Quarkus provide a convenient library to connect to an unreliable third party external system, and that is SmallRye Fault Tolerance. In this sample, we are trying to simulate a connection to https://reqres.in/ while creating a random IOException.
public Users getUser(Integer id) throws IOException {
Random random = new Random();
if(random.nextBoolean()) {
logger.debug("==== simulate random exception ====");
throw new IOException();
}
return userRestClient.get(id);
}Retries for at most 2times, and only when IOException occurs. And give a default response when failed for more than 2 times.
@GET
@Path("/user/{id}")
@Produces(MediaType.APPLICATION_JSON)
@Retry(maxRetries = 2, retryOn= IOException.class)
@Fallback(fallbackMethod = "getEmptyUser")
public Response getUser(@PathParam("id") Integer id) throws IOException {
Users users = userService.getUser(id);
return Response
.status(200)
.entity(users)
.build();
}$ mvn quarkus:dev
__ ____ __ _____ ___ __ ____ ______
--/ __ \/ / / / _ | / _ \/ //_/ / / / __/
-/ /_/ / /_/ / __ |/ , _/ ,< / /_/ /\ \
--\___\_\____/_/ |_/_/|_/_/|_|\____/___/
2023-05-03 15:30:53,510 INFO [io.quarkus] (Quarkus Main Thread) quarkus-retry 1.0-SNAPSHOT on JVM (powered by Quarkus 2.16.6.Final) started in 0.385s. Listening on: http://localhost:8080
2023-05-03 15:30:53,511 INFO [io.quarkus] (Quarkus Main Thread) Profile dev activated. Live Coding activated.
2023-05-03 15:30:53,511 INFO [io.quarkus] (Quarkus Main Thread) Installed features: [cdi, rest-client, resteasy, resteasy-jackson, smallrye-context-propagation, smallrye-fault-tolerance, vertx]
2023-05-03 15:30:53,511 INFO [io.qua.dep.dev.RuntimeUpdatesProcessor] (vert.x-worker-thread-0) Live reload total time: 0.550s
2023-05-03 15:30:56,199 DEBUG [com.edw.ser.UserService] (executor-thread-0) ==== simulate random exception ====
2023-05-03 15:30:56,200 DEBUG [com.edw.ser.UserService] (executor-thread-0) ==== simulate random exception ====
2023-05-03 15:30:56,200 DEBUG [com.edw.con.HelloWorldController_Subclass] (executor-thread-0) ==== giving default response ====
As we can see, there are 2 exceptions when we are accessing http://localhost:8080/user/2 but we still got success response because application is retrying it at most for 2 times until succeeded. And when failing, it will give a default response.