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• implementing a high level function in a script to call a low level function in the game engine

  - by eat_a_lemon

  In my 2d game engine I have a function that does pathfinding, find_shortest_path. It executes for each time step in the game loop and calculates the next coordinate pair in the series of coordinates to reach the destination object. Now I want to call this function in a scripting language and have it only return the last coordinate pair result. I want the game engine to go about the business of rendering the incremental steps but I don't want the high level script to care about the rendering. The high level script is only for ai game logic. Now I know how to bind a method from C to python but how can I signal and coordinate the wait time between the incremental steps without the high level function returning until its time for the last step?

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• How is jQuery so fast?

  - by ClarkeyBoy

  Hey, I have a rather large application which, on the admin frontend, takes a few seconds to load a page because of all the pageviews that it has to load into objects before displaying anything. Its a bit complex to explain how the system works, but a few of my other questions explains the system in great detail. The main difference between what they say and the current system is that the customer frontend no longer loads all the pageviews into objects when a customer first views the page - it simply adds the pageview to the database and creates an object in an unsynchronised list... to put it simply, when a customer views a page it no longer loads all the pageviews into objects; but the admin frontend still does. I have been working on some admin tools on the customer frontend recently, so if an administrator clicks the description of an item in the catalogue then the right hand column will display statistics and available actions for the selected item. To do this the page which gets loaded (through $('action-container').load(bla bla bla);) into the right hand column has to loop through ALL the pageviews - this ultimately means that ALL the pageviews are loaded into objects if they haven't been already. For some reason this loads really REALLY fast. The difference in speed is only like a second on my dev site, but the live site has thousands of pageviews so the difference is quite big... So my question is: why is it that the admin frontend loads so slowly while using $(bla).load(bla); is so fast? I mean whatever method jQuery uses, can't browsers use this method too and load pages super-fast? Obviously not as someone would've done that by now - but I am interested to know just why the difference is so big... is it just my system or is there a major difference in speed between the browser getting a page and jQuery getting a page? Do other people experience the same kind of differences? Thanks in advance, Regards, Richard

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• Speeding up a soap powered website

  - by ChrisRamakers

  Hi all, We're currently looking into doing some performance tweaking on a website which relies heavily on a Soap webservice. But ... our servers are located in Belgium and the webservice we connect to is locate in San Francisco so it's a long distance connection to say the least. Our website is PHP powered, using PHP's built in SoapClient class. On average a call to the webservice takes 0.7 seconds and we are doing about 3-5 requests per page. All possible request/response caching is already implemented so we are now looking at other ways to improved the connection speed. This is the code which instantiates the SoapClient, what i'm looking for now is other ways/methods to improve speed on single requestes. Anyone has idea's or suggestions? private function _createClient() { try { $wsdl = sprintf($this->config->wsUrl.'?wsdl', $this->wsdl); $client = new SoapClient($wsdl, array( 'soap_version' => SOAP_1_1, 'encoding' => 'utf-8', 'connection_timeout' => 5, 'cache_wsdl' => 1, 'trace' => 1, 'features' => SOAP_SINGLE_ELEMENT_ARRAYS )); $header_tags = array('username' => new SOAPVar($this->config->wsUsername, XSD_STRING, null, null, null, $this->ns), 'password' => new SOAPVar(md5($this->config->wsPassword), XSD_STRING, null, null, null, $this->ns)); $header_body = new SOAPVar($header_tags, SOAP_ENC_OBJECT); $header = new SOAPHeader($this->ns, 'AuthHeaderElement', $header_body); $client->__setSoapHeaders($header); } catch (SoapFault $e){ controller('Error')->error($id.': Webservice connection error '.$e->getCode()); exit; } $this->client = $client; return $this->client; }

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• Language+IDE for teaching high school students?

  - by daveagp

  I'm investigating languages and IDEs for a project involving teaching high-school students (around grade 11). It will teach basics of programming as an introduction to computer science (e.g., including how numbers/strings/characters are represented, using procedures and arrays, control flow, a little bit of algorithms, only very basic I/O). The non-negotiable requirements for this project are: a free up-to-date cross-platform IDE (Win & Mac incl. 64-bit) with debug a compiler where it's easy to learn from your mistakes together with the IDE, a gentle installation+learning curve So far, the best options I see are the following. Are there others I should know about? I am giving a short explanation with each one to generally show what I am looking for. In order from most to least promising: Pascal + FreePascal IDE (it seems a little buggy but actively developed?) Python + Eclipse + PyDev (good but features are overwhelming/hard to navigate) Groovy + Eclipse ('') Python + IDLE (looks unnatural to do debugging, to me) Pascal + Lazarus (IDE overwhelming, e.g. not obvious how to "start from scratch") Preferably, as a rule of thumb, the language should be direct enough that you don't need to wrap every program in a class, don't need to reference a System object to println, etc. I tried a little bit to see if there is something in JavaScript or (non-Visual) Basic along the lines of what I want, but found nothing so far. I would say that C/C++/C#, Java, Ruby, Lisp, VB do not fit my criteria for languages for this project. To reiterate my questions: are any of those 5 options really awesome or un-awesome? Are there other options which are even MORE awesome? Anything for Basic or JavaScript which meets all of the criteria? Thanks!

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• Optimising RSS parsing on App Engine to avoid high CPU warnings

  - by Danny Tuppeny

  I'm pulling some RSS feeds into a datastore in App Engine to serve up to an iPhone app. I use cron to schedule updating the RSS every x minutes. Each task only parses one RSS feed (which has 15-20 items). I frequently get warnings about high CPU usage in the App Engine dashboard, so I'm looking for ways to optimise my code. Currently, I use minidom (since it's already there on App Engine), but I suspect it's not very efficient! Here's the code: dom = minidom.parseString(urlfetch.fetch(url).content) if dom: items = [] for node in dom.getElementsByTagName('item'): item = RssItem( key_name = self.getText(node.getElementsByTagName('guid')[0].childNodes), title = self.getText(node.getElementsByTagName('title')[0].childNodes), description = self.getText(node.getElementsByTagName('description')[0].childNodes), modified = datetime.now(), link = self.getText(node.getElementsByTagName('link')[0].childNodes), categories = [self.getText(category.childNodes) for category in node.getElementsByTagName('category')] ); items.append(item); db.put(items); def getText(self, nodelist): rc = '' for node in nodelist: if node.nodeType == node.TEXT_NODE: rc = rc + node.data return rc There isn't much going on, but the scripts often take 2-6 seconds CPU time, which seems a bit excessive for looping through 20ish items and reading a few attributes. What can I do to make this faster? Is there anything particularly bad in the above code, or should I change to another way of parsing? Are there are any libraries (that work on App Engine) that would be better, or would I be better parsing the RSS myself?

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• Alternatives to LINQ To SQL on high loaded pages

  - by Alex

  To begin with, I LOVE LINQ TO SQL. It's so much easier to use than direct querying. But, there's one great problem: it doesn't work well on high loaded requests. I have some actions in my ASP.NET MVC project, that are called hundreds times every minute. I used to have LINQ to SQL there, but since the amount of requests is gigantic, LINQ TO SQL almost always returned "Row not found or changed" or "X of X updates failed". And it's understandable. For instance, I have to increase some value by one with every request. var stat = DB.Stats.First(); stat.Visits++; // .... DB.SubmitChanges(); But while ASP.NET was working on those //... instructions, the stats.Visits value stored in the table got changed. I found a solution, I created a stored procedure UPDATE Stats SET Visits=Visits+1 It works well. Unfortunately now I'm getting more and more moments like that. And it sucks to create stored procedures for all cases. So my question is, how to solve this problem? Are there any alternatives that can work here? I hear that Stackoverflow works with LINQ to SQL. And it's more loaded than my site.

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• node.js UDP data lost at high package rates

  - by koleto

  I am observing a significant data-lost on a UDP connection with node.js 0.6.18 and 0.8.0 . It appears at high packet rates about 1200 packet per second with frames about 1500 byte limit. Each data packages has a incrementing number so it easy to track the number of lost packages. var server = dgram.createSocket("udp4"); server.on("message", function (message, rinfo) { //~processData(message); //~ writeData(message, null, 5000); }).bind(10001); On the receiving callback I tested two cases I first saved 5000 packages in a file. The result ware no dropped packages. After I have included a data processing routine and got about 50% drop rate. What I expected was that the process data routine should be completely asynchronous and should not introduce dead time to the system, since it is a simple parser to process binary data in the package and to emits events to a further processing routine. It seems that the parsing routine introduce dead time in which the event handler is unable to handle each packets. At the low package rates (< 1200 packages/sec) there are no data lost observed! Is this a bug or I am doing something wrong?

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• How to convert string with double high/wide characters to normal string [VC++6]

  - by Shaitan00

  My application typically recieves a string in the following format: " Item $5.69 " Some contants I always expect: - the LENGHT always 20 characters - the start index of the text always [5] - and most importantly the index of the DECIMAL for the price always [14] In order to identify this string correctly I validate all the expected contants listed above .... Some of my clients have now started sending the string with Doube-High / Double-Wide values (pair of characters which represent a single readable character) similar to the following: " Item $x80x90.x81x91x82x92 " For testing I simply scan the string character-by-character, compare char[i] and char[i+1] and replace these pairs with their corresponding single character when a match is found (works fine) as follows: [Code] for (int i=0; i < sData.length(); i++) { char ch = sData[i] & 0xFF; char ch2 = sData[i+1] & 0xFF; if (ch == '\x80' && ch2 == '\x90') zData.replace("\x80\x90", "0"); else if (ch == '\x81' && ch2 == '\x91') zData.replace("\x81\x91", "1"); else if (ch == '\x82' && ch2 == '\x92') zData.replace("\x82\x92", "2"); ... ... ... } [/Code] But the result is something like this: " Item $5.69 " Notice how this no longer matches my expectation: the lenght is now 17 (instead of 20) due to the 3 conversions and the decimal is now at index 13 (instead of 14) due to the conversion of the "5" before the decimal point. Ideally I would like to convert the string to a normal readable format keeping the constants (length, index of text, index of decimal) at the same place (so the rest of my application is re-usable) ... or any other suggestion (I'm pretty much stuck with this)... Is there a STANDARD way of dealing with these type of characters? Any help would be greatly appreciated, I've been stuck on this for a while now ... Thanks,

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• C++ bughunt - High-score insertion in a vector crashes the program

  - by Francisco P.

  Hello, everyone! I have a game I'm working on. My players are stored in a vector, and, at the end of the game, the game crashes when trying to insert the high-scores in the correct positions. Here's what I have (please ignore the portuguese comments, the code is pretty straightforward :P): //TOTAL_HIGHSCORES is the max. number of hiscores that i'm willing to store. This is set as 10. bool Game::updateHiScores() { bool stopIterating; bool scoresChanged = false; //Se ainda nao existirem TOTAL_HISCORES melhores pontuacoes ou se a pontuacao for melhor que uma das existentes for (size_t i = 0; i < players.size(); ++i) { //&& !(players[i].isAI()) if (players[i].getScoreValue() > 0 && (hiScores.size() < TOTAL_HISCORES || hiScores.back() < players[i].getScore())) { scoresChanged = true; if(hiScores.empty() || hiScores.back() >= players[i].getScore()) hiScores.push_back(players[i].getScore()); else { //Ciclo que encontra e insere a pontuacao no lugar desejado stopIterating = false; for(vector<Score>::iterator it = hiScores.begin(); it < hiScores.end() && !(stopIterating); ++it) { if(*it <= players[i].getScore()) { //E inserida na posicao 'it' o Score correspondente hiScores.insert(it, players[i].getScore()); //Verifica se o comprimento do vector esta dentro do desejado, se nao estiver, este e rectificado if (hiScores.size() > TOTAL_HISCORES) hiScores.pop_back(); stopIterating = true; } } } } } if (scoresChanged) sort(hiScores.begin(), hiScores.end(), higher); return scoresChanged; } What am I doing wrong here? Thanks for your time, fellas.

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• MS SQL - High performance data inserting with stored procedures

  - by Marks

  Hi. Im searching for a very high performant possibility to insert data into a MS SQL database. The data is a (relatively big) construct of objects with relations. For security reasons i want to use stored procedures instead of direct table access. Lets say i have a structure like this: Document MetaData User Device Content ContentItem[0] SubItem[0] SubItem[1] SubItem[2] ContentItem[1] ... ContentItem[2] ... Right now I think of creating one big query, doing somehting like this (Just pseudo-code): EXEC @DeviceID = CreateDevice ...; EXEC @UserID = CreateUser ...; EXEC @DocID = CreateDocument @DeviceID, @UserID, ...; EXEC @ItemID = CreateItem @DocID, ... EXEC CreateSubItem @ItemID, ... EXEC CreateSubItem @ItemID, ... EXEC CreateSubItem @ItemID, ... ... But is this the best solution for performance? If not, what would be better? Split it into more querys? Give all Data to one big stored procedure to reduce size of query? Any other performance clue? I also thought of giving multiple items to one stored procedure, but i dont think its possible to give a non static amount of items to a stored procedure. Since 'INSERT INTO A VALUES (B,C),(C,D),(E,F) is more performant than 3 single inserts i thought i could get some performance here. Thanks for any hints, Marks

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• USB Drive Not recognized

  - by user36582

  My Friend's Pen Drive, which was working well very well just few days ago, is not being recognized after getting used by a virus affected machine. Its not on fdisk -l or lsusb However in dmesg I can see the following: [ 977.300013] usb 5-2: new full speed USB device using uhci_hcd and address 2 [ 977.420014] usb 5-2: device descriptor read/64, error -71 [ 977.644023] usb 5-2: device descriptor read/64, error -71 [ 977.860013] usb 5-2: new full speed USB device using uhci_hcd and address 3 [ 977.980013] usb 5-2: device descriptor read/64, error -71 [ 978.204013] usb 5-2: device descriptor read/64, error -71 [ 978.420013] usb 5-2: new full speed USB device using uhci_hcd and address 4 [ 978.828015] usb 5-2: device not accepting address 4, error -71 [ 978.940015] usb 5-2: new full speed USB device using uhci_hcd and address 5 [ 979.348013] usb 5-2: device not accepting address 5, error -71 [ 979.348292] hub 5-0:1.0: unable to enumerate USB device on port 2 [ 1017.848015] usb 5-2: new full speed USB device using uhci_hcd and address 6 [ 1017.968012] usb 5-2: device descriptor read/64, error -71 [ 1018.192017] usb 5-2: device descriptor read/64, error -71 [ 1018.408014] usb 5-2: new full speed USB device using uhci_hcd and address 7 [ 1018.528012] usb 5-2: device descriptor read/64, error -71 [ 1018.752023] usb 5-2: device descriptor read/64, error -71 [ 1018.968012] usb 5-2: new full speed USB device using uhci_hcd and address 8 [ 1019.376019] usb 5-2: device not accepting address 8, error -71 [ 1019.488011] usb 5-2: new full speed USB device using uhci_hcd and address 9 [ 1019.896016] usb 5-2: device not accepting address 9, error -71 [ 1019.896308] hub 5-0:1.0: unable to enumerate USB device on port 2 [ 1049.984016] usb 5-1: new full speed USB device using uhci_hcd and address 10 [ 1050.104014] usb 5-1: device descriptor read/64, error -71 [ 1050.328014] usb 5-1: device descriptor read/64, error -71 [ 1050.544014] usb 5-1: new full speed USB device using uhci_hcd and address 11 [ 1050.664018] usb 5-1: device descriptor read/64, error -71 [ 1050.888019] usb 5-1: device descriptor read/64, error -71 [ 1051.104025] usb 5-1: new full speed USB device using uhci_hcd and address 12 [ 1051.512014] usb 5-1: device not accepting address 12, error -71 [ 1051.624101] usb 5-1: new full speed USB device using uhci_hcd and address 13 [ 1052.032014] usb 5-1: device not accepting address 13, error -71 [ 1052.032991] hub 5-0:1.0: unable to enumerate USB device on port 1 What these Errors actually mean and how Can I get this pen drive Back to work ??

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• SqlBulkCopy is slow, doesn't utilize full network speed

  - by Alex

  Hi, for that past couple of weeks I have been creating generic script that is able to copy databases. The goal is to be able to specify any database on some server and copy it to some other location, and it should only copy the specified content. The exact content to be copied over is specified in a configuration file. This script is going to be used on some 10 different databases and run weekly. And in the end we are copying only about 3%-20% of databases which are as large as 500GB. I have been using the SMO assemblies to achieve this. This is my first time working with SMO and it took a while to create generic way to copy the schema objects, filegroups ...etc. (Actually helped find some bad stored procs). Overall I have a working script which is lacking on performance (and at times times out) and was hoping you guys would be able to help. When executing the WriteToServer command to copy large amount of data ( 6GB) it reaches my timeout period of 1hr. Here is the core code for copying table data. The script is written in PowerShell. $query = ("SELECT * FROM $selectedTable " + $global:selectiveTables.Get_Item($selectedTable)).Trim() Write-LogOutput "Copying $selectedTable : '$query'" $cmd = New-Object Data.SqlClient.SqlCommand -argumentList $query, $source $cmd.CommandTimeout = 120; $bulkData = ([Data.SqlClient.SqlBulkCopy]$destination) $bulkData.DestinationTableName = $selectedTable; $bulkData.BulkCopyTimeout = $global:tableCopyDataTimeout # = 3600 $reader = $cmd.ExecuteReader(); $bulkData.WriteToServer($reader); # Takes forever here on large tables The source and target databases are located on different servers so I kept track of the network speed as well. The network utilization never went over 1% which was quite surprising to me. But when I just transfer some large files between the servers, the network utilization spikes up to 10%. I have tried setting the $bulkData.BatchSize to 5000 but nothing really changed. Increasing the BulkCopyTimeout to an even greater amount would only solve the timeout. I really would like to know why the network is not being used fully. Anyone else had this problem? Any suggestions on networking or bulk copy will be appreciated. And please let me know if you need more information. Thanks. UPDATE I have tweaked several options that increase the performance of SqlBulkCopy, such as setting the transaction logging to simple and providing a table lock to SqlBulkCopy instead of the default row lock. Also some tables are better optimized for certain batch sizes. Overall, the duration of the copy was decreased by some 15%. And what we will do is execute the copy of each database simultaneously on different servers. But I am still having a timeout issue when copying one of the databases. When copying one of the larger databases, there is a table for which I consistently get the following exception: System.Data.SqlClient.SqlException: Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding. It is thrown about 16 after it starts copying the table which is no where near my BulkCopyTimeout. Even though I get the exception that table is fully copied in the end. Also, if I truncate that table and restart my process for that table only, the tables is copied over without any issues. But going through the process of copying that entire database fails always for that one table. I have tried executing the entire process and reseting the connection before copying that faulty table, but it still errored out. My SqlBulkCopy and Reader are closed after each table. Any suggestions as to what else could be causing the script to fail at the point each time?

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• how to speed up the code??

  - by kaushik

  i have very huge code about 600 lines plus. cant post the whole thing here. but a particular code snippet is taking so much time,leading to problems. here i post that part of code please tell me what to do speed up the processing.. please suggest the part which may be the reason and measure to improve them if this small part of code is understandable. using_data={} def join_cost(a , b): global using_data #print a #print b save_a=[] save_b=[] print 1 #for i in range(len(m)): #if str(m[i][0])==str(a): save_a=database_index[a] #for i in range(len(m)): # if str(m[i][0])==str(b): #print 'save_a',save_a #print 'save_b',save_b print 2 save_b=database_index[b] using_data[save_a[0]]=save_a s=str(save_a[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') print 3 for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) end_time=save_a[4] #print end_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(end_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 q=[] print 4 l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') q=k3.split(' ') #print q print 5 s=str(save_b[1]).replace('phone','text') s=str(s)+'.pm' p=os.path.join("c:/begpython/wavnk/",s) x=open(p , 'r') for i in range(6): x.readline() k2='a' j=0 o=[] while k2 is not '': k2=x.readline() k2=k2.rstrip('\n') oj=k2.split(' ') o=o+[oj] #print o[j] j=j+1 #print j #print o[2][0] temp=long(1232332) strt_time=save_b[3] #print strt_time k=(j-1) for i in range(k): diff=float(o[i][0])-float(strt_time) if diff<0: diff=diff*(-1) if temp>diff: temp=diff pm_row=i #print pm_row #print temp #print o[pm_row] #pm_row=3 w=[] l=str(p).replace('.pm','.mcep') z=open(l ,'r') for i in range(pm_row): z.readline() k3=z.readline() k3=k3.rstrip('\n') w=k3.split(' ') #print w cost=0 for i in range(12): #print q[i] #print w[i] h=float(q[i])-float(w[i]) cost=cost+math.pow(h,2) j_cost=math.sqrt(cost) #print cost return j_cost def target_cost(a , b): a=(b+1)*3 b=(a+1)*2 t_cost=(a+b)*5/2 return t_cost r1='shht:ra_77' r2='grx_18' g=[] nodes=[] nodes=nodes+[[r1]] for i in range(len(y_in_db_format)): g=y_in_db_format[i] #print g #print g[0] g.remove(str(g[0])) nodes=nodes+[g] nodes=nodes+[[r2]] print nodes print "lenght of nodes",len(nodes) lists=[] #lists=lists+[r1] for i in range(len(nodes)): for j in range(len(nodes[i])): lists=lists+[nodes[i][j]] #lists=lists+[r2] print lists distance={} for i in range(len(lists)): if i==0: distance[str(lists[i])]=0 else: distance[str(lists[i])]=long(123231223) #print distance group_dist=[] infinity=long(123232323) for i in range(len(nodes)): distances=[] for j in range(len(nodes[i])): #distances=[] if i==0: distances=distances+[[nodes[i][j], 0]] else: distances=distances+[[nodes[i][j],infinity]] group_dist=group_dist+[distances] #print distances print "group_distances",group_dist #print "check",group_dist[0][0][1] #costs={} #for i in range(len(lists)): #if i==0: # costs[str(lists[i])]=1 #else: # costs[str(lists[i])]=get_selfcost(lists[i]) path=[] for i in range(len(nodes)): mini=[] if i!=(len(nodes)-1): #temp=long(123234324) #Now calculate the cost between the current node and each of its neighbour for k in range(len(nodes[(i+1)])): for j in range(len(nodes[i])): current=nodes[i][j] #print "current_node",current j_distance=join_cost( current , nodes[i+1][k]) #t_distance=target_cost( current , nodes[i+1][k]) t_distance=34 #print distance #print "distance between current and neighbours",distance total_distance=(.5*(float(group_dist[i][j][1])+float(j_distance))+.5*(float(t_distance))) #print "total distance between the intial_nodes and current neighbour",total_distance if int(group_dist[i+1][k][1]) > int(total_distance): group_dist[i+1][k][1]=total_distance #print "updated distance",group_dist[i+1][k][1] a=current #print "the neighbour",nodes[i+1][k],"updated the value",a mini=mini+[[str(nodes[i+1][k]),a]] print mini

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• Books and resources for Java Performance tuning - when working with databases, huge lists

  - by Arvind

  Hi All, I am relatively new to working on huge applications in Java. I am working on a Java web service which is pretty heavily used by various clients. The service basically queries the database (hibernate) and then works with a lot of Lists (there are adapters to convert list returned from DB to the interface which the service publishes) and I am seeing lot of issues with the service like high CPU usage or high heap space. While I can troubleshoot the performance issues using a profiler, I want to actually learn about what all I need to take care when I actually write code. Like what kind of List to use or things like using StringBuilder instead of String, etc... Is there any book or blogs which I can refer which will help me while I write new services? Also my application is multithreaded - each service call from a client is a new thread, and I want to know some best practices around that area as well. I did search the web but I found many tips which are not relevant in the latest Java 6 releases, so wanted to know what kind of resources would help a developer starting out now on Java for heavily used applications. Arvind

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• heartbeat: Bad nodename in /etc/ha.d//haresources [node1]

  - by Richard

  I'm trying to start heartbeat on Ubuntu 10.04 with service heartbeat start, but getting the following errors: heartbeat[24829]: 2011/11/22_19:31:07 ERROR: Bad nodename in /etc/ha.d//haresources [node1] heartbeat[24829]: 2011/11/22_19:31:07 ERROR: Configuration error, heartbeat not started. On on server uname -n produces loadb1, on the second server uname -n produces loadb2. The two servers can ping each other okay with those names. This is /etc/ha.d/ha.cnf on both servers: debugfile /var/log/ha-debug logfile /var/log/ha-log logfacility local0 keepalive 2 deadtime 10 udpport 694 bcast eth1 ucast eth0 my.external.ip ucast eth0 my.external.ip ucast eth1 10.0.0.5 ucast eth1 10.0.0.6 #udp eth0 node loadb1 node loadb2 auto_failback off And this is /etc/ha.d/haresources on both servers: node1 IPaddr::46.20.121.113 httpd smb dhcpd Authkeys is also set up. What am I doing wrong? The part where I'm least clear is the ucast/bcast lines.

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• Exchange 2010 DAG Automatic Failover Testing/Issue. Not always automatically failing over to health

  - by Richard

  Ok I've got 2 exchange 2010 servers that run client access/hub transport/mailbox roles and one exchange 2010 server running just client access/hub transport roles and acts as my bridgehead. The two mailbox servers are running one database setup in a DAG. Server A shows the DB Mounted and Server B shows Healthy. If I reboot Server A via windows GUI Server B switches from healthy to mounted and I see hardly any interruption in service using Outlook 2007. Server A shows "Service down", then "Failed" then "Healthy" and leaves the DB mounted on Server B. This is how it should work, so far so good. Now if I test Server A being shut down cold, or unplugging both nics from network to simulate failure, Server B switches from Healthy to Mounted and server A switches to "Service Down" but my outlook client never connects to the DB mounted on server B! I can connect to server C (client access/hub transport) and get to my email and even send new email out, but incoming email doesn't deliver until Server A is brought back online and it's DB goes back to Healthy status. So I don't understand why it auto fail-overs when I reboot the server with the mounted DB copy, causing very little outlook 2007 hiccup if any. But when I shutdown or DC the mounted DB server it DOES mount the healthy copy but outlook 2007 clients can't connect.. I hope the picture I'm trying to paint makes some sense, it's driving me a little batty. Any help would be appreciated!

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• Unexpected start of already-primary server processes when heartbeat on secondary is stopped.

  - by vorik

  Hi, I've got an active-passive Heartbeat cluster with Apache, MySQL, ActiveMQ and DRBD. Today, I wanted to perform hardware-maintenance on the secondary node (node04), so I stopped the heartbeat service before shutting it down. Then, the primary node (node03) received a shutdown notice from the secondary node (node04). This logging comes from the primary node: node03 heartbeat[4458]: 2010/03/08_08:52:56 info: Received shutdown notice from 'node04.companydomain.nl'. heartbeat[4458]: 2010/03/08_08:52:56 info: Resources being acquired from node04.companydomain.nl. harc[27522]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/status status heartbeat[27523]: 2010/03/08_08:52:56 info: Local Resource acquisition completed. mach_down[27567]: 2010/03/08_08:52:56 info: /usr/share/heartbeat/mach_down: nice_failback: foreign resources acquired mach_down[27567]: 2010/03/08_08:52:56 info: mach_down takeover complete for node node04.companydomain.nl. heartbeat[4458]: 2010/03/08_08:52:56 info: mach_down takeover complete. harc[27620]: 2010/03/08_08:52:56 info: Running /etc/ha.d/rc.d/ip-request-resp ip-request-resp ip-request-resp[27620]: 2010/03/08_08:52:56 received ip-request-resp drbddisk OK yes ResourceManager[27645]: 2010/03/08_08:52:56 info: Acquiring resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:56 info: Running /etc/ha.d/resource.d/drbddisk start Filesystem[27700]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/mysql start mysql[27783]: 2010/03/08_08:52:57 Starting MySQL[ OK ] apache[27853]: 2010/03/08_08:52:57 INFO: Running OK ResourceManager[27645]: 2010/03/08_08:52:57 info: Running /etc/ha.d/resource.d/monitor start monitor[28160]: 2010/03/08_08:52:58 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq start activemq[28210]: 2010/03/08_08:52:58 Starting ActiveMQ Broker... ActiveMQ Broker is already running. ResourceManager[27645]: 2010/03/08_08:52:58 ERROR: Return code 1 from /etc/ha.d/resource.d/activemq ResourceManager[27645]: 2010/03/08_08:52:58 CRIT: Giving up resources due to failure of activemq ResourceManager[27645]: 2010/03/08_08:52:58 info: Releasing resource group: node03.companydomain.nl drbddisk Filesystem::/dev/drbd0::/data::ext3 mysql apache::/etc/httpd/conf/httpd.conf LVSSyncDaemonSwap::master monitor activemq tivoli-cluster MailTo::[email protected]::DRBDFailureDrisAcc MailTo::[email protected]::DRBDFailureDrisAcc 1.2.3.212 ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/IPaddr 1.2.3.212 stop IPaddr[28329]: 2010/03/08_08:52:58 INFO: ifconfig eth0:0 down IPaddr[28312]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28378]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/MailTo [email protected] DRBDFailureDrisAcc stop MailTo[28433]: 2010/03/08_08:52:58 INFO: Success ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/tivoli-cluster stop ResourceManager[27645]: 2010/03/08_08:52:58 info: Running /etc/ha.d/resource.d/activemq stop activemq[28503]: 2010/03/08_08:53:01 Stopping ActiveMQ Broker... Stopped ActiveMQ Broker. ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/monitor stop monitor[28681]: 2010/03/08_08:53:01 ResourceManager[27645]: 2010/03/08_08:53:01 info: Running /etc/ha.d/resource.d/LVSSyncDaemonSwap master stop LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster down LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncbackup up LVSSyncDaemonSwap[28714]: 2010/03/08_08:53:02 info: ipvs_syncmaster released ResourceManager[27645]: 2010/03/08_08:53:02 info: Running /etc/ha.d/resource.d/apache /etc/httpd/conf/httpd.conf stop apache[28782]: 2010/03/08_08:53:03 INFO: Killing apache PID 18390 apache[28782]: 2010/03/08_08:53:03 INFO: apache stopped. apache[28771]: 2010/03/08_08:53:03 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:03 info: Running /etc/ha.d/resource.d/mysql stop mysql[28851]: 2010/03/08_08:53:24 Shutting down MySQL.....................[ OK ] ResourceManager[27645]: 2010/03/08_08:53:24 info: Running /etc/ha.d/resource.d/Filesystem /dev/drbd0 /data ext3 stop Filesystem[29010]: 2010/03/08_08:53:25 INFO: Running stop for /dev/drbd0 on /data Filesystem[29010]: 2010/03/08_08:53:25 INFO: Trying to unmount /data Filesystem[29010]: 2010/03/08_08:53:25 ERROR: Couldn't unmount /data; trying cleanup with SIGTERM Filesystem[29010]: 2010/03/08_08:53:25 INFO: Some processes on /data were signalled Filesystem[29010]: 2010/03/08_08:53:27 INFO: unmounted /data successfully Filesystem[28999]: 2010/03/08_08:53:27 INFO: Success ResourceManager[27645]: 2010/03/08_08:53:27 info: Running /etc/ha.d/resource.d/drbddisk stop heartbeat[4458]: 2010/03/08_08:53:29 WARN: node node04.companydomain.nl: is dead heartbeat[4458]: 2010/03/08_08:53:29 info: Dead node node04.companydomain.nl gave up resources. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth0 dead. heartbeat[4458]: 2010/03/08_08:53:29 info: Link node04.companydomain.nl:eth1 dead. hb_standby[29193]: 2010/03/08_08:53:57 Going standby [foreign]. heartbeat[4458]: 2010/03/08_08:53:57 info: node03.companydomain.nl wants to go standby [foreign] Soo... What just happened here??? Heartbeat on node04 stopped and told node03, which was the active node at the time. Somehow, node03 decided to start the cluster processes that were already running. (For the processes that are not critical, I always return a 0 from the startupscript so it does not stops the entire cluster when a non-essential part fails.) When starting ActiveMQ, it returns status 1 because it is already running. This fails the node and shuts everything down. As heartbeat is not running on the secondary node, it cannot failover to there. When I tried to run ha_takeover to restart the resources, absolutely nothing happened. Only after I restarted heartbeat on the primary node the resources could be started (after a delay of 2 minutes). These are my questions: Why does heartbeat on the primary node try to start the cluster processes again? Why did ha_takeover not work? What can I do to prevent this from happening? Server configuration: DRBD: version: 8.3.7 (api:88/proto:86-91) GIT-hash: ea9e28dbff98e331a62bcbcc63a6135808fe2917 build by [email protected], 2010-01-20 09:14:48 0: cs:Connected ro:Secondary/Primary ds:UpToDate/UpToDate B r---- ns:0 nr:6459432 dw:6459432 dr:0 al:0 bm:301 lo:0 pe:0 ua:0 ap:0 ep:1 wo:d oos:0 uname -a Linux node04 2.6.18-164.11.1.el5 #1 SMP Wed Jan 6 13:26:04 EST 2010 x86_64 x86_64 x86_64 GNU/Linux haresources node03.companydomain.nl \ drbddisk \ Filesystem::/dev/drbd0::/data::ext3 \ mysql \ apache::/etc/httpd/conf/httpd.conf \ LVSSyncDaemonSwap::master \ monitor \ activemq \ tivoli-cluster \ MailTo::[email protected]::DRBDFailureDrisAcc \ MailTo::[email protected]::DRBDFailureDrisAcc \ 1.2.3.212 ha.cf debugfile /var/log/ha-debug logfile /var/log/ha-log keepalive 500ms deadtime 30 warntime 10 initdead 120 udpport 694 mcast eth0 225.0.0.3 694 1 0 mcast eth1 225.0.0.4 694 1 0 auto_failback off node node03.companydomain.nl node node04.companydomain.nl respawn hacluster /usr/lib64/heartbeat/dopd apiauth dopd gid=haclient uid=hacluster Thank you very much in advance, Ger Apeldoorn

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• Managing scalability and availability with two servers running Apache Httpd, Apache Mina and MySQL

  - by celalo

  Hello, I am not a developer and I don't much experience with scalable server architectures. But I am in need of a highly available and scalable system for one of my projects. There is going to be two servers I am going to use for the time being. Both with 4 core CPUs and 8 GB RAM with RAID structures running CentOS 5.4. I will also have feature called "Failover IP" which enables to direct an IP address to another server within short time. The applications which will be run on the servers: There is going to be a Java application based on Apache Mina server for handling TCP requests from some hundreds of network devices where the devices are going to send request as much as one request per minute. Handling those requests, includes parsing the requests and inserting a few rows to the Database. Parsing requests before inserting data to the DB does take neglectable time. There is going to be MySQL server, as I stated above. Also there is going to be a PHP web application running on Apache Httpd Server which uses the same DB with the Java application. What I wish to have is to make use of those two servers at the most. I was imagining to have the servers identical, sharing the work load. MySQL could be a cluster maybe? And if some application fails or the whole machine goes down, the other will continue serving the requests seamlessly. Reminding that a "Failover IP" feature will be available for me to take advantage of. Also, It should be kept in mind that number of servers could increase in time, to meet the demand. What can you suggest? Which kind of tools I can make use of? Which kind of monitoring software (paid/unpaid) I have? Thanks in advance.

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• Do disabled Firefox extensions make Firefox slower?

  - by inothemo

  Do disabled Firefox extensions make Firefox slower? I know that extensions make browsing slower, but what about extensions that are disabled and not in use?

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• ACPI Throttling in Ubuntu

  - by Evan

  I'm looking to throttle my cpu through the ACPI. I've read up on it, but I keep receiving permission denied statements. I have 8 available throttling states. Here are the outcomes of my atttempts: evan@evan-laptop:/proc/acpi/processor/CPU0$ echo 3 /proc/acpi/processor/CPU0/throttling bash: /proc/acpi/processor/CPU0/throttling: Permission denied evan@evan-laptop:/proc/acpi/processor/CPU0$ sudo echo 3 /proc/acpi/processor/CPU0/throttling bash: /proc/acpi/processor/CPU0/throttling: Permission denied EDIT: For reference, I am running Ubuntu Karmic with Intel Core Duo T2500 with ACPI enabled

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• Avoiding DNS timeouts when a dns server fails

  - by user65124

  Hi there. We have a small datacenter with about a hundred hosts pointing to 3 internal dns servers (bind 9). Our problem comes when one of the internal dns servers becomes unavailable. At that point all the clients that point to that server start performing very slowly. The problem seems to be that the stock linux resolver doesn't really have the concept of "failing over" to a different dns server. You can adjust the timeout and number of retries it uses, (and set rotate so it will work through the list), but no matter what settings one uses our services perform much more slowly if a primary dns server becomes unavailable. At the moment this is one of the largest sources of service disruptions for us. My ideal answer would be something like "RTFM: tweak /etc/resolv.conf like this...", but if that's an option I haven't seen it. I was wondering how other folks handled this issue? I can see 3 possible types of solutions: Use linux-ha/Pacemaker and failover ips (so the dns IP VIPs are "always" available). Alas, we don't have a good fencing infrastructure, and without fencing pacemaker doesn't work very well (in my experience Pacemaker lowers availability without fencing). Run a local dns server on each node, and have resolv.conf point to localhost. This would work, but it would give us a lot more services to monitor and manage. Run a local cache on each node. Folks seem to consider nscd "broken", but dnrd seems to have the right feature set: it marks dns servers as up or down, and won't use 'down' dns servers. Any-casting seems to work only at the ip routing level, and depends on route updates for server failure. Multi-casting seemed like it would be a perfect answer, but bind does not support broadcasting or multi-casting, and the docs I could find seem to suggest that multicast dns is more aimed at service discovery and auto-configuration rather than regular dns resolving. Am I missing an obvious solution?

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• What is the difference between Anycast and GeoDNS / GeoIP wrt HA?

  - by Riyad

  Based on the Wikipedia description of Anycast, it includes both the distribution of a domain-name-to-many-IP-mapping across many DNS servers as well as replying to clients with the most geographically close (or fastest) server. In the context of a globally distributed, highly available site like google.com (or any CDN service with many global edge locations) this sounds like the two key features one would need. DNS services like Amazon's Route53, EasyDNS and DNSMadeEasy all advertise themselves as Anycast-enabled networks. Therefore my assumption is that each of these DNS services transparently offer me those two killer features: multi-IP-to-domain mapping AND routing clients to the closest node. However, each of these services seem to separate out these two functionalities, referring to the 2nd one (routing clients to closest node) as "GeoDNS", "GeoIP" or "Global Traffic Director" and charge extra for the service. If a core tenant of an Anycast-capable system is to already do this, why is this functionality being earmarked as this extra feature? What is this "GeoDNS" feature doing that a standard Anycast DNS service won't do (according to the definition of Anycast from Wikipedia -- I understand what is being advertised, just not why it isn't implied already). I get extra-confused when a DNS service like Route53 that doesn't support this nebulous "GeoDNS" feature lists functionality like: Fast – Using a global anycast network of DNS servers around the world, Route 53 is designed to automatically route your users to the optimal location depending on network conditions. As a result, the service offers low query latency for your end users, as well as low update latency for your DNS record management needs. ... which sounds exactly like what GeoDNS is intended to do, but geographically directing clients is something they explicitly don't support it yet. Ultimately I am looking for the two following features from a DNS provider: Map multiple IP addresses to a single domain name (like google.com, amazon.com, etc. does) Utilize a DNS service that will respond to client requests for that domain with the IP address of the nearest server to the requestee. As mentioned, it seems like this is all part of an "Anycast" DNS service (all of which these services are), but the features and marketing I see from them suggest otherwise, making me think I need to learn a bit more about how DNS works before making a deployment choice. Thanks in advance for any clarifications.

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• Which Linux is the most efficient?

  - by quandary

  Simple question: There is a gazillion Linux distributions out there. Which one (distribution/incl. window manager) makes (technically) the most efficient use of my (aging) computer ? I have appx. 1 GB RAM and a 1.6 GHz processor, 120 GB hd. I develop applications (C++/.NET/mono/ASP/PostGre SQL/). Usually, I prefer distros with apt-get. Anybody knows which one takes the most care of my limited RAM, and wich one is the fastest/slimmest of them all, that has a decent repo and is damn fast)

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• Bluray Drives: 2x vs 4x vs 6x vs 8x read/writespeed.

  - by Wesley

  Hi all, I couldn't find a duplicate question, but I was wondering what the differences are between different read/write speeds for Bluray drive. I'm planning on buying one for a build but don't know if I can cheap out on getting a Bluray 2x drive or spend more money for a quality Bluray 8x drive. Will I just experience more lag/buffering times for Bluray discs on a 2x and none for a 6x or 8x? Thanks in advance.

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