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  • Problem with Javascript object and accessing property which exists

    - by Newbie
    I have something like this: var test = {}; function blah() { test[2] = 'filled'; } console.log(test); //result test -> 2:"filled" console.log(test[2]); //result undefined I don't understand why I'm getting 'undefined' in the second instance when according to the first instance, the property of that object clearly exists! Does anyone have any ideas? Thanks

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  • Loop through array, print with string.

    - by Adam
    I have a simple array like: var myArr=["one","two","three"]; an I have a counting loop, which increases the value of var i by one. What I want to do is print the next value from the array each time the loop runs, next to a text string, like so: alert('value number '+myArr[i]+); But for some reason I can't get this to work. The following code works, so I'm assuming I'm not calling the counter right: alert('value number '+myArr[0]+);

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  • managed object subclasses are not generating implementation files and are incorrectly named

    - by mkc842
    In Xcode 4.6, I generated plenty of managed object subclass files without any problem. But now that I'm trying to do it in Xcode 5, it generates only a .h file. The header file has the correct properties, but it takes the name of my project, rather than the name of the core data entity I selected. Just to be sure I hadn't forgotten something, I carefully followed these steps . What could be going on? Thanks

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  • PHP $array[0] in $string for JSON

    - by user1907696
    I am trying to use PHP to make a JSON file. Part of the code is as follow $array = array("hello", "world"); $string='{"person": [ { "name":'$array[0];', "age":'$array[1];' } ] }'; The file created. However, $array[0] and $array[1] doesn't return the values "hello" and "world" but as $array[0] and $array[1] Any idea? Thanks

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  • Remove substring from a string

    - by xRobot
    I want to remove the first characters from a string. Is there a function that work like this ?: . a = "BarackObama" print myfunction(4,a) "ckObama" b = "The world is mine" print myfunction(6,b) "rld is mine"

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  • Saving an Object for use later

    - by Eclipsed4utoo
    As part of my widget, I use an instance of the Camera object. This is what I want to do. The user will click on my widget, I get an instance of the Camera(if it's not already stored), use it, then store it. If they click the widget again, I want to use that same instance that I used previously. Is this possible?

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  • Protecting from crashes (beyond bounds) with [object objectAtIndex:]

    - by Tom
    Hi! I'd like to know if there's a way to verify if an index exists before getting it. So it'd be way to protect my code against: *** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[NSCFArray objectAtIndex:]: index (2) beyond bounds (0)' Like in PHP you can do: isset($object[10]); and it'll return true if it exists. Is there such a method in Objective-C/Cocoa? Thanks!

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  • IE: ‘nodeType’ is null or not an object

    - by Patrick
    hi, I'm having this issue on my website in IE (6,7,8): ‘nodeType’ is null or not an object The error refers to "f.nodeType" property. Basically f is undefined, so the issue is before, but I cannot fix it. Could you give me some help ? www.donatellabernardi.ch/drupal Thanks

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  • When I do ""+1 I get a String - Why

    - by steve
    Hi, Please understand firstly that I fully understand that Java will return a String when I use ""+int. What I'm really not sure about is what exactly is happening down at the memory aspect. How exactly is java performing this conversion. I mean this in a very indepth way, not 'auto boxing' or anything like that :) I'm hoping someone with a deeper understanding can explain what exactly is done.

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  • Reference string as object

    - by xintron
    I've got the following function that manipulates an element according to the data being sent (an object). function manipulateElem (elem, data) { for (var key in data) { elem[key] = data[key]; }; } manipulateElem(document.getElementById('test'), {'href': '/home/', 'style.color': '#000000'}); As you can imagine, the later (style.color) doesn't work. How would one solve this the best way?

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  • options[Text] is null or not an object in javascript

    - by user9167
    I am getting options[text] is null or not an object error. What i am trying to do here is i am checking what all multi select lookup column values are selected , comparing them with the value in an array and then removing them var responsibleselected = returntags("select","Responsibility selected values"); for(var i=0;i<responsibleselected.options.length;i++) { if(responsibleselected.options[i].selected == true) { for(var j=0;j< ResponsibleArray.length;j++) { if(responsibleselected.options[i].text == ResponsibleArray[j])//throws error here { GipRemoveSelectedItems(ctl00_m_g_6ad915a8_68ea_4c76_b67a_ad1215320288_ff391_ctl00_ctl00_MultiLookupPicker_m); } } } }

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  • ?# string analysis

    - by Sergei
    I have a string for example like " :)text :)text:) :-) word :-( " i need append it in textbox(or somewhere else), with condition: Instead of ':)' ,':-(', etc. need to call function which enter specific symbol I thinck exists solution with Finite-state machine, but how implement it don't know. Waiting for advises.

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  • Original object is also changed when values of cloned object are changed.

    - by fari
    I am trying to use clone but the original object is also changed when values of cloned object are changed. As you can see KalaGameState does not use any objects so a shallow copy should work. /** * This class represents the current state of a Kala game, including * which player's turn it is along with the state of the board; i.e. the * numbers of stones in each side pit, and each player's 'kala'). */ public class KalaGameState implements Cloneable { // your code goes here private int turn; private int[] sidePit; private boolean game; public Object clone() { try { return super.clone(); } catch (CloneNotSupportedException e) { // This should never happen throw new InternalError(e.toString()); } } /** * Constructs a new GameState with a specified number of stones in each * player's side pits. * @param startingStones the number of starting stones in each side pit. * @throws InvalidStartingStonesException if startingStones not in the range 1-10. */ public KalaGameState(int startingStones) throws InvalidStartingStonesException { game=true; turn=0; sidePit=new int[14]; for (int i=0; i <= 13 ; i++) { sidePit[i] = startingStones; } sidePit[6] =0; sidePit[13] =0; // your code goes here } /** * Returns the ID of the player whose turn it is. * @return A value of 0 = Player A, 1 = Player B. */ public int getTurn() { return turn; // your code goes here } /** * Returns the current kala for a specified player. * @param playerNum A value of 0 for Player A, 1 for Player B. * @throws IllegalPlayerNumException if the playerNum parameter * is not 0 or 1. */ public int getKala(int playerNum) throws IllegalPlayerNumException { if(playerNum!=0 || playerNum!=1) throw new IllegalPlayerNumException(playerNum); if(playerNum==0) return sidePit[6]; else return sidePit[13]; // your code goes here } /** * Returns the current number of stones in the specified pit for * the player whose turn it is. * @param sidePitNum the side pit being queried in the range 1-6. * @throws IllegalSidePitNumException if the sidePitNum parameter. * is not in the range 1-6. */ public int getNumStones(int sidePitNum) throws IllegalSidePitNumException { if(turn==0) { if(sidePitNum>6 ) throw new IllegalSidePitNumException(sidePitNum); } else if(sidePitNum>12) throw new IllegalSidePitNumException(sidePitNum); if(turn==0) return sidePit[sidePitNum]; else return sidePit[sidePitNum+6]; // your code goes here } /** * Returns the current number of stones in the specified pit for a specified player. * @param playerNum the player whose kala is sought. (0 = Player A, 1 = Player B). * @param sidePitNum the side pit being queried (in the range 1-6). * @throws IllegalPlayerNumException if the playerNum parameter is not 0 or 1. * @throws IllegalSidePitNumException if the sidePitNum parameter is not in the * range 1-6. */ public int getNumStones(int playerNum, int sidePitNum) throws IllegalPlayerNumException, IllegalSidePitNumException { /*if(playerNum>2) throw new IllegalPlayerNumException(playerNum); if(turn==0) { if(sidePitNum>6 ) throw new IllegalSidePitNumException(sidePitNum); } else if(sidePitNum>12) throw new IllegalSidePitNumException(sidePitNum); */ if(playerNum==0) return sidePit[sidePitNum]; else if(playerNum==1) return sidePit[sidePitNum+7]; else return sidePit[sidePitNum]; } /** * Returns the current score for a specified player - the player's * kala plus the number of stones in each of their side pits. * @param playerNum the player whose kala is sought. (0 = Player A, 1 = Player B). * @throws IllegalPlayerNumException if the playerNum parameter is not 0 or 1. */ public int getScore(int playerNum) throws IllegalPlayerNumException { if(playerNum>1) throw new IllegalPlayerNumException(playerNum); int score=0; if(playerNum==0) { for(int i=0;i<=5;i++) score=score+sidePit[i]; score=score+sidePit[6]; } else { for(int i=7;i<=12;i++) score=score+sidePit[i]; score=score+sidePit[13]; } // your code goes here return score; } private int getSidePitArrayIndex(int sidePitNum) throws IllegalSidePitNumException { if(turn==0) { if(sidePitNum>6 ) throw new IllegalSidePitNumException(sidePitNum); } else if(sidePitNum>12) throw new IllegalSidePitNumException(sidePitNum); if(turn==0) { return sidePitNum--; } else { return sidePitNum+6; } } public boolean gameOver() { int stone=0; if(turn==0) for(int i=0;i<=5;i++) stone=stone+getNumStones(i); else for(int i=7;i<=12;i++) stone=stone+getNumStones(i-7); if (stone==0) game=false; return game; } /** * Makes a move for the player whose turn it is. * @param sidePitNum the side pit being queried (should be in the range 1-6) * @throws IllegalSidePitNumException if the sidePitNum parameter is not in the range 1-6. * @throws IllegalMoveException if the side pit is empty and has no stones in it. */ public void makeMove(int sidePitNum) throws IllegalSidePitNumException, IllegalMoveException { if(turn==0) { if(sidePitNum>6 ) throw new IllegalSidePitNumException(sidePitNum); } else if(sidePitNum>12) throw new IllegalSidePitNumException(sidePitNum); /* if(turn==0) { if(sidePit[sidePitNum-1]==0) throw new IllegalMoveException(sidePitNum); } else { if(sidePit[sidePitNum-1+7]==0) throw new IllegalMoveException(sidePitNum); } */ sidePitNum--; int temp=sidePitNum; int pitNum=sidePitNum+1; int stones=getNumStones(turn,sidePitNum); if(turn==0) sidePit[sidePitNum]=0; else { sidePitNum=sidePitNum+7; sidePit[sidePitNum]=0; pitNum=pitNum+7; } while(stones!=0) { if(turn==0) { sidePit[pitNum]=sidePit[pitNum]+1; stones--; pitNum++; if(pitNum==13) pitNum=0; } else { sidePit[pitNum]=sidePit[pitNum]+1; stones--; pitNum++; if(pitNum==6) pitNum=7; else if(pitNum==14) pitNum=0; } } boolean res=anotherTurn(pitNum); if(!res){ capture(pitNum,temp); if(turn==0) turn=1; else turn=0;} } private boolean anotherTurn(int pitNum) {pitNum--; boolean temp=false; if(turn==0) {if(pitNum==6) {turn=0; temp=true; } } else if(pitNum==-1) {turn=1; temp=true; } return temp; } private void capture(int pitNum, int pit) { pitNum--; if(turn==0){ if(sidePit[pitNum]==1 && pitNum<6) { if(pitNum==0) { sidePit[6]=sidePit[6]+sidePit[12]+1; sidePit[12]=0; } else if(pitNum==1) { sidePit[6]=sidePit[6]+sidePit[11]+1; sidePit[11]=0; } else if(pitNum==2) { sidePit[6]=sidePit[6]+sidePit[10]+1; sidePit[10]=0; } else if(pitNum==3) { sidePit[6]=sidePit[6]+sidePit[9]+1; sidePit[9]=0; } else if(pitNum==4) { sidePit[6]=sidePit[6]+sidePit[8]+1; sidePit[8]=0; } else if(pitNum==5) { sidePit[6]=sidePit[6]+sidePit[7]+1; sidePit[7]=0; } sidePit[pitNum]=0; } } if(turn==1) { //pitNum=pitNum; if(sidePit[pitNum]==1 && pit+7>6) { if(pitNum==7) { sidePit[13]=sidePit[13]+sidePit[5]+1; sidePit[7]=0; } else if(pitNum==8) { sidePit[13]=sidePit[13]+sidePit[4]+1; sidePit[4]=0; } else if(pitNum==9) { sidePit[13]=sidePit[13]+sidePit[3]+1; sidePit[3]=0; } else if(pitNum==10) { sidePit[13]=sidePit[13]+sidePit[2]+1; sidePit[2]=0; } else if(pitNum==11) { sidePit[13]=sidePit[13]+sidePit[1]+1; sidePit[1]=0; } else if(pitNum==12) { sidePit[13]=sidePit[13]+sidePit[0]+1; sidePit[0]=0; } sidePit[pitNum]=0; } } } } import java.io.BufferedReader; import java.io.InputStreamReader; public class RandomPlayer extends KalaPlayer{ //KalaGameState state; public int chooseMove(KalaGameState gs) throws NoMoveAvailableException {int[] moves; moves=getMoves(gs); try{ for(int i=0;i<=5;i++) System.out.println(moves[i]); for(int i=0;i<=5;i++) { if(moves[i]==1) { KalaGameState state=(KalaGameState) gs.clone(); state.makeMove(moves[i]); gs.getTurn(); moves[i]=evalValue(state.getScore(0),state.getScore(1)); } } } catch(IllegalMoveException e) { System.out.println(e); //chooseMove(state); } return 10; } private int evalValue(int score0,int score1) { int score=0; //int score0=0; // int score1=0; //getScore(0); //score1=state.getScore(1); //if((state.getTurn())==0) score=score1-score0; //else //score=score1-score0; System.out.println("score: "+score); return score; } public int[] getMoves(KalaGameState gs) { int[] moves=new int[6]; for(int i=1;i<=6;i++) { if(gs.getNumStones(i)!=0) moves[i-1]=1; else moves[i-1]=0; } return moves; } } Can you explain what is going wrong, please?

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  • Reading Data from DDFS ValueError: No JSON object could be decoded

    - by secumind
    I'm running dozens of map reduce jobs for a number of different purposes using disco. My data has grown enormous and I thought I would try using DDFS for a change rather than standard txt files. I've followed the DISCO map/reduce example Counting Words as a map/reduce job, without to much difficulty and with the help of others, Reading JSON specific data into DISCO I've gotten past one of my latest problems. I'm trying to read data in/out of ddfs to better chunk and distribute it but am having a bit of trouble. Here's an example file: file.txt {"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "I'll call him back tomorrow I guess", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016843603968", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/305726905/FASHION-3.png", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1818996723/image_normal.jpg", "profile_sidebar_fill_color": "292727", "is_translator": false, "id": 113532729, "profile_text_color": "000000", "followers_count": 78, "protected": false, "location": "With My Niggas In Paris!", "default_profile_image": false, "listed_count": 0, "utc_offset": -21600, "statuses_count": 6733, "description": "Made in CHINA., Educated && Making My Own $$. Fear GOD && Put Him 1st. #TeamFollowBack #TeamiPhone\n", "friends_count": 74, "profile_link_color": "b03f3f", "profile_image_url": "http://a2.twimg.com/profile_images/1818996723/image_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "1f9199", "id_str": "113532729", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/305726905/FASHION-3.png", "name": "Bee'Jay", "lang": "en", "profile_background_tile": true, "favourites_count": 19, "screen_name": "OohMyBEEsNice", "url": "http://www.bitchimpaid.org", "created_at": "Fri Feb 12 03:32:54 +0000 2010", "contributors_enabled": false, "time_zone": "Central Time (US & Canada)", "profile_sidebar_border_color": "000000", "default_profile": false, "following": null}, "in_reply_to_screen_name": null, "retweet_count": 0, "geo": null, "id": 168931016843603968, "source": "<a href=\"http://twitter.com/#!/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>"} {"favorited": false, "in_reply_to_user_id": 50940453, "contributors": null, "truncated": false, "text": "@LegaMrvica @MimozaBand makasi om artis :D kadoo kadoo", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": "168653037894770688", "coordinates": null, "in_reply_to_user_id_str": "50940453", "entities": {"user_mentions": [{"indices": [0, 11], "screen_name": "LegaMrvica", "id": 50940453, "name": "Lega_thePianis", "id_str": "50940453"}, {"indices": [12, 23], "screen_name": "MimozaBand", "id": 375128905, "name": "Mimoza", "id_str": "375128905"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": 168653037894770688, "id_str": "168931016868761600", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "profile_sidebar_fill_color": "DDFFCC", "is_translator": false, "id": 48293450, "profile_text_color": "333333", "followers_count": 182, "protected": false, "location": "\u00dcT: -6.906799,107.622383", "default_profile_image": false, "listed_count": 0, "utc_offset": -28800, "statuses_count": 3052, "description": "Fashion design maranatha '11 // traditional dancer (bali) at sanggar tampak siring & Natya Nataraja", "friends_count": 206, "profile_link_color": "0084B4", "profile_image_url": "http://a3.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "9AE4E8", "id_str": "48293450", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "name": "nana afiff", "lang": "en", "profile_background_tile": true, "favourites_count": 2, "screen_name": "hasnfebria", "url": null, "created_at": "Thu Jun 18 08:50:29 +0000 2009", "contributors_enabled": false, "time_zone": "Pacific Time (US & Canada)", "profile_sidebar_border_color": "BDDCAD", "default_profile": false, "following": null}, "in_reply_to_screen_name": "LegaMrvica", "retweet_count": 0, "geo": null, "id": 168931016868761600, "source": "<a href=\"http://blackberry.com/twitter\" rel=\"nofollow\">Twitter for BlackBerry\u00ae</a>"} {"favorited": false, "in_reply_to_user_id": 27260086, "contributors": null, "truncated": false, "text": "@justinbieber u were born to be somebody, and u're super important in beliebers' life. thanks for all biebs. I love u. follow me? 84", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": "27260086", "entities": {"user_mentions": [{"indices": [0, 13], "screen_name": "justinbieber", "id": 27260086, "name": "Justin Bieber", "id_str": "27260086"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016856178688", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/416005864/Captura.JPG", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "profile_sidebar_fill_color": "f5e7f3", "is_translator": false, "id": 406750700, "profile_text_color": "333333", "followers_count": 1122, "protected": false, "location": "Adentro de una supra.", "default_profile_image": false, "listed_count": 0, "utc_offset": -14400, "statuses_count": 20966, "description": "Mi \u00eddolo es @justinbieber , si te gusta \u00a1genial!, si no, solo respetalo. El cambi\u00f3 mi vida completamente y mi sue\u00f1o es conocerlo #TrueBelieber . ", "friends_count": 1015, "profile_link_color": "9404b8", "profile_image_url": "http://a1.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "f9fcfa", "id_str": "406750700", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/416005864/Captura.JPG", "name": "neversaynever,right?", "lang": "es", "profile_background_tile": false, "favourites_count": 22, "screen_name": "True_Belieebers", "url": "http://www.wehavebieber-fever.tumblr.com", "created_at": "Mon Nov 07 04:17:40 +0000 2011", "contributors_enabled": false, "time_zone": "Santiago", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "in_reply_to_screen_name": "justinbieber", "retweet_count": 0, "geo": null, "id": 168931016856178688, "source": "<a href=\"http://yfrog.com\" rel=\"nofollow\">Yfrog</a>"} I load it into DDFS with: # ddfs chunk data:test1 ./file.txt created: disco://localhost/ddfs/vol0/blob/44/file_txt-0$549-db27b-125e1 I test that the file is indeed loaded into ddfs with: # ddfs xcat data:test1 {"favorited": false, "in_reply_to_user_id": null, "contributors": null, "truncated": false, "text": "I'll call him back tomorrow I guess", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": null, "entities": {"user_mentions": [], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016843603968", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/305726905/FASHION-3.png", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1818996723/image_normal.jpg", "profile_sidebar_fill_color": "292727", "is_translator": false, "id": 113532729, "profile_text_color": "000000", "followers_count": 78, "protected": false, "location": "With My Niggas In Paris!", "default_profile_image": false, "listed_count": 0, "utc_offset": -21600, "statuses_count": 6733, "description": "Made in CHINA., Educated && Making My Own $$. Fear GOD && Put Him 1st. #TeamFollowBack #TeamiPhone\n", "friends_count": 74, "profile_link_color": "b03f3f", "profile_image_url": "http://a2.twimg.com/profile_images/1818996723/image_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "1f9199", "id_str": "113532729", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/305726905/FASHION-3.png", "name": "Bee'Jay", "lang": "en", "profile_background_tile": true, "favourites_count": 19, "screen_name": "OohMyBEEsNice", "url": "http://www.bitchimpaid.org", "created_at": "Fri Feb 12 03:32:54 +0000 2010", "contributors_enabled": false, "time_zone": "Central Time (US & Canada)", "profile_sidebar_border_color": "000000", "default_profile": false, "following": null}, "in_reply_to_screen_name": null, "retweet_count": 0, "geo": null, "id": 168931016843603968, "source": "<a href=\"http://twitter.com/#!/download/iphone\" rel=\"nofollow\">Twitter for iPhone</a>"} {"favorited": false, "in_reply_to_user_id": 50940453, "contributors": null, "truncated": false, "text": "@LegaMrvica @MimozaBand makasi om artis :D kadoo kadoo", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": "168653037894770688", "coordinates": null, "in_reply_to_user_id_str": "50940453", "entities": {"user_mentions": [{"indices": [0, 11], "screen_name": "LegaMrvica", "id": 50940453, "name": "Lega_thePianis", "id_str": "50940453"}, {"indices": [12, 23], "screen_name": "MimozaBand", "id": 375128905, "name": "Mimoza", "id_str": "375128905"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": 168653037894770688, "id_str": "168931016868761600", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "profile_sidebar_fill_color": "DDFFCC", "is_translator": false, "id": 48293450, "profile_text_color": "333333", "followers_count": 182, "protected": false, "location": "\u00dcT: -6.906799,107.622383", "default_profile_image": false, "listed_count": 0, "utc_offset": -28800, "statuses_count": 3052, "description": "Fashion design maranatha '11 // traditional dancer (bali) at sanggar tampak siring & Natya Nataraja", "friends_count": 206, "profile_link_color": "0084B4", "profile_image_url": "http://a3.twimg.com/profile_images/1803845596/Picture_20124_normal.jpg", "notifications": null, "show_all_inline_media": false, "geo_enabled": true, "profile_background_color": "9AE4E8", "id_str": "48293450", "profile_background_image_url": "http://a0.twimg.com/profile_background_images/347686061/Galungan_dan_Kuningan.jpg", "name": "nana afiff", "lang": "en", "profile_background_tile": true, "favourites_count": 2, "screen_name": "hasnfebria", "url": null, "created_at": "Thu Jun 18 08:50:29 +0000 2009", "contributors_enabled": false, "time_zone": "Pacific Time (US & Canada)", "profile_sidebar_border_color": "BDDCAD", "default_profile": false, "following": null}, "in_reply_to_screen_name": "LegaMrvica", "retweet_count": 0, "geo": null, "id": 168931016868761600, "source": "<a href=\"http://blackberry.com/twitter\" rel=\"nofollow\">Twitter for BlackBerry\u00ae</a>"} {"favorited": false, "in_reply_to_user_id": 27260086, "contributors": null, "truncated": false, "text": "@justinbieber u were born to be somebody, and u're super important in beliebers' life. thanks for all biebs. I love u. follow me? 84", "created_at": "Mon Feb 13 05:34:27 +0000 2012", "retweeted": false, "in_reply_to_status_id_str": null, "coordinates": null, "in_reply_to_user_id_str": "27260086", "entities": {"user_mentions": [{"indices": [0, 13], "screen_name": "justinbieber", "id": 27260086, "name": "Justin Bieber", "id_str": "27260086"}], "hashtags": [], "urls": []}, "in_reply_to_status_id": null, "id_str": "168931016856178688", "place": null, "user": {"follow_request_sent": null, "profile_use_background_image": true, "profile_background_image_url_https": "https://si0.twimg.com/profile_background_images/416005864/Captura.JPG", "verified": false, "profile_image_url_https": "https://si0.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "profile_sidebar_fill_color": "f5e7f3", "is_translator": false, "id": 406750700, "profile_text_color": "333333", "followers_count": 1122, "protected": false, "location": "Adentro de una supra.", "default_profile_image": false, "listed_count": 0, "utc_offset": -14400, "statuses_count": 20966, "description": "Mi \u00eddolo es @justinbieber , si te gusta \u00a1genial!, si no, solo respetalo. El cambi\u00f3 mi vida completamente y mi sue\u00f1o es conocerlo #TrueBelieber . ", "friends_count": 1015, "profile_link_color": "9404b8", "profile_image_url": "http://a1.twimg.com/profile_images/1808883280/Captura6_normal.JPG", "notifications": null, "show_all_inline_media": false, "geo_enabled": false, "profile_background_color": "f9fcfa", "id_str": "406750700", "profile_background_image_url": "http://a3.twimg.com/profile_background_images/416005864/Captura.JPG", "name": "neversaynever,right?", "lang": "es", "profile_background_tile": false, "favourites_count": 22, "screen_name": "True_Belieebers", "url": "http://www.wehavebieber-fever.tumblr.com", "created_at": "Mon Nov 07 04:17:40 +0000 2011", "contributors_enabled": false, "time_zone": "Santiago", "profile_sidebar_border_color": "C0DEED", "default_profile": false, "following": null}, "in_reply_to_screen_name": "justinbieber", "retweet_count": 0, "geo": null, "id": 168931016856178688, "source": "<a href=\"http://yfrog.com\" rel=\"nofollow\">Yfrog</a> At this point everything is great, I load up the script that resulted from a previous Stack Post: from disco.core import Job, result_iterator import gzip def map(line, params): import unicodedata import json r = json.loads(line).get('text') s = unicodedata.normalize('NFD', r).encode('ascii', 'ignore') for word in s.split(): yield word, 1 def reduce(iter, params): from disco.util import kvgroup for word, counts in kvgroup(sorted(iter)): yield word, sum(counts) if __name__ == '__main__': job = Job().run(input=["tag://data:test1"], map=map, reduce=reduce) for word, count in result_iterator(job.wait(show=True)): print word, count NOTE: That this script runs file if the input=["file.txt"], however when I run it with "tag://data:test1" I get the following error: # DISCO_EVENTS=1 python count_normal_words.py Job@549:db30e:25bd8: Status: [map] 0 waiting, 1 running, 0 done, 0 failed 2012/11/25 21:43:26 master New job initialized! 2012/11/25 21:43:26 master Starting job 2012/11/25 21:43:26 master Starting map phase 2012/11/25 21:43:26 master map:0 assigned to solice 2012/11/25 21:43:26 master ERROR: Job failed: Worker at 'solice' died: Traceback (most recent call last): File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/__init__.py", line 329, in main job.worker.start(task, job, **jobargs) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/__init__.py", line 290, in start self.run(task, job, **jobargs) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/classic/worker.py", line 286, in run getattr(self, task.mode)(task, params) File "/home/DISCO/data/solice/01/Job@549:db30e:25bd8/usr/local/lib/python2.7/site-packages/disco/worker/classic/worker.py", line 299, in map for key, val in self['map'](entry, params): File "count_normal_words.py", line 12, in map File "/usr/lib64/python2.7/json/__init__.py", line 326, in loads return _default_decoder.decode(s) File "/usr/lib64/python2.7/json/decoder.py", line 366, in decode obj, end = self.raw_decode(s, idx=_w(s, 0).end()) File "/usr/lib64/python2.7/json/decoder.py", line 384, in raw_decode raise ValueError("No JSON object could be decoded") ValueError: No JSON object could be decoded 2012/11/25 21:43:26 master WARN: Job killed Status: [map] 1 waiting, 0 running, 0 done, 1 failed Traceback (most recent call last): File "count_normal_words.py", line 28, in <module> for word, count in result_iterator(job.wait(show=True)): File "/usr/local/lib/python2.7/site-packages/disco/core.py", line 348, in wait timeout, poll_interval * 1000) File "/usr/local/lib/python2.7/site-packages/disco/core.py", line 309, in check_results raise JobError(Job(name=jobname, master=self), "Status %s" % status) disco.error.JobError: Job Job@549:db30e:25bd8 failed: Status dead The Error states: ValueError: No JSON object could be decoded. Again, this works fine using the text file as input but now DDFS. Any ideas, I'm open to suggestions?

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  • WatiN screenshot saver

    - by Brian Schroer
    In addition to my automated unit, system and integration tests for ASP.NET projects, I like to give my customers something pretty that they can look at and visually see that the web site is behaving properly. I use the Gallio test runner to produce a pretty HTML report, and WatiN (Web Application Testing In .NET) to test the UI and create screenshots. I have a couple of issues with WatiN’s “CaptureWebPageToFile” method, though: It blew up the first (and only) time I tried it, possibly because… It scrolls down to capture the entire web page (I tried it on a very long page), and I usually don’t need that Also, sometimes I don’t need a picture of the whole browser window - I just want a picture of the element that I'm testing (for example, proving that a button has the correct caption). I wrote a WatiN screenshot saver helper class with these methods: SaveBrowserWindowScreenshot(Watin.Core.IE ie)  / SaveBrowserWindowScreenshot(Watin.Core.Element element) saves a screenshot of the browser window SaveBrowserWindowScreenshotWithHighlight(Watin.Core.Element element) saves a screenshot of the browser window, with the specified element scrolled into view and highlighted SaveElementScreenshot(Watin.Core.Element element) saves a picture of only the specified element The element highlighting improves on the built-in WatiN method (which just gives the element a yellow background, and makes the element pretty much unreadable when you have a light foreground color) by adding the ability to specify a HighlightCssClassName that points to a style in your site’s stylesheet. This code is specifically for testing with Internet Explorer (‘cause that’s what I have to test with at work), but you’re welcome to take it and do with it what you want… using System; using System.Drawing; using System.Drawing.Imaging; using System.IO; using System.Reflection; using System.Runtime.InteropServices; using System.Text; using System.Threading; using SHDocVw; using WatiN.Core; using mshtml; namespace BrianSchroer.TestHelpers { public static class WatinScreenshotSaver { public static void SaveBrowserWindowScreenshotWithHighlight (Element element, string screenshotName) { HighlightElement(element, true); SaveBrowserWindowScreenshot(element, screenshotName); HighlightElement(element, false); } public static void SaveBrowserWindowScreenshotWithHighlight(Element element) { HighlightElement(element, true); SaveBrowserWindowScreenshot(element); HighlightElement(element, false); } public static void SaveBrowserWindowScreenshot(Element element, string screenshotName) { SaveScreenshot(GetIe(element), screenshotName, SaveBitmapForCallbackArgs); } public static void SaveBrowserWindowScreenshot(Element element) { SaveScreenshot(GetIe(element), null, SaveBitmapForCallbackArgs); } public static void SaveBrowserWindowScreenshot(IE ie, string screenshotName) { SaveScreenshot(ie, screenshotName, SaveBitmapForCallbackArgs); } public static void SaveBrowserWindowScreenshot(IE ie) { SaveScreenshot(ie, null, SaveBitmapForCallbackArgs); } public static void SaveElementScreenshot(Element element, string screenshotName) { // TODO: Figure out how to get browser window "chrome" size and not have to go to full screen: var iex = (InternetExplorerClass) GetIe(element).InternetExplorer; bool fullScreen = iex.FullScreen; if (!fullScreen) iex.FullScreen = true; ScrollIntoView(element); SaveScreenshot(GetIe(element), screenshotName, args => SaveElementBitmapForCallbackArgs(element, args)); iex.FullScreen = fullScreen; } public static void SaveElementScreenshot(Element element) { SaveElementScreenshot(element, null); } private static void SaveScreenshot(IE browser, string screenshotName, Action<ScreenshotCallbackArgs> screenshotCallback) { string fileName = string.Format("{0:000}{1}{2}.jpg", ++_screenshotCount, (string.IsNullOrEmpty(screenshotName)) ? "" : " ", screenshotName); string path = Path.Combine(ScreenshotDirectoryName, fileName); Console.WriteLine(); // Gallio HTML-encodes the following display, but I have a utility program to // remove the "HTML===" and "===HTML" and un-encode the rest to show images in the Gallio report: Console.WriteLine("HTML===<div><b>{0}:</br></b><img src=\"{1}\" /></div>===HTML", screenshotName, new Uri(path).AbsoluteUri); MakeBrowserWindowTopmost(browser); try { var args = new ScreenshotCallbackArgs { InternetExplorerClass = (InternetExplorerClass)browser.InternetExplorer, ScreenshotPath = path }; Thread.Sleep(100); screenshotCallback(args); } catch (Exception ex) { Console.WriteLine(ex.Message); } } public static void HighlightElement(Element element, bool doHighlight) { if (!element.Exists) return; if (string.IsNullOrEmpty(HighlightCssClassName)) { element.Highlight(doHighlight); return; } string jsRef = element.GetJavascriptElementReference(); if (string.IsNullOrEmpty(jsRef)) return; var sb = new StringBuilder("try { "); sb.AppendFormat(" {0}.scrollIntoView(false);", jsRef); string format = (doHighlight) ? "{0}.className += ' {1}'" : "{0}.className = {0}.className.replace(' {1}', '')"; sb.AppendFormat(" " + format + ";", jsRef, HighlightCssClassName); sb.Append("} catch(e) {}"); string script = sb.ToString(); GetIe(element).RunScript(script); } public static void ScrollIntoView(Element element) { string jsRef = element.GetJavascriptElementReference(); if (string.IsNullOrEmpty(jsRef)) return; var sb = new StringBuilder("try { "); sb.AppendFormat(" {0}.scrollIntoView(false);", jsRef); sb.Append("} catch(e) {}"); string script = sb.ToString(); GetIe(element).RunScript(script); } public static void MakeBrowserWindowTopmost(IE ie) { ie.BringToFront(); SetWindowPos(ie.hWnd, HWND_TOPMOST, 0, 0, 0, 0, TOPMOST_FLAGS); } public static string HighlightCssClassName { get; set; } private static int _screenshotCount; private static string _screenshotDirectoryName; public static string ScreenshotDirectoryName { get { if (_screenshotDirectoryName == null) { var asm = Assembly.GetAssembly(typeof(WatinScreenshotSaver)); var uri = new Uri(asm.CodeBase); var fileInfo = new FileInfo(uri.LocalPath); string directoryName = fileInfo.DirectoryName; _screenshotDirectoryName = Path.Combine( directoryName, string.Format("Screenshots_{0:yyyyMMddHHmm}", DateTime.Now)); Console.WriteLine("Screenshot folder: {0}", _screenshotDirectoryName); Directory.CreateDirectory(_screenshotDirectoryName); } return _screenshotDirectoryName; } set { _screenshotDirectoryName = value; _screenshotCount = 0; } } [DllImport("user32.dll")] [return: MarshalAs(UnmanagedType.Bool)] private static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X, int Y, int cx, int cy, uint uFlags); private static readonly IntPtr HWND_TOPMOST = new IntPtr(-1); private const UInt32 SWP_NOSIZE = 0x0001; private const UInt32 SWP_NOMOVE = 0x0002; private const UInt32 TOPMOST_FLAGS = SWP_NOMOVE | SWP_NOSIZE; private static IE GetIe(Element element) { if (element == null) return null; var container = element.DomContainer; while (container as IE == null) container = container.DomContainer; return (IE)container; } private static void SaveBitmapForCallbackArgs(ScreenshotCallbackArgs args) { InternetExplorerClass iex = args.InternetExplorerClass; SaveBitmap(args.ScreenshotPath, iex.Left, iex.Top, iex.Width, iex.Height); } private static void SaveElementBitmapForCallbackArgs(Element element, ScreenshotCallbackArgs args) { InternetExplorerClass iex = args.InternetExplorerClass; Rectangle bounds = GetElementBounds(element); SaveBitmap(args.ScreenshotPath, iex.Left + bounds.Left, iex.Top + bounds.Top, bounds.Width, bounds.Height); } /// <summary> /// This method is used instead of element.NativeElement.GetElementBounds because that /// method has a bug (http://sourceforge.net/tracker/?func=detail&aid=2994660&group_id=167632&atid=843727). /// </summary> private static Rectangle GetElementBounds(Element element) { var ieElem = element.NativeElement as WatiN.Core.Native.InternetExplorer.IEElement; IHTMLElement elem = ieElem.AsHtmlElement; int left = elem.offsetLeft; int top = elem.offsetTop; for (IHTMLElement parent = elem.offsetParent; parent != null; parent = parent.offsetParent) { left += parent.offsetLeft; top += parent.offsetTop; } return new Rectangle(left, top, elem.offsetWidth, elem.offsetHeight); } private static void SaveBitmap(string path, int left, int top, int width, int height) { using (var bitmap = new Bitmap(width, height)) { using (Graphics g = Graphics.FromImage(bitmap)) { g.CopyFromScreen( new Point(left, top), Point.Empty, new Size(width, height) ); } bitmap.Save(path, ImageFormat.Jpeg); } } private class ScreenshotCallbackArgs { public InternetExplorerClass InternetExplorerClass { get; set; } public string ScreenshotPath { get; set; } } } }

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  • Sending Messages to SignalR Hubs from the Outside

    - by Ricardo Peres
    Introduction You are by now probably familiarized with SignalR, Microsoft’s API for real-time web functionality. This is, in my opinion, one of the greatest products Microsoft has released in recent time. Usually, people login to a site and enter some page which is connected to a SignalR hub. Then they can send and receive messages – not just text messages, mind you – to other users in the same hub. Also, the server can also take the initiative to send messages to all or a specified subset of users on its own, this is known as server push. The normal flow is pretty straightforward, Microsoft has done a great job with the API, it’s clean and quite simple to use. And for the latter – the server taking the initiative – it’s also quite simple, just involves a little more work. The Problem The API for sending messages can be achieved from inside a hub – an instance of the Hub class – which is something that we don’t have if we are the server and we want to send a message to some user or group of users: the Hub instance is only instantiated in response to a client message. The Solution It is possible to acquire a hub’s context from outside of an actual Hub instance, by calling GlobalHost.ConnectionManager.GetHubContext<T>(). This API allows us to: Broadcast messages to all connected clients (possibly excluding some); Send messages to a specific client; Send messages to a group of clients. So, we have groups and clients, each is identified by a string. Client strings are called connection ids and group names are free-form, given by us. The problem with client strings is, we do not know how these map to actual users. One way to achieve this mapping is by overriding the Hub’s OnConnected and OnDisconnected methods and managing the association there. Here’s an example: 1: public class MyHub : Hub 2: { 3: private static readonly IDictionary<String, ISet<String>> users = new ConcurrentDictionary<String, ISet<String>>(); 4:  5: public static IEnumerable<String> GetUserConnections(String username) 6: { 7: ISet<String> connections; 8:  9: users.TryGetValue(username, out connections); 10:  11: return (connections ?? Enumerable.Empty<String>()); 12: } 13:  14: private static void AddUser(String username, String connectionId) 15: { 16: ISet<String> connections; 17:  18: if (users.TryGetValue(username, out connections) == false) 19: { 20: connections = users[username] = new HashSet<String>(); 21: } 22:  23: connections.Add(connectionId); 24: } 25:  26: private static void RemoveUser(String username, String connectionId) 27: { 28: users[username].Remove(connectionId); 29: } 30:  31: public override Task OnConnected() 32: { 33: AddUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 34: return (base.OnConnected()); 35: } 36:  37: public override Task OnDisconnected() 38: { 39: RemoveUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 40: return (base.OnDisconnected()); 41: } 42: } As you can see, I am using a static field to store the mapping between a user and its possibly many connections – for example, multiple open browser tabs or even multiple browsers accessing the same page with the same login credentials. The user identity, as is normal in .NET, is obtained from the IPrincipal which in SignalR hubs case is stored in Context.Request.User. Of course, this property will only have a meaningful value if we enforce authentication. Another way to go is by creating a group for each user that connects: 1: public class MyHub : Hub 2: { 3: public override Task OnConnected() 4: { 5: this.Groups.Add(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 6: return (base.OnConnected()); 7: } 8:  9: public override Task OnDisconnected() 10: { 11: this.Groups.Remove(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 12: return (base.OnDisconnected()); 13: } 14: } In this case, we will have a one-to-one equivalence between users and groups. All connections belonging to the same user will fall in the same group. So, if we want to send messages to a user from outside an instance of the Hub class, we can do something like this, for the first option – user mappings stored in a static field: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4: 5: foreach (String connectionId in HelloHub.GetUserConnections(username)) 6: { 7: context.Clients.Client(connectionId).sendUserMessage(message); 8: } 9: } And for using groups, its even simpler: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4:  5: context.Clients.Group(username).sendUserMessage(message); 6: } Using groups has the advantage that the IHubContext interface returned from GetHubContext has direct support for groups, no need to send messages to individual connections. Of course, you can wrap both mapping options in a common API, perhaps exposed through IoC. One example of its interface might be: 1: public interface IUserToConnectionMappingService 2: { 3: //associate and dissociate connections to users 4:  5: void AddUserConnection(String username, String connectionId); 6:  7: void RemoveUserConnection(String username, String connectionId); 8: } SignalR has built-in dependency resolution, by means of the static GlobalHost.DependencyResolver property: 1: //for using groups (in the Global class) 2: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new GroupsMappingService()); 3:  4: //for using a static field (in the Global class) 5: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new StaticMappingService()); 6:  7: //retrieving the current service (in the Hub class) 8: var mapping = GlobalHost.DependencyResolver.Resolve<IUserToConnectionMappingService>(); Now all you have to do is implement GroupsMappingService and StaticMappingService with the code I shown here and change SendUserMessage method to rely in the dependency resolver for the actual implementation. Stay tuned for more SignalR posts!

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  • Scaling-out Your Services by Message Bus based WCF Transport Extension &ndash; Part 1 &ndash; Background

    - by Shaun
    Cloud computing gives us more flexibility on the computing resource, we can provision and deploy an application or service with multiple instances over multiple machines. With the increment of the service instances, how to balance the incoming message and workload would become a new challenge. Currently there are two approaches we can use to pass the incoming messages to the service instances, I would like call them dispatcher mode and pulling mode.   Dispatcher Mode The dispatcher mode introduces a role which takes the responsible to find the best service instance to process the request. The image below describes the sharp of this mode. There are four clients communicate with the service through the underlying transportation. For example, if we are using HTTP the clients might be connecting to the same service URL. On the server side there’s a dispatcher listening on this URL and try to retrieve all messages. When a message came in, the dispatcher will find a proper service instance to process it. There are three mechanism to find the instance: Round-robin: Dispatcher will always send the message to the next instance. For example, if the dispatcher sent the message to instance 2, then the next message will be sent to instance 3, regardless if instance 3 is busy or not at that moment. Random: Dispatcher will find a service instance randomly, and same as the round-robin mode it regardless if the instance is busy or not. Sticky: Dispatcher will send all related messages to the same service instance. This approach always being used if the service methods are state-ful or session-ful. But as you can see, all of these approaches are not really load balanced. The clients will send messages at any time, and each message might take different process duration on the server side. This means in some cases, some of the service instances are very busy while others are almost idle. For example, if we were using round-robin mode, it could be happened that most of the simple task messages were passed to instance 1 while the complex ones were sent to instance 3, even though instance 1 should be idle. This brings some problem in our architecture. The first one is that, the response to the clients might be longer than it should be. As it’s shown in the figure above, message 6 and 9 can be processed by instance 1 or instance 2, but in reality they were dispatched to the busy instance 3 since the dispatcher and round-robin mode. Secondly, if there are many requests came from the clients in a very short period, service instances might be filled by tons of pending tasks and some instances might be crashed. Third, if we are using some cloud platform to host our service instances, for example the Windows Azure, the computing resource is billed by service deployment period instead of the actual CPU usage. This means if any service instance is idle it is wasting our money! Last one, the dispatcher would be the bottleneck of our system since all incoming messages must be routed by the dispatcher. If we are using HTTP or TCP as the transport, the dispatcher would be a network load balance. If we wants more capacity, we have to scale-up, or buy a hardware load balance which is very expensive, as well as scaling-out the service instances. Pulling Mode Pulling mode doesn’t need a dispatcher to route the messages. All service instances are listening to the same transport and try to retrieve the next proper message to process if they are idle. Since there is no dispatcher in pulling mode, it requires some features on the transportation. The transportation must support multiple client connection and server listening. HTTP and TCP doesn’t allow multiple clients are listening on the same address and port, so it cannot be used in pulling mode directly. All messages in the transportation must be FIFO, which means the old message must be received before the new one. Message selection would be a plus on the transportation. This means both service and client can specify some selection criteria and just receive some specified kinds of messages. This feature is not mandatory but would be very useful when implementing the request reply and duplex WCF channel modes. Otherwise we must have a memory dictionary to store the reply messages. I will explain more about this in the following articles. Message bus, or the message queue would be best candidate as the transportation when using the pulling mode. First, it allows multiple application to listen on the same queue, and it’s FIFO. Some of the message bus also support the message selection, such as TIBCO EMS, RabbitMQ. Some others provide in memory dictionary which can store the reply messages, for example the Redis. The principle of pulling mode is to let the service instances self-managed. This means each instance will try to retrieve the next pending incoming message if they finished the current task. This gives us more benefit and can solve the problems we met with in the dispatcher mode. The incoming message will be received to the best instance to process, which means this will be very balanced. And it will not happen that some instances are busy while other are idle, since the idle one will retrieve more tasks to make them busy. Since all instances are try their best to be busy we can use less instances than dispatcher mode, which more cost effective. Since there’s no dispatcher in the system, there is no bottleneck. When we introduced more service instances, in dispatcher mode we have to change something to let the dispatcher know the new instances. But in pulling mode since all service instance are self-managed, there no extra change at all. If there are many incoming messages, since the message bus can queue them in the transportation, service instances would not be crashed. All above are the benefits using the pulling mode, but it will introduce some problem as well. The process tracking and debugging become more difficult. Since the service instances are self-managed, we cannot know which instance will process the message. So we need more information to support debug and track. Real-time response may not be supported. All service instances will process the next message after the current one has done, if we have some real-time request this may not be a good solution. Compare with the Pros and Cons above, the pulling mode would a better solution for the distributed system architecture. Because what we need more is the scalability, cost-effect and the self-management.   WCF and WCF Transport Extensibility Windows Communication Foundation (WCF) is a framework for building service-oriented applications. In the .NET world WCF is the best way to implement the service. In this series I’m going to demonstrate how to implement the pulling mode on top of a message bus by extending the WCF. I don’t want to deep into every related field in WCF but will highlight its transport extensibility. When we implemented an RPC foundation there are many aspects we need to deal with, for example the message encoding, encryption, authentication and message sending and receiving. In WCF, each aspect is represented by a channel. A message will be passed through all necessary channels and finally send to the underlying transportation. And on the other side the message will be received from the transport and though the same channels until the business logic. This mode is called “Channel Stack” in WCF, and the last channel in the channel stack must always be a transport channel, which takes the responsible for sending and receiving the messages. As we are going to implement the WCF over message bus and implement the pulling mode scaling-out solution, we need to create our own transport channel so that the client and service can exchange messages over our bus. Before we deep into the transport channel, let’s have a look on the message exchange patterns that WCF defines. Message exchange pattern (MEP) defines how client and service exchange the messages over the transportation. WCF defines 3 basic MEPs which are datagram, Request-Reply and Duplex. Datagram: Also known as one-way, or fire-forgot mode. The message sent from the client to the service, and no need any reply from the service. The client doesn’t care about the message result at all. Request-Reply: Very common used pattern. The client send the request message to the service and wait until the reply message comes from the service. Duplex: The client sent message to the service, when the service processing the message it can callback to the client. When callback the service would be like a client while the client would be like a service. In WCF, each MEP represent some channels associated. MEP Channels Datagram IInputChannel, IOutputChannel Request-Reply IRequestChannel, IReplyChannel Duplex IDuplexChannel And the channels are created by ChannelListener on the server side, and ChannelFactory on the client side. The ChannelListener and ChannelFactory are created by the TransportBindingElement. The TransportBindingElement is created by the Binding, which can be defined as a new binding or from a custom binding. For more information about the transport channel mode, please refer to the MSDN document. The figure below shows the transport channel objects when using the request-reply MEP. And this is the datagram MEP. And this is the duplex MEP. After investigated the WCF transport architecture, channel mode and MEP, we finally identified what we should do to extend our message bus based transport layer. They are: Binding: (Optional) Defines the channel elements in the channel stack and added our transport binding element at the bottom of the stack. But we can use the build-in CustomBinding as well. TransportBindingElement: Defines which MEP is supported in our transport and create the related ChannelListener and ChannelFactory. This also defines the scheme of the endpoint if using this transport. ChannelListener: Create the server side channel based on the MEP it’s. We can have one ChannelListener to create channels for all supported MEPs, or we can have ChannelListener for each MEP. In this series I will use the second approach. ChannelFactory: Create the client side channel based on the MEP it’s. We can have one ChannelFactory to create channels for all supported MEPs, or we can have ChannelFactory for each MEP. In this series I will use the second approach. Channels: Based on the MEPs we want to support, we need to implement the channels accordingly. For example, if we want our transport support Request-Reply mode we should implement IRequestChannel and IReplyChannel. In this series I will implement all 3 MEPs listed above one by one. Scaffold: In order to make our transport extension works we also need to implement some scaffold stuff. For example we need some classes to send and receive message though out message bus. We also need some codes to read and write the WCF message, etc.. These are not necessary but would be very useful in our example.   Message Bus There is only one thing remained before we can begin to implement our scaling-out support WCF transport, which is the message bus. As I mentioned above, the message bus must have some features to fulfill all the WCF MEPs. In my company we will be using TIBCO EMS, which is an enterprise message bus product. And I have said before we can use any message bus production if it’s satisfied with our requests. Here I would like to introduce an interface to separate the message bus from the WCF. This allows us to implement the bus operations by any kinds bus we are going to use. The interface would be like this. 1: public interface IBus : IDisposable 2: { 3: string SendRequest(string message, bool fromClient, string from, string to = null); 4:  5: void SendReply(string message, bool fromClient, string replyTo); 6:  7: BusMessage Receive(bool fromClient, string replyTo); 8: } There are only three methods for the bus interface. Let me explain one by one. The SendRequest method takes the responsible for sending the request message into the bus. The parameters description are: message: The WCF message content. fromClient: Indicates if this message was came from the client. from: The channel ID that this message was sent from. The channel ID will be generated when any kinds of channel was created, which will be explained in the following articles. to: The channel ID that this message should be received. In Request-Reply and Duplex MEP this is necessary since the reply message must be received by the channel which sent the related request message. The SendReply method takes the responsible for sending the reply message. It’s very similar as the previous one but no “from” parameter. This is because it’s no need to reply a reply message again in any MEPs. The Receive method takes the responsible for waiting for a incoming message, includes the request message and specified reply message. It returned a BusMessage object, which contains some information about the channel information. The code of the BusMessage class is 1: public class BusMessage 2: { 3: public string MessageID { get; private set; } 4: public string From { get; private set; } 5: public string ReplyTo { get; private set; } 6: public string Content { get; private set; } 7:  8: public BusMessage(string messageId, string fromChannelId, string replyToChannelId, string content) 9: { 10: MessageID = messageId; 11: From = fromChannelId; 12: ReplyTo = replyToChannelId; 13: Content = content; 14: } 15: } Now let’s implement a message bus based on the IBus interface. Since I don’t want you to buy and install the TIBCO EMS or any other message bus products, I will implement an in process memory bus. This bus is only for test and sample purpose. It can only be used if the service and client are in the same process. Very straightforward. 1: public class InProcMessageBus : IBus 2: { 3: private readonly ConcurrentDictionary<Guid, InProcMessageEntity> _queue; 4: private readonly object _lock; 5:  6: public InProcMessageBus() 7: { 8: _queue = new ConcurrentDictionary<Guid, InProcMessageEntity>(); 9: _lock = new object(); 10: } 11:  12: public string SendRequest(string message, bool fromClient, string from, string to = null) 13: { 14: var entity = new InProcMessageEntity(message, fromClient, from, to); 15: _queue.TryAdd(entity.ID, entity); 16: return entity.ID.ToString(); 17: } 18:  19: public void SendReply(string message, bool fromClient, string replyTo) 20: { 21: var entity = new InProcMessageEntity(message, fromClient, null, replyTo); 22: _queue.TryAdd(entity.ID, entity); 23: } 24:  25: public BusMessage Receive(bool fromClient, string replyTo) 26: { 27: InProcMessageEntity e = null; 28: while (true) 29: { 30: lock (_lock) 31: { 32: var entity = _queue 33: .Where(kvp => kvp.Value.FromClient == fromClient && (kvp.Value.To == replyTo || string.IsNullOrWhiteSpace(kvp.Value.To))) 34: .FirstOrDefault(); 35: if (entity.Key != Guid.Empty && entity.Value != null) 36: { 37: _queue.TryRemove(entity.Key, out e); 38: } 39: } 40: if (e == null) 41: { 42: Thread.Sleep(100); 43: } 44: else 45: { 46: return new BusMessage(e.ID.ToString(), e.From, e.To, e.Content); 47: } 48: } 49: } 50:  51: public void Dispose() 52: { 53: } 54: } The InProcMessageBus stores the messages in the objects of InProcMessageEntity, which can take some extra information beside the WCF message itself. 1: public class InProcMessageEntity 2: { 3: public Guid ID { get; set; } 4: public string Content { get; set; } 5: public bool FromClient { get; set; } 6: public string From { get; set; } 7: public string To { get; set; } 8:  9: public InProcMessageEntity() 10: : this(string.Empty, false, string.Empty, string.Empty) 11: { 12: } 13:  14: public InProcMessageEntity(string content, bool fromClient, string from, string to) 15: { 16: ID = Guid.NewGuid(); 17: Content = content; 18: FromClient = fromClient; 19: From = from; 20: To = to; 21: } 22: }   Summary OK, now I have all necessary stuff ready. The next step would be implementing our WCF message bus transport extension. In this post I described two scaling-out approaches on the service side especially if we are using the cloud platform: dispatcher mode and pulling mode. And I compared the Pros and Cons of them. Then I introduced the WCF channel stack, channel mode and the transport extension part, and identified what we should do to create our own WCF transport extension, to let our WCF services using pulling mode based on a message bus. And finally I provided some classes that need to be used in the future posts that working against an in process memory message bus, for the demonstration purpose only. In the next post I will begin to implement the transport extension step by step.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Parent Objects

    - by Ali Bahrami
    Support for Parent Objects was added in Solaris 11 Update 1. The following material is adapted from the PSARC arc case, and the Solaris Linker and Libraries Manual. A "plugin" is a shared object, usually loaded via dlopen(), that is used by a program in order to allow the end user to add functionality to the program. Examples of plugins include those used by web browsers (flash, acrobat, etc), as well as mdb and elfedit modules. The object that loads the plugin at runtime is called the "parent object". Unlike most object dependencies, the parent is not identified by name, but by its status as the object doing the load. Historically, building a good plugin is has been more complicated than it should be: A parent and its plugin usually share a 2-way dependency: The plugin provides one or more routines for the parent to call, and the parent supplies support routines for use by the plugin for things like memory allocation and error reporting. It is a best practice to build all objects, including plugins, with the -z defs option, in order to ensure that the object specifies all of its dependencies, and is self contained. However: The parent is usually an executable, which cannot be linked to via the usual library mechanisms provided by the link editor. Even if the parent is a shared object, which could be a normal library dependency to the plugin, it may be desirable to build plugins that can be used by more than one parent, in which case embedding a dependency NEEDED entry for one of the parents is undesirable. The usual way to build a high quality plugin with -z defs uses a special mapfile provided by the parent. This mapfile defines the parent routines, specifying the PARENT attribute (see example below). This works, but is inconvenient, and error prone. The symbol table in the parent already describes what it makes available to plugins — ideally the plugin would obtain that information directly rather than from a separate mapfile. The new -z parent option to ld allows a plugin to link to the parent and access the parent symbol table. This differs from a typical dependency: No NEEDED record is created. The relationship is recorded as a logical connection to the parent, rather than as an explicit object name However, it operates in the same manner as any other dependency in terms of making symbols available to the plugin. When the -z parent option is used, the link-editor records the basename of the parent object in the dynamic section, using the new tag DT_SUNW_PARENT. This is an informational tag, which is not used by the runtime linker to locate the parent, but which is available for diagnostic purposes. The ld(1) manpage documentation for the -z parent option is: -z parent=object Specifies a "parent object", which can be an executable or shared object, against which to link the output object. This option is typically used when creating "plugin" shared objects intended to be loaded by an executable at runtime via the dlopen() function. The symbol table from the parent object is used to satisfy references from the plugin object. The use of the -z parent option makes symbols from the object calling dlopen() available to the plugin. Example For this example, we use a main program, and a plugin. The parent provides a function named parent_callback() for the plugin to call. The plugin provides a function named plugin_func() to the parent: % cat main.c #include <stdio.h> #include <dlfcn.h> #include <link.h> void parent_callback(void) { printf("plugin_func() has called parent_callback()\n"); } int main(int argc, char **argv) { typedef void plugin_func_t(void); void *hdl; plugin_func_t *plugin_func; if (argc != 2) { fprintf(stderr, "usage: main plugin\n"); return (1); } if ((hdl = dlopen(argv[1], RTLD_LAZY)) == NULL) { fprintf(stderr, "unable to load plugin: %s\n", dlerror()); return (1); } plugin_func = (plugin_func_t *) dlsym(hdl, "plugin_func"); if (plugin_func == NULL) { fprintf(stderr, "unable to find plugin_func: %s\n", dlerror()); return (1); } (*plugin_func)(); return (0); } % cat plugin.c #include <stdio.h> extern void parent_callback(void); void plugin_func(void) { printf("parent has called plugin_func() from plugin.so\n"); parent_callback(); } Building this in the traditional manner, without -zdefs: % cc -o main main.c % cc -G -o plugin.so plugin.c % ./main ./plugin.so parent has called plugin_func() from plugin.so plugin_func() has called parent_callback() As noted above, when building any shared object, the -z defs option is recommended, in order to ensure that the object is self contained and specifies all of its dependencies. However, the use of -z defs prevents the plugin object from linking due to the unsatisfied symbol from the parent object: % cc -zdefs -G -o plugin.so plugin.c Undefined first referenced symbol in file parent_callback plugin.o ld: fatal: symbol referencing errors. No output written to plugin.so A mapfile can be used to specify to ld that the parent_callback symbol is supplied by the parent object. % cat plugin.mapfile $mapfile_version 2 SYMBOL_SCOPE { global: parent_callback { FLAGS = PARENT }; }; % cc -zdefs -Mplugin.mapfile -G -o plugin.so plugin.c However, the -z parent option to ld is the most direct solution to this problem, allowing the plugin to actually link against the parent object, and obtain the available symbols from it. An added benefit of using -z parent instead of a mapfile, is that the name of the parent object is recorded in the dynamic section of the plugin, and can be displayed by the file utility: % cc -zdefs -zparent=main -G -o plugin.so plugin.c % elfdump -d plugin.so | grep PARENT [0] SUNW_PARENT 0xcc main % file plugin.so plugin.so: ELF 32-bit LSB dynamic lib 80386 Version 1, parent main, dynamically linked, not stripped % ./main ./plugin.so parent has called plugin_func() from plugin.so plugin_func() has called parent_callback() We can also observe this in elfedit plugins on Solaris systems running Solaris 11 Update 1 or newer: % file /usr/lib/elfedit/dyn.so /usr/lib/elfedit/dyn.so: ELF 32-bit LSB dynamic lib 80386 Version 1, parent elfedit, dynamically linked, not stripped, no debugging information available Related Other Work The GNU ld has an option named --just-symbols that can be used in a similar manner: --just-symbols=filename Read symbol names and their addresses from filename, but do not relocate it or include it in the output. This allows your output file to refer symbolically to absolute locations of memory defined in other programs. You may use this option more than once. -z parent is a higher level operation aimed specifically at simplifying the construction of high quality plugins. Although it employs the same operation, it differs from --just symbols in 2 significant ways: There can only be one parent. The parent is recorded in the created object, and can be displayed by 'file', or other similar tools.

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