【Software Testing】Dryrun

Dry-run

A dry run (or a practice run) is a testing process where the effects of a possible failure are intentionally mitigated. For example, an aerospace company may conduct a “dry run” test of a jet’s new pilot ejection seat while the jet is parked on the ground, rather than while it is in flight.

The usage of “dry run” in acceptance procedures (for example in the so-called FAT = factory acceptance testing) is meant as following: the factory — which is a subcontractor — must perform a complete test of the system it has to deliver before the actual acceptance by customer.

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Posted by Wei on 2021-10-07, Last Modified on 2025-08-11

【Golang】Reactor in Golang

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Posted by Wei on 2021-10-03, Last Modified on 2025-08-11

【Golang】关键字 - select

Overall

The select statement provides another way to handle multiple channels.

It’s like a switch, but each case is a communication:

All channels are evaluated.
Selection blocks until one communication can proceed, which then does.
If multiple can proceed, select chooses pseudo-randomly.
A default clause, if present, executes immediately if no channel is ready.

    select {
    case v1 := <-c1:
        fmt.Printf("received %v from c1\n", v1)
    case v2 := <-c2:
        fmt.Printf("received %v from c2\n", v1)
    case c3 <- 23:
        fmt.Printf("sent %v to c3\n", 23)
    default:
        fmt.Printf("no one was ready to communicate\n")
    }

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Posted by Wei on 2021-10-03, Last Modified on 2025-08-11

【Golang】设计模式 - Pipeline

Pipeline Pattern

Pipeline这种技术在可以很容易的把代码按单一职责的原则拆分成多个高内聚低耦合的小模块，然后可以很方便地（通过channel）拼装起来去完成比较复杂的功能。

Informally, a pipeline is a series of stages connected by channels, where each stage is a group of goroutines running the same function. In each stage, the goroutines

receive values from upstream via inbound channels
perform some function on that data, usually producing new values
send values downstream via outbound channels

Each stage has any number of inbound and outbound channels, except the first and last stages, which have only outbound or inbound channels, respectively. The first stage is sometimes called the source or producer; the last stage, the sink or consumer.

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Posted by Wei on 2021-10-03, Last Modified on 2025-08-11

【Golang】设计模式 - Generator

Generator Pattern

Channels are first-class values, just like strings or integers.

package main

import (
	"fmt"
	"math/rand"
	"time"
)

func boring(msg string) <-chan string { // Returns receive-only channel of strings.
	c := make(chan string)
	go func() { // We launch the goroutine from inside the function.
		for i := 0; ; i++ {
			c <- fmt.Sprintf("%s %d", msg, i)
			time.Sleep(time.Duration(rand.Intn(1e3)) * time.Millisecond)
		}
	}()
	return c // Return the channel to the caller.
}

func main() {
	c := boring("boring!") // Function returning a channel.
	for i := 0; i < 5; i++ {
		fmt.Printf("You say: %q\n", <-c)
	}
	fmt.Println("You're boring; I'm leaving.")
}

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Posted by Wei on 2021-10-03, Last Modified on 2025-08-11

【Performance】Concurrency vs Parallelism

Concurrency is not parallelism, although it enables parallelism.

If you have only one processor, your program can still be concurrent but it cannot be parallel.

On the other hand, a well-written concurrent program might run efficiently in parallel on a multiprocessor. That property could be important…

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Posted by Wei on 2021-10-03, Last Modified on 2025-08-11

【Golang】使用 epoll

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Posted by Wei on 2021-09-30, Last Modified on 2025-08-11

【Golang】源码 - netpoll

Go netpoll

Go netpoll 通过在底层对 epoll/kqueue/iocp 的封装，从而实现了使用同步编程模式达到异步执行的效果。总结来说，所有的网络操作都以网络描述符 netFD 为中心实现。netFD 与底层 PollDesc 结构绑定，当在一个 netFD 上读写遇到 EAGAIN 错误时，就将当前 goroutine 存储到这个 netFD 对应的 PollDesc 中，同时调用 gopark 把当前 goroutine 给 park 住，直到这个 netFD 上再次发生读写事件，才将此 goroutine 给 ready 激活重新运行。显然，在底层通知 goroutine 再次发生读写等事件的方式就是 epoll/kqueue/iocp 等事件驱动机制。

net.Listen("tcp", ":8888") 方法返回了一个 TCPListener，它是一个实现了 net.Listener 接口的 struct。

通过 listener.Accept() 接收的新连接 TCPConn 则是一个实现了 net.Conn 接口的 struct，它内嵌了 net.conn struct。

不管是 Listener 的 Accept 还是 Conn 的 Read/Write 方法，都是基于一个 netFD 的数据结构的操作
netFD 是一个网络描述符，类似于 Linux 的文件描述符的概念，netFD 中包含一个 poll.FD 数据结构
而 poll.FD 中包含两个重要的数据结构 Sysfd 和 pollDesc，前者是真正的系统文件描述符，后者对是底层事件驱动的封装，所有的读写超时等操作都是通过调用后者的对应方法实现的

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Posted by Wei on 2021-09-30, Last Modified on 2025-08-11

【Operating System】memory

User Space And Kernel Space

现在操作系统都是采用虚拟存储器，那么对 32 位操作系统而言，它的寻址空间（虚拟存储空间）为 4G（2 的 32 次方）。操作系统的核心是内核，独立于普通的应用程序，可以访问受保护的内存空间，也有访问底层硬件设备的所有权限。为了保证用户进程不能直接操作内核（kernel），保证内核的安全，操心系统将虚拟空间划分为两部分，一部分为内核空间，一部分为用户空间。针对 Linux 操作系统而言，将最高的 1G 字节（从虚拟地址 0xC0000000 到 0xFFFFFFFF），供内核使用，称为内核空间，而将较低的 3G 字节（从虚拟地址 0x00000000 到 0xBFFFFFFF），供各个进程使用，称为用户空间。

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Posted by Wei on 2021-09-29, Last Modified on 2025-08-11

【Linux】I/O 轮询技术 - poll

`poll`

poll在select的基础之上进行改进，并避免不需要的检查。但是，当 fd 较多的时候，它的性能还是十分低下的。通过poll 实现的轮询与select相似，但性能限制有所改善。

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Posted by Wei on 2021-09-29, Last Modified on 2025-08-11

西维蜀黍

【Software Testing】Dryrun

Dry-run

【Golang】Reactor in Golang

【Golang】关键字 - select

Overall

【Golang】设计模式 - Pipeline

Pipeline Pattern

【Golang】设计模式 - Generator

Generator Pattern

【Performance】Concurrency vs Parallelism

【Golang】使用 epoll

【Golang】源码 - netpoll

Go netpoll

【Operating System】memory

User Space And Kernel Space

【Linux】I/O 轮询技术 - poll

`poll`

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