Package io.airlift.concurrent

Class AsyncSemaphore<T,R>

java.lang.Object
io.airlift.concurrent.AsyncSemaphore<T,R>
@ThreadSafe public class AsyncSemaphore<T,R> extends Object
Guarantees that no more than maxPermits of tasks will be run concurrently. The class will rely on the ListenableFuture returned by the submitter function to determine when a task has been completed. The submitter function NEEDS to be thread-safe and is recommended to do the bulk of its work asynchronously.

  • Constructor Summary

    Constructors
    Constructor
    Description
    AsyncSemaphore(int maxPermits, Executor submitExecutor, Function<T,com.google.common.util.concurrent.ListenableFuture<R>> submitter)
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static <T, R> com.google.common.util.concurrent.ListenableFuture<List<R>>
    processAll(List<T> tasks, Function<T,com.google.common.util.concurrent.ListenableFuture<R>> submitter, int maxConcurrency, Executor submitExecutor)
    Process a list of tasks as a single unit (similar to Futures.allAsList(ListenableFuture[])) with limiting the number of tasks running in parallel.
    com.google.common.util.concurrent.ListenableFuture<R>
    submit(T task)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Constructor Details

    • AsyncSemaphore

      public AsyncSemaphore(int maxPermits, Executor submitExecutor, Function<T,com.google.common.util.concurrent.ListenableFuture<R>> submitter)

  • Method Details

    • processAll

      public static <T, R> com.google.common.util.concurrent.ListenableFuture<List<R>> processAll(List<T> tasks, Function<T,com.google.common.util.concurrent.ListenableFuture<R>> submitter, int maxConcurrency, Executor submitExecutor)
      Process a list of tasks as a single unit (similar to Futures.allAsList(ListenableFuture[])) with limiting the number of tasks running in parallel.

      This method may be useful for limiting the number of concurrent requests sent to a remote server when trying to load multiple related entities concurrently:

      For example: 

      
 List<Integer> userIds = Lists.of(1, 2, 3);
 ListenableFuture<List<UserInfo>> future = processAll(ids, client::getUserInfoById, 2, executor);
 List<UserInfo> userInfos = future.get(...);
      Parameters:
      tasks - tasks to process
      submitter - task submitter
      maxConcurrency - maximum number of tasks allowed to run in parallel
      submitExecutor - task submission executor
      Returns:
      ListenableFuture containing a list of values returned by the tasks. The order of elements in the list matches the order of tasks. If the result future is cancelled all the remaining tasks are cancelled (submitted tasks will be cancelled, pending tasks will not be submitted). If any of the submitted tasks fails or are cancelled, the result future is too. If any of the submitted tasks fails or are cancelled, the remaining tasks are cancelled.

    • submit

      public com.google.common.util.concurrent.ListenableFuture<R> submit(T task)