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• Insufficient channel capacity of 1GBit

  - by Roman S

  There is a Caching Server (Varnish): it receives data from Amazon S3 on request, saves it for some time and gives it to the client. We have encountered the problem of insufficient channel capacity of 1GBit. Peak load within 4 hours completely chokes the channel. Server performance is sufficient for now. Approximately 4.5TB of data are transmitted per day. More than 100TB are accumulated per month. The first thought that comes to mind is simply to add one more 1GBit port and sleep peacefully until 2GBit are not enough (it may happen quite quickly) or one server is not able to handle it. And then we just need to add new Caching Servers. But now we need a Load Balancer, which will send requests on one and the same URL, always on one and the same server (to avoid multiple copies of the same cached objects). Here are the questions: Does a Balancer need a band equal to sum of all bands of Caching Servers? What shall we do in case there are no ports in a Balancer? Should we add more Balancers or solve the problem by means of Round robin DNS? What are the standard approaches to such problems? Can anyone advise hosting-companies, which can solve this problem? We are interested in American and European markets.

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• Apache2: Limit simultaneous requests & throttle bandwidth per IP/client?

  - by xentek

  I want to limit simultaneous requests & throttle bandwidth per IP/Client on a single apache vhost. In other words, I want to ensure that this site, which hosts large media files, doesn't get hammered by someone trying to download everything all at once (just happened the other night). I'd like to limit the outgoing transfer speed overall for this site, as well as limit the number of connections a single IP can make to the server to a sane default (i.e. within normal browser limits for multiple requests so page loads aren't effected too much). Bonus points if I can actually scope it to file types (i.e. leave web files alone, but apply these rules to just the media files). We're running Ubuntu 9.04 on all the servers, and have two apache/php servers being load balanced via Round Robin by a squid proxy server. MySQL is running on its own box as well. We've got plenty of bandwidth to give them, so I don't really want overall caps, but just want to throttle the amount of memory/CPU it takes to serve this site. There other sites on these servers that we don't want to apply these rules too, just want to keep this one from hogging all the resources. Let me know if you need more info! Thanks in advance for your suggestions!

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• How browsers handle multiple IPs

  - by Sandman4

  Can someone direct me to information on exact browsers behavior when browser gets multiple A records for a given hostname (say ip1 and ip2), and one of them is not accessible. I interested in EXACT details, like (but not limited to): Will browser get 2 IPs from OS, or it will get only one ? Which ip will browser try first (random or always the first one) ? Now, let's say browser started with the failed ip1 For how long will browser try ip1 ? If user hits "stop" while it waits for ip1, and then clicks refresh which IP will browser try ? What will happen when it times-out - will it start trying ip2 or give error ? (And if error, which ip will browser try when user clicks refresh). When user clicks refresh, will any browser attempt new DNS lookup ? Now let's assume browser tried working ip2 first. For the next page request, will browser still use ip2, or it may randomly switch ips ? For how long browsers keep IPs in their cache ? When browsers sends a new DNS request, and get SAME ips, will it CONTINUE to use the same known-to-be-working IP, or the process starts from scratch and it may try any of the two ? Of course it all may be browser dependent, and may also vary between versions and platforms, I'd be happy to have maximum of details. The purpose of this - I'm trying to understand what exactly users will experience when round-robin DNS based used and one of the hosts fails. Please, I'm NOT asking about how bad DNS load balancing is, and please refrain from answering "don't do it", "it's a bad idea", "you need heartbeat/proxy/BGP/whatever" and so on.

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• Squid reverse proxy array - siblings not communicating with each other

  - by V. Romanov

  I want to set up 2 squid servers to act as reverse proxy and cache for a webserver on our intranet. The load balancing will be done with DNS round robin or just different mappings for different clients. The thing is, I want both servers to try and contact each other to see if they have the object required in cache before contacting the webserver for it (the network that servers the webserver is the bottleneck and I'm trying to eliminate it) Both squids are configured the same, here are the relevant config lines : acl dvr1_cache_it_best_tv_com dstdomain dvr1.cache.it.best-tv.com acl squid1_it_best_tv_com dstdomain squid1.it.best-tv.com acl squid2_it_best_tv_com dstdomain squid2.it.best-tv.com http_access allow dvr1_cache_it_best_tv_com http_access allow squid1_it_best_tv_com http_access allow squid2_it_best_tv_com http_access allow all http_port 8081 accel defaultsite=dvr1.cache.it.best-tv.com cache_peer dvr1.origin.it.best-tv.com parent 80 0 no-query originserver name=Proxy_dvr1_origin_it_best_tv_com cache_peer squid1.it.best-tv.com sibling 8081 3130 weight=10 name=Proxy_Squid1_it_best_tv_com cache_peer squid2.it.best-tv.com sibling 8081 3130 weight=10 name=Proxy_Squid2_it_best_tv_com cache_peer_access Proxy_dvr1_origin_it_best_tv_com allow dvr1_cache_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow squid1_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow squid2_it_best_tv_com cache_peer_access Proxy_squid1_it_best_tv_com allow dvr1_cache_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow squid1_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow squid2_it_best_tv_com cache_peer_access Proxy_squid2_it_best_tv_com allow dvr1_cache_it_best_tv_com just to make it clear - dvr1.cache is the alias for the proxy servers. dvr1.origin is the web server. Both servers work, both serve content and cache it and work fine. However, when I clear the cache on one server and then access it, it gets the content from the parent (DVR1_ORIGIN) instead of going to the sibling squid. What did I configure wrong? Or perhaps I don't understand the architecture correctly? I read the squid manuals but as far as I see i did it all by the book and yet it doesn't work right. Any help will be appreciated!

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• Good Enough Failover Strategy for DNS / MySQL / Email

  - by IMB

  I've asked and read a lot questions regarding DNS failover but the more I read the more complicated it becomes, some people say it's good enough some say it isn't. No clear answers from what I read. I was wondering if we can set it straight once and for all, at least for the requirements of most websites out there. Right now let's assume the following: We don't need really need load-balancing, what we need is a failover solution. We are running a website based on LAMP on a VPS. We need to make sure that the Web Server, MySQL, Email are always accessible if not 99%. Basically here's my idea and questions about it: Web Server: We need at least one failover server (another VPS on a separate data center). Is DNS Failover via Round Robin good, if not, what's the best? And how do you exactly implement it? How do you make the files you upload/delete on Server A is also on Server B? MySQL: I've only read a brief intro to MySQL replication and I assume that I can replicate Server A to Server B and vice versa on the fly right? So just it case Server A fails and Server B is now running, it will continue to work and replicate to Server A when it becomes available. So in essence Server B is now the primary server, and will later on failover to Server A, should a failure happen again. Email: If we are gonna use DNS Failover, using webmail or relying on emails stored on the server is probably not a good idea right? Since some emails might be on Server A while some might be on Server B? I assume a basic email forwarder to a 3rdparty is good enough (like Gmail for example) to ensure all emails are kept in one place. Here's a basic diagram for a better picture: http://i.stack.imgur.com/KWSIi.png

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• Webcam security camera software that runs as a service

  - by hurfdurf

  I've been looking for Windows webcam software that will run as a Windows service without any user login. The goal is to use the webcam as a cheap security camera and log the results to secure networked storage (windows share, not FTP). The requirements are: Motion detection Video capture Runs as a service (should start recording immediately after reboot) Nice to have: Round-robin storage, e.g. 10Gb limit, oldest files overwritten/deleted when space gets low I've read the other webcam questions but still haven't stumbled across anything suitable. Evaluations thus far: Title MotionDetect Service Snapshots Video SpaceLimit License Yawcam Yes Yes Yes No No GPL WebCam ZoneTrigger Yes No Yes Yes No Commercial Dorgem Yes No Yes Yes No GPL AbelCam Yes No Yes Yes No Commercial Logitech Yes No Yes Yes No Paired with camera IspyConnect Yes No Yes Yes Yes Free SecureCam (SourcefoYes No Yes Yes No GPL AbelCam Yes No Yes Yes No Commercial Active WebCam Yes Yes(?) Yes Yes Volume Free Commercial WebCam Surveyor Yes No Yes Yes No Commercial WebCamsPy NA NA NA NA NA GPL Camera: Logitech Webcam Pro 9000 Windows 7 32-bit WebCamsPy failed to initialize so couldn't be tested So far, the contenders: Active Webcam comes the closest, and claims to run as a service, but i haven't been able to get it to record after a cold boot even though a service is running. Yawcam can be set up as a service but doesn't record video. IspyConnect has exactly the type of space limit I want and looks great, but doesn't run as a service (seems also to be a bit of a cpu hog) Any other suggestions? I'm locked into Windows so can't use linux Motion, which looks almost perfect. Any pointers to rich Windows webcam/motion detection libraries out there that could easily be turned into a command line program would also be appreciated.

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• Nginx proxy upstream cached?

  - by Julian H. Lam

  Attempting to resolve an issue that's been annoying me for a bit. I've distilled the symptoms into a set of reproducible steps: I have two sites, siteA, and siteB. They are both Node.js applications running on different ports (for the sake of example, 4567 and 4568) Both applications have their own file in sites_available (plus a symlink from sites_enabled), which contain the directives proxy_pass http://node_siteA/ and proxy_pass http://node_siteB/ respectively, inside of a location block. They also each have an upstream block (defined globally?): upstream node_siteA { upstream node_siteB { server 127.0.0.1:4567; server 127.0.0.1:4568; } } Site A and Site B have nothing to do with each other. Yes, I am restarting (reloading, actually) nginx every time I make a change. If I take down site B and attempt to access it via the web, I am served site A. Why is this? Thoughts Other times, when I create a new Site C, for example, nginx refuses to show me anything except "Welcome to nginx!" for ~5 minutes. This suggests a resolver timeout, perhaps? When I access Site B after its config has been deleted, and it sends me to Site A, this sounds like nginx sending me to servers in a round-robin fashion...

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• Apache Server with memcache, varnish and php slow request times

  - by coolestdude1

  My issue is that these servers are taking rather long for request about 2 seconds on average just to serve files. When we had just one server doing everything it was noticeably faster even with the same web app (Drupal 6 and Drupal 7). I want to get this number down to a reasonable level and so I need some help getting to the bottom of why the request times are so slow. This can cause the webapp to hang on post or put and generally leads to a bad user experience on my sites. PS: I am more of a server newbie so this has confounded me for quite some time. The domains: collabornation.net nptrainingworks.com (they run off the same two webservers using vhost configs) The Gear: Two Rackspace 4 Gig servers running CentOS 6.2 Final They have a mounted file system (gluster) that is used to keep files the same on both machines. They are behind a rackspace load balancer running round robin. Mysql is run using php-pdo and php-mysql as such mysql is run on another instance running memcache on that machine with phpMyAdmin located there as well. Apache version number 2.2.15-15.el6.centos.1 (httpd.x86_64) Varnish version number 3.0.2-1.el5 (varnish.x86_64) PHP version number 5.3.14-1.el6.remi (php.x86_64) Configs Linked Below Apache Conf Vhost Conf Varnish Backends Varnish Defaults Varnish Acl PHP INI Again need some help, much appreciated!

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• Apache load balancer with https real servers and client certificates

  - by Jack Scheible

  Our network requirements state that ALL network traffic must be encrypted. The network configuration looks like this: ------------ /-- https --> | server 1 | / ------------ |------------| |---------------|/ ------------ | Client | --- https --> | Load Balancer | ---- https --> | server 2 | |------------| |---------------|\ ------------ \ ------------ \-- https --> | server 3 | ------------ And it has to pass client certificates. I've got a config that can do load balancing with in-the-clear real servers: <VirtualHost *:8666> DocumentRoot "/usr/local/apache/ssl_html" ServerName vmbigip1 ServerAdmin [email protected] DirectoryIndex index.html <Proxy *> Order deny,allow Allow from all </Proxy> SSLEngine on SSLProxyEngine On SSLCertificateFile /usr/local/apache/conf/server.crt SSLCertificateKeyFile /usr/local/apache/conf/server.key <Proxy balancer://mycluster> BalancerMember http://1.2.3.1:80 BalancerMember http://1.2.3.2:80 # technically we aren't blocking anyone, but could here Order Deny,Allow Deny from none Allow from all # Load Balancer Settings # A simple Round Robin load balancer. ProxySet lbmethod=byrequests </Proxy> # balancer-manager # This tool is built into the mod_proxy_balancer module allows you # to do simple mods to the balanced group via a gui web interface. <Location /balancer-manager> SetHandler balancer-manager Order deny,allow Allow from all </Location> ProxyRequests Off ProxyPreserveHost On # Point of Balance # Allows you to explicitly name the location in the site to be # balanced, here we will balance "/" or everything in the site. ProxyPass /balancer-manager ! ProxyPass / balancer://mycluster/ stickysession=JSESSIONID </VirtualHost> What I need is for the servers in my load balancer to be BalancerMember https://1.2.3.1:443 BalancerMember https://1.2.3.2:443 But that does not work. I get SSL negotiation errors. Even when I do get that to work, I will need to pass client certificates. Any help would be appreciated.

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• What are the typical methods used to scale up/out email storage servers?

  - by nareshov

  Hi, What I've tried: I have two email storage architectures. Old and new. Old: courier-imapds on several (18+) 1TB-storage servers. If one of them show signs of running out of disk space, we migrate a few email accounts to another server. the servers don't have replicas. no backups either. New: dovecot2 on a single huge server with 16TB (SATA) storage and a few SSDs we store fresh mails on the SSDs and run a doveadm purge to move mails older than a day to the SATA disks there is an identical server which has a max-15min-old rsync backup from the primary server higher-ups/management wanted to pack in as much storage as possible per server in order to minimise the cost of SSDs per server the rsync'ing is done because GlusterFS wasn't replicating well under that high small/random-IO. scaling out was expected to be done with provisioning another pair of such huge servers on facing disk-crunch issues like in the old architecture, manual moving of email accounts would be done. Concerns/doubts: I'm not convinced with the synchronously-replicated filesystem idea works well for heavy random/small-IO. GlusterFS isn't working for us yet, I'm not sure if there's another filesystem out there for this use case. The idea was to keep identical pairs and use DNS round-robin for email delivery and IMAP/POP3 access. And if one the servers went down for whatever reasons (planned/unplanned), we'd move the IP to the other server in the pair. In filesystems like Lustre, I get the advantage of a single namespace whereby I do not have to worry about manually migrating accounts around and updating MAILHOME paths and other metadata/data. Questions: What are the typical methods used to scale up/out with the traditional software (courier-imapd / dovecot)? Do traditional software that store on a locally mounted filesystem pose a roadblock to scale out with minimal "problems"? Does one have to re-write (parts of) these to work with an object-storage of some sort - such as OpenStack object storage?

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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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• Developer’s Life – Every Developer is a Superman

  - by Pinal Dave

  I enjoyed comparing developers to Spiderman so much, that I have decided to continue the trend and encourage some of my favorite people (developers) with another favorite superhero – Superman.  Superman is probably the most famous superhero – and one of the most inspiring. Everyone has their own favorite, but Superman has been the longest enduring of all comic book characters.  Clark Kent has inspired multiple movie series, TV shows, books, cartoons, and costumes.  Superman’s enduring popularity has been attributed to his superhuman strength, integrity, dedication to good, and his humility in keeping his identity a secret. So how are developers like Superman? Well, read on my list of reasons. Secret Identities They have secret identities.  I’m not saying that all developers wear thick glasses and go by an alias like “Clark Kent.”  But developers certainly work in the background, making sure everything runs smoothly, often without recognition.  Like Superman, when they have done their job right, no one knows they were there. Working Alone You don’t have to work alone.  Superman doesn’t have a sidekick like Robin or Bat Girl, but he is a major player in the Justice League.  Developers have amazing skills, and they shouldn’t be afraid to unite those skills to solve some of the world’s major problems (like slow networks). Daily Inspiration Developers are inspiring.  Clark Kent works at The Daily Planet, Metropolis’ newspaper, which is lucky because he can keep some of the publicity Superman inspires under wraps.  Developers might go unnoticed sometimes, but when people hear about some of the tasks they accomplish on a daily basis, it inspires awe. Discover Your Superpowers You have to discover your superpowers.  Clark Kent didn’t just wake up one morning with the full understanding that he could fly, leap tall buildings in a single bound, and was stronger than a speeding locomotive.  He slowly discovered these powers (after a few comic book-worthy misunderstandings!).  Developers are always learning and growing as well.  You probably won’t wake up with super powers, either, but years of practice and continuing education can get you close. Every Day is a New Day The story continues.  The Superman comic books are still being printed, and have been in print since 1938.  There have been two TV series, (one, Smallville, was on TV for ten seasons) and multiple cartoon adaptations.  There have been multiple movies, with many different actors.  A new reboot came out last year, and another is set to premier in 2016.   So, developers, when you are having a bad day or a problem seems unsolvable – remember, the story will continue!  There is always tomorrow. I hope you are all enjoying reading about developers-as-superheroes as much as I am enjoying writing about them.  Please tell me how else developers are like Superheroes in the comments – especially if you know any developers who are faster than a speeding bullet and can leap tall buildings in a single bound. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL Tagged: Developer, Superhero

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• Do We Indeed Have a Future? George Takei on Star Wars.

  - by Bil Simser

  George Takei (rhymes with Okay), probably best known for playing Hikaru Sulu on the original Star Trek, has always had deep concerns for the present and the future. Whether on Earth or among the stars, he has the welfare of humanity very much at heart. I was digging through my old copies of Famous Monsters of Filmland, a great publication on monster and films that I grew up with, and came across this. This was his reaction to STAR WARS from issue 139 of Famous Monsters of Filmland and was written June 6, 1977. It is reprinted here without permission but I hope since the message is still valid to this day and has never been reprinted anywhere, nobody will mind me sharing it. STAR WARS is the most pre-posterously diverting galactic escape and at the same time the most hideously credible portent of the future yet.While I thrilled to the exploits that reminded me of the heroics of Errol Flynn as Robin Hood, Burt Lancaster as the Crimson Pirate and Buster Crabbe as Flash Gordon, I was at the same time aghast at the phantasmagoric violence technology can place at our disposal. STAR WARS raised in my mind the question - do we indeed have a future?It seems to me what George Lucas has done is to masterfully guide us on a journey through space and time and bring us back face to face with today's reality. STAR WARS is more than science fiction, I think it is science fictitious reality.Just yesterday, June 7, 1977, I read that the United States will embark on the production of a neutron bomb - a bomb that will kill people on a gigantic scale but will not destroy buildings. A few days before that, I read that the Pentagon is fearful that the Soviets may have developed a warhead that could neutralize ours that have a capacity for that irrational concept overkill to the nth power. Already, it seems we have the technology to realize the awesome special effects simulations that we saw in the film.The political scene of STAR WARS is that of government by force and power, of revolutions based on some unfathomable grievance, survival through a combination of cunning and luck and success by the harnessing of technology -  a picture not very much at variance from the political headlines that we read today.And most of all, look at the people; both the heroes in the film and the reaction of the audience. First, the heroes; Luke Skywalker is a pretty but easily led youth. Without any real philosophy to guide him, he easily falls under the influence of a mystical old man believed previously to be an eccentric hermit. Recognize a 1960's hippie or a 1970's moonie? Han Solo has a philosophy coupled with courage and skill. His philosophy is money. His proficiency comes for a price - the highest. Solo is a thoroughly avaricious mercenary. And the Princess, a decisive, strong, self-confident and chilly woman. The audience cheered when she wielded a gun. In all three, I missed qualities that could be called humane - love, kindness, yes, I missed sensuality. I also missed a sense of ideals and faith. In this regard the machines seemed more human. They demonstrated real affection for each other and an occasional poutiness. They exhibited a sense of fidelity and constancy. The machines were humanized and the humans conversely seemed mechanical.As a member of the audience, I was swept up by the sheer romantic escapsim of it all. The deering-dos, the rope swing escape across the pit, the ray gun battles and especially the swash buckle with the ray swords. Great fun!But I just hope that we weren't too intoxicated by the escapism to be able to focus on the recognizable. I hope the beauty of the effects didn't narcotize our sensitivity to violence. I hope the people see through the fantastically well done futuristic mirrors to the disquieting reflection of our own society. I hope they enjoy STAR WARS without being "purely entertained".

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• Why some links appear in a new tab, others in a new window?

  - by SAMIR BHOGAYTA

  Originally, it was made to resolve problems on IE8 32 bits when you use a 32 bits OS. I changed "%ProgramFiles(x86)%" var, and now my issue is resolved for IE8 32 bits on my Windows 7 64 bits. Please try it, and tell me if everything work for you. For Win 7 64 bits : 1 - Create a new notepad document and paste this text : @echo off echo. echo IEREREG Version 1.07 for IE8 27.03.2009 echo by Kai Schaetzl http://iefaq.info echo installs and registers (if suitable) all DLLs known to be used by IE8. echo should only take a few seconds, but please be patient echo. REM ****************************** echo registering IE files REM IE files (= part of setup) regsvr32 /s /i browseui.dll REM regsvr32 /s /i browseui.dll,NI (unnecessary) regsvr32 /s corpol.dll regsvr32 /s dxtmsft.dll regsvr32 /s dxtrans.dll REM simple HTML Mail API regsvr32 /s "%ProgramFiles(x86)%\internet explorer\hmmapi.dll" REM group policy snap-in regsvr32 /s ieaksie.dll REM smart screen regsvr32 /s ieapfltr.dll REM ieak branding regsvr32 /s iedkcs32.dll REM dev tools regsvr32 /s "%ProgramFiles(x86)%\internet explorer\iedvtool.dll" regsvr32 /s iepeers.dll REM Symptom: IE8 closes immediately on launch, missing from IE7 regsvr32 /s "%ProgramFiles(x86)%\internet explorer\ieproxy.dll" REM no install point anymore REM regsvr32 /s /i iesetup.dll REM no reg point anymore REM regsvr32 /s imgutil.dll regsvr32 /s /i /n inetcpl.cpl REM no install point anymore REM regsvr32 /s /i inseng.dll regsvr32 /s jscript.dll REM license manager regsvr32 /s licmgr10.dll REM regsvr32 /s msapsspc.dll REM regsvr32 /s mshta.exe REM VS debugger regsvr32 /s msdbg2.dll REM no install point anymore REM regsvr32 /s /i mshtml.dll regsvr32 /s mshtmled.dll regsvr32 /s msident.dll REM no reg point anymore REM regsvr32 /s msrating.dll REM multimedia timer regsvr32 /s mstime.dll REM no install point anymore REM regsvr32 /s /i occache.dll REM process debug manager regsvr32 /s "%ProgramFiles(x86)%\internet explorer\pdm.dll" REM no reg point anymore REM regsvr32 /s pngfilt.dll REM regsvr32 /s /i setupwbv.dll (not there anymore!) regsvr32 /s tdc.ocx regsvr32 /s /i urlmon.dll REM regsvr32 /s /i urlmon.dll,NI,HKLM regsvr32 /s vbscript.dll REM VML renderer regsvr32 /s "%CommonProgramFiles%\microsoft shared\vgx\vgx.dll" REM no install point anymore REM regsvr32 /s /i webcheck.dll regsvr32 /s /i /n wininet.dll REM ****************************** echo registering system files REM additional system dlls known to be used by IE REM added 11.05.2006 Symptom: Add-Ons-Manager menu entry is present but nothing happens regsvr32 /s extmgr.dll REM added 12.05.2006 Symptom: Javascript links don't work (Robin Walker) .NET hub file regsvr32 /s mscoree.dll REM added 23.03.2009 Symptom: Find on this page is blank regsvr32 /s oleacc.dll REM added 24.03.2009 Symptom: Printing problems, open in new window regsvr32 /s ole32.dll REM mscorier.dll REM mscories.dll REM Symptom: open in new tab/window not working regsvr32 /s actxprxy.dll regsvr32 /s asctrls.ocx regsvr32 /s cdfview.dll regsvr32 /s comcat.dll regsvr32 /s /i /n comctl32.dll regsvr32 /s cryptdlg.dll regsvr32 /s /i /n digest.dll regsvr32 /s dispex.dll regsvr32 /s hlink.dll regsvr32 /s mlang.dll regsvr32 /s mobsync.dll regsvr32 /s /i msieftp.dll REM regsvr32 /s msnsspc.dll #no entry point regsvr32 /s msr2c.dll regsvr32 /s msxml.dll regsvr32 /s oleaut32.dll REM regsvr32 /s plugin.ocx #no entry point regsvr32 /s proctexe.ocx REM plus DllRegisterServerEx ExA ExW ... ? regsvr32 /s /i scrobj.dll REM shdocvw.dll hasn't been updated for IE7 and IE8, it still registers itself for the Windows Internet Controls regsvr32 /s /i shdocvw.dll regsvr32 /s sendmail.dll REM ****************************** REM PKI/crypto functionality REM initpki can take very long to run and is rarely a problem REM if there are problems with crypto, SSL, certificates REM remove the three following REMs from the lines REM echo We are almost done except one crypto file REM echo but this will take very long, be patient! REM regsvr32 /s /i:A initpki.dll REM ****************************** REM tabbed browser, do at the end, why originally with /n ? regsvr32 /s /i ieframe.dll REM ****************************** echo correcting bugs in the registry REM do some corrective work REM Symptom: new tabs page cannot display content because it cannot access the controls (added 27. 3.2009) REM This is a result of a bug in shdocvw.dll (see above), probably only on Windows XP reg add "HKCR\TypeLib\{EAB22AC0-30C1-11CF-A7EB-0000C05BAE0B}\1.1\0\win32" /ve /t REG_SZ /d %systemroot%\system32\ieframe.dll /f REM ****************************** echo all tasks have been finished echo. pause 2 - Close all your IE windows and processes. 3 - Save your document on your Desktop by example, with the .bat extension. Right-click on it, and select "Run as administrator". 4 - Test if this tip resolved your issue by openning IE. If you use a Windows 32 bits version, please replace %ProgramFiles(x86)% by %ProgramFiles% in your .bat file.

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• SQL Azure: Notes on Building a Shard Technology

  - by Herve Roggero

  In Chapter 10 of the book on SQL Azure (http://www.apress.com/book/view/9781430229612) I am co-authoring, I am digging deeper in what it takes to write a Shard. It's actually a pretty cool exercise, and I wanted to share some thoughts on how I am designing the technology. A Shard is a technology that spreads the load of database requests over multiple databases, as transparently as possible. The type of shard I am building is called a Vertical Partition Shard  (VPS). A VPS is a mechanism by which the data is stored in one or more databases behind the scenes, but your code has no idea at design time which data is in which database. It's like having a mini cloud for records instead of services. Imagine you have three SQL Azure databases that have the same schema (DB1, DB2 and DB3), you would like to issue a SELECT * FROM Users on all three databases, concatenate the results into a single resultset, and order by last name. Imagine you want to ensure your code doesn't need to change if you add a new database to the shard (DB4). Now imagine that you want to make sure all three databases are queried at the same time, in a multi-threaded manner so your code doesn't have to wait for three database calls sequentially. Then, imagine you would like to obtain a breadcrumb (in the form of a new, virtual column) that gives you a hint as to which database a record came from, so that you could update it if needed. Now imagine all that is done through the standard SqlClient library... and you have the Shard I am currently building. Here are some lessons learned and techniques I am using with this shard: Parellel Processing: Querying databases in parallel is not too hard using the Task Parallel Library; all you need is to lock your resources when needed Deleting/Updating Data: That's not too bad either as long as you have a breadcrumb. However it becomes more difficult if you need to update a single record and you don't know in which database it is. Inserting Data: I am using a round-robin approach in which each new insert request is directed to the next database in the shard. Not sure how to deal with Bulk Loads just yet... Shard Databases:  I use a static collection of SqlConnection objects which needs to be loaded once; from there on all the Shard commands use this collection Extension Methods: In order to make it look like the Shard commands are part of the SqlClient class I use extension methods. For example I added ExecuteShardQuery and ExecuteShardNonQuery methods to SqlClient. Exceptions: Capturing exceptions in a multi-threaded code is interesting... but I kept it simple for now. I am using the ConcurrentQueue to store my exceptions. Database GUID: Every database in the shard is given a GUID, which is calculated based on the connection string's values. DataTable. The Shard methods return a DataTable object which can be bound to objects.  I will be sharing the code soon as an open-source project in CodePlex. Please stay tuned on twitter to know when it will be available (@hroggero). Or check www.bluesyntax.net for updates on the shard. Thanks!

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• How the number of indexes built on a table can impact performances?

  - by Davide Mauri

  We all know that putting too many indexes (I’m talking of non-clustered index only, of course) on table may produce performance problems due to the overhead that each index bring to all insert/update/delete operations on that table. But how much? I mean, we all agree – I think – that, generally speaking, having many indexes on a table is “bad”. But how bad it can be? How much the performance will degrade? And on a concurrent system how much this situation can also hurts SELECT performances? If SQL Server take more time to update a row on a table due to the amount of indexes it also has to update, this also means that locks will be held for more time, slowing down the perceived performance of all queries involved. I was quite curious to measure this, also because when teaching it’s by far more impressive and effective to show to attended a chart with the measured impact, so that they can really “feel” what it means! To do the tests, I’ve create a script that creates a table (that has a clustered index on the primary key which is an identity column) , loads 1000 rows into the table (inserting 1000 row using only one insert, instead of issuing 1000 insert of one row, in order to minimize the overhead needed to handle the transaction, that would have otherwise ), and measures the time taken to do it. The process is then repeated 16 times, each time adding a new index on the table, using columns from table in a round-robin fashion. Test are done against different row sizes, so that it’s possible to check if performance changes depending on row size. The result are interesting, although expected. This is the chart showing how much time it takes to insert 1000 on a table that has from 0 to 16 non-clustered indexes. Each test has been run 20 times in order to have an average value. The value has been cleaned from outliers value due to unpredictable performance fluctuations due to machine activity. The test shows that in a  table with a row size of 80 bytes, 1000 rows can be inserted in 9,05 msec if no indexes are present on the table, and the value grows up to 88 (!!!) msec when you have 16 indexes on it This means a impact on performance of 975%. That’s *huge*! Now, what happens if we have a bigger row size? Say that we have a table with a row size of 1520 byte. Here’s the data, from 0 to 16 indexes on that table: In this case we need near 22 msec to insert 1000 in a table with no indexes, but we need more that 500msec if the table has 16 active indexes! Now we’re talking of a 2410% impact on performance! Now we can have a tangible idea of what’s the impact of having (too?) many indexes on a table and also how the size of a row also impact performances. That’s why the golden rule of OLTP databases “few indexes, but good” is so true! (And in fact last week I saw a database with tables with 1700bytes row size and 23 (!!!) indexes on them!) This also means that a too heavy denormalization is really not a good idea (we’re always talking about OLTP systems, keep it in mind), since the performance get worse with the increase of the row size. So, be careful out there, and keep in mind the “equilibrium” is the key world of a database professional: equilibrium between read and write performance, between normalization and denormalization, between to few and too may indexes. PS Tests are done on a VMWare Workstation 7 VM with 2 CPU and 4 GB of Memory. Host machine is a Dell Precsioni M6500 with i7 Extreme X920 Quad-Core HT 2.0Ghz and 16Gb of RAM. Database is stored on a SSD Intel X-25E Drive, Simple Recovery Model, running on SQL Server 2008 R2. If you also want to to tests on your own, you can download the test script here: Open TestIndexPerformance.sql

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• Is Your Company Social on the Inside?

  - by Mike Stiles

  As we talk about the extension of social from an outbound-facing marketing tool to a platform that will reach across the entire enterprise, servicing multiple functions of that enterprise, it might be time to take a look at how social can be effectively employed for internal communications. Remember the printed company newsletter? Yeah, nobody reads it. Remember the emailed company newsletter? Yeah, nobody reads it. Why not? Shouldn’t your employees care about the company more than anything else in life and be voraciously hungry for any information related to it? The more realistic prospect is that a company’s employees don’t behave much differently at work where information is concerned than they do in their personal lives. They “tune in” to information that’s immediately relevant to them, that peaks their interest, and/or that’s presented in a visually engaging way. That currently makes an internal social platform the most ideal way to communicate within the organization. It not only facilitates more immediate, more targeted (and thus more relevant) messaging from the company out to employees, it sets a stage for employees to communicate with each other and efficiently get answers to questions from peers. It’s a collaboration tool on steroids. If you build such an internal social portal and you do it right, will employees use it? Considering social media has officially been declared more addictive than cigarettes, booze and sex…probably. But what does it mean to do an internal social platform “right”? The bar has been set pretty high. Your employees are used to Twitter and Facebook, and would roll their eyes at anything less simple or harder to navigate than those. All the Facebook best practices would apply to your internal social as well, including the importance of managing posting frequency, using photos and video, moderation & response, etc. And don’t worry, you won’t be the first to jump in. WPP's global digital agency Possible has its own social network called Colab. Nestle has “The Nest.” Red Robin’s got one. I myself got an in-depth look at McGraw-Hill’s internal social platform at Blogwell NYC. Some of these companies are building their own platforms, others are buying them off the shelf or customizing readymade solutions. But you won’t be the last either. Prescient Digital Media and the IABC learned 39% of companies don’t offer employees any social tools. Not a social network, not discussion forums, not even IM. And a great many continue to ban the use of Facebook and Twitter on the premises. That’s pretty astonishing since social has become as essential a modern day communications tool as the telephone. But such holdouts will pay a big price for being mired in fear while competitors exploit social connections unchallenged. Fish where the fish are. If social has become the way people communicate and take in information, let that be the way communication is trafficked in the organization.

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• How to get the millisecond value from a Timestamp field in firebird with Delphi 2007

  - by Re0sless

  I have a Firebird database (running on server version 2.1.3) and am connecting to it with Delphi 2007 using the DBExpress objects (using the Interbase driver) One of my tables in the database looks something like this CREATE TABLE MYTABLE ( MYDATE Timestamp NOT NULL, MYINDEX Integer NOT NULL, ... Snip ... PRIMARY KEY (MYDATE ,MYINDEX) ); I can add to the table OK, and in Flame Robin it shows the timestamp field as having a millisecond value. But when I do a select all (select * from MYTABLE) on the table I can not get the millisecond value, as it is always returned as 000. This causes major problems as it is part of the primary key (unfortunately I didn't design the table and don't have authority to change it). I have tried the following to get the millisecond value: sql1.fieldbyname('MYDATE').AsDateTime; sql1.fieldbyname('MYDATE').AsSQLTimeStamp; sql1.fieldbyname('MYDATE').AsStirng; sql1.fieldbyname('MYDATE').AsFloat; But they all return 14/09/2009 14:25:06.000 when formatted. How do I retrieve the millisecond from a timestamp? UPDATE: In case this helps anyone in the future, here are the drivers I tried for DBExpress and the results. Embarcadero - dbExpress Driver for Firebird (Delphi 2010 Trial Version) - Milliseconds not supported in timestamps. Chau Chee Yang's - dbExpress Driver for Firebird (Delphi 2007) - Milliseconds not supported in timestamps. UpScene - InterXpress for Firebird (Delphi 2007) - Milliseconds are supported in timestamps. DevArt - dbExpress Driver for InterBase (Delphi 2007) - Milliseconds are supported in timestamps.

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• NonStop ODBC: how the connections (ODBC servers) are assigned to CPUs?

  - by Vladimir Dyuzhev

  We have an ODBC pool running on a NonStop server. The pool is connected to SQL/MX. This pool is used by a few external Java applications, each of which has an JDBC pool connected to ODBC pool (e.g. 14 connections per application). With time (after a few application recycles) we see an imbalance between CPUs -- some have 8 ODBC processes running, some only 5. That leads to CPU time imbalance too. Up to this point we assumed that a CPU is assigned to ODBC process in round-robin fashion. That would maintain the number of ODBC processes more or less equally distributed. It's not the case though. Is there any information on how ODBC pool decided which CPU to choose for every new allocated process? Does it look at CPU load? Available memory? Something else? Sadly, even HP's own people (available to us, that is) couldn't answer those questions with certainty. :-(

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• Looping through recordset with VBA

  - by Robert

  I am trying to assign salespeople (rsSalespeople) to customers (rsCustomers) in a round-robin fashion in the following manner: Navigate to first Customer, assign the first SalesPerson to the Customer. Move to Next Customer. If rsSalesPersons is not at EOF, move to Next SalesPerson; if rsSalesPersons is at EOF, MoveFirst to loop back to the first SalesPerson. Assign this (current) SalesPerson to the (current) Customer. Repeat step 2 until rsCustomers is at EOF (EOF = True, i.e. End-Of-Recordset). It's been awhile since I dealt with VBA, so I'm a bit rusty, but here is what I have come up with, so far: Private Sub Command31_Click() 'On Error GoTo ErrHandler Dim intCustomer As Integer Dim intSalesperson As Integer Dim rsCustomers As DAO.Recordset Dim rsSalespeople As DAO.Recordset Dim strSQL As String strSQL = "SELECT CustomerID, SalespersonID FROM Customers WHERE SalespersonID Is Null" Set rsCustomers = CurrentDb.OpenRecordset(strSQL) strSQL = "SELECT SalespersonID FROM Salespeople" Set rsSalespeople = CurrentDb.OpenRecordset(strSQL) rsCustomers.MoveFirst rsSalespeople.MoveFirst Do While Not rsCustomers.EOF intCustomers = rsCustomers!CustomerID intSalesperson = rsSalespeople!SalespersonID strSQL = "UPDATE Customers SET SalespersonID = " & intSalesperson & " WHERE CustomerID = " & intCustomer DoCmd.RunSQL (strSQL) rsCustomers.MoveNext If Not rsSalespeople.EOF Then rsSalespeople.MoveNext Else rsSalespeople.MoveFirst End If Loop ExitHandler: Set rsCustomers = Nothing Set rsSalespeople = Nothing Exit Sub ErrHandler: MsgBox (Err.Description) Resume ExitHandler End Sub My tables are defined like so: Customers --CustomerID --Name --SalespersonID Salespeople --SalespersonID --Name With ten customers and 5 salespeople, my intended result would like like: CustomerID--Name--SalespersonID 1---A---1 2---B---2 3---C---3 4---D---4 5---E---5 6---F---1 7---G---2 8---H---3 9---I---4 10---J---5 The above code works for the intitial loop through the Salespeople recordset, but errors out when the end of the recordset is found. Regardless of the EOF, it appears it still tries to execute the rsSalespeople.MoveFirst command. Am I not checking for the rsSalespeople.EOF properly? Any ideas to get this code to work?

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• Need help with WCF design

  - by Jason

  I have been tasked with creating a set of web services. We are a Microsoft shop, so I will be using WCF for this project. There is an interesting design consideration that I haven't been able to figure out a solution for yet. I'll try to explain it with an example: My WCF service exposes a method named Foo(). 10 different users call Foo() at roughly the same time. I have 5 special resources called R1, R2, R3, R4, and R5. We don't really need to know what the resource is, other than the fact that a particular resource can only be in use by one caller at a time. Foo() is responsible to performing an action using one of these special resources. So, in a round-robin fashion, Foo() needs to find a resource that is not in use. If no resources are available, it must wait for one to be freed up. At first, this seems like an easy task. I could maybe create a singleton that keeps track of which resources are currently in use. The big problem is the fact that I need this solution to be viable in a web farm scenario. I'm sure there is a good solution to this problem, but I've just never run across this scenario before. I need some sort of resource tracker / provider that can be shared between multiple WCF hosts. Any ideas from the architects out there would be greatly appreciated!

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• Why does Safari/Opera not work with this javascript code?

  - by robinjfisher

  Hi, I am working on a calendar that will show bookings. The height of containing the booking is calculated dynamically in proportion to the length of the booking. The following code works perfectly well in Firefox but not in Safari or Opera: function calculateBookingHeight(from, to) { var today = new Date; var end = new Date.UTC(today.getUTCFullYear(),today.getUTCMonth(),today.getUTCDate(),23); var start = new Date.UTC(today.getUTCFullYear(),today.getUTCMonth(),today.getUTCDate(),6); var from = new Date(from); var to = new Date(to); if (from > start && to < end) { var difference = (to - from) / 120000; } else if (from > start && to > end) { var difference = (end - from) / 120000; } else { var difference = 510 } return difference; } In summary, each hour on the calendar is a height of 30px. The second if statement deals with the end of the booking being the following day. If I replace the entire code block with return 510, Safari behaves as expected and sets the height of each booking to 510px so I assume it must be something in this function that is causing the problem. Any help would be appreciated. Thanks Robin

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• How to hold a queue of messages and have a group of working threads without polling?

  - by Mark

  I have a workflow that I want to looks something like this: / Worker 1 \ =Request Channel= - [Holding Queue|||] - Worker 2 - =Response Channel= \ Worker 3 / That is: Requests come in and they enter a FIFO queue Identical workers then pick up tasks from the queue At any given time any worker may work only one task When a worker is free and the holding queue is non-empty the worker should immediately pick up another task When tasks are complete, a worker places the result on the Response Channel I know there are QueueChannels in Spring Integration, but these channels require polling (which seems suboptimal). In particular, if a worker can be busy, I'd like the worker to be busy. Also, I've considered avoiding the queue altogether and simply letting tasks round-robin to all workers, but it's preferable to have a single waiting line as some tasks may be accomplished faster than others. Furthermore, I'd like insight into how many jobs are remaining (which I can get from the queue) and the ability to cancel all or particular jobs. How can I implement this message queuing/work distribution pattern while avoiding a polling? Edit: It appears I'm looking for the Message Dispatcher pattern -- how can I implement this using Spring/Spring Integration?

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• Importing external .jar file to Android project

  - by robintw

  I've read various answers to similar questions on StackOverflow, so I apologise if I'm repeating another question, but I can't seem to get this to work. I have a standard java project in which I've written code to parse some BBC Radio XML data from the internet. The project is called BBCSchedules and the class I'm interested in is called BBCChannel. I'm now trying to use the BBCChannel class in an android application. How should I go about doing this? I've tried various things, following various bits of advice on the internet, and the place I've got to at the moment is compiling my BBCSchedules project to a .jar file, and importing that to the Android project using the Build Path/Library/Add External Jar option. However, Eclispe still doesn't recognise the BBCChannel class, and won't let me run the application because of this. I guess I've done something silly wrong, but what is it? Cheers, Robin UPDATE: I've tried the steps listed in http://stackoverflow.com/questions/1334802/how-can-i-use-external-jars-in-an-android-project and various other StackOverflow questions I can find that seem to be related to this, but absolutely nothing seems to work. Any other ideas? UPDATE: The discussions I've had with the author of the first answer below suggest that it is something to do with how I am using Eclipse to attach the .jar file. The project he sent me with the .jar file already attached didn't work. Any other ideas anyone?

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• Varnish configuration to only cache for non-logged in users

  - by davidsmalley

  I have a Ruby on Rails application fronted by varnish+nginx. As most of the sites content is static unless you are a logged in user, I want to cache the site heavily with varnish when a user is logged out but only to cache static assets when they are logged in. When a user is logged in they will have the cookie 'user_credentials' present in their Cookie: header, in addition I need to skip caching on /login and /sessions in order that a user can get their 'user_credentials' cookie in the first place. Rails by default does not set a cache friendly Cache-control header, but my application sets a "public,s-max-age=60" header when a user is not logged in. Nginx is set to return 'far future' expires headers for all static assets. The configuration I have at the moment is totally bypassing the cache for everything when logged in, including static assets — and is returning cache MISS for everything when logged out. I've spent hours going around in circles and here is my current default.vcl director rails_director round-robin { { .backend = { .host = "xxx.xxx.xxx.xxx"; .port = "http"; .probe = { .url = "/lbcheck/lbuptest"; .timeout = 0.3 s; .window = 8; .threshold = 3; } } } } sub vcl_recv { if (req.url ~ "^/login") { pipe; } if (req.url ~ "^/sessions") { pipe; } # The regex used here matches the standard rails cache buster urls # e.g. /images/an-image.png?1234567 if (req.url ~ "\.(css|js|jpg|jpeg|gif|ico|png)\??\d*$") { unset req.http.cookie; lookup; } else { if (req.http.cookie ~ "user_credentials") { pipe; } } # Only cache GET and HEAD requests if (req.request != "GET" && req.request != "HEAD") { pipe; } } sub vcl_fetch { if (req.url ~ "^/login") { pass; } if (req.url ~ "^/sessions") { pass; } if (req.http.cookie ~ "user_credentials") { pass; } else { unset req.http.Set-Cookie; } # cache CSS and JS files if (req.url ~ "\.(css|js|jpg|jpeg|gif|ico|png)\??\d*$") { unset req.http.Set-Cookie; } if (obj.status >=400 && obj.status <500) { error 404 "File not found"; } if (obj.status >=500 && obj.status <600) { error 503 "File is Temporarily Unavailable"; } } sub vcl_deliver { if (obj.hits > 0) { set resp.http.X-Cache = "HIT"; } else { set resp.http.X-Cache = "MISS"; } }

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