20140626-1 选题

sources/talk/20140626 Joy of Programming--Fail Fast.md

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+Joy of Programming: Fail Fast!
+================================================================================
+![](http://www.opensourceforu.com/wp-content/uploads/2011/12/fail-350x262.jpg)
+
+> When a problem occurs in the software, it should fail immediately, in an easily noticeable way. This “fail fast” behaviour is desirable, and we’ll discuss this important concept in this column.
+
+At first, a “fail fast” might appear to be a bad practice affecting reliability — why should a system crash (or fail), when it can continue execution? For this, we need to understand that fail fast is very relevant in the context of Heisenbugs.
+
+Consider Bohrbugs, which always crash for a given input, for example, with a null-pointer access. These bugs are easier to test, reproduce and fix. Now, all experienced programmers would have faced situations where the bug that caused the crash just disappears when the software is restarted. No matter how much time and effort is spent to reproduce the problem, the bug eludes us. These bugs are known as Heisenbugs.
+
+The effort required to find, fix and test Heisenbugs is an order of magnitude more than the effort required for Bohrbugs. One strategy to avoid Heisenbugs is to turn them into Bohrbugs. How? By anticipating the possible cases in which Heisenbugs can arise, and trying to  make them Bohrbugs. Yes, it is not easy, and it is also not always possible, but let us look at a specific example where it is useful.
+
+Concurrent programming is one paradigm where Heisenbugs are common. Our example is a concurrency-related issue in Java. While iterating over a Java collection, we are supposed to modify the collection only through the Iterator methods, such as the remove() method. During iteration, if another thread attempts to modify that underlying collection (because of a programming mistake), the underlying collection will get corrupted (i.e., result in an incorrect state).
+
+Such an incorrect state can lead to an eventual failure — or if we are fortunate (actually, unfortunate!), the program continues execution without crashing, but gives the wrong results. It is difficult to reproduce and fix these bugs, because such programming mistakes are non-deterministic. In other words, it is a Heisenbug.
+
+Fortunately, the Java Iterators try to detect such concurrent modifications, and if found, will throw a `ConcurrentModificationException`, instead of failing late — and that too, silently. In other words, the Java Iterators follow the “fail fast” approach.
+
+What if a `ConcurrentModificationException` is observed in production software? As the Javadoc for this exception observes, it “…should be used only to detect bugs.” In other words, `ConcurrentModificationExceptions` are supposed to be found and fixed during software development, and should not leak to production code.
+
+Well, if production software does get this exception, it is certainly a bug in the software, and should be reported to the developer and fixed. At least, we know that there was an attempt for concurrent modification of the underlying data structure, and that’s why the software failed (instead of getting wrong results from the software, or failing later with some other symptoms, for which it is not feasible to trace the root cause).
+
+The “fail-safe” approach is meant for developing robust code. A very good example of writing fail-safe code is using assertions. Unfortunately, there is a lot of unnecessary controversy surrounding the use of asserts. The main criticism is this: the checks are enabled in the development version, and disabled in release versions.
+
+However, this criticism is wrong: asserts are never meant to replace the defensive checks that should be put in place in the release version of the software. For example, asserts should not be used to check if the argument passed to a function is null or not. Instead, an if condition should be used to check if the argument is passed correctly, or else an exception, or a premature return, should be performed, as appropriate to the context. However, asserts can be used to do additional checks for assumptions that are made in the code, which are supposed to hold true. For example, a condition that checks that the stack is not empty after a push operation is performed on it (i.e., checking for “invariants”).
+
+So, fail fast, be assertive, and you’re on the way to developing more robust code.
+
+
+
+--------------------------------------------------------------------------------
+
+via:http://www.opensourceforu.com/2011/12/joy-of-programming-fail-fast/ 
+
+译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
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sources/talk/20140626 Linux Administration--A Smart Career Choice.md

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+Linux Administration: A Smart Career Choice
+================================================================================
+![](http://www.opensourceforu.com/wp-content/uploads/2014/04/linux.jpeg)
+
+> This is a good year for IT professionals with a number of new jobs in emerging technologies like Big Data and Analytics, and Social Mobile Analytics and Cloud (SMAC) as employers look to strengthen their technological force.
+
+If we were to believe the reports by [Dice.com][1] and Linux foundation released in mid Feb, 2014, this year will be a high octane year for Linux professionals and aspirants particularly. Thus it only makes sense to be future-ready and find out about the details of career opportunities such as that of a Linux administrator.
+
+Dice.com, the leading job site for tech professionals and Linux Foundation did a comprehensive survey to find out about the advantage Linux professionals have in the current technology landscape. The findings were heavily skewed in favor of those who are looking for a good job opportunity on Linux platform.
+
+While seventy seven percent of hiring managers surveyed consider hiring Linux talent as one of their top priorities (up from 70 percent in 2013), 64 percent of professionals chose to work with Linux owing to its ubiquitous nature in the present day technology infrastructure. More than nine in ten recruitment manager is planning to hire a Linux professional in the next six months.  This demand is surely going to translate in form of a lot of interview calls from employers. Most hiring managers also agree to the fact that it is rather difficult to find experienced professionals, and those who have the right mix of skills, knowledge, certifications and experience are being aggressively recruited.
+
+### Why Linux administration? ###
+
+The findings of this report make it clear that Linux professionals are amongst the most sought after in the current tech market. However, a more interesting finding of the report is that amongst all the skills, the hiring managers are most actively seeking system administration, with 58 percent confirming they were on look out of professionals with good system administration skills. The reason is quite simple. There aren’t too many good system administrators out there, which is also driving the salaries of system admins northwards.
+Getting started in Linux administration
+
+Armed with all this data, it wouldn’t come as surprise if you decide right away to pursue a career in Linux administration. So, how do you become a pro Linux system admin? Well, the right mix of certification, education and experience will obviously land you the perfect Linux job, but if you are clueless about a place to start, then a degree in computers is what you should be looking at.  This could be B.Tech with Computer Science or IT as specialisation or Bachelors in Computer Application or even a Bachelor in Science with IT as specialisation will do.  This would actually make you familiar with the various aspects of computer science as a subject, likes of programming, hardware, and software. This understanding would come handy in the advancement of your career, when you climb the next ladder through certifications.
+
+### Certifications ###
+
+It is widely believed that IT certifications do help one in career advancement.  However, it ultimately boils down to selecting the right certification to gain the maximum RoI. There are many Linux based certifications, the most famous of which is Red Hat Certification Program, which teaches general Linux related skills along with specific system administration skills.
+
+In addition to the vendor sponsored certifications, there is a vendor-independent Linux Professional Institute Certification offered by Linux Professional Institute, a non-profit organisation based in Toronto, Canada.
+
+These exams can be taken by anyone irrespective of their nationalities. The LPI programs have three level hierarchies that include LPIC-1: Junior Level Linux Administration, LPIC-2: Advanced Level Linux Administration and LPIC 3: Senior Level Linux Administration. In order to be considered seriously for any system administrator job opportunity in one must possess at least one of the above described certifications.   The LPI also has partnerships with SUSE, which is the vendor for a famous enterprise operating system going by the same name. CompTIA, which is a global IT certification agency also provided a Linux+ certification which was phased out after an agreement between LPI and CompTIA.
+
+### Salaries and Benefits ###
+
+The compensations for Linux administrators are generally on the higher side. As per PayScale, the annual median salary is around INR 3 lacs for entry level professionals (as updated on 27th March, 2014). With experience, there is an exponential increase in the salary levels as individuals with 5+ years of experience getting annual packages in seven figures.
+Well, with the grass being greener for Linux professionals this year, you won’t get a better opportunity or time for pursuing career as a Linux system administrator.
+
+--------------------------------------------------------------------------------
+
+via: http://www.opensourceforu.com/2014/04/career-overview-linux-administrator/
+
+译者：[译者ID](https://github.com/译者ID) 校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创翻译，[Linux中国](http://linux.cn/) 荣誉推出
+
+[1]:http://dice.com/