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  • Custom stream wrappers, what could they be useful for in web applications?

    - by michael
    I suppose the concept is language agnostic, but I don't know what it's called in other languages. In PHP they're Stream Wrappers. In short, a wrapper class that allows manipulation of a streamable resource (resource that can be read to/written to/seek into, such as a file, a db, an url). For example, in a template engine (a view), upon including a template file such as: include "view.wrapper://path/to/my/template/file.phtml"; my custom wrapper, declared elsewhere and associated with "view.wrapper", would first intercepts the file to replace such things as short tags (<?=) with a more verbose counterpart (<?php echo). This allows developers to use short tags in views, even if the server isn't set to allow it. It can also be applied to the preprocessing of views pseudo syntax such as {@myVar} (e.g. replacing it with $this->myVar). This is only one application of custom stream wrappers, but the feature seems powerful enough to make me think that there are others that could make life a lot simpler for developers. What have you built, or thought about building, custom stream wrappers for? where have you seen some interesting implementations? I'm particularly interested in their applications in web development.

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  • Where to create/keep secret files for license information/trials on Windows/Mac OS X/Linux?

    - by BastiBense
    I'm writing a commercial product which uses a simple registration mechanism and allows the user to use the application for a demo period before purchasing. My application must somewhere store the registration information (if entered) and/or the date of the first launch to calculate if the user is still within the demo/trail period. While I'm pretty much finished with the registration mechanism itself, I now have to find a good way to store the registration information on the user's disk. The most obvious idea would be to store the trial period in the preferences file, but since user tend to delete/tinker with those from time to time, it might be a good idea to keep the registration information in a separate, more hidden file. So here's my question: What is the best place/strategy to keep and create such hidden files on Windows, Mac OS X and Linux? Here is what came to my mind so far: Linux/Mac OS X Most Unix-like systems are rather locked down when it comes to places a user can write files to. In most cases this is only the /tmp directory and the user's home directory. I guess the easiest here is probably to create a file with a dot-prefix to make it less visible, then give it a name that won't make it obvious that it's associated with my application. Windows Probably much like Linux/Mac OS X - more recent Windows versions become more restrictive when it comes to file system permissions. Anyway, I'd like to hear your ideas and thoughs. Even better if you have already implemented something similar in the past. Thanks! Update For me the places for such files is more relevant than the discussion of the question if this way for copy protection is good or bad.

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  • Books/resources for help with extracting useful feedback from clients?

    - by Eric
    I'm a web application developer looking for a book or something similar that can help with effectively communicating with clients who have a very vague or unrealistic idea of what they'd like out of the work I'm doing. Some fictional, though not by much, examples of situations: Clients who are not familiar with using the Internet, and insist on features that are not even remotely feasible (ex. time travel) Clients who are unable to express accurately what they're looking for (ex. "I know that's what I said and signed off on, but it's not what I meant") Clients who refuse to attend meetings or review sessions to answer questions or define requirements (which makes any agile development impossible) For the most part, I'm trying to find best practices for how to handle these kinds of things on a team-building level. The best ways to effectively address serious project roadblocks without sounding like a total jerk. Any recommendations for reading material on this topic?

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  • How do I identify and fix the cause of transaction log growth on SIMPLE recovery model databases?

    - by Stuart B
    I recently upgraded our SQL Server 2008 installations to service pack 2. One of our databases is on the simple recovery model, but its transaction log is growing extremely fast. The path I'm currently investigating is that we have a transaction somewhere out there stuck in active state. Here is why: select name, recovery_model_desc, log_reuse_wait_desc from sys.databases where name in ('SimpleDB') name recovery_model_desc log_reuse_wait_desc SimpleDB SIMPLE ACTIVE_TRANSACTION When I check my active transactions, I get the following. Note that I installed SP2 and restarted our server on 12/25 at around noonish. select transaction_id, name, transaction_begin_time, transaction_type from sys.dm_tran_active_transactions transaction_id name transaction_begin_time transaction_type 233 worktable 2010-12-25 12:44:29.283 2 236 worktable 2010-12-25 12:44:29.283 2 238 worktable 2010-12-25 12:44:29.283 2 240 worktable 2010-12-25 12:44:29.283 2 243 worktable 2010-12-25 12:44:29.283 2 245 worktable 2010-12-25 12:44:29.283 2 62210 tran_sp_MScreate_peer_tables 2010-12-25 12:45:00.880 1 55422856 user_transaction 2010-12-28 16:41:56.703 1 55422889 SELECT 2010-12-28 16:41:57.303 2 470 LobStorageProviderSession 2010-12-25 12:44:30.510 2 Note that according to the documentation a transaction_type of 1 means read/write, and 2 means read-only. So, my line of thinking is that the trans_sp_MScreate_peer_tables transaction is stuck for some reason and holding up transaction log truncation. Is this a plausible scenario? Correct me if my line of thinking is off, as I'm not a SQL Server expert. If this is correct, how do I erase that transaction so that my transaction log is truncated as usual?

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  • How use DNS server to create simple HA (High availability) of my website?

    - by marc22
    Welcome, How can i use DNS server to create simple HA (High availability) of website ? For example if my web-server ( for better understanding i use internal IP in real it will be other hosting companies) 192.168.0.120 :80 (is offline) traffic go to 192.168.0.130 :80 You have right, i use bad word "hight avability" of course i was thinking about failover. Using few IP in A records is good for simple load-balancing. But not in case, if i want notice user about failure (for example display page, Oops something is wrong without our server, we working on it) against "can't establish connection". I was thinking about setting up something like this 2 DNS servers, one installed on www server Both have low TTL on my domain, set up 2 ns records first for DNS with my apache server second to other dns If user try connect he will get ip of www server using first dns, if that dns is offline (probably www server is also down) so it will try second NS record, what will point to another dns, that dns will point to "backup" page. That's what i would like to do. If You have other idea please share. Reverse proxy is not option, because IP of server can change, or i can use other country for backup.

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  • What is a suitable simple, open web server for Windows?

    - by alficles
    I'm looking for a dead simple web server for Windows. Load will not be high as it will be primarily serving binaries for a WPKG update service. It needs to serve the entire contents of a single folder over HTTP on a configurable (high) port. No CGI or other scripting is required, but it might be nice for future features. I started with Mongoose, since it doesn't even have an installation requirement (a very nice perk), but it fails to start when run as a service. (Technically, it acts as it's own installer.) I've investigated LighTPD as well, but it appears to be minimally (at best) tested on Windows. And naturally, I'm looking for something free. As in beer is good, but speech is better, as always. Edit: I didn't mention this initially, but non-tech people will be doing the install. They'll have whatever script I write for the install, but the goal is a simple system that is easy to troubleshoot. (I almost worded this question "What is the best...", but Serverfault rightly observed that that is a subjective question. And it's really not an optimization problem, any suitable solution will work. I just can't seem to find one for Windows.)

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  • Recommendation for a simple no-frills Windows PDF printer driver?

    - by Scott Bussinger
    I'm looking for an extremely simple Windows PDF printer driver that I can recommend to clients. Ideally it would have these characteristics: When you print something, it should just create it as a temporary file and then display it in their default PDF viewer with no prompting. If they want to save it, they can save it manually from inside the viewer. This workflow should be with no special post-install configuration. Installation should be very simple. A double click the installation program and click "Finish" sort of thing. No complicated multi-step installation, no asking questions your grandmother wouldn't know the answer to (preferably no questions at all), no extra crap being installed. An option for a completely silent installation would be nice, but not necessary. Ideally it would be free to simplify their installing on a small network, but low cost is an option. I've tried a quite a few but none really fit the bill. Some can achieve the first goal but only after careful configuration, some try to install extra toolbars, some have other installation complexities that would make it hard for extremely novice users to succeed. Any suggestions? Thanks!

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  • Managing Database Clusters - A Whole Lot Simpler

    - by mat.keep(at)oracle.com
    Clustered computing brings with it many benefits: high performance, high availability, scalable infrastructure, etc.  But it also brings with it more complexity.Why ?  Well, by its very nature, there are more "moving parts" to monitor and manage (from physical, virtual and logical hosts) to fault detection and failover software to redundant networking components - the list goes on.  And a cluster that isn't effectively provisioned and managed will cause more downtime than the standalone systems it is designed to improve upon.  Not so great....When it comes to the database industry, analysts already estimate that 50% of a typical database's Total Cost of Ownership is attributable to staffing and downtime costs.  These costs will only increase if a database cluster is to hard to properly administer.Over the past 9 months, monitoring and management has been a major focus in the development of the MySQL Cluster database, and on Tuesday 12th January, the product team will be presenting the output of that development in a new webinar.Even if you can't make the date, it is still worth registering so you will receive automatic notification when the on-demand replay is availableIn the webinar, the team will cover:    * NDBINFO: released with MySQL Cluster 7.1, NDBINFO presents real-time status and usage statistics, providing developers and DBAs with a simple means of pro-actively monitoring and optimizing database performance and availability.    * MySQL Cluster Manager (MCM): available as part of the commercial MySQL Cluster Carrier Grade Edition, MCM simplifies the creation and management of MySQL Cluster by automating common management tasks, delivering higher administration productivity and enhancing cluster agility. Tasks that used to take 46 commands can be reduced to just one!    * MySQL Cluster Advisors & Graphs: part of the MySQL Enterprise Monitor and available in the commercial MySQL Cluster Carrier Grade Edition, the Enterprise Advisor includes automated best practice rules that alert on key performance and availability metrics from MySQL Cluster data nodes.You'll also learn how you can get started evaluating and using all of these tools to simplify MySQL Cluster management.This session will last round an hour and will include interactive Q&A throughout. You can learn more about MySQL Cluster Manager from this whitepaper and on-line demonstration.  You can also download the packages from eDelivery (just select "MySQL Database" as the product pack, select your platform, click "Go" and then scroll down to get the software).While managing clusters will never be easy, the webinar will show hou how it just got a whole lot simpler !

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  • MySQL Cluster 7.2: Over 8x Higher Performance than Cluster 7.1

    - by Mat Keep
    0 0 1 893 5092 Homework 42 11 5974 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary The scalability enhancements delivered by extensions to multi-threaded data nodes enables MySQL Cluster 7.2 to deliver over 8x higher performance than the previous MySQL Cluster 7.1 release on a recent benchmark What’s New in MySQL Cluster 7.2 MySQL Cluster 7.2 was released as GA (Generally Available) in February 2012, delivering many enhancements to performance on complex queries, new NoSQL Key / Value API, cross-data center replication and ease-of-use. These enhancements are summarized in the Figure below, and detailed in the MySQL Cluster New Features whitepaper Figure 1: Next Generation Web Services, Cross Data Center Replication and Ease-of-Use Once of the key enhancements delivered in MySQL Cluster 7.2 is extensions made to the multi-threading processes of the data nodes. Multi-Threaded Data Node Extensions The MySQL Cluster 7.2 data node is now functionally divided into seven thread types: 1) Local Data Manager threads (ldm). Note – these are sometimes also called LQH threads. 2) Transaction Coordinator threads (tc) 3) Asynchronous Replication threads (rep) 4) Schema Management threads (main) 5) Network receiver threads (recv) 6) Network send threads (send) 7) IO threads Each of these thread types are discussed in more detail below. MySQL Cluster 7.2 increases the maximum number of LDM threads from 4 to 16. The LDM contains the actual data, which means that when using 16 threads the data is more heavily partitioned (this is automatic in MySQL Cluster). Each LDM thread maintains its own set of data partitions, index partitions and REDO log. The number of LDM partitions per data node is not dynamically configurable, but it is possible, however, to map more than one partition onto each LDM thread, providing flexibility in modifying the number of LDM threads. The TC domain stores the state of in-flight transactions. This means that every new transaction can easily be assigned to a new TC thread. Testing has shown that in most cases 1 TC thread per 2 LDM threads is sufficient, and in many cases even 1 TC thread per 4 LDM threads is also acceptable. Testing also demonstrated that in some instances where the workload needed to sustain very high update loads it is necessary to configure 3 to 4 TC threads per 4 LDM threads. In the previous MySQL Cluster 7.1 release, only one TC thread was available. This limit has been increased to 16 TC threads in MySQL Cluster 7.2. The TC domain also manages the Adaptive Query Localization functionality introduced in MySQL Cluster 7.2 that significantly enhanced complex query performance by pushing JOIN operations down to the data nodes. Asynchronous Replication was separated into its own thread with the release of MySQL Cluster 7.1, and has not been modified in the latest 7.2 release. To scale the number of TC threads, it was necessary to separate the Schema Management domain from the TC domain. The schema management thread has little load, so is implemented with a single thread. The Network receiver domain was bound to 1 thread in MySQL Cluster 7.1. With the increase of threads in MySQL Cluster 7.2 it is also necessary to increase the number of recv threads to 8. This enables each receive thread to service one or more sockets used to communicate with other nodes the Cluster. The Network send thread is a new thread type introduced in MySQL Cluster 7.2. Previously other threads handled the sending operations themselves, which can provide for lower latency. To achieve highest throughput however, it has been necessary to create dedicated send threads, of which 8 can be configured. It is still possible to configure MySQL Cluster 7.2 to a legacy mode that does not use any of the send threads – useful for those workloads that are most sensitive to latency. The IO Thread is the final thread type and there have been no changes to this domain in MySQL Cluster 7.2. Multiple IO threads were already available, which could be configured to either one thread per open file, or to a fixed number of IO threads that handle the IO traffic. Except when using compression on disk, the IO threads typically have a very light load. Benchmarking the Scalability Enhancements The scalability enhancements discussed above have made it possible to scale CPU usage of each data node to more than 5x of that possible in MySQL Cluster 7.1. In addition, a number of bottlenecks have been removed, making it possible to scale data node performance by even more than 5x. Figure 2: MySQL Cluster 7.2 Delivers 8.4x Higher Performance than 7.1 The flexAsynch benchmark was used to compare MySQL Cluster 7.2 performance to 7.1 across an 8-node Intel Xeon x5670-based cluster of dual socket commodity servers (6 cores each). As the results demonstrate, MySQL Cluster 7.2 delivers over 8x higher performance per data nodes than MySQL Cluster 7.1. More details of this and other benchmarks will be published in a new whitepaper – coming soon, so stay tuned! In a following blog post, I’ll provide recommendations on optimum thread configurations for different types of server processor. You can also learn more from the Best Practices Guide to Optimizing Performance of MySQL Cluster Conclusion MySQL Cluster has achieved a range of impressive benchmark results, and set in context with the previous 7.1 release, is able to deliver over 8x higher performance per node. As a result, the multi-threaded data node extensions not only serve to increase performance of MySQL Cluster, they also enable users to achieve significantly improved levels of utilization from current and future generations of massively multi-core, multi-thread processor designs.

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  • Why Keep These 10 A Penny " How Long Will It Take To Program in Blah Blah Blah Language Questions" Open Yet Close This Question..? [migrated]

    - by user866190
    Why keep this question open and others like it open which basically asks how long does it take to learn a programming language? Yet I ask a valid question which basically asks how esteemed is a mathematics degree from the UK open university and would software employers hire whilst you are the course.. and it gets closed I love the advice I get from this site and I appreciate the fact that Software Technicians of all types use this site, but it's a bit shallow if you can't ask a question with a little bit of the real world involved

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  • MySQL simple replication problem: 'show master status' produces 'Empty set'?

    - by simon
    I've been setting up MySQL master replication (on Debian 6.0.1) following these instructions faithfully: http://www.neocodesoftware.com/replication/ I've got as far as: mysql > show master status; but this is unfortunately producing the following, rather than any useful output: Empty set (0.00 sec) The error log at /var/log/mysql.err is just an empty file, so that's not giving me any clues. Any ideas? This is what I have put in /etc/mysql/my.cnf on one server (amended appropriately for the other server): server-id = 1 replicate-same-server-id = 0 auto-increment-increment = 2 auto-increment-offset = 1 master-host = 10.0.0.3 master-user = <myusername> master-password = <mypass> master-connect-retry = 60 replicate-do-db = fruit log-bin = /var/log/mysql-replication.log binlog-do-db = fruit And I have set up users and can connect from MySQL on Server A to the database on Server B using the username/password/ipaddress above.

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  • Getting the innermost .NET Exception

    - by Rick Strahl
    Here's a trivial but quite useful function that I frequently need in dynamic execution of code: Finding the innermost exception when an exception occurs, because for many operations (for example Reflection invocations or Web Service calls) the top level errors returned can be rather generic. A good example - common with errors in Reflection making a method invocation - is this generic error: Exception has been thrown by the target of an invocation In the debugger it looks like this: In this case this is an AJAX callback, which dynamically executes a method (ExecuteMethod code) which in turn calls into an Amazon Web Service using the old Amazon WSE101 Web service extensions for .NET. An error occurs in the Web Service call and the innermost exception holds the useful error information which in this case points at an invalid web.config key value related to the System.Net connection APIs. The "Exception has been thrown by the target of an invocation" error is the Reflection APIs generic error message that gets fired when you execute a method dynamically and that method fails internally. The messages basically says: "Your code blew up in my face when I tried to run it!". Which of course is not very useful to tell you what actually happened. If you drill down the InnerExceptions eventually you'll get a more detailed exception that points at the original error and code that caused the exception. In the code above the actually useful exception is two innerExceptions down. In most (but not all) cases when inner exceptions are returned, it's the innermost exception that has the information that is really useful. It's of course a fairly trivial task to do this in code, but I do it so frequently that I use a small helper method for this: /// <summary> /// Returns the innermost Exception for an object /// </summary> /// <param name="ex"></param> /// <returns></returns> public static Exception GetInnerMostException(Exception ex) { Exception currentEx = ex; while (currentEx.InnerException != null) { currentEx = currentEx.InnerException; } return currentEx; } This code just loops through all the inner exceptions (if any) and assigns them to a temporary variable until there are no more inner exceptions. The end result is that you get the innermost exception returned from the original exception. It's easy to use this code then in a try/catch handler like this (from the example above) to retrieve the more important innermost exception: object result = null; string stringResult = null; try { if (parameterList != null) // use the supplied parameter list result = helper.ExecuteMethod(methodToCall,target, parameterList.ToArray(), CallbackMethodParameterType.Json,ref attr); else // grab the info out of QueryString Values or POST buffer during parameter parsing // for optimization result = helper.ExecuteMethod(methodToCall, target, null, CallbackMethodParameterType.Json, ref attr); } catch (Exception ex) { Exception activeException = DebugUtils.GetInnerMostException(ex); WriteErrorResponse(activeException.Message, ( HttpContext.Current.IsDebuggingEnabled ? ex.StackTrace : null ) ); return; } Another function that is useful to me from time to time is one that returns all inner exceptions and the original exception as an array: /// <summary> /// Returns an array of the entire exception list in reverse order /// (innermost to outermost exception) /// </summary> /// <param name="ex">The original exception to work off</param> /// <returns>Array of Exceptions from innermost to outermost</returns> public static Exception[] GetInnerExceptions(Exception ex) {     List<Exception> exceptions = new List<Exception>();     exceptions.Add(ex);       Exception currentEx = ex;     while (currentEx.InnerException != null)     {         exceptions.Add(ex);     }       // Reverse the order to the innermost is first     exceptions.Reverse();       return exceptions.ToArray(); } This function loops through all the InnerExceptions and returns them and then reverses the order of the array returning the innermost exception first. This can be useful in certain error scenarios where exceptions stack and you need to display information from more than one of the exceptions in order to create a useful error message. This is rare but certain database exceptions bury their exception info in mutliple inner exceptions and it's easier to parse through them in an array then to manually walk the exception stack. It's also useful if you need to log errors and want to see the all of the error detail from all exceptions. None of this is rocket science, but it's useful to have some helpers that make retrieval of the critical exception info trivial. Resources DebugUtils.cs utility class in the West Wind Web Toolkit© Rick Strahl, West Wind Technologies, 2005-2011Posted in CSharp  .NET  

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  • What OS would you use for a simple fileserver and why?

    - by barfoon
    Hey everyone, Im looking to set up a simple fileserver: 5 - 7 clients - Mixed Windows, Linux, Mac OSX - connecting over wireless and wired Serving ~200GB content - Photos, MP3's, ISO's etc What OS would you recommend for this fileserver? I understand XP limits the number of when connecting to different shares so this probably isnt the best choice. Any recommendations are appreciated. Thank you,

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  • Can I get simple name resolution on the local network without DNS, on a Mac?

    - by tim
    I've got Mantis running on a Linux VM with a Win2k8 server host. I installed Samba with the following configuration: [global] workgroup = COMPANY netbios name = MANTIS security = share Now on all our windows machines people can simple go to http://mantis, rather than http://172.16.0.20. However, this doesn't appear to work on the Mac machines. Any ideas how I can sort this without changing anything on the Windows server?

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  • Is there a simple way to detect ISP port blocking?

    - by Will M
    Is there a way to tell the difference between my ISP blocking traffic on certain ports and my NAT router/firewall blocking that traffic? The sites “Shields Up” and “Can you see me” show my ports closed or not accessible, but I assume that is primarily due to the NAT router. (Obviously, I could just remove the router, connect directly and use those sites, but is there a simple way to test without doing that?)

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  • What are the alternative simple softwares for MS Paint?

    - by hkBattousai
    MS Paint is good but it lacks quality on some of its tools. I want to try its alternative software. Can you please give me a list of its alternatives. I'm looking for simple software as MS Paint is. Please don't suggest me complicated software like Gimp and Photoshop. I have already tried Paint.NET, but it is too dependent on Microsoft .NET Framework, so it is very problematic to install in the first place.

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  • Simple, current how-to install mod-security on cPanel server?

    - by linux911
    Does anyone have or know of a simple, up to date how to for installing mod-security on cPanel and configuring it after install? Every how to on the web I've found is at least two years old and is based on a mod-security addon function in cPanel which doesn't exist anymore. There are a couple of free add ons to simplify selecting rule files (configserver's for example) but there's no documentation on which rules a cPanel system "should" be using and so on.

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  • Keep the current Jquery accordion pane open after asp.net postback?

    - by Xaisoft
    I have a jquery accordion on an asp.net aspx weppage. Inside the panes, I have asp.net buttons. When I click on the button, the pane I was in, closes and reloads the page, defaulting to the first pane. I don't mind the reload, but is there a way to keep the current pane open after the reload. Right now, I am just calling accordion() on a div with the id of accordion.

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  • How to design a command line program and keep it open for a future GUI?

    - by systempuntoout
    What are some best practices to keep in mind when developing a script program that could be integrated with a GUI, probably by somebody else, in the future? Example scenario: i develop a fancy python CLI program that scrapes every unicorn images from the web i decide to publish it on github a unicorn fan programmer decide to take the sources and build a GUI on them. he gives up because my code is a mess How do i avoid step 4 and let unicorn fan programmer build his GUI without hassle?

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  • HowTo Crypt/Encrypt some string (e.g. Password) on Qt simple

    - by mosg
    Hi. Here what I have got: Qt SDK version 4.6.2 Windows XP Question: how can I simply crypt and encrypt simple QString value? I need this to be able to save some crypted string into the INI file, and after reopening application encrypt string to normal password string value. PS: I'm looking simple and nice solution. Thanks for help!

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  • MySQL Cluster 7.3 Labs Release – Foreign Keys Are In!

    - by Mat Keep
    0 0 1 1097 6254 Homework 52 14 7337 14.0 Normal 0 false false false EN-US JA X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin:0cm; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:Cambria; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-ansi-language:EN-US;} Summary (aka TL/DR): Support for Foreign Key constraints has been one of the most requested feature enhancements for MySQL Cluster. We are therefore extremely excited to announce that Foreign Keys are part of the first Labs Release of MySQL Cluster 7.3 – available for download, evaluation and feedback now! (Select the mysql-cluster-7.3-labs-June-2012 build) In this blog, I will attempt to discuss the design rationale, implementation, configuration and steps to get started in evaluating the first MySQL Cluster 7.3 Labs Release. Pace of Innovation It was only a couple of months ago that we announced the General Availability (GA) of MySQL Cluster 7.2, delivering 1 billion Queries per Minute, with 70x higher cross-shard JOIN performance, Memcached NoSQL key-value API and cross-data center replication.  This release has been a huge hit, with downloads and deployments quickly reaching record levels. The announcement of the first MySQL Cluster 7.3 Early Access lab release at today's MySQL Innovation Day event demonstrates the continued pace in Cluster development, and provides an opportunity for the community to evaluate and feedback on new features they want to see. What’s the Plan for MySQL Cluster 7.3? Well, Foreign Keys, as you may have gathered by now (!), and this is the focus of this first Labs Release. As with MySQL Cluster 7.2, we plan to publish a series of preview releases for 7.3 that will incrementally add new candidate features for a final GA release (subject to usual safe harbor statement below*), including: - New NoSQL APIs; - Features to automate the configuration and provisioning of multi-node clusters, on premise or in the cloud; - Performance and scalability enhancements; - Taking advantage of features in the latest MySQL 5.x Server GA. Design Rationale MySQL Cluster is designed as a “Not-Only-SQL” database. It combines attributes that enable users to blend the best of both relational and NoSQL technologies into solutions that deliver web scalability with 99.999% availability and real-time performance, including: Concurrent NoSQL and SQL access to the database; Auto-sharding with simple scale-out across commodity hardware; Multi-master replication with failover and recovery both within and across data centers; Shared-nothing architecture with no single point of failure; Online scaling and schema changes; ACID compliance and support for complex queries, across shards. Native support for Foreign Key constraints enables users to extend the benefits of MySQL Cluster into a broader range of use-cases, including: - Packaged applications in areas such as eCommerce and Web Content Management that prescribe databases with Foreign Key support. - In-house developments benefiting from Foreign Key constraints to simplify data models and eliminate the additional application logic needed to maintain data consistency and integrity between tables. Implementation The Foreign Key functionality is implemented directly within MySQL Cluster’s data nodes, allowing any client API accessing the cluster to benefit from them – whether using SQL or one of the NoSQL interfaces (Memcached, C++, Java, JPA or HTTP/REST.) The core referential actions defined in the SQL:2003 standard are implemented: CASCADE RESTRICT NO ACTION SET NULL In addition, the MySQL Cluster implementation supports the online adding and dropping of Foreign Keys, ensuring the Cluster continues to serve both read and write requests during the operation. An important difference to note with the Foreign Key implementation in InnoDB is that MySQL Cluster does not support the updating of Primary Keys from within the Data Nodes themselves - instead the UPDATE is emulated with a DELETE followed by an INSERT operation. Therefore an UPDATE operation will return an error if the parent reference is using a Primary Key, unless using CASCADE action, in which case the delete operation will result in the corresponding rows in the child table being deleted. The Engineering team plans to change this behavior in a subsequent preview release. Also note that when using InnoDB "NO ACTION" is identical to "RESTRICT". In the case of MySQL Cluster “NO ACTION” means “deferred check”, i.e. the constraint is checked before commit, allowing user-defined triggers to automatically make changes in order to satisfy the Foreign Key constraints. Configuration There is nothing special you have to do here – Foreign Key constraint checking is enabled by default. If you intend to migrate existing tables from another database or storage engine, for example from InnoDB, there are a couple of best practices to observe: 1. Analyze the structure of the Foreign Key graph and run the ALTER TABLE ENGINE=NDB in the correct sequence to ensure constraints are enforced 2. Alternatively drop the Foreign Key constraints prior to the import process and then recreate when complete. Getting Started Read this blog for a demonstration of using Foreign Keys with MySQL Cluster.  You can download MySQL Cluster 7.3 Labs Release with Foreign Keys today - (select the mysql-cluster-7.3-labs-June-2012 build) If you are new to MySQL Cluster, the Getting Started guide will walk you through installing an evaluation cluster on a singe host (these guides reflect MySQL Cluster 7.2, but apply equally well to 7.3) Post any questions to the MySQL Cluster forum where our Engineering team will attempt to assist you. Post any bugs you find to the MySQL bug tracking system (select MySQL Cluster from the Category drop-down menu) And if you have any feedback, please post them to the Comments section of this blog. Summary MySQL Cluster 7.2 is the GA, production-ready release of MySQL Cluster. This first Labs Release of MySQL Cluster 7.3 gives you the opportunity to preview and evaluate future developments in the MySQL Cluster database, and we are very excited to be able to share that with you. Let us know how you get along with MySQL Cluster 7.3, and other features that you want to see in future releases. * Safe Harbor Statement This information is intended to outline our general product direction. It is intended for information purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or functionality, and should not be relied upon in making purchasing decisions. The development, release, and timing of any features or functionality described for Oracle’s products remains at the sole discretion of Oracle.

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