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• What is meant by "streaming data access" in HDFS?

  - by Van Gale

  According to the HDFS Architecture page HDFS was designed for "streaming data access". I'm not sure what that means exactly, but would guess it means an operation like seek is either disabled or has sub-optimal performance. Would this be correct? I'm interested in using HDFS for storing audio/video files that need to be streamed to browser clients. Most of the streams will be start to finish, but some could have a high number of seeks. Maybe there is another file system that could do this better?

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• Performance Testing through distributed jmeter instances and bamboo

  - by user1617754

  I´m working on performance test for several services running in an Amazon network. Our architecture is: Continuous Integration server running in our facilities (Bamboo); A Jmeter server instance in the same network than the services to test; A Jmeter client connected to the JMeter server (ssh tunnels) in our facilities. I want to start the execution of tests from bamboo, and see the different results on it too. Bamboo with <---------> Jmeter server <--------> WebService Jmeter client on Amazon on Amazon Has anybody tried something like this?

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• How do you keep your business rules DRY?

  - by Mario

  I periodically ponder how to best design an application whose every business rule exists in just a single location. (While I know there is no proverbial “best way” and that designs are situational, people must have a leaning toward one practice or another.) I work for a shop where they prefer to house as much of the business rules as possible in the database. This requires developers in many cases to perform identical front-end validations to avoid sending data to the database that will result in an exception—not very DRY. It grates me anytime I find myself duplicating any kind of logic—even lowly validation logic. I am a single-point-of-truth purist to an anal degree. On the other end of the spectrum, I know of shops that create dumb databases (the Rails community leans in this direction) and handle all of the business logic in a separate tier (in Rails the models would house “most” of this). Note the word “most” which implies that some business logic does end up spilling into other places (in Rails it might spill over into the controllers). In way, a clean separation of concerns where all business logic exists in a single core location is a Utopian fantasy that’s hard to uphold (n-tiered architecture or not). Furthermore, is see the “Database as a fortress” and would agree that it should be built on constraints that cause it to reject bad data. As such, I hold principles that cause a degree of angst as I attempt to balance them. How do you balance the database-as-a-fortress view with the desire to have a single-point-of-truth?

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• Apache error_log showing which command output

  - by Unai Rodriguez

  Apache's error_log shows lines like the following: --- snip --- which: no ruby in (/sbin:/usr/sbin:/bin:/usr/bin) which: no locate in (/sbin:/usr/sbin:/bin:/usr/bin) which: no suidperl in (/sbin:/usr/sbin:/bin:/usr/bin) which: no get in (/sbin:/usr/sbin:/bin:/usr/bin) which: no fetch in (/sbin:/usr/sbin:/bin:/usr/bin) which: no links in (/sbin:/usr/sbin:/bin:/usr/bin) which: no lynx in (/sbin:/usr/sbin:/bin:/usr/bin) which: no lwp-mirror in (/sbin:/usr/sbin:/bin:/usr/bin) which: no lwp-download in (/sbin:/usr/sbin:/bin:/usr/bin) which: no kav in (/sbin:/usr/sbin:/bin:/usr/bin) --- end --- The architecture is: Internet - Load Balancer - Varnish - Apache There are several web servers behind the load balancer and I have checked at least one of them with rkhunter (link) and couldn't find anything suspicious. Versions: CentOS 5.7 Varnish 2.1.5 Apache 2.2.3 PHP 5.2.17 Does this mean that someone has executed the command which through Apache? How can that happen? Thank you so much.

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• iPhone Shell - is there any?

  - by alee

  While working on iphone security architecture, i came to know that i can run applications from other applications in iphone. referring to the following url http://iphonedevelopertips.com/cocoa/launching-other-apps-within-an-iphone-application.html for example, i can put a link in a website with following hyperlink skype:// will result skype to run and call at particular number. Now i have few concerns here. is there a shell running in background in iphone, so that it allows other application to run basic app commands. if the above statement is true then how can i enable or run commands directly into iphone shell? if above statements are false, then could you please explain how these commands are being executed? is this part of iPhone SDK? or this funcationality is iPhone OS

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• IIS 7 503 error, application pool stop crash, defdoc.dll could not be loaded due to a configuration

  - by optician

  Hi All, Currently trying to get iis 7 to work, but every time I request a page, the application pool goes into stopped status. In the event log this is what comes back. The Module DLL 'C:\Windows\System32\inetsrv\defdoc.dll' could not be loaded due to a configuration problem. The current configuration only supports loading images built for a x86 processor architecture. The data field contains the error number. I've already re installed iis, any other ideas, I read that someone fixed this by downloading the dll again, but this seems like an odd solution. Thanks. EDIT I have now replaced the file with one I downloaded off the internet, and now it says The Module DLL 'C:\Windows\System32\inetsrv\protsup.dll' could not be loaded due to a configuration problem. I hope I don't have to get 100's of these.

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• IIS - Forwarding requests to a folder to another port

  - by user1231958

  Context I currently installed Glassfish 3 in a server that currently holds ASP and PHP inside Internet Information Server 7 so we can start moving to a new system architecture (the information system is being remade). Obviously, Glassfish uses another port and without too much configuration (all I had to do is to install it) it worked. If I write www.domain.com:8080, the person will be redirected to the Glassfish server. Issue Obviously I don't want the person to write the port! I also believe it might also hold some security issues. Requirement I need the server to take an address of the form www.domain.com/gf or new.domain.com or something alike, and when it receives such a request, "redirect" (masking the URL) the user to the Glassfish website (www.domain.com:8080). Thank you beforehand!

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• While porting a windows application to web, is it better to stick to conventional web technologies o

  - by Kabeer

  Hello. The web based application I am working on currently is a port from a windows application. This application is very data intensive. There are scores of modules and each of these modules have number of forms (data entry screens) and reports whereas the forms have many many fields and likewise the reports. I have been trying to identify the most suitable architecture for the presentation tier. There are many functions that are not very easily portable, for example printing (this too is very complex). For most of the others, I am planning to us "Ext JS" library which looks like capable of handling about 70% of complexity out of the box while for the remaining I would be custom coding or extending Ext JS. Having said that (sorry for being so descriptive), I wonder, if this is an Intranet application, why not port the entire application to SilverLight? While I am good at .Net, I'm somewhat alien to SilverLight. Considering I know my target audience and that the software will be used per seat license, would it be better to ride on SilverLight or is it better to stick to conventional web (XHTML, JS, CSS, etc)? Further, I have to support multiple devices in future and considering that SilverLight plug-ins for many devices are yet not out, would it be a risk?

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• Debian as USB hardware portable as possible

  - by James Mitch

  I have recent hardware, 64 bit, pae and so on. But I'd like to have my Debian installation on a USB HDD. Installing Debian to USB is solved. I used the i386 architecture image. But a pae kernel has been installed. I want to be able to travel with my USB HDD and therefore I want best possible hardware compatibility. My friends and family have sometimes older hardware, but always i386, just sometimes without 64 bit or pae. Never met someone with sparc or other architectures. What should I do to get non-pae kernel and maximum hardware compatibility?

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• Convert MSDN Windows 7 Enterprise installation to Ultimate

  - by stimms

  Related question: When reinstalling Windows 7, does the language, version, architecture (64-bit or 32-bit) or source (OEM, retail, or MSDN) matter? Unthinkingly I installed Windows 7 Enterprise on my development box at work rather than the Ultimate version. Now windows is complaining that it is unable to activate because it can't contact a KMS (Key Management Service) which my company doesn't have. Is there any way to change this install such that it believes it is Windows 7 Ultimate and will take an ultimate key? I have MSDN so the licensing is not an issue.

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• How to change MySQL data directory?

  - by Jonathan Frank

  I want to place my databases in another directory, so I can store them in an ESB (elastic block storage, just a fancy name for a virtualized harddisk) together with my web-apps and other persistent data. I have tried to walk through a tutorial at http://crashmag.net/change-the-default-mysql-data-directory-with-selinux-enabled. Everything seems fine until I type this command: # semanage fcontext -a -t mysqld_db_t "/srv/mysql(/.*)?" Then the command fails and tells me that mysqld_db_t is an invalid SELinux context even if the default MySQL data directory is labelled with this context. I am running Fedora 15 on Virtualbox (behaves like an ordinary x86-compatible box) and Amazon EC2 (based on Xen) so the tutorial should be compatible. It is also worth to mention that turning off SELinux globally or just for the MySQL process is not an option, because such a solution will decrease the security of the system if a hacker gains access to the system via the MySQL server. I have never seen this problem before I changed to the Redhat/Fedora architecture, so it could be a distribution specific issue. Any help is highly appreciated

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• What version of SCO Open Server are guys using out there and on what hardware?

  - by Gath

  I have some old applications which are running on SCO Open Server 5.0.5, and i would love to move them to SCO Open Server 5.0.7 and on modern hardware(servers), currently am running SCO on old IBM PL 300 personal computer, on 92MB Memory, one processor, and it has been serving the clients pretty well. Now i have New Modern IBM xseries Servers and i would love to migrate the same applications to those new servers. Problem is, SCO 5.0.5 is unable to detect some of the hardware components in the new servers. I read somewhere that SCO 5.0.7 is able to detect the newer hardware even the USB ports etc. Is there anyone running SCO Openserver out there, and on what hardware architecture are they running on? Gath

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• TCP/IP- what is it exactly?

  - by OckhamsRazor

  I know that this question sounds stupid, but over all these years, I still have difficulty explaining TCP/IP to people. I don't completely get it myself, and even after reading up on it, the distinction is not very clear. What I get so far is that IP deals with networks while TCP involves delivery of messages over that network. I'm not totally convinced though. Also, they reside on different layers of the Internet architecture. Could anyone disambiguate this distinction using a simple analogy or examples? Also, I read this somewhere The difference is that TCP is responsible for the data delivery of a packet and IP is responsible for the logical addressing. In other words, IP obtains the address and TCP guarantees delivery of data to that address. Is this correct? Thanks for helping me out. One last thing- Where does the ethernet come in all of this?

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• No sound on Debian unstable Intel Corporation 82801JD/DO (ICH10 Family) HD Audio Controller

  - by Dave Roger

  I have no sound on my Debian unstable. # cat /etc/issue Debian GNU/Linux squeeze/sid # lspci |grep -i audio 00:1b.0 Audio device: Intel Corporation 82801JD/DO (ICH10 Family) HD Audio Controller (rev 02) # lsmod | grep -i snd snd_hda_codec_realtek 235506 1 snd_hda_intel 19907 0 snd_hda_codec 54244 2 snd_hda_codec_realtek,snd_hda_intel snd_hwdep 5380 1 snd_hda_codec snd_pcm_oss 32591 0 snd_mixer_oss 12606 1 snd_pcm_oss snd_pcm 60471 3 snd_hda_intel,snd_hda_codec,snd_pcm_oss snd_seq_midi 4400 0 snd_rawmidi 15515 1 snd_seq_midi snd_seq_midi_event 4628 1 snd_seq_midi snd_seq 42881 2 snd_seq_midi,snd_seq_midi_event snd_timer 15582 2 snd_pcm,snd_seq snd_seq_device 4493 3 snd_seq_midi,snd_rawmidi,snd_seq snd 46446 11 snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device soundcore 4598 1 snd snd_page_alloc 6249 2 snd_hda_intel,snd_pcm # cat /proc/asound/version Advanced Linux Sound Architecture Driver Version 1.0.21. # uname -r 2.6.32-5-amd64

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• Out of memory Problem

  - by Sunil

  I'm running a C++ program in Ubuntu 10.04 (32-bit system architecture). If I calculate the amount of memory that my program uses, it comes up to 800MB. I have a 4GB RAM in place. But still before the program even finishes it throws an out of memory exception. Why is that happening ? Is it because of the structure of the memory or implementation problems or what could possibly trigger this issue ? I've had seen this problem quite a number of times before but never understood the reason behind it. Have any of you handled this case before ?

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• Should I use an ssl terminator or just haproxy?

  - by Justin Meltzer

  I'm trying to figure out how to set up my architecture for a socket.io app that will require both https and wss connections. I've found many tutorials on the web suggesting that you use something like stud or stunnel in front of haproxy, which then routes your unencrypted traffic to your app. If I were to go this route, is it suggested that haproxy and the ssl terminator be on separate instances, or is it fine if they are on the same EC2 server instance? If I do not want to use a separate ssl terminator, could I use haproxy to terminate the ssl? Or instead would it be possible to proxy these https and wss connections to my application and have the node app terminate the ssl itself?

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• UEC - Can the Cluster Controller and Storage Controller be seperate systems?

  - by Jeremy Hajek

  My department is implementing an Ubuntu Enterprise Cloud. I have done the testing and am quite comfortable with the 4 pieces, CC/SC, CLC, WS, NC. Looking at various documents below it appears the the Storage Controller and Cluster Controller (eucalyptus-sc and eucalyptus-cc) are always installed on the same system. My question is this: can I install the storage controller and the cluster controller on separate systems? http://open.eucalyptus.com/wiki/EucalyptusAdvanced_v2.0 the picture indicates that cc and sc are two different machines http://www.canonical.com/sites/default/files/active/Whitepaper-UbuntuEnterpriseCloudArchitecture-v1.pdf P.10 1st paragraph uses the word "machine(s)" http://software.intel.com/file/31966 P. 8 indicates the same separate architecture BUT... https://help.ubuntu.com/community/UEC/PackageInstallSeparate indicates below that the SC and CC are to be on the same system.

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• How does ARM Cortex A8 compare with a modern x86 processor

  - by thomasrutter

  I was wondering how does a modern ARM chip based on ARM Cortex A8 compare, in clock-for-clock performance and capability, to a modern x86 chip such as a Core 2 Duo or Core i5? I realise due to the different instruction sets it'll depend heavily on what you're doing. To put it another way, rendering a web page in webkit on a 1GHz ARM Cortex A8 based chip should be about equivalent to doing in on a Core i5 at __ MHz? Update October 2013: Since I asked this question years ago it's become a lot more common, when reading about mobile devices, to see architecture-agnostic benchmarks that you can compare across platforms - for example, in-browser benchmarks like Sunspider in Webkit will run on just about anything and you see these in reviews all the time now. And there's things like Geekbench now.

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• What's the best way to share folder between guest and host machine in VMWARE over VPN?

  - by melaos

  i have a win 7 host machine and i'm running my vmware which is a win server machine. So i'm doing windows development work on my vmware. the source codes are in my win 7 machine which i access using a shared folder method. My only problem now is when my vmware connects to VPN to the deploy the codes, the folder gets disconnected. as i don't really understand the networking or the vmware architecture, what can i do so that i can share the folder from my win 7 host machine to my vmware without getting disconnected when i connect to VPN using my guest (win server) machine? please advise. stuck on vmware thanks

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• Is the Cloud ready for an Enterprise Java web application? Seeking a JEE hosting advice.

  - by Jakub Holý

  Greetings to all the smart people around here! I'd like to ask whether it is feasible or a good idea at all to deploy a Java enterprise web application to a Cloud such as Amazon EC2. More exactly, I'm looking for infrastructure options for an application that shall handle few hundred users with long but neither CPU nor memory intensive sessions. I'm considering dedicated servers, virtual private servers (VPSs) and EC2. I've noticed that there is a project called JBoss Cloud so people are working on enabling such a deployment, on the other hand it doesn't seem to be mature yet and I'm not sure that the cloud is ready for this kind of applications, which differs from the typical cloud-based applications like Twitter. Would you recommend to deploy it to the cloud? What are the pros and cons? The application is a Java EE 5 web application whose main function is to enable users to compose their own customized Product by combining the available Parts. It uses stateless and stateful session beans and JPA for persistence of entities to a RDBMS and fetches information about Parts from the company's inventory system via a web service. Aside of external users it's used also by few internal ones, who are authenticated against the company's LDAP. The application should handle around 300-400 concurrent users building their product and should be reasonably scalable and available though these qualities are only of a medium importance at this stage. I've proposed an architecture consisting of a firewall (FW) and load balancer supporting sticky sessions and https (in the Cloud this would be replaced with EC2's Elastic Load Balancing service and FW on the app. servers, in a physical architecture the load-balancer would be a HW), then two physical clustered application servers combined with web servers (so that if one fails, a user doesn't loose his/her long built product) and finally a database server. The DB server would need a slave backup instance that can replace the master instance if it fails. This should provide reasonable availability and fault tolerance and provide good scalability as long as a single RDBMS can keep with the load, which should be OK for quite a while because most of the operations are done in the memory using a stateful bean and only occasionally stored or retrieved from the DB and the amount of data is low too. A problematic part could be the dependency on the remote inventory system webservice but with good caching of its outputs in the application it should be OK too. Unfortunately I've only vague idea of the system resources (memory size, number and speed of CPUs/cores) that such an "average Java EE application" for few hundred users needs. My rough and mostly unfounded estimate based on actual Amazon offerings is that 1.7GB and a single, 2-core "modern CPU" with speed around 2.5GHz (the High-CPU Medium Instance) should be sufficient for any of the two application servers (since we can handle higher load by provisioning more of them). Alternatively I would consider using the Large instance (64b, 7.5GB RAM, 2 cores at 1GHz) So my question is whether such a deployment to the cloud is technically and financially feasible or whether dedicated/VPS servers would be a better option and whether there are some real-world experiences with something similar. Thank you very much! /Jakub Holy PS: I've found the JBoss EAP in a Cloud Case Study that shows that it is possible to deploy a real-world Java EE application to the EC2 cloud but unfortunately there're no details regarding topology, instance types, or anything :-(

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• VPN Network intermittantly fails to provide internet: What could be possible causes

  - by Jake M

  We have a small office with our own VPN setup. We occasionally experience failures in our internet connection where we cannot access the internet. Most of the time the internet connection will resume by itself(without me doing anything) after a period of time(10 mins). Would you be able to suggest possible causes of the connection failure so I can then go and run some tests? Our network architecture is like so: A 'Billion' brand router that is connected to the internet via phone cable and then connected to our Cisco Switch A Cisco Switch/Bus which is connected to all our office nodes, our external harddrive and also to our router as stated above. All connections are via ethernet cable A series of work computers(nodes) connected via ethernet cable to the Cisco switch. Our ISP is TPG Australia We have a Virtual Private Network All the ethernet cables are about 3 years old Do you think that the causes of our intermittant connection problems could be due to the following: Data collisions in the ethernet cables Old/Faulty ethernet cables Our ISP has bad service Can you think of any other causes of the problem?

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• One bigger Virtual Machine in Cloud

  - by flyer

  I just setup virtual machines on one hardware with Vagrant (this is just a test environment, not production!). I want to use a Puppet to configure them and next try to setup OpenStack. I am not sure If I am understanding how this should look at the end. Is it possible to have below architecture with OpenStack after all where I will run one Virtual Machine with e.g. 12 cores? ------------------------------- | VM (12c) | ------------------------------- | NOVA | NOVA | NOVA | ------------------------------- | OpenStack | ------------------------------- | VM (4c) | VM (4c) | VM (4c) | ------------------------------- | Bare Metal (8c) | ------------------------------- I need this information to have a bigger picture to continue.

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• No option for keeping installed programs when upgrading Windows 7 to Windows 8

  - by Nison Maël

  (Related : How can I upgrade from Windows 7 to Windows 8 and keep my files and applications? ) I'm trying to upgrade my Windows 7 Pro (msdnaa) to Windows 8 Pro (msdnaa). The Windows 8 is the final version (I don't have access to previews on msdnaa anymore). As you can see on the related question accepted answer, Windows 8 should give an option to keep installed programs. But it does not. The only available options are "Keep only personal datas" and "Nothing". Any idea ? I'm running with SP1. I've got two partitions (one of them only contains data of a virtual machine). The two operating systems have the same architecture (64 bits). Screenshot:

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• Linq to sql DataContext cannot set load options after results been returned

  - by David Liddle

  I have two tables A and B with a one-to-many relationship respectively. On some pages I would like to get a list of A objects only. On other pages I would like to load A with objects in B attached. This can be handled by setting the load options DataLoadOptions options = new DataLoadOptions(); options.LoadWith<A>(a => a.B); dataContext.LoadOptions = options; The trouble occurs when I first of all view all A's with load options, then go to edit a single A (do not use load options), and after edit return to the previous page. I understand why the error is occurring but not sure how to best get round this problem. I would like the DataContext to be loaded up per request. I thought I was achieving this by using StructureMap to load up my DataContext on a per request basis. This is all part of an n-tier application where my Controllers call Services which in turn call Repositories. ForRequestedType<MyDataContext>() .CacheBy(InstanceScope.PerRequest) .TheDefault.Is.Object(new MyDataContext()); ForRequestedType<IAService>() .TheDefault.Is.OfConcreteType<AService>(); ForRequestedType<IARepository>() .TheDefault.Is.OfConcreteType<ARepository>(); Here is a brief outline of my Repository public class ARepository : IARepository { private MyDataContext db; public ARepository(MyDataContext context) { db = context; } public void SetLoadOptions(DataLoadOptions options) { db.LoadOptions = options; } public IQueryable<A> Get() { return from a in db.A select a; } So my ServiceLayer, on View All, sets the load options and then gets all A's. On editing A my ServiceLayer should spin up a new DataContext and just fetch a list of A's. When sql profiling, I can see that when I go to the Edit page it is requesting A with B objects.

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• .NET WF4: Should it be in the middle of everything?

  - by stimpy77

  I am aware that WF4 (Windows Workflow 4.0, part of .NET 4.0) is a significant rework and redesign of WF3, where much of what made WF3 a poor technology choice has been cleaned up in WF4. For example, as far as I can tell, WF4 (Windows Workflow 4.0) activities are more or less testable with [TestMethod] and mocking. This among other things, like improved performance, has grabbed my attention about the technology again, whereas I had previously pooh-poohed WF3. I'm working on a new architecture for essentially an n-tier collaborative application (not enterprise-class, just a smallish project with potential to grow significantly) where I'm already trying to discipline myself to use IoC and, to some extent, TDD, and I'm wondering, in general terms, whether it is wiser to just hand-code workflow logic or if I should delve into learning and integrating WF4 so that WF becomes literally the controller of the entire application, i.e. the practical C in "MVC" (not ASP.NET MVC but rather the pattern). So should workflow activities in WF4 be the primary controller for a highly expandable/growable web-based collaborative application? Or am I asking entirely the wrong question? This is a vague question, I'm sure, so abstract answers are as welcome as specific ones.

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