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• Why do I have to set the max length of every damn text column in the database?

  - by John Leidegren

  Why is it that every RDBMS insists that you tell it what the max length of a text field is going to be... why can't it just infer this information form the data that's put into the database? I've mostly worked with MS SQL Server, but every other database I know also demands that you set these arbitrary limits on your data schema. The reality is that this is not particulay helpful or friendly to work with becuase the business requirements change all the time and almost every day some end-user is trying to put a lot of text into that column. Does any one with some inner working knowledge of a RDBMS know why we just don't infer the limits from the data that's put into the storage? I'm not talking about guessing the type information, but guessing the limits of a particular text column. I mean, there's a reason why I don't use nvarchar(max) on every text column in the database.

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• password limitations in SQL Server and MySql

  - by asteroid

  Does MySql 5.1 and SQL Server 2008 (Web edition, Standard) have any functional password limitations other than length limits? Are metacharacters in any form a bad idea to use, like bang, pipe, hash, any slash, carrot, and so on? I know that MySql 5.1 has a password length limitation of 16 characters that is hardcoded, but I was wondering, are any metacharacters (i.e. non alphanumerics) a bad idea to use? And is this true in SQL Server 2008 Web edition, Standard? So specifically: can symbols like: /`~:}{[]^ be used successfully? I would hope it doesn't matter to the database, but I don't understand enough about password storage in enterprise database systems yet to know for sure, and I was looking for confirmation or an explanation.

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• Background audio not working in windows 8 store / metro app

  - by roryok

  I've tried setting background audio through both a mediaElement in XAML <MediaElement x:Name="MyAudio" Source="Assets/Sound.mp3" AudioCategory="BackgroundCapableMedia" AutoPlay="False" /> And programmatically async void setUpAudio() { var package = Windows.ApplicationModel.Package.Current; var installedLocation = package.InstalledLocation; var storageFile = await installedLocation.GetFileAsync("Assets\\Sound.mp3"); if (storageFile != null) { var stream = await storageFile.OpenAsync(Windows.Storage.FileAccessMode.Read); _soundEffect = new MediaElement(); _soundEffect.AudioCategory = AudioCategory.BackgroundCapableMedia; _soundEffect.AutoPlay = false; _soundEffect.SetSource(stream, storageFile.ContentType); } } // and later... _soundEffect.Play(); But neither works for me. As soon as I minimise the app the music fades out

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• Mobile web apps - Is this the right approach?

  - by Pasta

  I need to build a cross platform mobile app (iphone, android, etc). The app is for a company like a cellular operator (Tmobile, ATT). The app needs to do the following: Show previous bills (cached so that it does not have to download everytime) Need an internet connection to download newer bills, view recent data, etc. Can I build a mobile web app to handle this? I understand that there is offline storage and iPhone has good support for web apps (full screen, good icons, offline, etc). Will a web app be the best approach to take as the app requires to be online? The app will not be used by lots of people, just customers of the website who don't want to use an existing website. We are all web developers and a mobile web app looks like the best way to approach this.

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• How can I use Amazon's API in PHP to search for books?

  - by TerranRich

  I'm working on a Facebook app for book sharing, reviewing, and recommendations. I've scoured the web, searched Google using every search phrase I could think of, but I could not find any tutorials on how to access the Amazon.com API for book information. I signed up for an AWS account, but even the tutorials on their website didn't help me one bit. They're all geared toward using cloud computing for file storage and processing, but that's not what I want. I just want to access their API to search info on books. Kind of like how http://openlibrary.org/ does it, where it's a simple URL call to get information on a book (but their databases aren't nearly as populated as Amazon's). Why is it so hard to find the information I need on Amazon's AWS site? If anybody could help, I would greatly appreciate it.

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• The data structure of libev watchers

  - by changchang

  Libev uses three data structures to storage different watchers. Heap: for watchers that sorted by time, such as ev_timer and ev_periodic. Linked list: such as ev_io, ev_signal, ev_child and etc. Array: such as ev_prepare, ev_check, ev_async and etc. There is no doubt about that uses heap to store timer watcher. But what is the criteria of selecting linked list and array? The data structure that stores ev_io watchers seems a little complex. It first is an array that with fd as its index and the element in the array is a linked list of ev_io watcher. It is more convenient to allocate space for array if use linked list as element. Is it the reason? Or just because of the insert or remove operation of ev_io is more frequently and the ev_prepare seems more stable? Or any other reasons?

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• How often does memcache on Google AppEngine lose data?

  - by Freed

  Memcache in general and on AppEngine in specific is unreliable in the sense that my data may be deleted from the cache for whatever reason at any point in time. However, in some cases there might be cases where a small risk may be worth the added performance using memcache could give, such as updating some data in memcache that gets saved periodically to some other, more reliable storage. Are there any numbers from Google that could give me an indication of the actual probability that a memcache entry would be lost from the cache before its expiration time, given that I keep within my quotas? Are there any reasons other than hardware failure and administrative operations such as machines at the data centers being upgraded/moved/replaced that would cause entries to be removed from memcache prematurely?

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• Uploading Files to AWS S3 from an Android App

  - by Abhishek Kaushik

  Edited 7th June,14 My Android app needs to have a feature where clients can upload their files. I want AWS S3 as my storage. Moreover i dont want to use SECRET_KEY and ACCESS_KEY_ID on client side. What is the the best way to do this. Can someone provide the working code too ? I read that i can request to AWS for a signed URL and then make client directly upload to that URL. How to achieve this ?

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• C++: String and unions

  - by sub

  I'm having a (design) problem: I'm building an interpreter and I need some storage for variables. There are basically two types of content a variable here can have: string or int. I'm using a simple class for the variables, all variables are then stored in a vector. However, as a variable can hold a number or a string, I don't want C++ to allocate both and consume memory for no reason. That's why I wanted to use unions: union { string StringValue; int IntValue; } However, strings don't work with unions. Is there any workaround so no memory gets eaten for no reason?

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• What Android version to target?

  - by Richard Eng

  I'm about to write my first Android app. It's a fairly basic app that doesn't use any special features beyond being able to schedule notifications and read/write image files to the device's local storage. Reaching the broadest audience is my top priority. If I target Android 1.5, is the app guaranteed to run fine all the way up to ICS? Should I target Android 2.1, which seems to be the new baseline for common phones in use? Since the app is fairly basic, if I target ICS, would it run on versions going all the way back to 2.1? Maybe this is a stupid question.

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• What is the answer to this homework about maps and collections? [closed]

  - by Bishan

  Maps collection is referred to an dictionary because of the way it works. Each entry into a maps collection involves a pair of objects. In a maps collection, an object associates the key which determines where the object is stored in the map. The key object in the maps collection can be duplicated. A stack which has Last In First Out storage mechanism can be considered as a maps collection. I think #1,#2,#3 and #5 are Correct in above, but I have doubt with #5. Am I correct?

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• C++ vector that *doesn't* initialize its members?

  - by Mehrdad

  I'm making a C++ wrapper for a piece of C code that returns a large array, and so I've tried to return the data in a vector<unsigned char>. Now the problem is, the data is on the order of megabytes, and vector unnecessarily initializes its storage, which essentially turns out to cut down my speed by half. How do I prevent this? Or, if it's not possible -- is there some other STL container that would avoid such needless work? Or must I end up making my own container? (Pre-C++11) Note: I'm passing the vector as my output buffer. I'm not copying the data from elsewhere.

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• Numeric literals in sql server 2008

  - by costa

  What is the type that sql server assigns to the numeric literal: 2. , i.e. 2 followed by a dot? I was curious because: select convert(varchar(50), 2.) union all select convert(varchar(50), 2.0) returns: 2 2.0 which made me ask what's the difference between 2. and 2.0 type wise? Sql server seems to assign types to numeric literals depending on the number itself by finding the minimal storage type that can hold the number. A value of 1222333 is stored as int while 1152921504606846975 is stored as big int. thanks

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• Why does do this code do if(sz !=sz2) sz = sz2 !?!

  - by acidzombie24

  For the first time i created a linq to sql classes. I decided to look at the class and found this. What... why is it doing if(sz !=sz2) { sz = sz2; }. I dont understand. Why isnt the set generated as this._Property1 = value? private string _Property1; [Column(Storage="_Property1", CanBeNull=false)] public string Property1 { get { return this._Property1; } set { if ((this._Property1 != value)) { this._Property1 = value; } } }

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• A step-up from TiddlyWiki that is still 100% portable?

  - by Smandoli

  TiddlyWiki is a great idea, brilliantly implemented. I'm using it as a portable personal "knowledge manager," and these are the prize virtues: It travels on my USB flash memory stick and runs on any computer, regardless of operating system No software installation is needed on the computer (TiddlyWiki merely uses the Internet browser) No Internet connection is needed In terms of data retrieval functionality, it mimics a relational database (use of tags and internal links) Let's say I've got a million words of prose in 4,000 tiddlers (posts). I'm still testing, but it looks like TiddlyWiki gets very slow. Is there an app like TiddlyWiki that keeps all the virtues I listed above, and allows more storage? NOTE: Separation of content and presentation would be ideal. It's nifty that TiddlyWiki has everything in a single HTML document, but it's unhelpful in many ways. I don't care if a directory of assorted docs is needed (SQLite, XML?), as long as it's functionally self-contained.

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• 2-Bay External HDD Enclosure in JBOD mode fails to detect both drives (Linux & Windows)

  - by mgc8888

  I recently purchased a couple of USB 3.0 External HDD Enclosures to use for storage and backup; the idea was to have one act as backup to the other, with 4 x 3TB drives in total. However, the second drive in each is not accessible in either Linux nor Windows, and I could not determine the reason. 1. Situation The two enclosures are slightly different (couldn't find them in stock at the same time) yet from many little details appear to be the same Chinese base design with a tweaked outer shell. The models are: Sharkoon 2-Bay RAID Box Fantec MR-35DU3 The drives are Seagate 3TB Barracuda ST33000651AS, firmware CC44, all identical. From reading manuals and online sources, I determined that JBOD would be the optimal setup for my needs -- addressing the two drives separately in each enclosure would be important, making it easy to swap drives and mix&match them if needed; all the other modes implied the controller doing a combination of the drives. The software used was Debian GNU/Linux - testing/wheezy - kernel 2.6.39-2 and Windows 7 Ultimate. 2. Description of the problem Now, here comes the problem: every time I connect either of the enclosures to a PC using the supplied cable (tried a different one as well), only the HDD in the top bay is readable, the one below is detected yet errors out in various ways. According to the manuals, it should not happen: in JBOD, the system should be able to "see" two separate drives upon connection. This happens with both enclosures and any combination of HDDs (i.e. if I swap them, the same thing happens), so the HDDs are good and I think so are the enclosures (two different companies making similar products that failed in an identical fashion would be very unlikely). The top HDD can be used fine every time, I actually tried a speed test from Linux and got about 150MiB/s reads, so all is working as it should; the one below refuses to work every time. So the failure is consistent. To make sure this was not some obscure Linux bug, I tried the same under Windows 7, and the system also only created one drive letter for a drive of 3TB size (so it was only seeing one instead of both). Placing an older, known good, 2TB drive in the top bay made that the one recognised, so we have the same issue under Windows as well. Log entries under Linux (tested here with a 3TB and a 2TB drive so I could differentiate them; either one works in the top enclosure, in the test setup the 3TB one is on top). You can see them being detected, the top one is ok, but for the bottom one only errors: Jul 19 23:28:15 media kernel: [260150.582436] usb 6-1: New USB device found, idVendor=1ca1, idProduct=18ae Jul 19 23:28:15 media kernel: [260150.582440] usb 6-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3 Jul 19 23:28:15 media kernel: [260150.582442] usb 6-1: Product: Usb Sata Bridge Jul 19 23:28:15 media kernel: [260150.582444] usb 6-1: Manufacturer: SYMWAVE Jul 19 23:28:15 media kernel: [260150.582446] usb 6-1: SerialNumber: 39584B304C4E3441 Jul 19 23:28:15 media kernel: [260150.870412] scsi11 : usb-storage 6-1:1.0 Jul 19 23:28:16 media kernel: [260151.882087] scsi 11:0:0:0: Direct-Access SYMWAVE ST33000651AS CC44 PQ: 0 ANSI: 4 Jul 19 23:28:16 media kernel: [260151.882242] scsi 11:0:0:1: Direct-Access SYMWAVE ST32000641AS CC12 PQ: 0 ANSI: 4 Jul 19 23:28:16 media kernel: [260151.882677] sd 11:0:0:0: Attached scsi generic sg2 type 0 Jul 19 23:28:16 media kernel: [260151.882774] sd 11:0:0:0: [sdb] Very big device. Trying to use READ CAPACITY(16). Jul 19 23:28:16 media kernel: [260151.882857] sd 11:0:0:1: Attached scsi generic sg3 type 0 Jul 19 23:28:16 media kernel: [260151.882893] sd 11:0:0:0: [sdb] 5860533168 512-byte logical blocks: (3.00 TB/2.72 TiB) Jul 19 23:28:16 media kernel: [260151.883085] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.883582] sd 11:0:0:0: [sdb] Write Protect is off Jul 19 23:28:16 media kernel: [260151.883961] sd 11:0:0:1: [sdc] 3907029168 512-byte logical blocks: (2.00 TB/1.81 TiB) Jul 19 23:28:16 media kernel: [260151.884145] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.884570] sd 11:0:0:1: [sdc] Write Protect is off Jul 19 23:28:16 media kernel: [260151.884855] sd 11:0:0:0: [sdb] Very big device. Trying to use READ CAPACITY(16). Jul 19 23:28:16 media kernel: [260151.885286] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.885807] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.909595] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.910159] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.910163] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.910167] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.910169] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.910172] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 Jul 19 23:28:16 media kernel: [260151.910182] quiet_error: 2 callbacks suppressed Jul 19 23:28:16 media kernel: [260151.910570] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.911153] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.911156] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.911159] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.911161] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.911164] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 Jul 19 23:28:16 media kernel: [260151.911385] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.911902] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.911905] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.911908] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.911910] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.911913] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 Jul 19 23:28:16 media kernel: [260151.912128] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.912650] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.912653] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.912656] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.912657] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.912660] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 Jul 19 23:28:16 media kernel: [260151.912876] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.913439] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.913442] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.913445] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.913446] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.913449] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 Jul 19 23:28:16 media kernel: [260151.945227] xhci_hcd 0000:03:00.0: WARN: Stalled endpoint Jul 19 23:28:16 media kernel: [260151.945863] sd 11:0:0:1: [sdc] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE Jul 19 23:28:16 media kernel: [260151.945866] sd 11:0:0:1: [sdc] Sense Key : Illegal Request [current] Jul 19 23:28:16 media kernel: [260151.945870] Info fld=0x0 Jul 19 23:28:16 media kernel: [260151.945871] sd 11:0:0:1: [sdc] Add. Sense: Invalid field in cdb Jul 19 23:28:16 media kernel: [260151.945875] sd 11:0:0:1: [sdc] CDB: Read(10): 28 20 00 00 00 00 00 00 08 00 (...) and so on for like 10 seconds until it gives up (...) 3. Question So, my question would be: what is causing this? Am I missing something, should I configure things differently, is this a known limitation? Searching online for more information did not yield any useful results... Thank you in advance for any help!

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• Cisco ASA: Allowing and Denying VPN Access based on membership to an AD group

  - by milkandtang

  I have a Cisco ASA 5505 connecting to an Active Directory server for VPN authentication. Usually we'd restrict this to a particular OU, but in this case users which need access are spread across multiple OUs. So, I'd like to use a group to specify which users have remote access. I've created the group and added the users, but I'm having trouble figuring out how to deny users which aren't in that group. Right now, if someone connects they get assigned the correct group policy "companynamera" if they are in that group, so the LDAP mapping is working. However, users who are not in that group still authenticate fine, and their group policy becomes the LDAP path of their first group, i.e. CN=Domain Users,CN=Users,DC=example,DC=com, and then are still allowed access. How do I add a filter so that I can map everything that isn't "companynamera" to no access? Config I'm using (with some stuff such as ACLs and mappings removed, since they are just noise here): gateway# show run : Saved : ASA Version 8.2(1) ! hostname gateway domain-name corp.company-name.com enable password gDZcqZ.aUC9ML0jK encrypted passwd gDZcqZ.aUC9ML0jK encrypted names name 192.168.0.2 dc5 description FTP Server name 192.168.0.5 dc2 description Everything server name 192.168.0.6 dc4 description File Server name 192.168.0.7 ts1 description Light Use Terminal Server name 192.168.0.8 ts2 description Heavy Use Terminal Server name 4.4.4.82 primary-frontier name 5.5.5.26 primary-eschelon name 172.21.18.5 dmz1 description Kerio Mail Server and FTP Server name 4.4.4.84 ts-frontier name 4.4.4.85 vpn-frontier name 5.5.5.28 ts-eschelon name 5.5.5.29 vpn-eschelon name 5.5.5.27 email-eschelon name 4.4.4.83 guest-frontier name 4.4.4.86 email-frontier dns-guard ! interface Vlan1 nameif inside security-level 100 ip address 192.168.0.254 255.255.255.0 ! interface Vlan2 description Frontier FiOS nameif outside security-level 0 ip address primary-frontier 255.255.255.0 ! interface Vlan3 description Eschelon T1 nameif backup security-level 0 ip address primary-eschelon 255.255.255.248 ! interface Vlan4 nameif dmz security-level 50 ip address 172.21.18.254 255.255.255.0 ! interface Vlan5 nameif guest security-level 25 ip address 172.21.19.254 255.255.255.0 ! interface Ethernet0/0 switchport access vlan 2 ! interface Ethernet0/1 switchport access vlan 3 ! interface Ethernet0/2 switchport access vlan 4 ! interface Ethernet0/3 switchport access vlan 5 ! interface Ethernet0/4 ! interface Ethernet0/5 ! interface Ethernet0/6 ! interface Ethernet0/7 ! ftp mode passive clock timezone PST -8 clock summer-time PDT recurring dns domain-lookup inside dns server-group DefaultDNS name-server dc2 domain-name corp.company-name.com same-security-traffic permit intra-interface access-list companyname_splitTunnelAcl standard permit 192.168.0.0 255.255.255.0 access-list companyname_splitTunnelAcl standard permit 172.21.18.0 255.255.255.0 access-list inside_nat0_outbound extended permit ip any 172.21.20.0 255.255.255.0 access-list inside_nat0_outbound extended permit ip any 172.21.18.0 255.255.255.0 access-list bypassingnat_dmz extended permit ip 172.21.18.0 255.255.255.0 192.168.0.0 255.255.255.0 pager lines 24 logging enable logging buffer-size 12288 logging buffered warnings logging asdm notifications mtu inside 1500 mtu outside 1500 mtu backup 1500 mtu dmz 1500 mtu guest 1500 ip local pool VPNpool 172.21.20.50-172.21.20.59 mask 255.255.255.0 no failover icmp unreachable rate-limit 1 burst-size 1 no asdm history enable arp timeout 14400 global (outside) 1 interface global (outside) 2 email-frontier global (outside) 3 guest-frontier global (backup) 1 interface global (dmz) 1 interface nat (inside) 0 access-list inside_nat0_outbound nat (inside) 2 dc5 255.255.255.255 nat (inside) 1 192.168.0.0 255.255.255.0 nat (dmz) 0 access-list bypassingnat_dmz nat (dmz) 2 dmz1 255.255.255.255 nat (dmz) 1 172.21.18.0 255.255.255.0 access-group outside_access_in in interface outside access-group dmz_access_in in interface dmz route outside 0.0.0.0 0.0.0.0 4.4.4.1 1 track 1 route backup 0.0.0.0 0.0.0.0 5.5.5.25 254 timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00 ldap attribute-map RemoteAccessMap map-name memberOf IETF-Radius-Class map-value memberOf CN=RemoteAccess,CN=Users,DC=corp,DC=company-name,DC=com companynamera dynamic-access-policy-record DfltAccessPolicy aaa-server ActiveDirectory protocol ldap aaa-server ActiveDirectory (inside) host dc2 ldap-base-dn dc=corp,dc=company-name,dc=com ldap-scope subtree ldap-login-password * ldap-login-dn cn=administrator,ou=Admins,dc=corp,dc=company-name,dc=com server-type microsoft aaa-server ADRemoteAccess protocol ldap aaa-server ADRemoteAccess (inside) host dc2 ldap-base-dn dc=corp,dc=company-name,dc=com ldap-scope subtree ldap-login-password * ldap-login-dn cn=administrator,ou=Admins,dc=corp,dc=company-name,dc=com server-type microsoft ldap-attribute-map RemoteAccessMap aaa authentication enable console LOCAL aaa authentication ssh console LOCAL http server enable http 192.168.0.0 255.255.255.0 inside no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart sla monitor 123 type echo protocol ipIcmpEcho 4.4.4.1 interface outside num-packets 3 frequency 10 sla monitor schedule 123 life forever start-time now crypto ipsec transform-set ESP-3DES-SHA esp-3des esp-sha-hmac crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 crypto dynamic-map outside_dyn_map 20 set pfs crypto dynamic-map outside_dyn_map 20 set transform-set ESP-3DES-SHA crypto map outside_map 65535 ipsec-isakmp dynamic outside_dyn_map crypto map outside_map interface outside crypto isakmp enable outside crypto isakmp policy 10 authentication pre-share encryption 3des hash sha group 2 lifetime 86400 ! track 1 rtr 123 reachability telnet timeout 5 ssh 192.168.0.0 255.255.255.0 inside ssh timeout 5 ssh version 2 console timeout 0 management-access inside dhcpd auto_config outside ! threat-detection basic-threat threat-detection statistics access-list no threat-detection statistics tcp-intercept webvpn group-policy companynamera internal group-policy companynamera attributes wins-server value 192.168.0.5 dns-server value 192.168.0.5 vpn-tunnel-protocol IPSec password-storage enable split-tunnel-policy tunnelspecified split-tunnel-network-list value companyname_splitTunnelAcl default-domain value corp.company-name.com split-dns value corp.company-name.com group-policy companyname internal group-policy companyname attributes wins-server value 192.168.0.5 dns-server value 192.168.0.5 vpn-tunnel-protocol IPSec password-storage enable split-tunnel-policy tunnelspecified split-tunnel-network-list value companyname_splitTunnelAcl default-domain value corp.company-name.com split-dns value corp.company-name.com username admin password IhpSqtN210ZsNaH. encrypted privilege 15 tunnel-group companyname type remote-access tunnel-group companyname general-attributes address-pool VPNpool authentication-server-group ActiveDirectory LOCAL default-group-policy companyname tunnel-group companyname ipsec-attributes pre-shared-key * tunnel-group companynamera type remote-access tunnel-group companynamera general-attributes address-pool VPNpool authentication-server-group ADRemoteAccess LOCAL default-group-policy companynamera tunnel-group companynamera ipsec-attributes pre-shared-key * ! class-map type inspect ftp match-all ftp-inspection-map class-map inspection_default match default-inspection-traffic ! ! policy-map type inspect ftp ftp-inspection-map parameters class ftp-inspection-map policy-map type inspect dns migrated_dns_map_1 parameters message-length maximum 512 policy-map global_policy class inspection_default inspect dns migrated_dns_map_1 inspect ftp inspect h323 h225 inspect h323 ras inspect http inspect ils inspect netbios inspect rsh inspect rtsp inspect skinny inspect sqlnet inspect sunrpc inspect tftp inspect sip inspect xdmcp inspect icmp inspect icmp error inspect esmtp inspect pptp ! service-policy global_policy global prompt hostname context Cryptochecksum:487525494a81c8176046fec475d17efe : end gateway# Thanks so much!

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• Troubleshooting latency spikes on ESXi NFS datastores

  - by exo_cw

  I'm experiencing fsync latencies of around five seconds on NFS datastores in ESXi, triggered by certain VMs. I suspect this might be caused by VMs using NCQ/TCQ, as this does not happen with virtual IDE drives. This can be reproduced using fsync-tester (by Ted Ts'o) and ioping. For example using a Grml live system with a 8GB disk: Linux 2.6.33-grml64: root@dynip211 /mnt/sda # ./fsync-tester fsync time: 5.0391 fsync time: 5.0438 fsync time: 5.0300 fsync time: 0.0231 fsync time: 0.0243 fsync time: 5.0382 fsync time: 5.0400 [... goes on like this ...] That is 5 seconds, not milliseconds. This is even creating IO-latencies on a different VM running on the same host and datastore: root@grml /mnt/sda/ioping-0.5 # ./ioping -i 0.3 -p 20 . 4096 bytes from . (reiserfs /dev/sda): request=1 time=7.2 ms 4096 bytes from . (reiserfs /dev/sda): request=2 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=3 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=4 time=0.9 ms 4096 bytes from . (reiserfs /dev/sda): request=5 time=4809.0 ms 4096 bytes from . (reiserfs /dev/sda): request=6 time=1.0 ms 4096 bytes from . (reiserfs /dev/sda): request=7 time=1.2 ms 4096 bytes from . (reiserfs /dev/sda): request=8 time=1.1 ms 4096 bytes from . (reiserfs /dev/sda): request=9 time=1.3 ms 4096 bytes from . (reiserfs /dev/sda): request=10 time=1.2 ms 4096 bytes from . (reiserfs /dev/sda): request=11 time=1.0 ms 4096 bytes from . (reiserfs /dev/sda): request=12 time=4950.0 ms When I move the first VM to local storage it looks perfectly normal: root@dynip211 /mnt/sda # ./fsync-tester fsync time: 0.0191 fsync time: 0.0201 fsync time: 0.0203 fsync time: 0.0206 fsync time: 0.0192 fsync time: 0.0231 fsync time: 0.0201 [... tried that for one hour: no spike ...] Things I've tried that made no difference: Tested several ESXi Builds: 381591, 348481, 260247 Tested on different hardware, different Intel and AMD boxes Tested with different NFS servers, all show the same behavior: OpenIndiana b147 (ZFS sync always or disabled: no difference) OpenIndiana b148 (ZFS sync always or disabled: no difference) Linux 2.6.32 (sync or async: no difference) It makes no difference if the NFS server is on the same machine (as a virtual storage appliance) or on a different host Guest OS tested, showing problems: Windows 7 64 Bit (using CrystalDiskMark, latency spikes happen mostly during preparing phase) Linux 2.6.32 (fsync-tester + ioping) Linux 2.6.38 (fsync-tester + ioping) I could not reproduce this problem on Linux 2.6.18 VMs. Another workaround is to use virtual IDE disks (vs SCSI/SAS), but that is limiting performance and the number of drives per VM. Update 2011-06-30: The latency spikes seem to happen more often if the application writes in multiple small blocks before fsync. For example fsync-tester does this (strace output): pwrite(3, "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"..., 1048576, 0) = 1048576 fsync(3) = 0 ioping does this while preparing the file: [lots of pwrites] pwrite(3, "********************************"..., 4096, 1036288) = 4096 pwrite(3, "********************************"..., 4096, 1040384) = 4096 pwrite(3, "********************************"..., 4096, 1044480) = 4096 fsync(3) = 0 The setup phase of ioping almost always hangs, while fsync-tester sometimes works fine. Is someone capable of updating fsync-tester to write multiple small blocks? My C skills suck ;) Update 2011-07-02: This problem does not occur with iSCSI. I tried this with the OpenIndiana COMSTAR iSCSI server. But iSCSI does not give you easy access to the VMDK files so you can move them between hosts with snapshots and rsync. Update 2011-07-06: This is part of a wireshark capture, captured by a third VM on the same vSwitch. This all happens on the same host, no physical network involved. I've started ioping around time 20. There were no packets sent until the five second delay was over: No. Time Source Destination Protocol Info 1082 16.164096 192.168.250.10 192.168.250.20 NFS V3 WRITE Call (Reply In 1085), FH:0x3eb56466 Offset:0 Len:84 FILE_SYNC 1083 16.164112 192.168.250.10 192.168.250.20 NFS V3 WRITE Call (Reply In 1086), FH:0x3eb56f66 Offset:0 Len:84 FILE_SYNC 1084 16.166060 192.168.250.20 192.168.250.10 TCP nfs > iclcnet-locate [ACK] Seq=445 Ack=1057 Win=32806 Len=0 TSV=432016 TSER=769110 1085 16.167678 192.168.250.20 192.168.250.10 NFS V3 WRITE Reply (Call In 1082) Len:84 FILE_SYNC 1086 16.168280 192.168.250.20 192.168.250.10 NFS V3 WRITE Reply (Call In 1083) Len:84 FILE_SYNC 1087 16.168417 192.168.250.10 192.168.250.20 TCP iclcnet-locate > nfs [ACK] Seq=1057 Ack=773 Win=4163 Len=0 TSV=769110 TSER=432016 1088 23.163028 192.168.250.10 192.168.250.20 NFS V3 GETATTR Call (Reply In 1089), FH:0x0bb04963 1089 23.164541 192.168.250.20 192.168.250.10 NFS V3 GETATTR Reply (Call In 1088) Directory mode:0777 uid:0 gid:0 1090 23.274252 192.168.250.10 192.168.250.20 TCP iclcnet-locate > nfs [ACK] Seq=1185 Ack=889 Win=4163 Len=0 TSV=769821 TSER=432716 1091 24.924188 192.168.250.10 192.168.250.20 RPC Continuation 1092 24.924210 192.168.250.10 192.168.250.20 RPC Continuation 1093 24.924216 192.168.250.10 192.168.250.20 RPC Continuation 1094 24.924225 192.168.250.10 192.168.250.20 RPC Continuation 1095 24.924555 192.168.250.20 192.168.250.10 TCP nfs > iclcnet_svinfo [ACK] Seq=6893 Ack=1118613 Win=32625 Len=0 TSV=432892 TSER=769986 1096 24.924626 192.168.250.10 192.168.250.20 RPC Continuation 1097 24.924635 192.168.250.10 192.168.250.20 RPC Continuation 1098 24.924643 192.168.250.10 192.168.250.20 RPC Continuation 1099 24.924649 192.168.250.10 192.168.250.20 RPC Continuation 1100 24.924653 192.168.250.10 192.168.250.20 RPC Continuation 2nd Update 2011-07-06: There seems to be some influence from TCP window sizes. I was not able to reproduce this problem using FreeNAS (based on FreeBSD) as a NFS server. The wireshark captures showed TCP window updates to 29127 bytes in regular intervals. I did not see them with OpenIndiana, which uses larger window sizes by default. I can no longer reproduce this problem if I set the following options in OpenIndiana and restart the NFS server: ndd -set /dev/tcp tcp_recv_hiwat 8192 # default is 128000 ndd -set /dev/tcp tcp_max_buf 1048575 # default is 1048576 But this kills performance: Writing from /dev/zero to a file with dd_rescue goes from 170MB/s to 80MB/s. Update 2011-07-07: I've uploaded this tcpdump capture (can be analyzed with wireshark). In this case 192.168.250.2 is the NFS server (OpenIndiana b148) and 192.168.250.10 is the ESXi host. Things I've tested during this capture: Started "ioping -w 5 -i 0.2 ." at time 30, 5 second hang in setup, completed at time 40. Started "ioping -w 5 -i 0.2 ." at time 60, 5 second hang in setup, completed at time 70. Started "fsync-tester" at time 90, with the following output, stopped at time 120: fsync time: 0.0248 fsync time: 5.0197 fsync time: 5.0287 fsync time: 5.0242 fsync time: 5.0225 fsync time: 0.0209 2nd Update 2011-07-07: Tested another NFS server VM, this time NexentaStor 3.0.5 community edition: Shows the same problems. Update 2011-07-31: I can also reproduce this problem on the new ESXi build 4.1.0.433742.

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• SQL IO and SAN troubles

  - by James

  We are running two servers with identical software setup but different hardware. The first one is a VM on VMWare on a normal tower server with dual core xeons, 16 GB RAM and a 7200 RPM drive. The second one is a VM on XenServer on a powerful brand new rack server, with 4 core xeons and shared storage. We are running Dynamics AX 2012 and SQL Server 2008 R2. When I insert 15 000 records into a table on the slow tower server (as a test), it does so in 13 seconds. On the fast server it takes 33 seconds. I re-ran these tests several times with the same results. I have a feeling it is some sort of IO bottleneck, so I ran SQLIO on both. Here are the results for the slow tower server: C:\Program Files (x86)\SQLIO>test.bat C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -frandom -b8 -BH -LS C:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 14318180 counts per second 8 threads writing for 120 secs to file C:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: C:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 226.97 MBs/sec: 1.77 latency metrics: Min_Latency(ms): 0 Avg_Latency(ms): 281 Max_Latency(ms): 467 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 99 C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -frandom -b8 -BH -LS C:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 14318180 counts per second 8 threads reading for 120 secs from file C:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: C:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 91.34 MBs/sec: 0.71 latency metrics: Min_Latency(ms): 14 Avg_Latency(ms): 699 Max_Latency(ms): 1124 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -fsequential -b64 -BH -LS C :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 14318180 counts per second 8 threads writing for 120 secs to file C:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: C:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 1094.50 MBs/sec: 68.40 latency metrics: Min_Latency(ms): 0 Avg_Latency(ms): 58 Max_Latency(ms): 467 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -fsequential -b64 -BH -LS C :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 14318180 counts per second 8 threads reading for 120 secs from file C:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: C:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 1155.31 MBs/sec: 72.20 latency metrics: Min_Latency(ms): 17 Avg_Latency(ms): 55 Max_Latency(ms): 205 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 Here are the results of the fast rack server: C:\Program Files (x86)\SQLIO>test.bat C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -frandom -b8 -BH -LS E:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads writing for 120 secs to file E:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) open_file: CreateFile (E:\TestFile.dat for write): The system cannot find the pa th specified. exiting C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -frandom -b8 -BH -LS E:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads reading for 120 secs from file E:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) open_file: CreateFile (E:\TestFile.dat for read): The system cannot find the pat h specified. exiting C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -fsequential -b64 -BH -LS E :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads writing for 120 secs to file E:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) open_file: CreateFile (E:\TestFile.dat for write): The system cannot find the pa th specified. exiting C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -fsequential -b64 -BH -LS E :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads reading for 120 secs from file E:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) open_file: CreateFile (E:\TestFile.dat for read): The system cannot find the pat h specified. exiting C:\Program Files (x86)\SQLIO>test.bat C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -frandom -b8 -BH -LS c:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads writing for 120 secs to file c:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: c:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 2575.77 MBs/sec: 20.12 latency metrics: Min_Latency(ms): 1 Avg_Latency(ms): 24 Max_Latency(ms): 655 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 5 8 9 9 9 8 5 3 1 1 1 1 0 0 0 0 0 0 0 0 0 37 C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -frandom -b8 -BH -LS c:\Tes tFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads reading for 120 secs from file c:\TestFile.dat using 8KB random IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: c:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 1141.39 MBs/sec: 8.91 latency metrics: Min_Latency(ms): 1 Avg_Latency(ms): 55 Max_Latency(ms): 652 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 91 C:\Program Files (x86)\SQLIO>sqlio -kW -t8 -s120 -o8 -fsequential -b64 -BH -LS c :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads writing for 120 secs to file c:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: c:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 341.37 MBs/sec: 21.33 latency metrics: Min_Latency(ms): 5 Avg_Latency(ms): 186 Max_Latency(ms): 120037 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 C:\Program Files (x86)\SQLIO>sqlio -kR -t8 -s120 -o8 -fsequential -b64 -BH -LS c :\TestFile.dat sqlio v1.5.SG using system counter for latency timings, 62500000 counts per second 8 threads reading for 120 secs from file c:\TestFile.dat using 64KB sequential IOs enabling multiple I/Os per thread with 8 outstanding buffering set to use hardware disk cache (but not file cache) using current size: 5120 MB for file: c:\TestFile.dat initialization done CUMULATIVE DATA: throughput metrics: IOs/sec: 1024.07 MBs/sec: 64.00 latency metrics: Min_Latency(ms): 5 Avg_Latency(ms): 61 Max_Latency(ms): 81632 histogram: ms: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24+ %: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 100 Three of the four tests are, to my mind, within reasonable parameters for the rack server. However, the 64 write test is incredibly slow on the rack server. (68 mb/sec on the slow tower vs 21 mb/s on the rack). The read speed for 64k also seems slow. Is this enough to say there is some sort of bottleneck with the shared storage? I need to know if I can take this evidence and say we need to launch an investigation into this. Any help is appreciated.

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• Very slow compile times on Visual Studio

  - by johnc

  We are getting very slow compile times, which can take upwards of 20+ minutes on dual core 2GHz, 2G Ram machines. A lot of this is due to the size of our solution which has grown to 70+ projects, as well as VSS which is a bottle neck in itself when you have a lot of files. (swapping out VSS is not an option unfortunately, so I don't want this to descend into a VSS bash) We are looking at combing projects (not nice, as we like the separation of concerns, but is a good opportunity to refactor away some dead wood). We are also looking at having multiple solutions to achieve greater separation of concerns and quicker compile times for each element of the application. This I can see will become a dll hell as we try to keep things in synch. I am interested to know how other teams have dealt with this scaling issue, what do you do when your code base reaches a critical mass that you are wasting half the day watching the status bar deliver compile messages UPDATE Apologies, I neglected to mention this is a C# solution. Thanks for all the cpp suggestions, but it's been a few years since I've had to worry about headers. At a distance I say I miss C++, but I'm not sure I want to go back EDIT: Nice suggestions that have helped so far (not saying there aren't other nice suggestions below, just what has helped) New 3GHz laptop - the power of lost utilization works wonders when whinging to management Disable Anti Virus during compile 'Disconnecting' from VSS (actually the network) during compile - I may get us to remove VS-VSS integration altogether and stick to using the VSS UI Still not rip-snorting through a compile, but every bit helps. Orion did mention in a comment that generics may have a play also. From my tests there does appear to be a minimal performance hit, but not high enough to sure - compile times can be inconsistent due to disc activity. Due to time limitations, my tests didn't include as many Generics, or as much code, as would appear in live system, so that may accumulate. I wouldn't avoid using generics where they are supposed to be used, just for compile time performance WORKAROUND We are testing the practice of building new areas of the application in new solutions, importing in the latest dlls as required, them integrating them into the larger solution when we are happy with them. We may also do them same to existing code by creating temporary solutions that just encapsulate the areas we need to work on, and throwing them away after reintegrating the code. We need to weigh up the time it will take to reintegrate this code against the time we gain by not having Rip Van Winkle like experiences with rapid recompiling during development.

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• 2d trajectory planning of a spaceship with physics.

  - by egarcia

  I'm implementing a 2D game with ships in space. In order to do it, I'm using LÖVE, which wraps Box2D with Lua. But I believe that my question can be answered by anyone with a greater understanding of physics than myself - so pseudo code is accepted as a response. My problem is that I don't know how to move my spaceships properly on a 2D physics-enabled world. More concretely: A ship of mass m is located at an initial position {x, y}. It has an initial velocity vector of {vx, vy} (can be {0,0}). The objective is a point in {xo,yo}. The ship has to reach the objective having a velocity of {vxo, vyo} (or near it), following the shortest trajectory. There's a function called update(dt) that is called frequently (i.e. 30 times per second). On this function, the ship can modify its position and trajectory, by applying "impulses" to itself. The magnitude of the impulses is binary: you can either apply it in a given direction, or not to apply it at all). In code, it looks like this: def Ship:update(dt) m = self:getMass() x,y = self:getPosition() vx,vy = self.getLinearVelocity() xo,yo = self:getTargetPosition() vxo,vyo = self:getTargetVelocity() thrust = self:getThrust() if(???) angle = ??? self:applyImpulse(math.sin(angle)*thrust, math.cos(angle)*thrust)) end end The first ??? is there to indicate that in some occasions (I guess) it would be better to "not to impulse" and leave the ship "drift". The second ??? part consists on how to calculate the impulse angle on a given dt. We are in space, so we can ignore things like air friction. Although it would be very nice, I'm not looking for someone to code this for me; I put the code there so my problem is clearly understood. What I need is an strategy - a way of attacking this. I know some basic physics, but I'm no expert. For example, does this problem have a name? That sort of thing. Thanks a lot.

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• F# Add Constructor to a Record?

  - by akaphenom

  Basically I want to have a single construct to deal with serializing to both JSON and formatted xml. Records workd nicley for serializing to/from json. However XmlSerializer requires a parameterless construtor. I don't really want to have to go through the exercise of building class objects for these constructs (principal only). I was hoping there could be some shortcut for getting a parameterless constructor onto a record (perhaps with a wioth statement or something). I can't get it to behave - has anybody in the community had any luck? module JSONExample open System open System.IO open System.Net open System.Text open System.Web open System.Xml open System.Security.Authentication open System.Runtime.Serialization //add assemnbly reference System.Runtime.Serialization System.Xml open System.Xml.Serialization open System.Collections.Generic [<DataContract>] type ChemicalElementRecord = { [<XmlAttribute("name")>] [<field: DataMember(Name="name") >] Name:string [<XmlAttribute("name")>] [<field: DataMember(Name="boiling_point") >] BoilingPoint:string [<XmlAttribute("atomic-mass")>] [<field: DataMember(Name="atomic_mass") >] AtomicMass:string } [<XmlRoot("freebase")>] [<DataContract>] type FreebaseResultRecord = { [<XmlAttribute("code")>] [<field: DataMember(Name="code") >] Code:string [<XmlArrayAttribute("results")>] [<XmlArrayItem(typeof<ChemicalElementRecord>, ElementName = "chemical-element")>] [<field: DataMember(Name="result") >] Result: ChemicalElementRecord array [<XmlElement("message")>] [<field: DataMember(Name="message") >] Message:string } let getJsonFromWeb() = let query = "[{'type':'/chemistry/chemical_element','name':null,'boiling_point':null,'atomic_mass':null}]" let query = query.Replace("'","\"") let queryUrl = sprintf "http://api.freebase.com/api/service/mqlread?query=%s" "{\"query\":"+query+"}" let request : HttpWebRequest = downcast WebRequest.Create(queryUrl) request.Method <- "GET" request.ContentType <- "application/x-www-form-urlencoded" let response = request.GetResponse() let result = try use reader = new StreamReader(response.GetResponseStream()) reader.ReadToEnd(); finally response.Close() let data = Encoding.Unicode.GetBytes(result); let stream = new MemoryStream() stream.Write(data, 0, data.Length); stream.Position <- 0L stream let test = // get some JSON from the web let stream = getJsonFromWeb() // convert the stream of JSON into an F# Record let JsonSerializer = Json.DataContractJsonSerializer(typeof<FreebaseResultRecord>) let result: FreebaseResultRecord = downcast JsonSerializer.ReadObject(stream) // save the Records to disk as JSON use fs = new FileStream(@"C:\temp\freebase.json", FileMode.Create) JsonSerializer.WriteObject(fs,result) fs.Close() // save the Records to disk as System Controlled XML let xmlSerializer = DataContractSerializer(typeof<FreebaseResultRecord>); use fs = new FileStream(@"C:\temp\freebase.xml", FileMode.Create) xmlSerializer.WriteObject(fs,result) fs.Close() use fs = new FileStream(@"C:\temp\freebase-pretty.xml", FileMode.Create) let xmlSerializer = XmlSerializer(typeof<FreebaseResultRecord>) xmlSerializer.Serialize(fs,result) fs.Close() ignore(test)

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• physics game programming box2d - orientating a turret-like object using torques

  - by egarcia

  This is a problem I hit when trying to implement a game using the LÖVE engine, which covers box2d with Lua scripting. The objective is simple: A turret-like object (seen from the top, on a 2D environment) needs to orientate itself so it points to a target. The turret is on the x,y coordinates, and the target is on tx, ty. We can consider that x,y are fixed, but tx, ty tend to vary from one instant to the other (i.e. they would be the mouse cursor). The turret has a rotor that can apply a rotational force (torque) on any given moment, clockwise or counter-clockwise. The magnitude of that force has an upper limit called maxTorque. The turret also has certain rotational inertia, which acts for angular movement the same way mass acts for linear movement. There's no friction of any kind, so the turret will keep spinning if it has an angular velocity. The turret has a small AI function that re-evaluates its orientation to verify that it points to the right direction, and activates the rotator. This happens every dt (~60 times per second). It looks like this right now: function Turret:update(dt) local x,y = self:getPositon() local tx,ty = self:getTarget() local maxTorque = self:getMaxTorque() -- max force of the turret rotor local inertia = self:getInertia() -- the rotational inertia local w = self:getAngularVelocity() -- current angular velocity of the turret local angle = self:getAngle() -- the angle the turret is facing currently -- the angle of the like that links the turret center with the target local targetAngle = math.atan2(oy-y,ox-x) local differenceAngle = _normalizeAngle(targetAngle - angle) if(differenceAngle <= math.pi) then -- counter-clockwise is the shortest path self:applyTorque(maxTorque) else -- clockwise is the shortest path self:applyTorque(-maxTorque) end end ... it fails. Let me explain with two illustrative situations: The turret "oscillates" around the targetAngle. If the target is "right behind the turret, just a little clock-wise", the turret will start applying clockwise torques, and keep applying them until the instant in which it surpasses the target angle. At that moment it will start applying torques on the opposite direction. But it will have gained a significant angular velocity, so it will keep going clockwise for some time... until the target will be "just behind, but a bit counter-clockwise". And it will start again. So the turret will oscillate or even go in round circles. I think that my turret should start applying torques in the "opposite direction of the shortest path" before it reaches the target angle (like a car braking before stopping). Intuitively, I think the turret should "start applying torques on the opposite direction of the shortest path when it is about half-way to the target objective". My intuition tells me that it has something to do with the angular velocity. And then there's the fact that the target is mobile - I don't know if I should take that into account somehow or just ignore it. How do I calculate when the turret must "start braking"?

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• iphone cocos2d sprites disappearing

  - by jer

  I've been working on a game and implementing the physics stuff with chipmunk. All was going fine on the cocos2d part until the integration with chipmunk. A bit of background: The game is a game with blocks. Levels are defined in a property list, where positions, size of the blocks, gravitational forces, etc., are all defined for each block to be shown in the level. The problem is with the blocks showing up. I have a method on my BlockLayer class which is part of my game's main scene. Upon creation of the layer, the property list is read, and all the blocks are created. The following method is called to create the blocks: - (void)createBlock:(Block*)block withAssets:(NSBundle*)assets { Sprite* sprite; switch(block.blockColour) { case kBlockColourGreen: sprite = [Sprite spriteWithFile:[assets pathForResource:@"green" ofType:@"png" inDirectory:@"Blocks"]]; break; case kBlockColourOrange: sprite = [Sprite spriteWithFile:[assets pathForResource:@"orange" ofType:@"png" inDirectory:@"Blocks"]]; break; case kBlockColourRed: sprite = [Sprite spriteWithFile:[assets pathForResource:@"red" ofType:@"png" inDirectory:@"Blocks"]]; break; case kBlockColourBlue: sprite = [Sprite spriteWithFile:[assets pathForResource:@"blue" ofType:@"png" inDirectory:@"Blocks"]]; break; } sprite.position = block.bounds.origin; [self addChild:sprite]; if(block.blockColour == kBlockColourGreen || block.blockColour == kBlockColourRed) space-gravity = cpvmult(cpv(0, 10), 1000); cpVect verts[] = { cpv(-block.bounds.size.width, -block.bounds.size.height), cpv(-block.bounds.size.width, block.bounds.size.height), cpv(block.bounds.size.width, block.bounds.size.height), cpv(block.bounds.size.width, -block.bounds.size.height) }; cpBody* blockBody = cpBodyNew([block.mass floatValue], INFINITY); blockBody-p = cpv(block.bounds.origin.x, block.bounds.origin.y); blockBody-v = cpvzero; cpSpaceAddBody(space, blockBody); cpShape* blockShape = cpPolyShapeNew(blockBody, 4, verts, cpvzero); blockShape-e = 0.9f; blockShape-u = 0.9f; blockShape-data = sprite; cpSpaceAddShape(space, blockShape); } With the above code, the sprites never show up. However, if I comment out the "cpSpaceAddBody(space, blockBody);" line, the sprites show up. The position and size of the blocks are stored in the "bounds" property of instances of the Block class, which is a CGRect. Not sure if it's important, but the orientation of the app is in landscape left, and all the coordinates are based on that orientation. Any help would be greatly appreciated.

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• How to launch a Windows service network process to listen to a port on a localhost socket that is vi

  - by rwired

  Here's the code (in a standard TService in Delphi): const ProcessExe = 'MyNetApp.exe'; function RunService: Boolean; var StartInfo : TStartupInfo; ProcInfo : TProcessInformation; CreateOK : Boolean; begin CreateOK := false; FillChar(StartInfo,SizeOf(TStartupInfo),#0); FillChar(ProcInfo,SizeOf(TProcessInformation),#0); StartInfo.cb := SizeOf(TStartupInfo); CreateOK := CreateProcess(nil, PChar(ProcessEXE),nil,nil,False, CREATE_NEW_PROCESS_GROUP+NORMAL_PRIORITY_CLASS, nil, PChar(InstallDir), StartInfo, ProcInfo); CloseHandle(ProcInfo.hProcess); CloseHandle(ProcInfo.hThread); Result := CreateOK; end; procedure TServicel.ServiceExecute(Sender: TService); const IntervalsBetweenRuns = 4; //no of IntTimes between checks IntTime = 250; //ms var Count: SmallInt; begin Count := IntervalsBetweenRuns; //first time run immediately while not Terminated do begin Inc(Count); if Count >= IntervalsBetweenRuns then begin Count := 0; //We check to see if the process is running, //if not we run it. That's all there is to it. //if ProcessEXE crashes, this service host will just rerun it if processExists(ProcessEXE)=0 then RunService; end; Sleep(IntTime); ServiceThread.ProcessRequests(False); end; end; MyNetApp.exe is a SOCKS5 proxy listening on port 9870. Users configure their browser to this proxy which acts as a secure-tunnel/anonymizer. All works perfectly fine on 2000/XP/2003, but on Vista/Win7 with UAC the service runs in Session0 under LocalSystem and port 9870 doesn't show up in netstat for the logged-in user or Administrator. Seems UAC is getting in my way. Is there something I can do with the SECURITY_ATTRIBUTES or CreateProcess, or is there something I can do with CreateProcessAsUser or impersonation to ensure that a network socket on a service is available to logged-in users on the system (note, this app is for mass deployment, I don't have access to user credentials, and require the user elevate their privileges to install a service on Vista/Win7)

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