Read software engineering at Google (15)

read 《Software Engineering at Google》（15）—— Deprecation

：@Google, The code is assumed to be a liability （liability）, Code is not an asset （asset）

： Abandoning （Deprecation）vs  compatible （Compatibility）, The former takes courage , The latter also requires courage , One is to throw away the old and move forward easily , The so-called loss of courage , One is to carry the old load forward , The so-called courage to hold . Although it's all courage , The courage of the former will bring more confidence and opportunities , The latter continues to weaken their courage , Until fear breeds .

： The so-called debt , Just lack , Then pay the debt , Abandonment is debt cancellation , That makes sense . But why code is debt , In intuition , Or all the time , Codes are considered valuable assets , Such a cognitive reversal , Why there is , How to produce , How to reverse , My brain is a little tangled .

： Forced scrap , This is conventional in mechanical products . Wear to a certain extent , Security risks continue to rise , This reason is enough to start mandatory scrapping . The process of scrapping and replacing , Is in the process of upgrading iteration . software system , No matter how you run, you won't CPU Or memory is damaged by grinding , But that doesn't mean there's no security problem . The software system is based on the technology and use environment , All in rapid iterative improvement , The evolution route of this progress has many factors , Especially the change of use environment caused by network factors , Cause the safety problem is not considered from the beginning , To the final direct exposure . Such security problems , Enough to be a reason to start software scrapping .

： Keep asking , What factors , It can promote the continuous improvement of software system , Until there is a new replacement . The ship of Theseus , Change a part every day , After a period of time , Almost everywhere are new parts . The replacement is abandoned , It's compatible , In the end, it's the ship Theseus . If it can shoot artillery at first , Then replace... Anyway , Will not have the ability to launch cruise missiles . Yes . If the function does not change , At least there is no revolutionary change , That is, continuous compatible replacement . Only the subversive functional difference from artillery to cruise missile , The wooden ship is to be abandoned , A cruiser made of steel and iron . Think again , I haven't heard the saying that warships can change a little every day . It also says , The more powerful 、 The more dedicated the system , When its functions are eliminated , That is, when its software system is abandoned . In the software industry , From single system to distributed system , The reason why there is no need to replace the hardware , The reason lies in the basic operating system software on top of the hardware , A radical innovation , The result is still compatible with the software under the single system , This is the magic reproduction of software plus one layer .