Question

我是RxJava的新手，并试图从链接执行多个Observable的并行执行示例： RxJava Fetching Observables In Parallel

虽然上面链接中提供的示例是并行执行observable，但是当我在forEach方法中添加了Thread.sleep（TIME_IN_MILLISECONDS）时，系统一次开始执行一个Observable。请帮助我理解为什么Thread.sleep正在停止并行执行Observables。

以下是导致多个observable同步执行的修改示例：

import rx.Observable;
import rx.Subscriber;
import rx.schedulers.Schedulers;

public class ParallelExecution {

    public static void main(String[] args) {
        System.out.println("------------ mergingAsync");
        mergingAsync();
    }

    private static void mergingAsync() {
        Observable.merge(getDataAsync(1), getDataAsync(2)).toBlocking()
        .forEach(x -> { try{Thread.sleep(4000);}catch(Exception ex){}; 
        System.out.println(x + " " + Thread.currentThread().getId());});
    }

    // artificial representations of IO work
    static Observable<Integer> getDataAsync(int i) {
        return getDataSync(i).subscribeOn(Schedulers.io());
    }

    static Observable<Integer> getDataSync(int i) {
        return Observable.create((Subscriber<? super Integer> s) -> {
            // simulate latency
            try {
                Thread.sleep(1000);
            } catch (Exception e) {
                e.printStackTrace();
            }
            s.onNext(i);
            s.onCompleted();
        });
    }
}

在上面的例子中，我们使用了observable的subscribeOn方法并提供了一个ThreadPool（Schedules.io）来执行，因此每个Observable的订阅将在不同的线程上进行。

Thread.sleep有可能在线程之间锁定任何共享对象，但我仍然不清楚它。请帮忙。

Answer 1

实际上，您的示例并行执行确实发生了，您只是错误地查看它，执行工作的位置和发出通知的位置之间存在差异。

如果您将日期的线程ID设置为SELECT [Project13].[PostStatusId] AS [PostStatusId], [Project13].[PostId] AS [PostId], [Project13].[Content] AS [Content], [Project13].[Image] AS [Image], [Project13].[Location] AS [Location], [Project13].[Video] AS [Video], [Project13].[CreatedDate] AS [CreatedDate], [Project13].[DateOfUpdate] AS [DateOfUpdate], [Project13].[Id] AS [Id], [Project13].[VisualId] AS [VisualId], [Project13].[ProfilePicUrl] AS [ProfilePicUrl], [Project13].[DateCreated] AS [DateCreated], [Project13].[Activated] AS [Activated], [Project13].[ActivationCode] AS [ActivationCode], [Project13].[RoleId] AS [RoleId], [Project13].[TeamId] AS [TeamId], [Project13].[RegisterToken] AS [RegisterToken], [Project13].[Email] AS [Email], [Project13].[EmailConfirmed] AS [EmailConfirmed], [Project13].[PasswordHash] AS [PasswordHash], [Project13].[SecurityStamp] AS [SecurityStamp], [Project13].[PhoneNumber] AS [PhoneNumber], [Project13].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project13].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project13].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project13].[LockoutEnabled] AS [LockoutEnabled], [Project13].[AccessFailedCount] AS [AccessFailedCount], [Project13].[UserName] AS [UserName], [Project13].[C1] AS [C1], [Project13].[C4] AS [C2], [Project13].[C5] AS [C3], [Project13].[C6] AS [C4], [Project13].[C2] AS [C5], [Project13].[CommentId] AS [CommentId], [Project13].[CommentText] AS [CommentText], [Project13].[PostId1] AS [PostId1], [Project13].[CommentDate] AS [CommentDate], [Project13].[UserId] AS [UserId], [Project13].[RowVersion] AS [RowVersion] FROM ( SELECT [Project11].[PostId] AS [PostId], [Project11].[Content] AS [Content], [Project11].[PostStatusId] AS [PostStatusId], [Project11].[Image] AS [Image], [Project11].[Location] AS [Location], [Project11].[Video] AS [Video], [Project11].[CreatedDate] AS [CreatedDate], [Project11].[DateOfUpdate] AS [DateOfUpdate], [Project11].[Id] AS [Id], [Project11].[VisualId] AS [VisualId], [Project11].[ProfilePicUrl] AS [ProfilePicUrl], [Project11].[DateCreated] AS [DateCreated], [Project11].[Activated] AS [Activated], [Project11].[ActivationCode] AS [ActivationCode], [Project11].[RoleId] AS [RoleId], [Project11].[TeamId] AS [TeamId], [Project11].[RegisterToken] AS [RegisterToken], [Project11].[Email] AS [Email], [Project11].[EmailConfirmed] AS [EmailConfirmed], [Project11].[PasswordHash] AS [PasswordHash], [Project11].[SecurityStamp] AS [SecurityStamp], [Project11].[PhoneNumber] AS [PhoneNumber], [Project11].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project11].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project11].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project11].[LockoutEnabled] AS [LockoutEnabled], [Project11].[AccessFailedCount] AS [AccessFailedCount], [Project11].[UserName] AS [UserName], [Project11].[C1] AS [C1], [Limit1].[CommentId] AS [CommentId], [Limit1].[CommentText] AS [CommentText], [Limit1].[PostId] AS [PostId1], [Limit1].[CommentDate] AS [CommentDate], [Limit1].[UserId] AS [UserId], [Limit1].[RowVersion] AS [RowVersion], 1 AS [C2], [Project11].[C2] AS [C3], [Project11].[C3] AS [C4], [Project11].[C4] AS [C5], [Project11].[C5] AS [C6] FROM (SELECT [Project9].[PostId] AS [PostId], [Project9].[Content] AS [Content], [Project9].[PostStatusId] AS [PostStatusId], [Project9].[Image] AS [Image], [Project9].[Location] AS [Location], [Project9].[Video] AS [Video], [Project9].[CreatedDate] AS [CreatedDate], [Project9].[DateOfUpdate] AS [DateOfUpdate], [Project9].[Id] AS [Id], [Project9].[VisualId] AS [VisualId], [Project9].[ProfilePicUrl] AS [ProfilePicUrl], [Project9].[DateCreated] AS [DateCreated], [Project9].[Activated] AS [Activated], [Project9].[ActivationCode] AS [ActivationCode], [Project9].[RoleId] AS [RoleId], [Project9].[TeamId] AS [TeamId], [Project9].[RegisterToken] AS [RegisterToken], [Project9].[Email] AS [Email], [Project9].[EmailConfirmed] AS [EmailConfirmed], [Project9].[PasswordHash] AS [PasswordHash], [Project9].[SecurityStamp] AS [SecurityStamp], [Project9].[PhoneNumber] AS [PhoneNumber], [Project9].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project9].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project9].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project9].[LockoutEnabled] AS [LockoutEnabled], [Project9].[AccessFailedCount] AS [AccessFailedCount], [Project9].[UserName] AS [UserName], CASE WHEN ( EXISTS (SELECT 1 AS [C1] FROM [dbo].[Likes] AS [Extent10] WHERE ([Project9].[PostId] = [Extent10].[PostId]) AND (([Extent10].[UserId] = @p__linq__4) OR (([Extent10].[UserId] IS NULL) AND (@p__linq__4 IS NULL))) )) THEN cast(1 as bit) ELSE cast(0 as bit) END AS [C1], [Project9].[C1] AS [C2], [Project9].[C2] AS [C3], [Project9].[C3] AS [C4], [Project9].[C4] AS [C5] FROM ( SELECT [Project8].[PostId] AS [PostId], [Project8].[Content] AS [Content], [Project8].[PostStatusId] AS [PostStatusId], [Project8].[Image] AS [Image], [Project8].[Location] AS [Location], [Project8].[Video] AS [Video], [Project8].[CreatedDate] AS [CreatedDate], [Project8].[DateOfUpdate] AS [DateOfUpdate], [Project8].[Id] AS [Id], [Project8].[VisualId] AS [VisualId], [Project8].[ProfilePicUrl] AS [ProfilePicUrl], [Project8].[DateCreated] AS [DateCreated], [Project8].[Activated] AS [Activated], [Project8].[ActivationCode] AS [ActivationCode], [Project8].[RoleId] AS [RoleId], [Project8].[TeamId] AS [TeamId], [Project8].[RegisterToken] AS [RegisterToken], [Project8].[Email] AS [Email], [Project8].[EmailConfirmed] AS [EmailConfirmed], [Project8].[PasswordHash] AS [PasswordHash], [Project8].[SecurityStamp] AS [SecurityStamp], [Project8].[PhoneNumber] AS [PhoneNumber], [Project8].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project8].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project8].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project8].[LockoutEnabled] AS [LockoutEnabled], [Project8].[AccessFailedCount] AS [AccessFailedCount], [Project8].[UserName] AS [UserName], [Project8].[C1] AS [C1], [Project8].[C2] AS [C2], [Project8].[C3] AS [C3], (SELECT COUNT(1) AS [A1] FROM [dbo].[SharePosts] AS [Extent9] WHERE [Project8].[PostId] = [Extent9].[PostId]) AS [C4] FROM ( SELECT [Project7].[PostId] AS [PostId], [Project7].[Content] AS [Content], [Project7].[PostStatusId] AS [PostStatusId], [Project7].[Image] AS [Image], [Project7].[Location] AS [Location], [Project7].[Video] AS [Video], [Project7].[CreatedDate] AS [CreatedDate], [Project7].[DateOfUpdate] AS [DateOfUpdate], [Project7].[Id] AS [Id], [Project7].[VisualId] AS [VisualId], [Project7].[ProfilePicUrl] AS [ProfilePicUrl], [Project7].[DateCreated] AS [DateCreated], [Project7].[Activated] AS [Activated], [Project7].[ActivationCode] AS [ActivationCode], [Project7].[RoleId] AS [RoleId], [Project7].[TeamId] AS [TeamId], [Project7].[RegisterToken] AS [RegisterToken], [Project7].[Email] AS [Email], [Project7].[EmailConfirmed] AS [EmailConfirmed], [Project7].[PasswordHash] AS [PasswordHash], [Project7].[SecurityStamp] AS [SecurityStamp], [Project7].[PhoneNumber] AS [PhoneNumber], [Project7].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project7].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project7].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project7].[LockoutEnabled] AS [LockoutEnabled], [Project7].[AccessFailedCount] AS [AccessFailedCount], [Project7].[UserName] AS [UserName], [Project7].[C1] AS [C1], [Project7].[C2] AS [C2], (SELECT COUNT(1) AS [A1] FROM [dbo].[Comments] AS [Extent8] WHERE [Project7].[PostId] = [Extent8].[PostId]) AS [C3] FROM ( SELECT [Project6].[PostId] AS [PostId], [Project6].[Content] AS [Content], [Project6].[PostStatusId] AS [PostStatusId], [Project6].[Image] AS [Image], [Project6].[Location] AS [Location], [Project6].[Video] AS [Video], [Project6].[CreatedDate] AS [CreatedDate], [Project6].[DateOfUpdate] AS [DateOfUpdate], [Project6].[Id] AS [Id], [Project6].[VisualId] AS [VisualId], [Project6].[ProfilePicUrl] AS [ProfilePicUrl], [Project6].[DateCreated] AS [DateCreated], [Project6].[Activated] AS [Activated], [Project6].[ActivationCode] AS [ActivationCode], [Project6].[RoleId] AS [RoleId], [Project6].[TeamId] AS [TeamId], [Project6].[RegisterToken] AS [RegisterToken], [Project6].[Email] AS [Email], [Project6].[EmailConfirmed] AS [EmailConfirmed], [Project6].[PasswordHash] AS [PasswordHash], [Project6].[SecurityStamp] AS [SecurityStamp], [Project6].[PhoneNumber] AS [PhoneNumber], [Project6].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Project6].[TwoFactorEnabled] AS [TwoFactorEnabled], [Project6].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Project6].[LockoutEnabled] AS [LockoutEnabled], [Project6].[AccessFailedCount] AS [AccessFailedCount], [Project6].[UserName] AS [UserName], [Project6].[C1] AS [C1], (SELECT COUNT(1) AS [A1] FROM [dbo].[Likes] AS [Extent7] WHERE [Project6].[PostId] = [Extent7].[PostId]) AS [C2] FROM ( SELECT [Project5].[PostId] AS [PostId], [Project5].[Content] AS [Content], [Project5].[PostStatusId] AS [PostStatusId], [Project5].[Image] AS [Image], [Project5].[Location] AS [Location], [Project5].[Video] AS [Video], [Project5].[CreatedDate] AS [CreatedDate], [Project5].[DateOfUpdate] AS [DateOfUpdate], [Extent6].[Id] AS [Id], [Extent6].[VisualId] AS [VisualId], [Extent6].[ProfilePicUrl] AS [ProfilePicUrl], [Extent6].[DateCreated] AS [DateCreated], [Extent6].[Activated] AS [Activated], [Extent6].[ActivationCode] AS [ActivationCode], [Extent6].[RoleId] AS [RoleId], [Extent6].[TeamId] AS [TeamId], [Extent6].[RegisterToken] AS [RegisterToken], [Extent6].[Email] AS [Email], [Extent6].[EmailConfirmed] AS [EmailConfirmed], [Extent6].[PasswordHash] AS [PasswordHash], [Extent6].[SecurityStamp] AS [SecurityStamp], [Extent6].[PhoneNumber] AS [PhoneNumber], [Extent6].[PhoneNumberConfirmed] AS [PhoneNumberConfirmed], [Extent6].[TwoFactorEnabled] AS [TwoFactorEnabled], [Extent6].[LockoutEndDateUtc] AS [LockoutEndDateUtc], [Extent6].[LockoutEnabled] AS [LockoutEnabled], [Extent6].[AccessFailedCount] AS [AccessFailedCount], [Extent6].[UserName] AS [UserName], [Project5].[C1] AS [C1] FROM (SELECT [Extent1].[PostId] AS [PostId], [Extent1].[Content] AS [Content], [Extent1].[PostStatusId] AS [PostStatusId], [Extent1].[UserId] AS [UserId], [Extent1].[Image] AS [Image], [Extent1].[Location] AS [Location], [Extent1].[Video] AS [Video], [Extent1].[CreatedDate] AS [CreatedDate], [Extent1].[DateOfUpdate] AS [DateOfUpdate], (SELECT COUNT(1) AS [A1] FROM [dbo].[Likes] AS [Extent5] WHERE [Extent1].[PostId] = [Extent5].[PostId]) AS [C1] FROM [dbo].[Posts] AS [Extent1] WHERE ( NOT (([Extent1].[UserId] = @p__linq__0) AND (0 = (CASE WHEN (@p__linq__0 IS NULL) THEN cast(1 as bit) ELSE cast(0 as bit) END)))) AND ([Extent1].[DateOfUpdate] > @p__linq__1) AND ( EXISTS (SELECT 1 AS [C1] FROM ( SELECT [Extent2].[UserId] AS [UserId] FROM [dbo].[Likes] AS [Extent2] WHERE [Extent1].[PostId] = [Extent2].[PostId] ) AS [Project1] WHERE EXISTS (SELECT 1 AS [C1] FROM [dbo].[FollowUsers] AS [Extent3] WHERE ([Extent3].[FollowFromUserId] = @p__linq__2) AND ([Extent3].[FollowToUserId] = [Project1].[UserId]) ) )) AND (1 = [Extent1].[PostStatusId]) AND (0 = [Extent1].[PostType]) AND ( NOT EXISTS (SELECT 1 AS [C1] FROM [dbo].[BlockedUsers] AS [Extent4] WHERE ([Extent4].[BlockerId] = @p__linq__3) AND (([Extent4].[BlockedId] = [Extent1].[UserId]) OR (CASE WHEN ([Extent4].[BlockedId] <> [Extent1].[UserId]) THEN cast(1 as bit) WHEN ([Extent4].[BlockedId] = [Extent1].[UserId]) THEN cast(0 as bit) END IS NULL)) )) ) AS [Project5] LEFT OUTER JOIN [dbo].[AspNetUsers] AS [Extent6] ON [Project5].[UserId] = [Extent6].[Id] ) AS [Project6] ) AS [Project7] ) AS [Project8] ) AS [Project9] ) AS [Project11] OUTER APPLY (SELECT TOP (1) [Project12].[CommentId] AS [CommentId], [Project12].[CommentText] AS [CommentText], [Project12].[PostId] AS [PostId], [Project12].[CommentDate] AS [CommentDate], [Project12].[UserId] AS [UserId], [Project12].[RowVersion] AS [RowVersion] FROM ( SELECT [Extent11].[CommentId] AS [CommentId], [Extent11].[CommentText] AS [CommentText], [Extent11].[PostId] AS [PostId], [Extent11].[CommentDate] AS [CommentDate], [Extent11].[UserId] AS [UserId], [Extent11].[RowVersion] AS [RowVersion] FROM [dbo].[Comments] AS [Extent11] WHERE [Project11].[PostId] = [Extent11].[PostId] ) AS [Project12] ORDER BY [Project12].[CommentDate] DESC ) AS [Limit1] ) AS [Project13] ORDER BY [Project13].[C3] DESC, [Project13].[PostId] ASC, [Project13].[Id] ASC, [Project13].[C2] ASC，您会注意到每个Observable同时在不同的线程上执行。但通知是连续发生的。这种行为与Observable合同的一部分一样，是observables必须连续向观察者发出通知（不是并行）。

为什么多个RXJava Observable没有发生并行执行？

1 个答案: