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  • SSH attcack CentOS Amazon EC2

    - by user37143
    Hi, I run a few Rightscale CentOS AMI based instances on Amazon EC2. Two months back I found that our SSHD security is compromised( I had added host.allow and host.deny for ssh). So I created new instances and done an IP based ssh that allows only our IPs through AWS Firewall(ec2-authorize) and chnaged the ssh 22 default port to some other port but two days back I found I was not able to login to the server and when I tried on 22 port the ssh got connected and I found that sshd_conf was changed and when I tried to edit sshd_config I found root had no write permission on the file. So I tried a chmod and it said access denied for 'root' user. This is very strange. I checked secure log and history and found nothing informative. I have PHP, Ruby On Rails, Java, Wordpress apps running on these server. This time I did a chkrootkit scan and found nothing. I renamed the /etc/ssh folder and reinstalled openssh through yum. I had faced this on 3 instances on CentOS(5.2, 5.4) I have instances on Debian as well those working fine. Is this a CentOS/Rightscale issue. Guys, what security measures I should take to prevent this. Please support me this is very critical. Thanks

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  • Loadbalancing with nginx and tomcat

    - by London
    Hello this should be fairly easy to answer for any system admin, the problem is that I'm not server admin but I have to complete this task, I'm very close but still not managing to do it. Here is what I mean, I have two tomcat instance running on machine1 and machine2. People usually access those by visiting urls : http://machine1:8080/appName http://machine2:9090/appName The problem is when I setup nginx with domain name i.e domain.com, nginx sends requests to http://machine1:8080/ and http://machine2:9090/ instead of http://machine1:8080/ and http://machine2:9090/appName Here is my configuration (very basic as it can be noted) : upstream backend { server machine1:8080; server machine2:9090; } server { listen 80; server_name www.mydomain.com mydomain.com; location / { # needed to forward user's IP address to rails proxy_set_header X-Real-IP $remote_addr; # needed for HTTPS proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; proxy_set_header Host $http_host; proxy_redirect off; proxy_max_temp_file_size 0; proxy_pass http://backend; } #end location } #end server What changes must I do to do the following : - when user visits mydomain.com - transfer him to either machine1:8080/appName or machine2:9090 Thank you

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  • passenger and apache memory usage

    - by Brent Faulkner
    On a "CentOS release 6.2 (Final)" server (with Ruby 1.9.3 and Rails 3.2), and using more memory than expected. Looking at passenger-memory-stats I see a couple of HUGE httpd processes... any thoughts on how I can figure out what's going on and reduce the memory usage? Stats are included here... thanks! ---------- Apache processes ----------- PID PPID VMSize Private Name --------------------------------------- 1371 1 202.1 MB 0.1 MB /usr/sbin/httpd 4573 1371 210.2 MB 5.0 MB /usr/sbin/httpd 4778 1371 202.5 MB 0.6 MB /usr/sbin/httpd 4780 1371 217.6 MB 9.4 MB /usr/sbin/httpd 4781 1371 217.1 MB 9.1 MB /usr/sbin/httpd 4856 1371 202.4 MB 0.5 MB /usr/sbin/httpd 4863 1371 204.1 MB 2.1 MB /usr/sbin/httpd 5027 1371 202.4 MB 0.5 MB /usr/sbin/httpd 5043 1371 202.4 MB 0.4 MB /usr/sbin/httpd 5044 1371 205.5 MB 2.7 MB /usr/sbin/httpd 5072 1371 202.4 MB 0.5 MB /usr/sbin/httpd 5084 1371 202.4 MB 0.5 MB /usr/sbin/httpd 32111 1371 1297.0 MB 246.5 MB /usr/sbin/httpd 32579 1371 1914.3 MB 215.5 MB /usr/sbin/httpd ### Processes: 14 ### Total private dirty RSS: 493.42 MB -------- Nginx processes -------- ### Processes: 0 ### Total private dirty RSS: 0.00 MB ----- Passenger processes ----- PID VMSize Private Name ------------------------------- 4180 280.5 MB 24.4 MB Passenger ApplicationSpawner: /var/www/apps/people/current 4345 309.5 MB 53.4 MB Rack: /var/www/apps/people/current 4800 300.2 MB 55.2 MB Rack: /var/www/apps/people/current 4808 297.8 MB 52.5 MB Rack: /var/www/apps/people/current 4815 297.4 MB 52.4 MB Rack: /var/www/apps/people/current 4822 302.7 MB 55.6 MB Rack: /var/www/apps/people/current 22780 209.0 MB 0.0 MB PassengerWatchdog 22783 991.5 MB 1.3 MB PassengerHelperAgent 22785 113.4 MB 1.1 MB Passenger spawn server 22788 144.6 MB 0.0 MB PassengerLoggingAgent 22911 310.4 MB 64.0 MB Rack: /var/www/apps/people/current 22939 311.6 MB 53.5 MB Rack: /var/www/apps/people/current 26175 304.1 MB 55.8 MB Rack: /var/www/apps/people/current 26182 310.4 MB 44.0 MB Rack: /var/www/apps/people/current ### Processes: 14 ### Total private dirty RSS: 513.24 MB

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  • How to track things that SHOULD happen, but might not have

    - by Kamiel Wanrooij
    I am running into a couple of issues with some applications we've deployed and maintain. I have the feeling we have approached this with some anti-patterns up to now, but I would like to see how to make this more flexible and stable. In one situation, we have a server at a client which pushes data to us to parse every night (yes, Windows Task Scheduler). This is highly unstable however, so once every month this doesn't happen because of reasons out of our control. This heavily impacts our business since we run with stale data in that situation. In another scenario we have a lot of background job processes that should be running. We already keep them up using bluepill ( http://www.github.com/arya/bluepill ) but obviously restarts happen, both automatically and manually, and people forget things or systems mess up. What I would like to track is events that should occur or should be available. Like the existence of a process, the execution of a program, or the creation/age of a file, and track it when they don't happen or exist. We develop most things in Ruby on Rails, use NewRelic, Bluepill and Munin, and run on Ubuntu. I've been toying around with counting ps aux | grep processname | wc -l in Munin scripts, or capturing the age of a file and raising alerts over 24-26 hours, stuff like that. Is there better tooling to track things that should happen, and raise alerts if they don't? P.S. I know some things are suboptimal, like manually having to define bluepill for applications and then forgetting to do so. The same goes for the push based approach of the first application, a dedicated daemon that manages that on the client side that we control and can track its connection to us might be a much better solution.

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  • Mysterious swap usage on EC2

    - by rusty
    We're in the middle of a project to move our infrastructure from a co-lo situation into Amazon EC2 and we've noticed some weird memory characteristics of the processes in our setup. Without going into too much detail about the specifics of our processes, we've noticed that on our EC2 instances "top" will show processes using a lot of swap space -- in fact, much greater than the amount of available swap or (if you add it all up) more than the available disk. Here's a sample top output: Mem: 7136868k total, 5272300k used, 1864568k free, 256876k buffers Swap: 1048572k total, 0k used, 1048572k free, 2526504k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ SWAP COMMAND 4121 jboss 20 0 5913m 603m 14m S 0.7 8.7 3:59.90 5.2g java 22730 root 20 0 2394m 4012 1976 S 2.0 0.1 4:20.57 2.3g PassengerHelper 20564 rails 20 0 2539m 220m 9828 S 0.3 3.2 0:23.58 2.3g java 1423 nscd 20 0 877m 1464 972 S 0.0 0.0 0:03.89 876m nscd You can see, for instance, that jboss is reportedly using 5.2 gigs of swap space which is definitely impossible since there's only 1G allocated and none is being used (probably because there's still 1.8G of RAM free). And here's the results of uname -a: Linux xxx.yyy.zzz 2.6.35.14-106.53.amzn1.x86_64 #1 SMP Fri Jan 6 16:20:10 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux We're running an AMI based off of the default Amazon Linux AMI (Amazon Linux AMI release 2011.09, so some RHEL5 and RHEL 6) with not too many customizations and definitely no kernel-level customizations. Something here tells me that on this particular kernel/distribution, the reporting of swap or maybe even total memory usage isn't what it appears to be... Any help would be appreciated!

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  • apache/httpd responds slower under EL6.1 than EL5.6 (centos)

    - by daniel
    I've read through other threads on performance differences between RHEL6 and RHEL5, but none seem a tight match to mine. My issue manifests itself in slightly slower average response time (20ms) per request. I have about 10/10 servers of the same hardware spec with Cent6.1 and Cent5.6. The issue is consistent across the group. I am running Ruby on Rails with Passenger. Apache config is identical (checked out from the same SVN repo) Ruby and Passenger are identical builds. Application is identical and being served traffic round robin. mod_worker An interesting clue from server-status: The Cent6.1 servers have a steady 20-40 threads in the "Reading Request" state while the Cent5.6 servers have around 1. I'm graphing this so I can see it trend over time. I also have a bunch of much newer machines that are significantly faster and are running Cent6.1. They dust all the older machines in response time, but I can see they also have a steady 20-40 threads in the "Reading Request" state. This makes me believe I can get their response time down, if I can figure out what is holding up these requests. My gut is telling me that I need to tune some network setting in sysctl, but I haven't figured it out yet. Help is appreciated.

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  • How to set up a server without a hosting control panel

    - by A4J
    I have always used a control panel on my dedicated servers - from cPanel to Plesk to Virtualmin, and I am now considering ditching a CP altogether and manually editing config files. My requirements are fairly simple, I will host multiple sites on the server; some Apache with PHP & Mysql and some Passenger with Rails & Postgres. All will require email smtp/pop. FTP/Stats will not be required. Could someone please give me a quick run-down of what I would need to do - in terms of installing software and configuration? My server will come with a base install of CentOS 6.4 minimal. My thoughts so far: Install/update latest versions of MySQL & Postgres (are they 'safe' out of the box? Or do I need to do anything else like set up root passwords etc?) Install Apache & PHP (again, are the base installs good to go or do they require security tweaks?) Set up nameservers/hostnames/reverse DNS etc (Any guides on how to do this please?) Install Rubygems Install and configure Dovecot and Postfix (any tips on doing this? Or links to how-tos that cover it please?) Set up each website - any links to guides on how to do this? Install/configure firewall (or is the default install good to go?) Any other tips or advice would be greatly appreciated, as would links to guides or how-tos.

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  • solution for an offline server

    - by dashmug
    I'm trying to setup a development server at work that will ideally be able to test drive a couple of projects in PHP, Rails, or Django (not always running at the same time). I develop the apps locally on a Mac and then I'll put the projects up on this server for testing with my actual users (non-techies) before deploying to a production server. My problem is that we have a very poor internet connection (almost negligible) at work and doing the usual apt-get/yum/ports (make, clean, install) processes for setting up servers always get their packages from online repositories somewhere. I know I could probably download the source and then compile them myself but that's going to be too much of a hassle for me. I'm thinking about two solutions: Plan A: Run a server VM on my Mac and then use this VM as the source repository for the offline server. I've read about Ubuntu's apt-proxy and it seems to be good enough though I haven't tried it yet. I'm not sure if this is possible but can I simply do apt-get install nginx --downloadonly so that the package and its dependencies will be downloaded into my VM and my server can use the VM as the source repo for apt-get? Plan B: Run a server VM on my Mac (which I can setup/update easily when I'm home) and then clone the VM to the offline development server. Maybe I should simply make the server a VM host so I can simply copy the VM over. I think this is okay for the first-time setup but subsequent updates will take too long (cloning the VM image). If I was working on Windows, I imagine it'd be easier because most services have an installer file that I can download and then run at the server. If you could suggest another way, it would be much appreciated. Update: From Michael Hampton's answer, I found a possible solution which is apt-cacher. I also found this page on Ubuntu's website. I wonder if there is a better tool than this one.

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  • What are the right questions to ask when deciding whether to use Chef or Puppet?

    - by John Feminella
    I am about to start a new project which will, in part, require deploying many identical nodes of approximately three different classes: Data nodes, which will run sharded instances of MongoDB. Application nodes, which will run instances of a Ruby on Rails application and an older ASP.NET MVC application. Processing nodes, which will run jobs requested by the application nodes. ALl the nodes will run on instances of Ubuntu 10.04, though they will have different packages installed. I have some familiarity with Chef from previous projects, though I don't consider myself an expert. In an effort to do due diligence, I have been investigating alternative possibilities. We have a number of folks in-house who are long-time Puppet users, and they have encouraged me to take a look. I am having trouble evaluating both choices, though. Chef and Puppet share many of the same domain terminology -- packages, resources, attributes, and so on, and they have a common history that stems from taking different approaches to the same problem. So in some sense they are very similar. But much of the comparison information I've found, like this article, is a little outdated. If you were starting this project today, what questions would you ask yourself to decide whether you should use Chef or Puppet for configuration management? (Note: I don't want answer to the question "Should I use Chef or Puppet?")

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  • Using Monit to monitor Resque

    - by Alex
    I'm trying to use resque as a job runner for Rails. I've tried this config, and many other ways of demonizing the rescue task (because running rake resque:work leaves the terminal tied to that command). Unfortunately, their example configuration doesn't work for me. Does the configuration look correct? Or is there another way to turn the process into a daemon? Thank you :) check process resque_worker_QUEUE with pidfile /data/APP_NAME/current/tmp/pids/resque_worker_QUEUE.pid start program = "/bin/sh -c 'cd /data/APP_NAME/current; RAILS_ENV=production QUEUE=queue_name VERBOSE=1 nohup rake environment resque:work& > log/resque_worker_QUEUE.log && echo $! > tmp/pids/resque_worker_QUEUE.pid'" as uid deploy and gid deploy stop program = "/bin/sh -c 'cd /data/APP_NAME/current && kill -s QUIT `cat tmp/pids/resque_worker_QUEUE.pid` && rm -f tmp/pids/resque_worker_QUEUE.pid; exit 0;'" if totalmem is greater than 300 MB for 10 cycles then restart # eating up memory?

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  • Strategy to isolate multiple nginx ssl apps with single domain via suburi's?

    - by icpu
    Warning: so far I have only learnt how to use nginx to serve apps with their own domain and server block. But I think its time to dive a little deeper. To mitigate the need for multiple SSL certificates or expensive wildcard certificates I would like to serve multiple apps (e.g. rails apps, php apps, node.js apps) from one nginx server_name. e.g. rooturl/railsapp rooturl/nodejsapp rooturl/phpshop rooturl/phpblog I am unsure on ideal strategy. Some examples I have seen and or thought about: Multiple location rules, this seems to cause conflicts between the individual app config requirements, e.g. differing rewrite and access requirements Isolated apps by backend internal port, is this possible? Each port routing to its own config? So config is isolated and can be bespoke to app requirements. Reverse proxy, I am little ignorant of how this works, is this what I need to research? is this actually 2 above? Help online seems to always proxy to another server e.g apache What is an effective way to isolate config requirements for apps served from a single domain via sub uris?

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  • CNAME vs A records

    - by deb
    I built a small rails app that allow users to make a simple site. It uses subdomain accounts ex: deb.myapp.com Whenever an user wanted to have a domain name associated with their site, they would change their NS records to point to slicehost where the application is hosted and I would manage the DNS records myself. However, as more people are using the application this is not an option for me anymore. I prefer users to keep their nameservers at goddady, register.com, etc, so they can log in and manage their own MX records or whatever else they need to change. My question is, should I have them change the A records to point to my server's ip, or should I have them create a CNAME record? Do they need to delete the default A records to allow the CNAME record to work? Will the A record take precedence and overrule the CNAME record? Thanks in advance. Sorry if this is a very basic question. I've read other posts and I can't find a definite answer.

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  • Eventlet or gevent or Stackless + Twisted, Pylons, Django and SQL Alchemy

    - by Khorkrak
    We're using Twisted extensively for apps requiring a great deal of asynchronous io. There are some cases where stuff is cpu bound instead and for that we spawn a pool of processes to do the work and have a system for managing these across multiple servers as well - all done in Twisted. Works great. The problem is that it's hard to bring new team members up to speed. Writing asynchronous code in Twisted requires a near vertical learning curve. It's as if humans just don't think that way naturally. We're considering a mixed approach perhaps. Maybe do the xmlrpc server part and process management in Twisted still but the other stuff in code that at least looks synchronous while not being as such. Then again I like explicit over implicit so hmmm. Anyway onto greenlets - how well does that stuff work? So there's Stackless and as you can see from my Gallentean avatar I'm well aware of the tremendous success in it's use for CCP's flagship EVE Online game first hand. What about Eventlet or gevent? Well for now only Eventlet works with Twisted. However gevent claims to be faster since it's not a pure python implementation it instead uses libevent. It also has fewer idiosyncrasies and defects supposedly. The documentation there is minimal in comparison to Eventlet and it's maintained by 1 guy as far as I can tell. This makes me leery but all great projects start this way so... Then there's PyPy - I haven't even finished reading about that one yet - just saw it in this thread: Drawbacks of Stackless. So confusing - I'm wondering what the heck to do - sounds like Eventlet is probably the best bet but is it really stable enough? Anyone out there have any experience with it? Should we go with Stackless instead as it's been around and is proven technology - just like Twisted is as well - and they do work together nicely. But still I hate having to have a separate version of Python to do this. what to do.... This somewhat obnoxious blog entry hit the nail on the head for me though: Asynchronous IO for Grownups We're stuck using MySQL as well - I never knew how great PostgreSQL was until having had to work on a production OLTP system in MySQL instead - but that's another story. But if that monkey patch thing really works then wow. Just wow.

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  • C# Monte Carlo Incremental Risk Calculation optimisation, random numbers, parallel execution

    - by m3ntat
    My current task is to optimise a Monte Carlo Simulation that calculates Capital Adequacy figures by region for a set of Obligors. It is running about 10 x too slow for where it will need to be in production and number or daily runs required. Additionally the granularity of the result figures will need to be improved down to desk possibly book level at some stage, the code I've been given is basically a prototype which is used by business units in a semi production capacity. The application is currently single threaded so I'll need to make it multi-threaded, may look at System.Threading.ThreadPool or the Microsoft Parallel Extensions library but I'm constrained to .NET 2 on the server at this bank so I may have to consider this guy's port, http://www.codeproject.com/KB/cs/aforge_parallel.aspx. I am trying my best to get them to upgrade to .NET 3.5 SP1 but it's a major exercise in an organisation of this size and might not be possible in my contract time frames. I've profiled the application using the trial of dotTrace (http://www.jetbrains.com/profiler). What other good profilers exist? Free ones? A lot of the execution time is spent generating uniform random numbers and then translating this to a normally distributed random number. They are using a C# Mersenne twister implementation. I am not sure where they got it or if it's the best way to go about this (or best implementation) to generate the uniform random numbers. Then this is translated to a normally distributed version for use in the calculation (I haven't delved into the translation code yet). Also what is the experience using the following? http://quantlib.org http://www.qlnet.org (C# port of quantlib) or http://www.boost.org Any alternatives you know of? I'm a C# developer so would prefer C#, but a wrapper to C++ shouldn't be a problem, should it? Maybe even faster leveraging the C++ implementations. I am thinking some of these libraries will have the fastest method to directly generate normally distributed random numbers, without the translation step. Also they may have some other functions that will be helpful in the subsequent calculations. Also the computer this is on is a quad core Opteron 275, 8 GB memory but Windows Server 2003 Enterprise 32 bit. Should I advise them to upgrade to a 64 bit OS? Any links to articles supporting this decision would really be appreciated. Anyway, any advice and help you may have is really appreciated.

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  • ** EDITED ** 'NoneType' object has no attribute 'day'

    - by Asinox
    Hi guy, i dont know where is my error, but Django 1.2.1 is give this error: 'NoneType' object has no attribute 'day' when i try to save form from the Administrator Area models.py from django.db import models from django.contrib.auth.models import User class Editorial(models.Model): titulo = models.CharField(max_length=250,help_text='Titulo del editorial') editorial = models.TextField(help_text='Editorial') slug = models.SlugField(unique_for_date='pub_date') autor = models.ForeignKey(User) pub_date = models.DateTimeField(auto_now_add=True) activa = models.BooleanField(verbose_name="Activa") enable_comments = models.BooleanField(verbose_name="Aceptar Comentarios",default=False) editorial_html = models.TextField(editable=False,blank=True) def __unicode__(self): return unicode(self.titulo) def get_absolute_url(self): return "/editorial/%s/%s/" % (self.pub_date.strftime("%Y/%b/%d").lower(), self.slug) class Meta: ordering=['-pub_date'] verbose_name_plural ='Editoriales' def save(self,force_insert=False, force_update=False): from markdown import markdown if self.editorial: self.editorial_html = markdown(self.editorial) super(Editorial,self).save(force_insert,force_update) i dont know why this error, COMPLETED ERROR: Traceback: File "C:\wamp\bin\Python26\lib\site-packages\django\core\handlers\base.py" in get_response 100. response = callback(request, *callback_args, **callback_kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\contrib\admin\options.py" in wrapper 239. return self.admin_site.admin_view(view)(*args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\utils\decorators.py" in _wrapped_view 76. response = view_func(request, *args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\views\decorators\cache.py" in _wrapped_view_func 69. response = view_func(request, *args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\contrib\admin\sites.py" in inner 190. return view(request, *args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\utils\decorators.py" in _wrapper 21. return decorator(bound_func)(*args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\utils\decorators.py" in _wrapped_view 76. response = view_func(request, *args, **kwargs) File "C:\wamp\bin\Python26\lib\site-packages\django\utils\decorators.py" in bound_func 17. return func(self, *args2, **kwargs2) File "C:\wamp\bin\Python26\lib\site-packages\django\db\transaction.py" in _commit_on_success 299. res = func(*args, **kw) File "C:\wamp\bin\Python26\lib\site-packages\django\contrib\admin\options.py" in add_view 777. if form.is_valid(): File "C:\wamp\bin\Python26\lib\site-packages\django\forms\forms.py" in is_valid 121. return self.is_bound and not bool(self.errors) File "C:\wamp\bin\Python26\lib\site-packages\django\forms\forms.py" in _get_errors 112. self.full_clean() File "C:\wamp\bin\Python26\lib\site-packages\django\forms\forms.py" in full_clean 269. self._post_clean() File "C:\wamp\bin\Python26\lib\site-packages\django\forms\models.py" in _post_clean 345. self.validate_unique() File "C:\wamp\bin\Python26\lib\site-packages\django\forms\models.py" in validate_unique 354. self.instance.validate_unique(exclude=exclude) File "C:\wamp\bin\Python26\lib\site-packages\django\db\models\base.py" in validate_unique 695. date_errors = self._perform_date_checks(date_checks) File "C:\wamp\bin\Python26\lib\site-packages\django\db\models\base.py" in _perform_date_checks 802. lookup_kwargs['%s__day' % unique_for] = date.day Exception Type: AttributeError at /admin/editoriales/editorial/add/ Exception Value: 'NoneType' object has no attribute 'day' thanks guys sorry with my English

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  • How much abstraction is too much?

    - by Daniel Bingham
    In an Object Oriented Program: How much abstraction is too much? How much is just right? I have always been a nuts and bolts kind of guy. I understood the concept behind high levels of encapsulation and abstraction, but always felt instinctively that adding too much would just confuse the program. I always tried to shoot for an amount of abstraction that left no empty classes or layers. And where in doubt, instead of adding a new layer to the hierarchy, I would try and fit something into the existing layers. However, recently I've been encountering more highly abstracted systems. Systems where everything that could require a representation later in the hierarchy gets one up front. This leads to a lot of empty layers, which at first seems like bad design. However, on second thought I've come to realize that leaving those empty layers gives you more places to hook into in the future with out much refactoring. It leaves you greater ability to add new functionality on top of the old with out doing nearly as much work to adjust the old. The two risks of this seem to be that you could get the layers you need wrong. In this case one would wind up still needing to do substantial refactoring to extend the code and would still have a ton of never used layers. But depending on how much time you spend coming up with the initial abstractions, the chance of screwing it up, and the time that could be saved later if you get it right - it may still be worth it to try. The other risk I can think of is the risk of over doing it and never needing all the extra layers. But is that really so bad? Are extra class layers really so expensive that it is much of a loss if they are never used? The biggest expense and loss here would be time that is lost up front coming up with the layers. But much of that time still might be saved later when one can work with the abstracted code rather than more low level code. So when is it too much? At what point do the empty layers and extra "might need" abstractions become overkill? How little is too little? Where's the sweet spot? Are there any dependable rules of thumb you've found in the course of your career that help you judge the amount of abstraction needed?

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  • SmoApplication.EnumAvailableSqlServers returns server names but not instance names (but only on one

    - by Matma
    Hi, There are a number of questions about this and a number of possible causes and thus far ive tried them all with no success. situation: i have an app that needs a db to work, onstartup it does a SmoApplication.EnumAvailableSqlServers(false) to get all the instances on the network, shows the user a dropdown, they pick one and i go connect to my db on that server. all good problem: this works on my machine, the guys next to me and others. HOWEVER it doesnt work on one of the tech guys machines (and potentially others). we are all on the same network domain, physically connected (no wireless), all logged on with network user names, all running the same sql express 2005 sp3, though im using win7 the other guys are running xppro. MSSMS on all machines can see all the instances when you select "Browse for more". yet on this one tech guys machine it lists his local instance (since its hardcoded to) and all the network servers, but has no instances names? i.e. .sqlexpress server1 server2 server3 server4 but on my machine and others we get: .sqlexpress server1/sqlexpress server2/sqlexpress server3/sqlexpress server4/sqlexpress the code im using: ' .... some code ' this populates my datatable dtServers = SmoApplication.EnumAvailableSqlServers(False) '.... some code '.... then later i ShowServers(...) Private dtServers As DataTable = Nothing Private Sub ShowServers(ByVal SQLInstance As String) ' Create a DataTable where we enumerate the available servers cmbServer.Items.Clear() cmbDatabase.Items.Clear() ' If there are any (network listed) servers at all If (dtServers.Rows.Count > 0) Then ' Loop through each server in the DataTable For Each drServer As DataRow In dtServers.Rows ' Add the name to the combobox cmbServer.Items.Add(drServer("Server") & "\" & drServer("Instance")) Next End If 'To make life simpler (add the local instance of sql express): cmbServer.Items.Add(SQLInstance) ' select first item If cmbServer.Items.Count > 0 Then cmbServer.SelectedIndex = 0 End If End Sub now i know this uses udp and its not 100%, but how come his machine is 100% consistent in not showing remote instances, and mine is 100 consistent showing them. even a udl file on his desktop cant see them, regarldess of provider i choose to use? some of the suggestions are to uninstall and re-install, but that doesnt seem like a solution as i (and most others) can see the instances, but one guy cant. this suggests its not the remote sql server but rather the local machine. Notes: ive tried firewall 1433, 1434 i can connect using a udl with full SERVERNAME\INSTANCENAME the browser service is running locally and on the remote machine ive tried stopping and restarting both the browser service on the local and remote machine. Ideas?

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  • Does my fat-client application belong in the MVC pattern?

    - by boatingcow
    The web-based application I’m currently working on is growing arms and legs! It’s basically an administration system which helps users to keep track of bookings, user accounts, invoicing etc. It can also be accessed via a couple of different websites using a fairly crude API. The fat-client design loosely follows the MVC pattern (or perhaps MVP) with a php/MySQL backend, Front Controller, several dissimilar Page Controllers, a liberal smattering of object-oriented and procedural Models, a confusing bunch of Views and templates, some JavaScripts, CSS files and Flash objects. The programmer in me is a big fan of the principle of “Separation of Concerns” and on that note, I’m currently trying to figure out the best way to separate and combine the various concerns as the project grows and more people contribute to it. The problem we’re facing is that although JavaScript (or Flash with ActionScript) is normally written with the template, hence part of the View and decoupled from the Controller and Model, we find that it actually encompasses the entire MVC pattern... Swap an image with an onmouseover event - that’s Behaviour. Render a datagrid - we’re manipulating the View. Send the result of reordering a list via AJAX - now we’re in Control. Check a form field to see if an email address is in a valid format - we’re consulting the Model. Is it wise to let the database people write up the validation Model with jQuery? Can the php programmers write the necessary Control structures in JavaScript? Can the web designers really write a functional AJAX form for their View? Should there be a JavaScript overlord for every project? If the MVC pattern could be applied to the people instead of the code, we would end up with this: Model - the database boffins - “SELECT * FROM mind WHERE interested IS NULL” Control - pesky programmers - “class Something extends NothingAbstractClass{…}” View - traditionally the domain of the graphic/web designer - “” …and a new layer: Behaviour - interaction and feedback designer - “CSS3 is the new black…” So, we’re refactoring and I’d like to stick to best practice design, but I’m not sure how to proceed. I don’t want to reinvent the wheel, so would anyone have any hints or tips as to what pattern I should be looking at or any code samples from someone who’s already done the dirty work? As the programmer guy, how can I rewrite the app for backend and front end whilst keeping the two separate? And before you ask, yes I’ve looked at Zend, CodeIgnitor, Symfony, etc., and no, they don’t seem to cross the boundary between server logic and client logic!

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  • Need help manipulating WAV (RIFF) Files at a byte level

    - by Eric
    I'm writing an an application in C# that will record audio files (*.wav) and automatically tag and name them. Wave files are RIFF files (like AVI) which can contain meta data chunks in addition to the waveform data chunks. So now I'm trying to figure out how to read and write the RIFF meta data to and from recorded wave files. I'm using NAudio for recording the files, and asked on their forums as well on SO for way to read and write RIFF tags. While I received a number of good answers, none of the solutions allowed for reading and writing RIFF chunks as easily as I would like. But more importantly I have very little experience dealing with files at a byte level, and think this could be a good opportunity to learn. So now I want to try writing my own class(es) that can read in a RIFF file and allow meta data to be read, and written from the file. I've used streams in C#, but always with the entire stream at once. So now I'm little lost that I have to consider a file byte by byte. Specifically how would I go about removing or inserting bytes to and from the middle of a file? I've tried reading a file through a FileStream into a byte array (byte[]) as shown in the code below. System.IO.FileStream waveFileStream = System.IO.File.OpenRead(@"C:\sound.wav"); byte[] waveBytes = new byte[waveFileStream.Length]; waveFileStream.Read(waveBytes, 0, waveBytes.Length); And I could see through the Visual Studio debugger that the first four byte are the RIFF header of the file. But arrays are a pain to deal with when performing actions that change their size like inserting or removing values. So I was thinking I could then to the byte[] into a List like this. List<byte> list = waveBytes.ToList<byte>(); Which would make any manipulation of the file byte by byte a whole lot easier, but I'm worried I might be missing something like a class in the System.IO name-space that would make all this even easier. Am I on the right track, or is there a better way to do this? I should also mention that I'm not hugely concerned with performance, and would prefer not to deal with pointers or unsafe code blocks like this guy. If it helps at all here is a good article on the RIFF/WAV file format.

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  • Binary Search Tree in C

    - by heapzero
    Hi, I'm a Python guy. Learning C language and I've been trying to implement Binary Search Tree in C. I wrote down the code, and I've been trying from few hours but, not able to get the output as expected. Please help! Please correct me. #include<stdlib.h> #include<stdio.h> typedef int ElementType; typedef struct TreeNode { ElementType element; struct TreeNode *left, *right; } TreeNode; TreeNode *createTree(){ //Create the root of tree TreeNode *tempNode; tempNode = malloc(sizeof(TreeNode)); tempNode->element = 0; tempNode->left = NULL; tempNode->right = NULL; return tempNode; } TreeNode *createNode(ElementType X){ //Create a new leaf node and return the pointer TreeNode *tempNode; tempNode = malloc(sizeof(TreeNode)); tempNode->element = X; tempNode->left = NULL; tempNode->right = NULL; return tempNode; } TreeNode *insertElement(TreeNode *node, ElementType X){ //insert element to Tree if(node==NULL){ return createNode(X); } else{ if(X < node->element){ node->left = insertElement(node->left, X); } else if(X > node->element){ node->right = insertElement(node->right, X); } else if(X == node->element){ printf("Oops! the element is already present in the tree."); } } } TreeNode *displayTree(TreeNode *node){ //display the full tree if(node==NULL){ return; } displayTree(node->left); printf("| %d ", node->element); displayTree(node->right); } main(){ //pointer to root of tree #2 TreeNode *TreePtr; TreeNode *TreeRoot; TreeNode *TreeChild; //Create the root of tree TreePtr = createTree(); TreeRoot = TreePtr; TreeRoot->element = 32; printf("%d\n",TreeRoot->element); insertElement(TreeRoot, 8); TreeChild = TreeRoot->left; printf("%d\n",TreeChild->element); insertElement(TreeRoot, 2); insertElement(TreeRoot, 7); insertElement(TreeRoot, 42); insertElement(TreeRoot, 28); insertElement(TreeRoot, 1); insertElement(TreeRoot, 4); insertElement(TreeRoot, 5); // the output is not as expected :( displayTree(TreeRoot); }

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  • collect2: ld returned 1 exit status error in Xcode

    - by user573949
    Hello, Im getting the error Command /Developer/usr/bin/gcc-4.2 failed with exit code 1 and when the full log is opened, the error is more accurately listed as: collect2: ld returned 1 exit status from this simple Cocoa script: #import "Controller.h" @implementation Controller int skillcheck (int level, int modifer, int difficulty) { if (level + modifer >= difficulty) { return 1; } if (level + modifer <= difficulty) { return 0; } } int main () { skillcheck(10, 2, 10); } @end the .h file is this: // // Controller.h // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import <Cocoa/Cocoa.h> @interface Controller : NSObject { int skillcheck; int contestcheck; } @end and no line was specified that the error came from, does anyone know what the source of this error is, and more importantly, how to fix it? EDIT: I removed the class so now I have this: // // Controller.m // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import "Controller.h" int skillcheck (int level, int modifer, int difficulty) { if (level + modifer >= difficulty) { return 1; } if (level + modifer <= difficulty) { return 0; } } int main () { skillcheck(10, 2, 10); } and for the .h file: // // Controller.h // // Created by Duo Oratar on 15/01/2011. // Copyright 2011 __MyCompanyName__. All rights reserved. // #import <Cocoa/Cocoa.h> and the log says: (thanks to the guy who said how to open it) Ld build/Debug/Calculator.app/Contents/MacOS/Calculator normal x86_64 cd /Users/kids/Desktop/Calculator setenv MACOSX_DEPLOYMENT_TARGET 10.6 /Developer/usr/bin/gcc-4.2 -arch x86_64 -isysroot /Developer/SDKs/MacOSX10.6.sdk -L/Users/kids/Desktop/Calculator/build/Debug -F/Users/kids/Desktop/Calculator/build/Debug -filelist /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Calculator.LinkFileList -mmacosx-version-min=10.6 -framework Cocoa -o /Users/kids/Desktop/Calculator/build/Debug/Calculator.app/Contents/MacOS/Calculator ld: duplicate symbol _main in /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Controller.o and /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/main.o collect2: ld returned 1 exit status Command /Developer/usr/bin/gcc-4.2 failed with exit code 1 ld: duplicate symbol _main in /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/Controller.o and /Users/kids/Desktop/Calculator/build/Calculator.build/Debug/Calculator.build/Objects-normal/x86_64/main.o Command /Developer/usr/bin/gcc-4.2 failed with exit code 1

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  • Cases of companies taking IP rights of your own personal projects developed outside company time

    - by GSS
    Hi, I have heard of cases where a developer working for a company is also making his own personal projects in his own time, using his own equipment yet the company he works for tries to claim ownership for the project. I really find this annoying, and bang out of order. It should also be illegal. I am in this position (work for a company and working on my own systems - from small class libraries used to practise what I learn in my exam revision to a large commercial-scale system). While I don't know if the company will try to take ownership, all I know is they say they do not want a conflict of interest. Fair enough, my system is developed in my own time using my own equipment. They also say that work time should be for work only, which it is. Funny thing that as work is so boring, easy and slow that I have plenty of free time, which I wish I could spend on something productive - said system. The problem is, my company does not take hiring technical talent seriously. This is my first job, I am a junior coder (but my status/position doesn't really reflect what I can do), but I am the only developer. Likewise with the guy who controls Windows Server. As the contract does not say anything about taking ownership, I would assume they would. They would try to milk my success (I've made a good impression so I am sure they would). How can this be allowed? Are there any examples of this happening to any fellow Stacker here? It really makes my blood boil. What I find funny is that my company hardly has the expertise and resources to even be able to successfully run a project of my size. What I do at work is an ASP.NET application consisting of five pages, and even then there are flaws in the project. If I told them that they would also have to take responsibility for flaws in the project, then they would think twice! It's exactly because of this I save the best code for myself and at work I write rubbish code full of code smells. The company don't really care about error handling, as long as the business functionality works (ie a scheduled email sends, but there is no error handling). They'd think twice when they see the embarassment and business cost of a YSOD...

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  • change password code error.......

    - by shimaTun
    I've created a code to change a password. Now it seem contain an error. When before I fill in the form to change password.the error is: Warning: Cannot modify header information - headers already sent by (output started at C:\Program Files\xampp\htdocs\e-Complaint(FYP)\userChangePass.php:7) in C:\Program Files\xampp\htdocs\e-Complaint(FYP)\userChangePass.php on line 126 the code: <?php # userChangePass.php //this page allows logged in user to change their password. $page_title='Change Your Password'; //if no first_name variable exists, redirect the user if(!isset($_SESSION['userid'])){ header("Location: http://" .$_SERVER['HTTP_HOST']. dirname($_SERVER['PHP_SELF'])."/index.php"); ob_end_clean(); exit(); }else{ if(isset($_POST['submit'])) {//handle form. require_once('connectioncomplaint.php'); //connec to the database //check for a new password and match againts the confirmed password. if(eregi ("^[[:alnum:]]{4,20}$", stripslashes(trim($_POST['password1'])))){ if($_POST['password1'] == $_POST['password2']){ $p =escape_data($_POST['password1']); }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Your password did not match the confirmed password!</font></p>'; } }else{ $p=FALSE; echo'<p><font color="red" size="+1"> Please Enter a valid password!</font></p>'; } if($p){ //if everything OK. //make the query $query="UPDATE access SET password=PASSWORD('$p') WHERE userid={$_SESSION['userid']}"; $result=@mysql_query($query);//run the query. if(mysql_affected_rows() == 1) {//if it run ok. //send an email,if desired. echo '<p><b>your password has been changed.</b></p>'; //include('templates/footer.inc');//include the HTML footer. exit(); }else{//if it did not run ok $message= '<p>Your password could not be change due to a system error.We apolpgize for any inconvenience.</p><p>' .mysql_error() .'</p>'; } mysql_close();//close the database connection. }else{//failed the validation test. echo '<p><font color="red" size="+1"> Please try again.</font></p>'; } }//end of the main Submit conditional. } ?> the error at this line:- header("Location: http://" .$_SERVER['HTTP_HOST']. dirname($_SERVER['PHP_SELF'])."/index.php"); please help me guy...

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  • PHP-based LaTeX parser -- where to begin?

    - by Alex Basson
    The project: I want to build a LaTeX-to-MathML translator in PHP. Why? Because I'm a mathematician, and I want to publish math on my Drupal site. It doesn't have to translate all of LaTeX, since the basic document-level stuff is ably handled by the CMS and wouldn't be written in LaTeX to begin with; it just has to translate math written in LaTeX into math written in MathML. Although I feel as though I've done my due diligence, this doesn't seem to exist already. Maybe I'm wrong---if you know of something that would serve this purpose, by all means let me know, and thank you in advance. But assuming it doesn't exist, I guess I have to go write it myself. Here's the thing, though: I've never done anything this ambitious. I don't really know where to begin. I've used PHP for years, but just to do the standard "build a CMS with PHP and MySQL"-type of stuff. I've never attempted anything as seemingly sophisticated as translation from one language to another. I'm just dumb enough to consider doing it with regex---after all, LaTeX is a much more formal language, and it doesn't allow for nearly the kinds of pathological edge-cases, as say, HTML. But on the other hand, I'm just smart enough to realize this is probably a terrible idea: now I have two problems, and I sure don't want to end up like this guy. So if that's not the way to go (right?), what is? How should I start thinking about this problem? Am I essentially writing a LaTeX compiler in PHP, and if so, what do I need to know to do that (like, should I just go read the Purple Dragon book first?)? I'm both really excited and pretty intimidated by the prospect of this project, but hey, this is how we all learn to be programmers, right? If something we need doesn't exist, we go and build it, necessity is the mother of... you get the point. Tremendous thanks to everyone in advance for any and all guidance you can offer.

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  • MalformedByteSequenceException while trying to pars XML

    - by poeschlorn
    Hey guy, maybe someone can help: I have the following .gpx data from wikipedia: <?xml version="1.0" encoding="UTF-8" standalone="no" ?> <gpx xmlns="http://www.topografix.com/GPX/1/1" creator="byHand" version="1.1" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.topografix.com/GPX/1/1 http://www.topografix.com/GPX/1/1/gpx.xsd"> <wpt lat="39.921055008" lon="3.054223107"> <ele>12.863281</ele> <time>2005-05-16T11:49:06Z</time> <name>Cala Sant Vicenç - Mallorca</name> <sym>City</sym> </wpt> </gpx> When I call my parsing method, I get a exception (see below) The call looks like this: Document tmpDoc = getParsedXML(currentGPX); My method to parse looks like this (standart parsing code, nothing exctiting....): public static Document getParsedXML(String fileWithPath){ DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db; Document doc = null; try { db = dbf.newDocumentBuilder(); doc = db.parse(new File(fileWithPath)); } catch (ParserConfigurationException e) { e.printStackTrace(); } catch (SAXException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } return doc; } This simple code throws following exception: com.sun.org.apache.xerces.internal.impl.io.MalformedByteSequenceException: Invalid byte 2 of 3-byte UTF-8 sequence. at com.sun.org.apache.xerces.internal.impl.io.UTF8Reader.invalidByte(Unknown Source) at com.sun.org.apache.xerces.internal.impl.io.UTF8Reader.read(Unknown Source) at com.sun.org.apache.xerces.internal.impl.XMLEntityScanner.load(Unknown Source) at com.sun.org.apache.xerces.internal.impl.XMLEntityScanner.skipChar(Unknown Source) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDriver.next(Unknown Source) at com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl.next(Unknown Source) at com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(Unknown Source) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source) at com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(Unknown Source) at com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(Unknown Source) at com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source) at com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source) at javax.xml.parsers.DocumentBuilder.parse(Unknown Source) at Zeugs.getParsedXML(Zeugs.java:38) at Zeugs.main(Zeugs.java:25) I guess the error lies within the format of the first file, but I don't know where exactly. Can you please give me a hint?

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