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• Bundling in visual studio 2012 for web optimization

  - by Jalpesh P. Vadgama

  I have been writing a series of posts about Visual Studio 2012 features. This series describes what are the new features in the Visual Studio 2012. This post will also be part of Visual Studio 2012 feature series. As we know now days web applications or site are providing more and more features and due to that we have include lots of JavaScript and CSS files in our web application.So once we load site then we will have all the JavaScript  js files and CSS files loaded in the browsers and If you have lots of JavaScript files then its consumes lots of time when browser request them. Following images show the same situation over there.   Here you can see total 25 files loaded into the system and it's almost more than 1MB of total size. As we need to have our web application of site very responsive and need to have high performance application/site, this will be a performance bottleneck to our site. In situation like this, the bundling feature of Visual Studio 2012 and ASP.NET 4.5 comes very handy. With the help of this feature we do optimization there and we can increase performance of our application. To enable this feature in Visual Studio 2012 we just made debug=”false” in web.config of our application like following. Now once you enable this feature and run this application in the browser to see your traffic it will have less items like following. As you can see in the above image there are only 8 items. So after enabling bundling it will automatically convert all js and css files into the one request. Isn’t that cool feature? This feature will surely going to have great impact on performance. Hope you like it. Stay tuned for more.. Till then happy programming!!

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• How to create an GUI that communicate with the USB Devices

  - by VINAYAK

  I am doing my Project using win 32 programming.I am just learning about win32 programming and able to create an UI.I want to communicate with an USB Device with that UI.SO,How can i go for that?Is there any predefined functions will be there are we need to create the function for communicating with the OS and get the devices List and got the details about them. My purpose is to , 1.Creating an UI that tells about the Basic information about the device(We want to send a control request to the device to get the descriptors). 2.For that first of all i want to communicate with the OS for device attachment.That will lead to get the information about the device and Enumeration takes place and then only i request the device information through descriptors by using standard Requests. 3.And also i want to create the driver for my device.That will also need to achieve for communicating with OS(Windows). So,can anyone help me about this?How can i achieve this or approach this? Note: I am at the entry level now so anyone give response will be in a detailed format like step by step process would be appreciable.

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• wget has a 4 second delay

  - by guisius

  Hello. I have tried to wget a page with windows/mac, and the response is instant while the linux vesion needs to wait for 4 seconds before it shows the response. I just hope this can be solved. More information added: in Ubuntu : wget xxx://192.168.0.135/test.cgi?cmd= -O test.txt --2011-03-04 14:21:17-- xxx://192.168.0.135/test.cgi?cmd= Connecting to 192.168.0.135:80... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] Saving to: `test.txt' [ <=> ] 17 --.-K/s in 0s 2011-03-04 14:21:22 (1.88 MB/s) - `test.txt' saved [17] while in Mac OS : wget xxx://192.168.0.135/test.cgi?cmd= -O test.txt --2011-03-04 14:22:33-- xxx://192.168.0.135/test.cgi?cmd= Connecting to 192.168.0.135:80... connected. HTTP request sent, awaiting response... 200 OK Length: unspecified [text/html] Saving to: `test.txt' [ <=> ] 17 --.-K/s in 0s 2011-03-04 14:22:33 (755 KB/s) - `test.txt' saved [17] in ubuntu it delays 4 seconds while windows and mac will not i believe it may related to some setting in the network config such as packet size , window frame , but i have no idea to set this PS: because the limit of the post not allow to post the url so i mark this as xxx

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• thick client migration to web based application

  - by user1151597

  This query is related to application design the technology that I should consider during migration. The Scenario: I have a C#.net Winform application which communicates with a device. One of the main feature of this application is monitoring cyclic data(rate 200ms) sent from the device to the application. The request to start the cyclic data is sent only once in the beginning and then the application starts receiving data from the device until it sends a stop request. Now this same application needs to be deployed over the web in a intranet. The application is composed of a business logic layer and a communication layer which communicates with the device through UDP ports. I am trying to look at a solution which will allow me to have a single instance of the application on the server so that the device thinks that it is connected as usual and then from the business logic layer I can manage the clients. I want to reuse the code of the business layer and the communication layer as much as possible. Please let me know if webserives/WCF/ etc what i should consider to design the migration. Thanks in advance.

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• Bridging two sockets

  - by Itehnological

  I wondered if it is possible to bridge two incoming tcp sockets. For example: Client A -----> Server <----- Client B The the server sends it's magic to both clients and then they connect to each other bypassing the server Server Client A ----------><---------- Client B UPDATE: The idea is when those clients can't bind to ports to listen to still be able to create connection between each other with the help of the server. For example Client A and Client B have tcp sockets with the server. User A decides to chat with User B and creates a new tcp connection with the server with the request to bridge it with User B. The server sends that request to Client B and it also opens up a new tcp connection with the server for that chat line. Now when the server has both chat connections from A and B it bridges them and they can work without the server, and as a result the server won't have to process all the messages and files the two users share. That's the idea/

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• Why is rsync.exe [cwRsync] trying to open a port when in client mode?

  - by hemancuso

  I'm trying to use a cygwin compiled version of rsync [the cwrsync package] on Windows and in seemingly whatever configuration I test in there is a request to the user presented by Windows Firewall to allow inbound traffic. If you deny this request, everything works fine - as expected. I'm doing a vanilla push rsync.exe localpath user@remotepath:/absolutepath and it works just fine. I've also attempted this command having deleted ssh from the path and using rsync on local paths - still a firewall prompt. Why is this listen() happening and is there a way I can force the client to not attempt to listen without recompiling and maintaing a patch?

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• Android From Local DB (DAO) to Server sync (JSON) - Design issue

  - by Taiko

  I sync data between my local DB and a Server. I'm looking for the cleanest way to modelise all of this. I have a com.something.db package That contains a Data Helper and couple of DAO classes that represents objects stored in the db (I didn't write that part) com.something.db --public DataHelper --public Employee @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary etc... (all in all 50 fields) I have a com.something.sync package That contains all the implementation detail on how to send data to the server. It boils down to a ConnectionManager that is fed by different classes that implements a 'Request' interface com.something.sync --public interface ConnectionManager --package ConnectionManagerImpl --public interface Request --package LoginRequest --package GetEmployeesRequest My issue is, at some point in the sync process, I have to JSONise and de-JSONise my data (E.g. the Employee class). But I really don't feel like having the same Employee class be responsible for both his JSONisation and his actual representation inside the local database. It really doesn't feel right, because I carefully decoupled the rest, I am only stuck on this JSON thing. What should I do ? Should I write 3 Employee classes ? EmployeeDB @DatabaseField e.g. "name" will be an actual column name in the DB -name @DatabaseField -salary -etc... 50 fields EmployeeInterface -getName -getSalary -etc... 50 fields EmployeeJSON -JSON_KEY_NAME = "name" The JSON key happens to be the same as the table name, but it isn't requirement -name -JSON_KEY_SALARY = "salary" -salary -etc... 50 fields It feels like a lot of duplicates. Is there a common pattern I can use there ?

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• Ubuntu getting wrong hostname from DHCP

  - by sam

  When provisioning new Ubuntu Precise (12.04) servers, the hostname they're getting seems to be generated from the DNS search path, not a reverse lookup on the hostname. Take the following configuration BIND is configured with the hostname, and reverse name Normal zone $TTL 600 $ORIGIN srv.local.net. @ IN SOA ns0.local.net. hostmaster.local.net. ( 2014082101 10800 3600 604800 600 ) @ IN NS ns0.local.net. @ IN MX 5 mail.local.net. my-new-server IN A 10.32.2.30 And reverse @ IN SOA ns0.local.net. hostmaster.local.net. ( 2014082101 10800 3600 604800 600 ) @ IN NS ns0.local.net. $ORIGIN 32.10.in-addr.arpa. 30.2 IN PTR my-new-server.srv.local.net. Then DHCPD is configured to hand out static leases based on mac addresses like so subnet 10.32.2.0 netmask 255.255.254.0 { option subnet-mask 255.255.254.0; option routers 10.32.2.1; option domain-name-servers 10.32.2.1; option domain-name "util.of1.local.net of1.local.net srv.local.net"; site-option-space "pxelinux"; option pxelinux.magic f1:00:74:7e; if exists dhcp-parameter-request-list { option dhcp-parameter-request-list = concat(option dhcp-parameter-request-list,d0,d1,d2,d3); } group { option pxelinux.configfile "pxelinux.cfg/pxeboot"; host my-new-server { fixed-address my-new-server.srv.local.net; hardware ethernet aa:aa:aa:bb:bb:bb; } } } So the hostname should be my-new-server.srv.local.net, however when building a Ubuntu 12.04 node, the hostname ends up as my-new-server.util.of1.local.net When building Lucid (10.04) hosts, the hostname will be correct, it's only on Precise/12.04 nodes we have the problem. Doing a normal and reverse lookup on the host and IP returns the correct result Sams-MacBook-Pro:~ sam$ host my-new-server my-new-server.srv.local.net has address 10.32.2.30 Sams-MacBook-Pro:~ sam$ host my-new-server.srv.local.net my-new-server.srv.local.net has address 10.32.2.30 Sams-MacBook-Pro:~ sam$ host 10.32.2.30 30.2.32.10.in-addr.arpa domain name pointer my-new-server.srv.local.net. The contents of the hosts file is incorrect too 127.0.0.1 localhost 127.0.1.1 my-new-server.util.of1.local.net of1.local.net srv.local.net my-new-server So it looks like when it creates the hosts file, it puts the entire contents of the DNS search path into the local address so the FQDN according to the server is the short hostname as defined, then the first domain in the search path. Is there a way to get around this behaviour, or fix this so it gets the hostname correctly? It's picking up the first part of the hostname, then the rest is wrong.

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• Poor backlink profile - search rankings not updated for 2+ months

  - by fistameeny

  I am carrying out some work on a website that is a PR2 with a few good quality, relevant backlinks (PR4-6). It has a presence on Twitter that is updated regularly, a Google Places listing, and listings on some decent directories (Qype etc). The site was rebuilt into Drupal 7 two months ago, with all the basics done - URL rewriting, XML Sitemap submitted to Google, and most importantly, good quality, structured content. I've noticed that Google is still showing "old" URL's from the previous version of the site that was ditched 8 weeks ago. I think the site may be penalised under the Penguin update, as a previous SEO company created many low quality links from link farms/directories. My question is what the correct way to deal with this is. Bing Webmaster Tools can "disavow" links, and I guess I can attempt to contact the link farms to have them removed. I've already submitted a request to Google to request that we have the penalty removed as we're trying to tidy up a bad history. We submit updated sitemaps to Google and Bing daily, and have built some further decent quality, relevant links. Is there anything further I can do?

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• Generate a Word document from list data

  - by PeterBrunone

  This came up on a discussion list lately, so I threw together some code to meet the need.  In short, a colleague needed to take the results of an InfoPath form survey and give them to the user in Word format.  The form data was already in a list item, so it was a simple matter of using the SharePoint API to get the list item, formatting the data appropriately, and using response headers to make the client machine treat the response as MS Word content.  The following rudimentary code can be run in an ASPX (or an assembly) in the 12 hive.  When you link to the page, send the list name and item ID in the querystring and use them to grab the appropriate data. // Clear the current response headers and set them up to look like a word doc.HttpContext.Current.Response.Clear();HttpContext.Current.Response.Charset ="";HttpContext.Current.Response.ContentType ="application/msword";string strFileName = "ThatWordFileYouWanted"+ ".doc";HttpContext.Current.Response.AddHeader("Content-Disposition", "inline;filename=" + strFileName);// Using the current site, get the List by name and then the Item by ID (from the URL).string myListName = HttpContext.Current.Request.Querystring["listName"];int myID = Convert.ToInt32(HttpContext.Current.Request.Querystring["itemID"]);SPSite oSite = SPContext.Current.Site;SPWeb oWeb = oSite.OpenWeb();SPList oList = oWeb.Lists["MyListName"];SPListItem oListItem = oList.Items.GetItemById(myID);// Build a string with the data -- format it with HTML if you like. StringBuilder strHTMLContent = newStringBuilder();// *// Here's where you pull individual fields out of the list item.// *// Once everything is ready, spit it out to the client machine.HttpContext.Current.Response.Write(strHTMLContent);HttpContext.Current.Response.End();HttpContext.Current.Response.Flush();

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• Capturing BizTalk 2004 SQLAdapter failures

  - by DanBedassa

  I was recently working on a BizTalk 2004 project where I encountered an issue with capturing exceptions (inside my orchestration) occurring from an external source. Like database server down, non-existing stored procedure, …   I thought I might write-up this in case it might help someone …   To reproduce an issue, I just rename the database to something different.   The orchestration was failing at the point where I make a SQL request via a Response-Request Port. The exception handlers were bypassed but I can see a warning in the event log saying: "The adapter failed to transmit message going to send port "   After scratching my head for a while (as a newbie to BTS 2004) to find a way to catch the exceptions from the SQLAdapter in an orchestration, here is the solution I had.   ·         Put the Send and Receive shapes inside a Scope shape ·         Set the Scope’s transaction type to “Long Running” ·         Add a Catch block expecting type “System.Exception” ·         Set the “Delivery Notification” of the associated Port to “Transmitted” ·         Change the “Retry Count” of the associated port to 0 (This will make sure BizTalk will raise the exception, instead of a warning, and you can capture that) ·         Now capture and do whatever with the exception inside the Catch block

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• Windows Advanced Firewall certificate based IPSEC

  - by Tim Brigham

  I'm working on migrating from using IPSEC settings stored under the 'IP Security Policies on Active Directory' to using the 'Windows Firewall with Advanced Security' for my 2008+ boxes. I have successfully been able to get this set up using Kerberos authentication, however my openswan implementation on my Linux boxes is using certificates. Whenever I try changing the authentication method to computer certificate (using RSA and my root CA) the connection is bombing out. I've made this change at both a connection request policy and on the IPSEC settings on the root Windows Firewall with Advanced Security node. The windows event log shows the authentication request is taking place but failing negotiating a mode. What am I missing here?

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• Service layer coupling

  - by Justin

  I am working on writing a service layer for an order system in php. It's the typical scenario, you have an Order that can have multiple Line Items. So lets say a request is received to store a line item with pictures and comments. I might receive a json request such as { 'type': 'Bike', 'color': 'Red', 'commentIds': [3193,3194] 'attachmentIds': [123,413] } My idea was to have a Service_LineItem_Bike class that knows how to take the json data and store an entity for a bike. My question is, the Service_LineItem class now needs to fetch comments and file attachments, and store the relationships. Service_LineItem seems like it should interact with a Service_Comment and a Service_FileUpload. Should instances of these two other services be instantiated and passed to the Service_LineItem constructor,or set by getters and setters? Dependency injection seems like the right solution, allowing a service access to a 'service fetching helper' seems wrong, and this should stay at the application level. I am using Doctrine 2 as a ORM, and I can technically write a dql query inside Service_LineItem to fetch the comments and file uploads necessary for the association, but this seems like it would have a tighter coupling, rather then leaving this up to the right service object.

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• Spreading incoming batched data into a real-time stream

  - by pr1001

  I would like to display some events in 'real-time'. However, I must fetch the data from another source. I can request the last X minutes, though the source is updated approximately every 5 minutes. This means that there will be a delay between the most recent data retrieved and the point in time that I make the request. Second, because I will be receiving a batch of data, I don't want to just fire out all the events down a socket once my fetcher has retrieved it: I would like to spread out the events so that they are both accurately spaced amongst each other and in sync with their original occurrences (e.g. an event is always displayed 6 minutes after it actually happened). My thought is to fetch the data every 5 minutes from the source, knowing that I won't get the very latest data. The original data would be then queued to be sent down the socket 7.5 minutes from its original timestamp – that is, at least ~2.5 minutes from when its batch was fetched and at most 7.5 minutes since then. My question is this: is this the best way to approach the problem? Does this problem have any standard approaches or associated literature related to implementation best-practices and edge cases? I am a bit worried that the frequency of my fetches and the frequency in which the source is updated will get out of sync, leading to points where no data will be retrieved from the source. However, since my socket delay is greater than my fetch frequency, the subsequent fetch should retrieve newer data before the socket queue is empty. Is that correct? Am I missing something? Thanks!

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• nginx automatic failover load balancing

  - by robinmag

  Hi, I'm using nginx and NginxHttpUpstreamModule for loadbalancing. My config is very simple: upstream lb { server 127.0.0.1:8081; server 127.0.0.1:8082; } server { listen 89; server_name localhost; location / { proxy_pass http://lb; proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; } } But with this config, when one of 2 backend server is down, nginx still routes request to it and it results in timeout half of the time :( Is there any solution to make nginx to automatically route the request to another server when it detects a downed server. Thank you.

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• How to collaborate on features using github

  - by Robert Dailey

  github encourages 1 fork per user, so that that user can work independently on a feature and then request that feature to be accepted into the main repository via pull request. However, what if 2 developers need to collaborate on that feature? What is the ideal workflow for this? I could see a number of options: Both developers fork the original repository. Each developer pulls/pushes changes between each other's repository. This seems like a lot of work (tiny micro operations) and also creates a delay between changes, so increases the window for conflicts. Developer 1 forks from the main repository, developer 2 forks from developer 1. Same as #1 mainly but hopefully simplifies Developer 2's life a little? Developer 1 gives Developer 2 permissions to his own fork, so they both work out of the same central repository. Not sure if this is ideal. I'm also curious where branches come into this. Obviously there would be a branch for the feature itself but that branch can't exist in a single place, it would have to exist on multiple forks and be synchronized. Basically just really confused about this workflow, would like an approach for how this can be best accomplished.

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• HTTP Caching Server that supports POST

  - by Jeroen

  I am hosting a REST service which is sending appropriate cache-control headers. I use Varnish as a caching server in front of my webserver. However, a limitation of varnish is that it doesn't support caching HTTP POST and HTTP PUT. Is there any alternate caching server that will be able to cache these requests? I understand that caching POST is a bit tricky because you cannot just cache based on the url as a key like for GET; it needs to actually inspect the request body. In case of multipart/form-data requests, there should probably be a limit on the size of the request body for it to be cached (so that big file uploads, etc won't be cached). Nevertheless I really want to be able to cache short HTTP POST, or at least the application/x-www-form-urlencoded ones.

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• xinet vs iptables for port forwarding performance

  - by jamie.mccrindle

  I have a requirement to run a Java based web server on port 80. The options are: Web proxy (apache, nginx etc.) xinet iptables setuid The baseline would be running the app using setuid but I'd prefer not to for security reasons. Apache is too slow and nginx doesn't support keep-alives so new connections are made for every proxied request. xinet is easy to set up but creates a new process for every request which I've seen cause problems in a high performance environment. The last option is port forwarding with iptables but I have no experience of how fast it is. Of course, the ideal solution would be to do this on a dedicated hardware firewall / load balancer but that's not an option at present.

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• Why won't IE let users login to a website unless in In Private mode?

  - by Richard Fawcett

  I'm not entirely sure this belongs on SuperUser.com. I also considered ServerFault.com and StackOverflow.com, but on balance, I think it should belong here? We host a website which has the same code responding to multiple domain names. On 28th December (without any changes deployed to the website) a percentage of users suddenly could not login, and the blank login page was just rendered again even when the correct credentials were entered. The issue is still ongoing. After remote controlling an affected user's PC, we've found the following: The issue affects Internet Explorer 9. The user can login from the same machine on Chrome. The user can login from an In Private browser session using IE9. The user can login if the website is added to the Trusted Sites security zone. The user can NOT login from an IE session in safe mode (started with iexplore -extoff). Only one hostname that the website responds to prevents login, the same user account on the other hostname works fine (note that this is identical code and database running server side), even though that site is not in trusted sites zone. Series of HTTP requests in the failure case: GET request to protected page, returns a 302 FOUND response to login page. GET request to login page. POST to login page, containing credentials, returns redirect to protected page. GET request to protected page... for some reason auth fails and browser is redirected to login page, as in step 1. Other information: Operating system is Windows 7 Ultimate Edition. AV system is AVG Internet Security 2012. I can think of lots of things that could be going wrong, but in every case, one of the findings above is incompatible with the theory. Any ideas what is causing login to fail? Update 06-Jan-2012 Enhanced logging has shown that the .ASPXAUTH cookie is being set in step 3. Its expiry date is 28 days in the future, its path is /, the domain is mysite.com, and its value is an encrypted forms ticket, as expected. However, the cookie is not being received by the web server during step 4. Other cookies are being presented to the server during step 4, it's just this one that is missing. I've seen that cookies are usually set with a domain starting with a period, but mine isn't. Should it be .mysite.com instead of mysite.com? However, if this was wrong, it would presumably affect all users?

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• Will new Twitter API 1.1 allow hashtag/tweet/trend queries without any authentication, i.e. for a client that does not use an user's account at all?

  - by P5music

  I see that, even not being logged in Twitter with an account, if I google hashtags or twitter accounts, twitter show them. I think it should be also possible to get those tweets programmatically but I do not know it for sure, so I ask for confirmation here, especially for the future with the new Twitter API resctrictions. I mean, will it be possible to get tweets from hashtags or accounts without logging in an user account, and so not wanting to access the user settings, subscriptions, etc (because I do not need it), thus not having to respect any token limit? I found these API 1.1 faqs, have I to be concerned? Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will an application have to request user authorization just to make public API calls? When API v1.1 is released, user authorization (and access tokens) are required for all API 1.1 requests. In the weeks following release, some methods will require only application-based authentication for certain "userless" contexts. Will the Search API require authentication? The Search API is now part of the official REST API in version 1.1. In addition to serving results in a format consistent with other Tweet resources, usage will also require authentication.

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• using munin-plugins-rails to monitor rails app perfromance

  - by user2099762

  I have been trying to configure munin-plugins-rails to monitor the performance of our rails apps from Munin. The graphs appear, but no data is shown in the graphs. The log files show Error output from : 2013/06/27-15:39:06 [5540] Request-log-analyzer, by Willem van Bergen and $ 2013/06/27-15:39:06 [5540] Website: http://railsdoctors.com I have tried running Request-log-analyzer manually and pointing it at the production log file, and this reports as % for every item. There is data in the log file. I have tried changing the version of the gems installed, and also the type of the log file, but no luck. Any ideas anyone? Thanks

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• Which built-in account is used for Anonymous Authentication in IIS 7?

  - by smwikipedia

  We know that Microsoft IIS 7.0 offer a slew of authentication methods such as Anonymous Authentication, Form Based Authentication, Digest Authentication, etc. I read from Professional IIS 7 published by Wrox that: When we use Anonymous Authentication, the end-user does not supply credentials, effectively mak- ing an anonymous request. IIS 7.0 impersonates a fixed user account when attempting to process the request (for example, to read the file off the hard disk). So, what is the fixed user account impersonated by IIS? Where can I see it? If I don't know what this account is, how could I assign proper permissions for the clients who are authenticated as anonymous users? Thanks.

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• ArchBeat Link-o-Rama for December 12, 2012

  - by Bob Rhubart

  “Cloud Integration in Minutes” – True or False? | Bruce Tierney The answer is 'True, but..." according to Bruce Tierney. "Connecting on-premise and cloud applications “in minutes” is true…provided you only consider the connectivity subset of integration and have a small number of cloud integration touch points." Get the rest of the story in Bruce's detailed post. Tech World Discovers New Species: The Cloud Architect | Wired Enterprise | Wired.com This Wired article by Cade Metz boils down to one essential conclusion: Cloud computing is a significant departure from "data center designs of the past," and the demand for the specialized skills of the cloud architect will only increase. But you already knew that, right? Oracle B2B - Synchronous Request Reply | A-Team - SOA "Beginning with Oracle SOA Suite PS5 (11.1.1.6), B2B supports synchronous request reply over http using the b2b/syncreceiver servlet," says C. D. Wright of the Fusion Middleware A-Team. His post includes a demo and everything you need to run it. Thought for the Day "Don't worry about what anybody else is going to do… The best way to predict the future is to invent it." — Alan Kay (Month Day, Year - Month Day, Year) Source: SoftwareQuotes.com

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• Why is domU faster than dom0 on IO?

  - by Paco

  I have installed debian 7 on a physical machine. This is the configuration of the machine: 3 hard drives using RAID 5 Strip element size: 1M Read policy: Adaptive read ahead Write policy: Write Through /boot 200 MB ext2 / 15 GB ext3 SWAP 10GB LVM rest (~500GB) emphasized text I installed postgresql, created a big database (over 1GB). I have an SQL request that takes a lot of time to run (a SELECT statement, so it only reads data from the database). This request takes approximately 5.5 seconds to run. Then, I installed XEN, created a domU, with another debian distro. On this OS, I also installed postgresql, with the same database. The same SQL request takes only 2.5 seconds to run. I checked the kernel on both dom0 and domU. uname-a returns "Linux debian 3.2.0-4-amd64 #1 SMP Debian 3.2.41-2+deb7u2 x86_64 GNU/Linux" on both systems. I checked the kernel parameters, which are approximately the same. For those that are relevant, I changed their values to make them match on both systems using sysctl. I saw no changes (the requests still take the same amount of time). After this, I checked the file systems. I used ext3 on domU. Still no changes. I installed hdparm, and ran hdparm -Tt on both systems, on all my partitions on both systems, and I get similar results. Now, I am stuck, I don't know what is different, and what could be the cause of such a big difference. Additional Info: Debian runs on a Dell server PowerEdge 2950 postgresql: 9.1.9 (both dom0 and domU) xen-linux-system: 3.2.0 xen-hypervisor: 4.1 Thanks EDIT: As Krzysztof Ksiezyk suggested, it might be due to some file caching system. I ran the dd command to test both the read and write speed. Here is domU: root@test1:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 18.8289 s, 107 MB/s root@test1:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 2020+0 records in 2020+0 records out 2020000000 bytes (2.0 GB) copied, 15.0549 s, 134 MB/s And here is dom0: root@debian:~# dd if=/dev/zero of=/root/dd count=5MB bs=1MB ^C1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 8.87281 s, 191 MB/s root@debian:~# dd if=/root/dd of=/dev/null count=5MB bs=1MB 1693+0 records in 1693+0 records out 1693000000 bytes (1.7 GB) copied, 0.501509 s, 3.4 GB/s What can be the cause of this caching system? And how can we "fix" it? Can we apply it to dom0? EDIT 2: I switched my virtual disk type. To do so I followed this article. I did a dd if=/dev/vg0/test1-disk of=/mnt/test1-disk.img bs=16M Then in /etc/xen/test1.cfg, I changed the disk parameter to use file: instead of phy: it should have removed the file caching, but I still get the same numbers (domU being much faster for Postgres)

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• Tomcat access logs - are failed requests included?

  - by Maxim Eliseev

  We have a RESTful web service (Java, hosted in Tomcat on Ubuntu on Amazon EC2). From time to time it fails (not every week). When it fails, Java CPU consumption goes to 100% and it takes all available memory. It does not finish by itself. I have to restart the server. There is nothing suspicious in Tomcat access logs. I guess one of our users could submit a very "heavy" request which brought the server down. Is it possible this request is not in Tomcat logs since it never finished?

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