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• Best way to do interprocess communication on Mac OS X

  - by jbrennan

  I'm looking at building a Cocoa application on the Mac with a back-end daemon process (really just a mostly-headless Cocoa app, probably), along with 0 or more "client" applications running locally (although if possible I'd like to support remote clients as well; the remote clients would only ever be other Macs or iPhone OS devices). The data being communicated will be fairly trivial, mostly just text and commands (which I guess can be represented as text anyway), and maybe the occasional small file (an image possibly). I've looked at a few methods for doing this but I'm not sure which is "best" for the task at hand. Things I've considered: Reading and writing to a file (…yes), very basic but not very scalable. Pure sockets (I have no experience with sockets but I seem to think I can use them to send data locally and over a network. Though it seems cumbersome if doing everything in Cocoa Distributed Objects: seems rather inelegant for a task like this NSConnection: I can't really figure out what this class even does, but I've read of it in some IPC search results I'm sure there are things I'm missing, but I was surprised to find a lack of resources on this topic.

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• What is optimal hardware configuration for heavy load LAMP application

  - by Piotr Kochanski

  I need to run Linux-Apache-PHP-MySQL application (Moodle e-learning platform) for a large number of concurrent users - I am aiming 5000 users. By concurrent I mean that 5000 people should be able to work with the application at the same time. "Work" means not only do database reads but writes as well. The application is not very typical, since it is doing a lot of inserts/updates on the database, so caching techniques are not helping to much. We are using InnoDB storage engine. In addition application is not written with performance in mind. For instance one Apache thread usually occupies about 30-50 MB of RAM. I would be greatful for information what hardware is needed to build scalable configuration that is able to handle this kind of load. We are using right now two HP DLG 380 with two 4 core processors which are able to handle much lower load (typically 300-500 concurrent users). Is it reasonable to invest in this kind of boxes and build cluster using them or is it better to go with some more high-end hardware? I am particularly curious how many and how powerful servers are needed (number of processors/cores, size of RAM) what network equipment should be used (what kind of switches, network cards) any other hardware, like particular disc storage solutions, etc, that are needed Another thing is how to put together everything, that is what is the most optimal architecture. Clustering with MySQL is rather hard (people are complaining about MySQL Cluster, even here on Stackoverflow).

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• In IIS6, how to provide authenticated access to static files on remote server

  - by frankadelic

  We have a library of ZIP files that we would like to make available for download at an ASP.NET site. The files are sitting on a NAS device that is accessible from out web farm. Here is our initial strategy: Map an IIS virtual directory to the shared drive at path /zipfiles Users can download the zip files when given the URL However, if users share links to the files, anyone can download them. We would instead like to make use of the ASP.NET forms authentication in our site to validate users' requests before initiating the file transfer. A few problems: A request for a zip file is handled by IIS, not ASP.NET. So it is not subject to forms authentication. In addition, we don't want ASP.NET to handle the request, because it uses up an ASP.NET thread and is not scalable for download of large files. So, configuring the asp.net dll to handle *.zip requests is not an option. Any ideas on this? One idea we've tossed around is this: Initial request for download will be for an ashx handler. This handler will, after authentication, generate a download token which is saved to a database. Then, the user is redirected to the file with token appended in QueryString (e.g. /files/xyz.zip?token=123456789). An ISAPI plugin will be used to check the token. Also, the token will expire after x amount of time. Any thoughts on this? I have not implemented an ISAPI plugin so I'm not sure if this will even work. I would like to avoid custom coding since security is an issue and I'd prefer to use a time-tested solution.

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• Database for Python Twisted

  - by Will

  There's an API for Twisted apps to talk to a database in a scalable way: twisted.enterprise.dbapi The confusing thing is, which database to pick? The database will have a Twisted app that is mostly making inserts and updates and relatively few selects, and then other strictly-read-only clients that are accessing the database directly making selects. (The read-only users are not necessarily selecting the data that the Twisted app is inserting; its not as though the database is being used as a message-queue) My understanding - which I'd like corrected/adviced - is that: Postgres is a great DB, but all the Python bindings - and there is a confusing maze of them - are abandonware There is psycopg2, but that makes a lot of noise about doing its own connection-pooling and things; does this co-exist gracefully/usefully/transparently with the Twisted async database connection pooling and such? SQLLite is a great database for little things but if used in a multi-user way it does whole-database locking, so performance would suck in the usage pattern I envisage MySQL - after the Oracle takeover, who'd want to adopt it now or adopt a fork? Is there anything else out there?

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• How to create extensible dynamic array in Java without using pre-made classes?

  - by AndrejaKo

  Yeah, it's a homework question, so givemetehkodezplsthx! :) Anyway, here's what I need to do: I need to have a class which will have among its attributes array of objects of another class. The proper way to do this in my opinion would be to use something like LinkedList, Vector or similar. Unfortunately, last time I did that, I got fire and brimstone from my professor, because according to his belief I was using advanced stuff without understanding basics. Now next obvious solution would be to create array with fixed number of elements and add checks to get and set which will see if the array is full. If it is full, they'd create new bigger array, copy older array's data to the new array and return the new array to the caller. If it's mostly empty, they'd create new smaller array and move data from old array to new. To me this looks a bit stupid. For my homework, there probably won't be more that 3 elements in an array, but I'd like to make a scalable solution without manually calculating statistics about how often is array filled, what is the average number of new elements added, then using results of calculation to calculate number of elements in new array and so on. By the way, there is no need to remove elements from the middle of the array. Any tips?

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• how to make the red div don't alert 'ss' when drag the black div on it ,

  - by zjm1126

  i using jquery and jquery-ui, this is my code: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta name="viewport" content="width=device-width, user-scalable=no"> </head> <body> <style type="text/css" media="screen"> </style> <div id=a style="width:300px;height:300px;background:blue;position:absolute;"></div> <div id=b style="width:100px;height:100px;background:red;position:absolute;"></div> <div id=c style="width:50px;height:50px;background:black;clear:both"></div> <script src="jquery-1.4.2.js" type="text/javascript"></script> <script src="jquery-ui-1.8rc3.custom.min.js" type="text/javascript"></script> <script type="text/javascript" charset="utf-8"> $("#c").draggable({}); $("#b").droppable('disable');//this is not useful $("#a").droppable({ drop: function(event,ui) { alert('ss') } }); </script> </body> </html>

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• Temporary storage for keeping data between program iterations?

  - by mr.b

  I am working on an application that works like this: It fetches data from many sources, resulting in pool of about 500,000-1,500,000 records (depends on time/day) Data is parsed Part of data is processed in a way to compare it to pre-existing data (read from database), calculations are made, and stored in database. Resulting dataset that has to be stored in database is, however, much smaller in size (compared to original data set), and ranges from 5,000-50,000 records. This process almost always updates existing data, perhaps adds few more records. Then, data from step 2 should be kept somehow, somewhere, so that next time data is fetched, there is a data set which can be used to perform calculations, without touching pre-existing data in database. I should point out that this data can be lost, it's not irreplaceable (key information can be read from database if needed), but it would speed up the process next time. Application components can (and will be) run off different computers (in the same network), so storage has to be reachable from multiple hosts. I have considered using memcached, but I'm not quite sure should I do so, because one record is usually no smaller than 200 bytes, and if I have 1,500,000 records, I guess that it would amount to over 300 MB of memcached cache... But that doesn't seem scalable to me - what if data was 5x that amount? If it were to consume 1-2 GB of cache only to keep data in between iterations (which could easily happen)? So, the question is: which temporary storage mechanism would be most suitable for this kind of processing? I haven't considered using mysql temporary tables, as I'm not sure if they can persist between sessions, and be used by other hosts in network... Any other suggestion? Something I should consider?

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• PHP News Feed Database & Design

  - by pws5068

  I'm designing a News Feed system using PHP/MySQL similar to facebook's. I have asked a similar question before but now I've changed the design and I'm looking for feedback. Example News: User_A commented on User_B's new album. "Hey man nice pictures!" User_B added a new Photo to [his/her] profile. [show photo thumbnail] Initially, I implemented this using excessive columns for Obj1:Type1 | Obj2:Type2 | etc.. Now the design is set up using a couple special keywords, and actor/receiver relationships. My database uses a table of messages joined on a table containing userid,actionid,receiverid,receiverObjectTypeID, Here's a condensed version of what it will look like once joined: News_ID | User_ID | Message | Timestamp 2643 A %a commented on %o's new %r. SomeTimestamp 2644 B %a added a new %r to [his/her] profile. SomeTimestamp %a = the User_ID of the person doing the action %r = the receiving object %o = the owner of the receiving object (for example the owner of the album) (NULL if %r is a user) Questions: Is this a smart (efficient/scalable) way to move forward? How can I show messages like: "User_B added 4 new photos to his profile."?

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• Choosing between .NET Service Bus Queues vs Azure Queue Service

  - by ChrisV

  Just a quick question regarding an Azure application. If I have a number of Web and Worker roles that need to communicate, documentation says to use the Azure Queue Service. However, I've just read that the new .NET Service Bus now also offers queues. These look to be more powerful as they appear to offer a much more detailed API. Whilst the .NSB looks more interesting it has a couple of issues that make me wary of using it in distributed application. (for example, Queue Expiration... if I cannot guarantee that a queue will be renewed on time I may lose it all!). Has anyone had any experience using either of these two technologies and could give any advice on when to choose one over the other. I suspect that whilst the service bus looks more powerful, as my use case is really just enabling Web/Worker roles to communicate between each other, that the Azure Queue Service is what I'm after. But I'm just really looking for confirmation of that before progamming myself in to a corner :-) Thanks in advance. UPDATE Have read up about the two systems over the break. It defo looks like .NET service bus is more specifically designed for integrating systems rather than providing a general purpose reliable messaging system. Azure Queues are distributed and so reliable and scalable in a way that .NSB queues are not and so more suitable for code hosted within Azure itself. Thanks for the responses.

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• how can I save/keep-in-sync an in-memory graph of objects with the database?

  - by Greg

  Question - What is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Background: That is say I have the classes Node and Relationship, and the application is building up a graph of related objects using these classes. There might be 1000 nodes with various relationships between them. The application needs to query the structure hence an in-memory approach is good for performance no doubt (e.g. traverse the graph from Node X to find the root parents) The graph does need to be persisted however into a database with tables NODES and RELATIONSHIPS. Therefore what is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Ideal requirements would include: build up changes in-memory and then 'save' afterwards (mandatory) when saving, apply updates to database in correct order to avoid hitting any database constraints (mandatory) keep persistence mechanism separate from model, for ease in changing persistence layer if needed, e.g. don't just wrap an ADO.net DataRow in the Node and Relationship classes (desirable) mechanism for doing optimistic locking (desirable) Or is the overhead of all this for a smallish application just not worth it and I should just hit the database each time for everything? (assuming the response times were acceptable) [would still like to avoid if not too much extra overhead to remain somewhat scalable re performance]

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• How do I get the WVGA Android browser to stop scaling my images?

  - by Dan Fabulich

  I'm designing an HTML page for display in Android browsers. Consider this simple example page: <html> <head><title>Simple!</title> </head> <body> <p><img src="http://sstatic.net/so/img/logo.png"></p> </body> </html> It looks just fine on the standard HVGA phones (320x480), but on HDPI WVGA sizes (480x800 or 480x854) the built-in browser automatically scales the image up; it looks ugly. I've read that I should be able to use this tag to force the browser to stop scaling my page: <meta name="viewport" content="width=device-width; initial-scale=1.0; maximum-scale=1.0; minimum-scale=1.0; user-scalable=0;" /> ... but all that does is disable user scaling (the zoom buttons disappear); it doesn't actually prevent the browser from scaling my image. Adjusting the scale factors (setting them all to 2.0 or 0.5) has no effect at all. How can I force the WVGA browser to stop scaling my images?

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• stop background of iphone webapp from responding to swipes

  - by JoeS

  I'm making a mobile version of my website, and trying to make it feel as native as possible on the iphone. However, any background areas of the page respond to swiping gestures such that you can shift the page partway off the screen. Specifically, if the user touches and swipes left, for example, the content shifts off the edge of the screen and one can see a gray background 'behind' the page. How can this be prevented? I'd like to have the page itself be 320x480 with scroll-swiping disabled (except on list elements that I choose). I have added the following meta tags to the top of the page: <meta name="viewport" content="width=320; height=480; initial-scale=1.0; maximum-scale=1.0; user-scalable=0;"/> <meta name="apple-mobile-web-app-capable" content="yes" /> <meta name="apple-mobile-web-app-status-bar-style" content="black" /> I've also tried the following as the event handler for the touchstart, touchmove, and touchend events of the body element: function cancelTouchEvent(e) { if (!e) var e = window.event; e.cancelBubble = true; if (e.stopPropagation) e.stopPropagation(); if (e.preventDefault) e.preventDefault(); return false; } It doesn't stop the swiping behavior, but does prevent clicks on all links on the page... Any help is much appreciated. Thanks!

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• IBM Worklight v6.1.0.1 : Error when using Ionic Framework with Worklight and run on IOS environment

  - by NickNguyen

  I have created demo app using Ionic with Worklight and it worked on Android but got error on IOS, when i used mobile browser simulator and debugged on IOS environment, i got the folowing error message: Uncaught InvalidCharacterError: Failed to execute 'add' on 'DOMTokenList': The token provided ('platform-ios - iphone') contains HTML space characters, which are not valid in tokens. I just add Ionic files in index.html: <!DOCTYPE HTML> <html> <head> <meta charset="UTF-8"> <title>index</title> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=0"> <link rel="shortcut icon" href="images/favicon.png"> <link rel="apple-touch-icon" href="images/apple-touch-icon.png"> <link rel="stylesheet" href="css/main.css"> <link rel="stylesheet" href="ionic/css/ionic.css"> <script src="ionic/js/ionic.bundle.js"></script> </head> <body style="display: none;"> <!--application UI goes here--> <div class="bar bar-header bar-positive"> <h1 class="title">bar-positive</h1> </div> <script src="js/initOptions.js"></script> <script src="js/main.js"></script> <script src="js/messages.js"></script> </body> </html> I also tested on mobile device on both Android and IOS and only got error on IOS device. I don't know how to fix this. Can anyone help? Thanks.

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• Best practices, PHP, tracking millions of impressions per day.

  - by John

  What do I have to do to make 20k mysql inserts per second possible (during peak hours around 1k/sec during slower times)? I've been doing some research and I've seen the "INSERT DELAYED" suggestion, writing to a flat file, "fopen(file,'a')", and then running a chron job to dump the "needed" data into mysql, etc. I've also heard you need multiple servers and "load balancers" which I've never heard of, to make something like this work. I've also been looking at these "cloud server" thing-a-ma-jigs, and their automatic scalability, but not sure about what's actually scalable. The application is just a tracker script, so if I have 100 websites that get 3 million page loads a day, there will be around 300 million inserts a day. The data will be ran through a script that will run every 15-30 minutes which will normalize the data and insert it into another mysql table. How do the big dogs do it? How do the little dogs do it? I can't afford a huge server anymore so any intuitive ways, if there are multiple ways of going at it, you smart people can think of.. please let me know :)

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• Show users a list of unique items on Java Google App Engine

  - by James

  I've been going round in circles with what must be a very simple challenge but I want to do it the most efficient way from the start. So, I've watched Brett Slatkin's Google IO videos (2008 & 2009) about building scalable apps including http://www.youtube.com/watch?v=AgaL6NGpkB8 and read the docs but as a n00b, I'm still not sure. I'm trying to build an app on GAEJ similar to the original 'hotornot' where a user is presented with an item which they rate. Once they rate it, they are presented with another one which they haven't seen before. My question is this; is it most efficient to do a query up front to grab x items (say 100) and put them in a list (stored in memcache?) or is it better to simply make a query for a new item after each rating. To keep track of the items a user has seen, I'm planning to keep those items' keys in a list property of the user's entity. Does that sound sensible? I've really got myself confused about this so any help would be much appreciated.

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• Kindle Fire Cant Fit My Webpage inside a Webview of specific size

  - by Madhavan Rangarao

  This is baffling to me. Please help, I could not figure it out ... In my sample html file I have set the meta tag to be <meta name="viewport" content="target-densitydpi=device-dpi, user-scalable=no"> to fit the webpage inside my webview of custom size say 800x600. In Android, I had to specify "target-densitydpi=device-dpi" and it did the job nicely. I tested my custom web page with nexus 7 tablet and the web page fits inside my web view correctly. The same code does not work in Kindle Fire. Only a part of my web page is shown and even if I set the 'initial-scale=1.0' did not help. I tried various settings programmatically but it did not help either. webview.getSettings().setBuiltInZoomControls(true); webview.getSettings().setSupportZoom(true); webview.getSettings().setLoadWithOverviewMode(true); webview.setInitialScale(1); webview.getSettings().setUseWideViewPort(true); Any pointers?

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• Fastest Java way to remove the first/top line of a file (like a stack)

  - by christangrant

  I am trying to improve an external sort implementation in java. I have a bunch of BufferedReader objects open for temporary files. I repeatedly remove the top line from each of these files. This pushes the limits of the Java's Heap. I would like a more scalable method of doing this without loosing speed because of a bunch of constructor calls. One solution is to only open files when they are needed, then read the first line and then delete it. But I am afraid that this will be significantly slower. So using Java libraries what is the most efficient method of doing this. --Edit-- For external sort, the usual method is to break a large file up into several chunk files. Sort each of the chunks. And then treat the sorted files like buffers, pop the top item from each file, the smallest of all those is the global minimum. Then continue until for all items. http://en.wikipedia.org/wiki/External_sorting My temporary files (buffers) are basically BufferedReader objects. The operations performed on these files are the same as stack/queue operations (peek and pop, no push needed). I am trying to make these peek and pop operations more efficient. This is because using many BufferedReader objects takes up too much space.

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• RetinaJS and LESS : Background image doesn't show on iOS

  - by jidma

  I am trying to make a background image into a retina image using LESS CSS and RetinaJs: in my index.html file : <html> <head> <meta http-equiv="content-type" content="text/html; charset=UTF-8"> <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=0, minimum-scale=1.0, maximum-scale=1.0"> <meta name="apple-mobile-web-app-capable" content="yes"> <meta name="apple-mobile-web-app-status-bar-style" content="black"> [...] <link type="text/css" rel="stylesheet/less" href="resources/css/retina.less"> <script type="text/javascript" src="resources/js/less-1.3.0.minjs" ></script> [...] </head> <body> [...] <script type="text/javascript" src="resources/js/retina.js"></script> </body> </html> in my retina.less file: .at2x(@path, @w: auto, @h: auto) { background-image: url("@{path}"); @at2x_path: ~`"@{path}".split('.').slice(0, "@{path}".split('.').length - 1).join(".") + "@2x" + "." + "@{path}".split('.')["@{path}".split('.').length - 1]`; @media all and (-webkit-min-device-pixel-ratio : 1.5) { background-image: url("@{at2x_path}"); background-size: @w @h; } } .topMenu { .at2x('../../resources/img/topMenuTitle.png'); } I have both topMenuTitle.png (320px x 40px) and [email protected] (640px x 80px) in the same folder. When test this code: In Firefox i have the normal Background In the XCode iPhone simulator I also have the normal Background In the iPhone device, I don't have any background at all. I'm using GWT if that matters. Any suggestions ? Thanks.

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• multi-shop orders table and sequential order numbers based on shop

  - by imanc

  Hey, I am looking at building a shop solution that needs to be scalable. Currently it retrieves 1-2000 orders on average per day across multiple country based shops (e.g. uk, us, de, dk, es etc.) but this order could be 10x this amount in two years. I am looking at either using separate country-shop databases to store the orders tables, or looking to combine all into one order table. If all orders exist in one table with a global ID (auto num) and country ID (e.g uk,de,dk etc.), each countries orders would also need to have sequential ordering. So in essence, we'd have to have a global ID and a country order ID, with the country order ID being sequential for countries only, e.g. global ID = 1000, country = UK, country order ID = 1000 global ID = 1001, country = DE, country order ID = 1000 global ID = 1002, country = DE, country order ID = 1001 global ID = 1003, country = DE, country order ID = 1002 global ID = 1004, country = UK, country order ID = 1001 THe global ID would be DB generated and not something I would need to worry about. But I am thinking that I'd have to do a query to get the current country order based ID+1 to find the next sequential number. Two things concern me about this: 1) query times when the table has potentially millions of rows of data and I'm doing a read before a write, 2) the potential for ID number clashes due to simultaneous writes/reads. With a MyISAM table the entire table could be locked whilst the last country order + 1 is retrieved, to prevent ID number clashes. I am wondering if anyone knows of a more elegant solution? Cheers, imanc

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• how to make a div element edit-able ,like a textarea when i click..

  - by zjm1126

  this is my code: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta name="viewport" content="width=device-width, user-scalable=no"> </head> <body> <style type="text/css" media="screen"> </style> <!--<div id="map_canvas" style="width: 500px; height: 300px;background:blue;"></div>--> <div class=b style="width: 200px; height: 200px;background:pink;position:absolute;left:500px;top:100px;"></div> <script src="jquery-1.4.2.js" type="text/javascript"></script> <script src="jquery-ui-1.8rc3.custom.min.js" type="text/javascript"></script> <script type="text/javascript" charset="utf-8"> </script> </body> </html> thanks

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• A good data model for finding a user's favorite stories

  - by wings

  Original Design Here's how I originally had my Models set up: class UserData(db.Model): user = db.UserProperty() favorites = db.ListProperty(db.Key) # list of story keys # ... class Story(db.Model): title = db.StringProperty() # ... On every page that displayed a story I would query UserData for the current user: user_data = UserData.all().filter('user =' users.get_current_user()).get() story_is_favorited = (story in user_data.favorites) New Design After watching this talk: Google I/O 2009 - Scalable, Complex Apps on App Engine, I wondered if I could set things up more efficiently. class FavoriteIndex(db.Model): favorited_by = db.StringListProperty() The Story Model is the same, but I got rid of the UserData Model. Each instance of the new FavoriteIndex Model has a Story instance as a parent. And each FavoriteIndex stores a list of user id's in it's favorited_by property. If I want to find all of the stories that have been favorited by a certain user: index_keys = FavoriteIndex.all(keys_only=True).filter('favorited_by =', users.get_current_user().user_id()) story_keys = [k.parent() for k in index_keys] stories = db.get(story_keys) This approach avoids the serialization/deserialization that's otherwise associated with the ListProperty. Efficiency vs Simplicity I'm not sure how efficient the new design is, especially after a user decides to favorite 300 stories, but here's why I like it: A favorited story is associated with a user, not with her user data On a page where I display a story, it's pretty easy to ask the story if it's been favorited (without calling up a separate entity filled with user data). fav_index = FavoriteIndex.all().ancestor(story).get() fav_of_current_user = users.get_current_user().user_id() in fav_index.favorited_by It's also easy to get a list of all the users who have favorited a story (using the method in #2) Is there an easier way? Please help. How is this kind of thing normally done?

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• Fastest way to become a MySQL expert?

  - by Kerry

  I have been using MySQL for years, mainly on smaller projects until the last year or so. I'm not sure if it's the nature of the language or my lack of real tutorials that gives me the feeling of being unsure if what I'm writing is the proper way for optimization purposes and scaling purposes. While self-taught in PHP I'm very sure of myself and the code I write, easily can compare it to others and so on. With MySQL, I'm not sure whether (and in what cases) an INNER JOIN or LEFT JOIN should be used, nor am I aware of the large amount of functionality that it has. While I've written code for databases that handled tens of millions of records, I don't know if it's optimum. I often find that a small tweak will make a query take less than 1/10 of the original time... but how do I know that my current query isn't also slow? I would like to become completely confident in this field in the ability to optimize databases and be scalable. Use is not a problem -- I use it on a daily basis in a number of different ways. So, the question is, what's the path? Reading a book? Website/tutorials? Recommendations?

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• Searching Natural Language Sentence Structure

  - by Cerin

  What's the best way to store and search a database of natural language sentence structure trees? Using OpenNLP's English Treebank Parser, I can get fairly reliable sentence structure parsings for arbitrary sentences. What I'd like to do is create a tool that can extract all the doc strings from my source code, generate these trees for all sentences in the doc strings, store these trees and their associated function name in a database, and then allow a user to search the database using natural language queries. So, given the sentence "This uploads files to a remote machine." for the function upload_files(), I'd have the tree: (TOP (S (NP (DT This)) (VP (VBZ uploads) (NP (NNS files)) (PP (TO to) (NP (DT a) (JJ remote) (NN machine)))) (. .))) If someone entered the query "How can I upload files?", equating to the tree: (TOP (SBARQ (WHADVP (WRB How)) (SQ (MD can) (NP (PRP I)) (VP (VB upload) (NP (NNS files)))) (. ?))) how would I store and query these trees in a SQL database? I've written a simple proof-of-concept script that can perform this search using a mix of regular expressions and network graph parsing, but I'm not sure how I'd implement this in a scalable way. And yes, I realize my example would be trivial to retrieve using a simple keyword search. The idea I'm trying to test is how I might take advantage of grammatical structure, so I can weed-out entries with similar keywords, but a different sentence structure. For example, with the above query, I wouldn't want to retrieve the entry associated with the sentence "Checks a remote machine to find a user that uploads files." which has similar keywords, but is obviously describing a completely different behavior.

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• Connection Pool Strategy: Good, Bad or Ugly?

  - by Drew

  I'm in charge of developing and maintaining a group of Web Applications that are centered around similar data. The architecture I decided on at the time was that each application would have their own database and web-root application. Each application maintains a connection pool to its own database and a central database for shared data (logins, etc.) A co-worker has been positing that this strategy will not scale because having so many different connection pools will not be scalable and that we should refactor the database so that all of the different applications use a single central database and that any modifications that may be unique to a system will need to be reflected from that one database and then use a single pool powered by Tomcat. He has posited that there is a lot of "meta data" that goes back and forth across the network to maintain a connection pool. My understanding is that with proper tuning to use only as many connections as necessary across the different pools (low volume apps getting less connections, high volume apps getting more, etc.) that the number of pools doesn't matter compared to the number of connections or more formally that the difference in overhead required to maintain 3 pools of 10 connections is negligible compared to 1 pool of 30 connections. The reasoning behind initially breaking the systems into a one-app-one-database design was that there are likely going to be differences between the apps and that each system could make modifications on the schema as needed. Similarly, it eliminated the possibility of system data bleeding through to other apps. Unfortunately there is not strong leadership in the company to make a hard decision. Although my co-worker is backing up his worries only with vagueness, I want to make sure I understand the ramifications of multiple small databases/connections versus one large database/connection pool.

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• Designing model/database for distance between any two locations (that may change)

  - by Yo Ludke

  We should create a web app which has a number of events each with a location (created as user-generated content, so the number of events will be increasingly large). The distance between any events should be available, for example to determine the top 5 closest events and such things. Users may change the locations of events. How should one design the database/model for this (in a scalable way)? I was thinking of doing it with a "distance table" (like so http://www.deutschland-tourist.info/images/entfernungstabelle.gif). Then every time, if a location changes, one row and one column have to be recalculated (this should be done with a delayed job, because it is not important to have the changes instantly). Possible problems in Scaling: Database to large (n² items for n events), too much calculation to be done. For example we should see if this is okay for 10.000 users. If each has created just one event, then this would be 100 million integers... Do you think this would be a good way to do it efficiently? How could one realize such a distance table with an rails model? Is it possible with a SQL databse? Would you start other approaches?

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