How to implement a nonblocking future processor in Java in order to retrieve processed results later-CodePudding

I am using an external library that has the code from below. I am sending a lot of commands and am interesed in the result for statistics to check how many calls failed and how many succeeded

public Future<CommandResult> sendCommand(Command command) {
    return command.execute();
}
CommandResult can be success or failure

However, if I use client.sendCommand(command).get(); then, I am waiting for the result synchronously, meanwhile the app is being blocked.

I would like to check only later (after 30 seconds which calls succeded and which failed). I am guaranteed to get an answer in 10 seconds. The problem is that the app waits for the computation to complete, and then retrieves its result.

CodePudding user response：

Future is a legacy java feature which does not allow for reactive non blocking functionalities. The CompletableFuture is a later enhancement in Java in order to allow such reactive non blocking functionalities.

You can based on

CodePudding user response：

I would like to check only later (after 30 seconds which calls succeeded and which failed). I am guaranteed to get an answer in 10 seconds. The problem is that the app waits for the computation to complete, and then retrieves its result.

I would use an ExecutorCompletionService which you can poll anytime to see if you have results. The poll is non-blocking.

// create your thread pool using fixed or other pool
Executor<Result> threadPool = Executors.newFixedThreadPool(5);
// wrap the Executor in a CompletionService
CompletionService<Result> completionService = new ExecutorCompletionService<>(e);
// submit jobs to the pool through the ExecutorCompletionService
for (Job job : jobs) {
   completionService.submit(job);
}
// after we have submitted all of the jobs we can shutdown the Executor
// the jobs submitted will continue to run
threadPool.shutdown();
...
// some point later you can do
int jobsRunning = jobs.size();
for (int jobsRunning = jobs.size(); jobsRunning > 0; ) {
   // do some processing ...
   // are any results available?
   Result result = completionService.poll();
   if (result != null) {
      // process a result if available
      jobsRunning--;
   }
}

Note that you will need to track how many jobs you submitted to the CompletionService.