Using third party http client on Armeria - armeria

Question

I'm discovering Armeria framework and I want to consume a REST service.
Using the Armeria WebClient:
WebClient webClient = WebClient.of("http://localhost:9090");
RequestHeaders getJson = RequestHeaders.of(HttpMethod.GET, "/some-service",
HttpHeaderNames.CONTENT_TYPE, "application/json", "SomeHeader", "armeriaTest");
return webClient.execute(getJson).aggregate().thenApply(resp->{
if(HttpStatus.OK.equals(resp.status())) {
return parseBody(resp.contentUtf8());
}else if(HttpStatus.BAD_REQUEST.equals(resp.status())){
throw new IllegalStateException("not exists");
}
throw new RuntimeException("Error");
});
This code returns a CompletionStage that will be resolved asynchronously, because if I do a join() or get() right here causes an "java.lang.IllegalStateException: Blocking event loop, don't do this."
My question is: What if I want to use a third party httpclient library (like Apache HttpClient) instead the Web?
The client call should be wrapped in a Future too?
How should I manage the client requests to fit in the framework approach and avoid the "Blocking event loop" issue?
Thanks to all!

Answer 1

Yes. You should never perform any blocking operations when your code is running in an event loop thread. You can perform a blocking operation by submitting it to other thread pool dedicated to handling blocking operations.
If you are using Armeria on the server side, you can get one via ServiceRequestContext.blockingTaskExecutor():
Server server = Server
.builder()
.service("/", (ctx, req) -> {
CompletableFuture<String> f1 = CompletableFuture.supplyAsync(() -> {
// Perform some blocking operations that return a string.
}, ctx.blockingTaskExecutor());
CompletableFuture<String> f2 = f1.thenApply(result -> {
// Transform the result into an HttpResponse.
return HttpResponse.of("Result: %s", result);
});
return HttpResponse.from(f2);
})
.build();
If you are not using Armeria on the server side, you can use other Executor provided by your platform, or you can even create a new ThreadPoolExecutor dedicated to handling blocking operations.