首页 \ 问答 \ App Engine Channel API的线程安全性/原子性(Thread safety / atomicity of App Engine Channel API)

App Engine Channel API的线程安全性/原子性(Thread safety / atomicity of App Engine Channel API)

 当我尝试使用Google App Engine的Channel API发送消息但是来自两个或更多goroutine和/或任务队列时会发生什么？ 例如 
 

go channel.Send(context, clientID, "Hello")
go channel.Send(context, clientID, "World")

 

 据我所知，在GAE Go中，所有goroutine都被复用到一个线程上。 但是，这仍然允许在I / O期间进行抢占，并且可能通道发送符合I / O的条件。 
 

 GAE开发服务器似乎序列化所有请求，因此我没有看到任何通道发送重叠。 生产服务器似乎允许一些请求并发，但是通道发送看起来是原子的，或者至少可以安全地从不同的线程/ goroutine调用。 

What happens when I try to send a message with Google App Engine's Channel API but from two or more goroutines and/or task queues? e.g.
 

go channel.Send(context, clientID, "Hello")
go channel.Send(context, clientID, "World")

 

I understand that in GAE Go, all goroutines are multiplexed onto a single thread. However this still allows for pre-emption during I/O, and presumably channel sends qualify as I/O.
 

The GAE dev server seems to serialize all requests so I don't see any channel sends overlapping. The production server seems to allow some request concurrency but the channel sends appear atomic or at least safe to call from different threads/goroutines.

原文：https://stackoverflow.com/questions/18674252
更新时间：2023-11-30 06:11

最满意答案

 正如@pjumble评论所述，您只是定义变量。 获取代码并添加额外的hello_world语句： 
 

$font-size: 16px;
$em: $font-size / 1em;

$column: 48px;
$gutter: 24px;

 $cols1: ( 1 * ($column + $gutter) - $gutter) / $em;
 $cols2: ( 2 * ($column + $gutter) - $gutter) / $em;
 $cols3: ( 3 * ($column + $gutter) - $gutter) / $em;
 $cols4: ( 4 * ($column + $gutter) - $gutter) / $em;
 $cols5: ( 5 * ($column + $gutter) - $gutter) / $em;
 $cols6: ( 6 * ($column + $gutter) - $gutter) / $em;
 $cols7: ( 7 * ($column + $gutter) - $gutter) / $em;
 $cols8: ( 8 * ($column + $gutter) - $gutter) / $em;
 $cols9: ( 9 * ($column + $gutter) - $gutter) / $em;
$cols10: (10 * ($column + $gutter) - $gutter) / $em;
$cols11: (11 * ($column + $gutter) - $gutter) / $em;
$cols12: (12 * ($column + $gutter) - $gutter) / $em;
$cols13: (13 * ($column + $gutter) - $gutter) / $em;
$cols14: (14 * ($column + $gutter) - $gutter) / $em;
$cols15: (15 * ($column + $gutter) - $gutter) / $em;
$cols16: (16 * ($column + $gutter) - $gutter) / $em;

.hello_world{ width: $column }

 

 命令sass grid.scss grid.css生成： 
 

.hello_world {
  width: 48px; }


As stated by @pjumble comment, you are only defining variables. Taking your code and adding the additional hello_world statement:
 

$font-size: 16px;
$em: $font-size / 1em;

$column: 48px;
$gutter: 24px;

 $cols1: ( 1 * ($column + $gutter) - $gutter) / $em;
 $cols2: ( 2 * ($column + $gutter) - $gutter) / $em;
 $cols3: ( 3 * ($column + $gutter) - $gutter) / $em;
 $cols4: ( 4 * ($column + $gutter) - $gutter) / $em;
 $cols5: ( 5 * ($column + $gutter) - $gutter) / $em;
 $cols6: ( 6 * ($column + $gutter) - $gutter) / $em;
 $cols7: ( 7 * ($column + $gutter) - $gutter) / $em;
 $cols8: ( 8 * ($column + $gutter) - $gutter) / $em;
 $cols9: ( 9 * ($column + $gutter) - $gutter) / $em;
$cols10: (10 * ($column + $gutter) - $gutter) / $em;
$cols11: (11 * ($column + $gutter) - $gutter) / $em;
$cols12: (12 * ($column + $gutter) - $gutter) / $em;
$cols13: (13 * ($column + $gutter) - $gutter) / $em;
$cols14: (14 * ($column + $gutter) - $gutter) / $em;
$cols15: (15 * ($column + $gutter) - $gutter) / $em;
$cols16: (16 * ($column + $gutter) - $gutter) / $em;

.hello_world{ width: $column }

 

The command sass grid.scss grid.css produces:
 

.hello_world {
  width: 48px; }

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