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Application of Perl Multi-process Technology in automatic Test

In the automation project of IT product system testing, there is often the need to deal with multiple sub-tasks in parallel. In order to improve the testing efficiency, Perl multi-process or multi-thread programming is needed. This paper introduces the usage and applicable scenarios of Perl multi-process, as well as the relationship between Perl multi-process and multi-thread. At the same time, combined with the automation characteristics of enterprise IT product system testing, the application of Perl multi-process in this aspect is introduced.

Perl multiprocess

Perl is a very powerful scripting language, which is widely used in system maintenance, CGI (CommonGatewayInterface) programming, database programming and automated testing.

Multitasking and concurrent processing were once seen as a feature of an excellent operating system; similarly, any excellent and popular programming language will have concurrent applications and have their own implementation methods. The first application of Perl in concurrency is Perl multiprocess.

The user interface of Perl multi-process is the fork () function and some module encapsulated by the system fork function. When programming in Perl, if a segment of a task can or needs to be executed concurrently, then we will use Perl multi-process programming, such as submitting multiple records to the database at the same time, collecting multiple system information at the same time, and so on.

Perl's Perl multi-process is implemented like this: for each fork child process of the main process, all the variables in the current memory space (of the main process) will be copied and transferred to the new process to achieve the purpose of data sharing. In addition, the main process and child processes can communicate through signals, pipes, and so on.

In the scheme of dealing with concurrency, Perl multi-processes rely on memory space to provide excellent fault tolerance and robustness. A Perl multi-process system does not crash because one of the processes is in a bad state. Each process operates relatively independently and rarely interacts with each other.

The exclusive memory space also creates the inevitable disadvantage of Perl multi-process: resource load and communication complexity, for Perl, each child process can be regarded as a copy of the main process, which is a bit of a waste of memory, and if the key variable of the main process is "shallow copy" to the child process, it will bring some unexpected errors. In addition, process creation and recycling brings a lot of additional load, so you should try to avoid creating processes frequently.

The communication methods between Perl multi-processes are socket, pipeline, semaphore and so on. On the Linux platform, files are the most commonly used for the interaction of a large amount of information between processes; this is most commonly used in the communication between user-space processes and system kernel space processes.

When talking about Perl multiprocess, it is inevitable to talk about its relationship with Perl multithreading.

The relationship between Perl multi-process and multi-thread

If we need to perform a variety of small tasks, they may be numerous, but the life cycle is relatively short, or they may share a large amount of data, and only a small number of variables are their own. At this time, it is natural to think of multithreading.

Since Perl5.005, the concept of multithreading has been introduced into the Perl language; it's just a concept. In Perl5.005, the threading model shares all data by default, and data sharing and access requires explicit synchronization operations. This model is called "5005threads", which is actually Perl multi-process, but the concept of "multi-threading" is changed.

When it comes to Perl5.6, a new threading model is introduced, where the data of each thread is private by default, and access to shared data requires explicit calls to relevant functions to ensure synchronization. This model is called "ithreads". In Perl5.6, the ithreads model does not provide some API for users to call, only as an internal API for extension.

When it comes to the Perl5.8,ithreads model, it is available to users through Perl's threads module, but Perl5.8 also retains the 5005threads model. Here, the user can choose which model to use through configuration.

The Perl5.10,5005threads model for * * is no longer used and has been removed from the Perl interpreter. So to use a real, stable multithreaded module, it is recommended to use the Perl5.10 interpreter. In March 2009, Perl5.10 was used by default in release's SLES11 installation package. At this point, Perl multiprocess and multithreading should be distinguished.

The multithreading provided by Perl's threads module is very effective for our classic multithreaded programming, such as SocketServer programming, hardware driver or adaptation layer programming, but it is powerless for some non-thread-safe functions or module calls, which will lead to unpredictable errors or the hanging or collapse of the main process.

Thank you for reading! This is the end of this article on "what is the use of Perl multi-process and multi-threading". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it out for more people to see!

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