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Medium 9781449304614

4. Data Safety and Consistency

Kristina Chodorow O'Reilly Media ePub

In an ideal world, all writes would be instantly, permanently saved to disks and be instantly retrievable from anywhere. Unfortunately, this is impossible in the real world, you can either take more time to make sure your data is safe or save it faster with less safety. MongoDB gives you more knobs to twiddle in this area than it has knobs for everything else combined and its important to understand your options.

Replication and journaling are the two approaches to data safety that you can take with MongoDB.

Generally, you should run with replication and have at least one of your servers journaled. The MongoDB blog has a good post on why you shouldnt run MongoDB (or any database) on a single server.

MongoDBs replication automatically copies all of your writes to other servers. If your current master goes down, you can bring up another server as the new master (this happens automatically with replica sets).

If a member of a replica set shuts down uncleanly and it was not running with --journal, MongoDB makes no guarantees about its data (it may be corrupt). You have to get a clean copy of the data: either wipe the data and resync it or load a backup and fastsync.

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Medium 9781449373719

Web Development: Ruby on Rails

Lucas Carlson O'Reilly Media ePub

Ruby on Rails is unquestionably Ruby’s killer app. It can take a lot of credit for lifting Ruby from obscurity outside its native Japan. No other programming language can boast a simple web application framework that also has almost all of that language’s developer mindshare.1 This chapter demonstrates the principles underlying basic Rails usage (in recipes like Recipe 16.6), gives Rails implementations of common web application patterns (Recipes 16.4 and 16.8) and shows how to use standard Ruby tools from within Rails (Recipes 16.22 and 16.23).

Despite its quality and popularity, Rails does not bring anything new to web development. Its foundations are in standard programming patterns like ActiveRecord and Model-View-Controller. It reuses many preexisting Ruby libraries (like Rake and ERb). The power of Rails is in combining these standard techniques with a ruthless dedication to automating menial tasks, and to asserting resonable default behaviors.

If Rails has a secret, it’s the power of naming conventions. The vast majority of web applications are CRUD applications; that is, they create, read, update, and delete information from a database. In these types of applications, Rails shines. You start with a database schema and with almost no code, but Rails ties together many pieces with naming conventions and shortcuts. This lets you put meat on your application very quickly.

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Medium 9781933671819

20. Learn More

Steve Sande TidBITS Publishing, Inc. ePub
Medium 9781601322432

Attendance Tracking

Hamid R. Arabnia, Azita Bahrami, Victor A. Clincy, Leonidas Deligiannidis, George Jandieri, Ashu M. G. Solo, Fernando G. Tinetti CSREA Press PDF

Int'l Conf. Frontiers in Education: CS and CE | FECS'13 |


Attendance Tracking


D. Deugo1

The School of Computer Science, Carleton University, Ottawa, Ontario, Canada

Abstract - We believe that a student’s attendance in their university courses is important for the successful completion of their courses and that student attendance is a marker one can use to identify students in need. The problem this paper addresses is how to track student attendance in university courses in a fast and efficient manner, given class sizes can be as small as 10 students and as large as 300. Our approach uses easily found, inexpensive hardware and makes use of students’ smartphones to help with the attendance tracking process. Our applications for the server and client portions of our system use open source software to minimize development and maintenance costs and do not require end users or system administrators to perform any installation.

Keywords: Attendance, Tracking, Smartphone, Web



The Science Student Success Centre (SSSC) at Carleton

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Medium 9781742204192


Lonely Planet Lonely Planet ePub

     Includes »


     Lille, Flanders the Somme




     Alsace Lorraine

     The Loire Valley

     Burgundy the Rhône Valley

     The French Alps Jura

     The Atlantic Coast



     The French Riviera Monaco


Few countries provoke such passion as La Belle France. Love it or loathe it, everyone has their own opinion about this Gallic Goliath. Snooty, sexy, superior, chic, infuriating, arrogant, officious and inspired in equal measures, the French have long lived according to their own idiosyncratic rules, and if the rest of the world doesn’t always see eye-to-eye with them, well, tant pis (too bad) – it’s the price you pay for being a culinary trendsetter, artistic pioneer and cultural icon.

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