How Perl programmers efficiently manage asynchronous program flows
Pyramid of Doom
Asynchronous program flow quickly degenerates into unreadable code if it lacks an overarching concept to provide structure. Fortunately, the JavaScript community has invented some functional tricks that also help tame asynchronous Perl code.
Even experts can unintentionally build race conditions into their code. Even they can easily overlook the side effects when multithreading suddenly interrupts the flow of code. Emergency teams later have to discover the causes, which involves a huge amount of effort. After all, the error the customer reports occurs only sporadically, because it only occurs given the temporal coincidence of certain events that cannot be easily reproduced by the development department.
One Thread Is Enough
If only one thread is running – as in a JavaScript application – then there can be no such race conditions, because the CPU runs the code as written, and nothing unexpected interrupts the flow. In other words, this approach has its benefits.
For a program with only one thread to run as fast as one with multiple threads, however, it must not be allowed to sit and twiddle its thumbs while, for example, a much slower network operation is in progress. To allow this to happen, the programmer relinquishes control over selected parts of the program to an event loop, which executes the events asynchronously. Once a programmer's brain has mastered the jump to asynchronous program flows, even complicated processes are wonderfully easy to write. Before that happens, however, some hurdles must be taken.
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