bodyHandler is set.
This is why you only see the exception from time to time.
If you want to set the bodyHandler later, you must pause the HttpClientResponse:
httpClient.request(method, port, host, requestUri)
.exceptionHandler { future.completeExceptionally(it) }
.handler { resp ->
resp.pause() // Pause the response
future.complete(Response(resp))
}
.end()
Then resume it after setting the bodyHandler:
resp.bodyHandler { buff -> future.complete(buff.toString())}
resp.resume()