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  • NoSQL for filesystem storage organization and replication?

    - by wheaties
    We've been discussing design of a data warehouse strategy within our group for meeting testing, reproducibility, and data syncing requirements. One of the suggested ideas is to adapt a NoSQL approach using an existing tool rather than try to re-implement a whole lot of the same on a file system. I don't know if a NoSQL approach is even the best approach to what we're trying to accomplish but perhaps if I describe what we need/want you all can help. Most of our files are large, 50+ Gig in size, held in a proprietary, third-party format. We need to be able to access each file by a name/date/source/time/artifact combination. Essentially a key-value pair style look-up. When we query for a file, we don't want to have to load all of it into memory. They're really too large and would swamp our server. We want to be able to somehow get a reference to the file and then use a proprietary, third-party API to ingest portions of it. We want to easily add, remove, and export files from storage. We'd like to set up automatic file replication between two servers (we can write a script for this.) That is, sync the contents of one server with another. We don't need a distributed system where it only appears as if we have one server. We'd like complete replication. We also have other smaller files that have a tree type relationship with the Big files. One file's content will point to the next and so on, and so on. It's not a "spoked wheel," it's a full blown tree. We'd prefer a Python, C or C++ API to work with a system like this but most of us are experienced with a variety of languages. We don't mind as long as it works, gets the job done, and saves us time. What you think? Is there something out there like this?

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  • Prevent unauthorised write access to a part of filesystem or partition

    - by gaurav
    Hello all I have some very important system files which I want to protect from accidental deletion even by root user. I can create a new partition for that and mount it with readonly access but the problem is that I want my application which handles those system files to have write access to that part and be able to modify them. Is that possible using VFS? As VFS handles access to the files I could have a module inserted in the VFS layer which can see if there is a write access to that part then see the authorization and allow it or otherwise reject it. If not please provide me suggestions regarding how can such a system be implemented what would I need in that case. If there exists a system like this please suggest about them also. I am using linux and want to implement this in C, I think it would be possible in C only. Edit: There are such kind of programs implemented in windows which can restrict access to administrator even, to some important folders, would that be possible in linux?

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  • PHP Filesystem Pagination

    - by Byron
    How does one paginate a large listing of files within a folder? I can't see any functions in the PHP documentation that mention any way to specify an 'offset'. Both glob() and scandir() simply return all the files in the folder, and I'm afraid that won't be a good idea for a huge directory. Is there any better way of doing this than simply going through all the files and chopping off the first X number of files?

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  • discovering files in the FileSystem, through SSIS

    - by cometbill
    I have a folder where files are going to be dropped for importing into my data warehouse. \\server\share\loading_area I have the following (inherited) code that uses xp_cmdshell shivers to call out to the command shell to run the DIR command and insert the resulting filenames into a table in SQL Server. I would like to 'go native' and reproduce this functionality in SSIS. Thanks in advance guys and girls. Here's the code USE MyDatabase GO declare @CMD varchar(500) declare @EXTRACT_PATH varchar(255) set @EXTRACT_PATH = '\\server\share\folder\' create table tmp_FILELIST([FILENUM] int identity(1,1), [FNAME] varchar(100), [FILE_STATUS] varchar(20) NULL CONSTRAINT [DF_FILELIST_FILE_STATUS] DEFAULT ('PENDING')) set @CMD = 'dir ' + @EXTRACT_PATH + '*.* /b /on' insert tmp_FILELIST([FNAME]) exec master..xp_cmdshell @CMD --remove the DOS reply when the folder is empty delete tmp_FILELIST where [FNAME] is null or [FNAME] = 'File Not Found' --Remove my administrative and default/common, files not for importing, such as readme.txt delete tmp_FILELIST where [FNAME] is null or [FNAME] = 'readme.txt'

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  • Optimal directory structure for filesystem

    - by Pankaj
    We have large scale web application which has millions of customer. Each customer can have document based on document type. We may have 20-30 types of documents. We are planning to use GlusterFS for storing these documents. I'm trying to find out what are the limitations of Gluster as far as number of files/directories ? Do we need to have hierarchical directory structure ? What would be the optimal directory structure ? Does this make sense - CustmerId Documenttype File1 File2

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  • PHP detecting filesystem encoding

    - by Evert
    Hi guys, I need to save files with non-latin filenames on a filesytem, using PHP. I want to make this work cross-platform. How do I know what encoding I can use to write the file? I understand many modern filesystems are UTF-8 based (is this correct?), but I doubt Windows XP is (for instance). So, is there a robust detection mechanism? Evert

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  • Writing Resources from filesystem in Android

    - by Markus
    Hi, as I need to get a specific Frame from a Website I want to display in an WebView, I decided to grab the .html from the net and save it under file:///data/data//files/file.html. Stroed there I can edit it using regex or String methods. Now two questions: Is there a way to bind this file to an resource. e.g. to /res/raw/file.html and get it updated dynamically as i edit it? Or can i write the File directly to the resources? Is this whole stuff I do there any good or performant at all? I mean maybe there is a better way to get the .html code between two tags from a Webpage and display it via WebView. Kind regards Markus

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  • General question: Filesystem or database?

    - by poeschlorn
    Hey guys, i want to create a small document management system. there are several users who store their files. each file which is uploaded contains an info which user uploaded it and the document content itself. In a view there are displayed all files of ONE specific user, ordered by date. What would be better: 1) giving the documents a name or metadata(XML) which contain the date and user (and iterate through them to get the metadata) or 2) giving the files a random/unique name and store metadata in a DB? something like this: date | user | filename What would you say and why? The used programming language is java and the DB is MySQL.

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  • MacPorts: violation of the ports-filesystem hierarchy in the destroot phase

    - by Dawood
    I'm in the process of developing a Portfile for my application and I'm running into problems during the destroot phase. According to the MacPorts guide, the destroot phase executes the following command: make install DESTDIR=${destroot} I think I may be misunderstanding how this is supposed to work in the Makefile. My application is very simple and the install rule only needs to copy a couple of directories to the DESTDIR so it is specified as follows: install: cp -R bin $(DESTDIR)/bin cp -R lib $(DESTDIR)/lib cp -R cfg $(DESTDIR)/cfg However, when I try to do a MacPort installation of my application, I get the following warnings: ---> Staging test into destroot Warning: violation by /bin Warning: violation by /lib Warning: violation by /cfg Warning: test violates the layout of the ports-filesystems! How do I fix this? Am I misunderstanding how the DESTDIR variable is used in the install rule or missing something altogether?

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  • Best Linux filesystem for MySQL with a 100% SELECT workload

    - by gmemon
    I have a MySQL database that contains millions of rows per table and there are 9 tables in total. The database is fully populated, and all I am doing is reads i.e., there are no INSERTs or UPDATEs. Data is stored in MyISAM tables. Given this scenario, which linux file system would work best? Currently, I have xfs. But, I read somewhere that xfs has horrible read performance. Is that true? Should I shift the database to an ext3 file system? Thanks

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  • Boost::Mutex & Malloc

    - by M. Tibbits
    Hi all, I'm trying to use a faster memory allocator in C++. I can't use Hoard due to licensing / cost. I was using NEDMalloc in a single threaded setting and got excellent performance, but I'm wondering if I should switch to something else -- as I understand things, NEDMalloc is just a replacement for C-based malloc() & free(), not the C++-based new & delete operators (which I use extensively). The problem is that I now need to be thread-safe, so I'm trying to malloc an object which is reference counted (to prevent excess copying), but which also contains a mutex pointer. That way, if you're about to delete the last copy, you first need to lock the pointer, then free the object, and lastly unlock & free the mutex. However, using malloc to create a boost::mutex appears impossible because I can't initialize the private object as calling the constructor directly ist verboten. So I'm left with this odd situation, where I'm using new to allocate the lock and nedmalloc to allocate everything else. But when I allocate a large amount of memory, I run into allocation errors (which disappear when I switch to malloc instead of nedmalloc ~ but the performance is terrible). My guess is that this is due to fragmentation in the memory and an inability of nedmalloc and new to place nice side by side. There has to be a better solution. What would you suggest?

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  • Why aren't these shared_ptrs pointing to the same container?

    - by BeeBand
    I have a class Model: class Model { ... boost::shared_ptr<Deck> _deck; boost::shared_ptr<CardStack> _stack[22]; }; Deck inherits from CardStack. I tried to make _stack[0] point to the same thing that _deck points to by going: { _deck = boost::shared_ptr<Deck>(new Deck()); _stack[0] = _deck; } It seems that the assignment to _deck of _stack[0] results in a copy of _deck being made. How can I get them to point to the same thing?

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  • shared_ptr requires complete type; cannot use it with lua_State*

    - by topright
    Hello! I'm writing a C++/OOP wrapper for Lua. My code is: class LuaState { boost::shared_ptr<lua_State> L; LuaState(): L( luaL_newstate(), LuaState::CustomDeleter ) { } } The problem is lua_State is incomplete type and shared_ptr constructor requires complete type. And I need safe pointer sharing. (Funny thing boost docs say most functions do not require complete type, but constructor requires, so there is no way of using it. http://www.boost.org/doc/libs/1_42_0/libs/smart_ptr/smart_ptr.htm) Can can I solve this? Thank you.

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  • Is there an easy way to make `boost::ptr_vector` more debugger friendly in Visual Studio?

    - by Billy ONeal
    I'm considering using boost::ptr_container as a result of the responses from this question. My biggest problem with the library is that I cannot view the contents of the collection in the debugger, because the MSVC debugger doesn't recognize it, and therefore I cannot see the contents of the containers. (All the data gets stored as void * internally) I've heard MSVC has a feature called "debugger visualizers" which would allow the user to make the debugger smarter about these kinds of things, but I've never written anything like this, and I'm not hugely firmiliar with such things. For example, compare the behavior of boost::shared_ptr with MSVC's own std::tr1::shared_ptr. In the debugger (i.e. in the Watch window), the boost version shows up as a big mess of internal variables used for implementing the shared pointer, but the MSVC version shows up as a plain pointer to the object (and the shared_ptr's innards are hidden). How can I get started either using or implementing such a thing?

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  • Preparing for the next C++ standard

    - by Neil Butterworth
    The spate of questions regarding BOOST_FOREACH prompts me to ask users of the Boost library what (if anything) they are doing to prepare their code for portability to the proposed new C++ standard (aka C++0x). For example, do you write code like this if you use shared_ptr: #ifdef CPPOX #include <memory> #else #include "boost/shared_ptr.hpp" #endif There is also the namespace issue - in the future, shared_ptr will be part of the std, namespace - how do you deal with that? I'm interested in these questions because I've decided to bite the bullet and start learning boost seriously, and I'd like to use best practices in my code. Not exactly a flood of answers - does this mean it's a non-issue? Anyway, thanks to those that replied; I'm accepting jalfs answer because I like being advised to do nothing!

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  • Released object crashes app

    - by John Smith
    I am using objective-C++ (+Boost) for iPhone development. I am in a rather tight loop and need to allocate and release a certain object. The code is something like this. for (int i=0;i<100;i++) { opt = [[FObj alloc] init]; //do stuff with opt [opt release]; } The FObj object is something like @interface FObj MyCPPObj * cppobj; @end In the implementation of FObj there is a dealloc method: -(void) dealloc { delete cppobj; //previously allocated with 'new' [super dealloc]; } I am afraid that if i don't release then the 'MyCPPObj's will just pile up. But releasing makes the app crash after the first loop. What am I doing wrong? Or perhaps should I make cppobj and boost::shared_ptr? (do boost shared pointers automatically release their objects when an objective-C++ object is deleted?)

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  • Get result type of function

    - by Robert
    I want to specialize a template function declared as: template<typename Type> Type read(std::istream& is); I then have a lot of static implementations static int read_integer(std::istream& is); a.s.o. Now I'd like to do a macro so that specialization of read is as simple as: SPECIALIZE_READ(read_integer) So I figured I'd go the boost::function_traits way and declare SPECIALIZE_READ as: #define SPECIALIZE_READ(read_function) \ template<> boost::function_traits<read_function>::result_type read(std::istream& is) { \ return read_function(is); \ } but VC++ (2008) compiler complains with: 'boost::function_traits' : 'read_integer' is not a valid template type argument for parameter 'Function' Ideas ?

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  • What filesystem for shared (read/write) PC/Mac external drive?

    - by webworm
    Is there a recommended filesystem to use when sharing an external drive between the Mac and PC? I understand there are options for Macs to read/write NTFS filesystems and also for PCs to read/write HFS+ filesystems. Is there a preferred filesystem or perhaps a different filesystem that both Mac and PC and read/write? I know I could use FAT32 but some of the files I use are larger than 4 GB (i.e. Virtual Machine images)

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  • MAC OS X: How to determine if filesystem is case sensitive?

    - by trojanfoe
    I have used the statfs(2) system call to get many characteristics of a Mac OS X filesystem, but it doesn't tell me if the filesystem is case-sensitive or not. I need this information as the application I am developing will be moving many files around and I want to detect potential loss of data due to files being moved from a case-sensitive filesystem to a case-insensitive filesystem. Can anyone suggest a way of detecting this?

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  • Bluescreen after Ubuntu 12.10 installation, after recommended boot repair "no filesystem found" please help!

    - by Phil
    After I tried to install Ubuntu 12.10 into my Windows 7 a black screen came up and nothing happened for over five minutes. So I force shutdown my computer and started again on the linux CD. I partitioned the Linux partitions manually and installed Ubuntu. At the next reboot I got a bluescreen from Windows three secounds after loading. I tried to repair the problem by using boot-repair. Then I got out the url: http://paste.ubuntu.com/1430803 And after the next restart he told me that he didn't found the filesystem. Because he didn't found the filesystem it was unable to repair it with the windows CD. Then I tried to repair it with TestDisk and was able to change the Windows Partition into NTFS, but I was not able to repair the windows 7 boot partition. Now I get the message that No Bootloader is found when I restart. Please help me.

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  • Learning low latency C++ and Java?

    - by user997112
    I'm currently in a role where I dont get to write any C++ or Java. However, the role is good because provides me with exposure to the business side (i'm interested in finance). Eventually I would like to get into high frequency trading infrastructure. Therefore, outside of work hours i'd like to maximise the knowledge I can gain about high performance Java and C++. I already have the Java Performance Tuning book, which is ok but not impressive. Can people recommend anymore latency blogs/books/websites for learning about making C++/C/Java or even Unix very fast? Or perhaps making the network parts of the OS (if re-writing Unix components) faster? EDIT: Or perhaps we could make this THE thread for advice on writing fast code

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  • Unix as opposed to Windows (Java and C++)

    - by user997112
    Firstly I should explain the background. I am interested in high frequency trading programming roles. After looking at many job specs it is very clear that there is a big demand for programmers who have programmed Java and C++ on Unix as opposed to Windows. My question is what are the differences a High Freq programmer would come across? It cannot be something in the language itself because syntactically they do not differ over OS? Therefore I thought it must be something which the programming language has to interface, resources etc? Could anyone please help me out as I am trying to improve my C++/Java on Unix, in order to aim for this type of career? ps I'm guessing part of this answer lies with the socket infrastructure on Unix?

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  • Why does installing Grub2 give an "ISO9660: filesystem destruction..." warning?

    - by Ettore
    I have installed Ubuntu 12.04 on my computer, but at the end of the installation it gave me an error and it didn't install grub2. Now I'm trying to install it using the live cd: This is my sudo fdisk -l: Disk /dev/sda: 500.1 GB, 500107862016 bytes 255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x6af447e6 Device Boot Start End Blocks Id System /dev/sda1 * 2048 781459455 390728704 7 HPFS/NTFS/exFAT /dev/sda2 781459456 789272575 3906560 82 Linux swap / Solaris /dev/sda3 789272576 976773119 93750272 83 Linux After mounting and chroot the linux partiton, I give grub-install /dev/sda command, and I get: /usr/sbin/grub-setup: error: hd0 appears to contain a iso9660 filesystem which isn't known to reserve space for DOS-style boot. Installing GRUB there could result in FILESYSTEM DESTRUCTION if valuable data is overwritten by grub-setup (--skip-fs-probe disables this check, use at your own risk). (same error even with grub-install --recheck /dev/sda) What can I do? I also tried boot-repair, but I get this error: http://paste.ubuntu.com/1069353/

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  • Help with infrequent segmentation fault in accessing boost::unordered_multimap or struct

    - by Sarah
    I'm having trouble debugging a segmentation fault. I'd appreciate tips on how to go about narrowing in on the problem. The error appears when an iterator tries to access an element of a struct Infection, defined as: struct Infection { public: explicit Infection( double it, double rt ) : infT( it ), recT( rt ) {} double infT; // infection start time double recT; // scheduled recovery time }; These structs are kept in a special structure, InfectionMap: typedef boost::unordered_multimap< int, Infection > InfectionMap; Every member of class Host has an InfectionMap carriage. Recovery times and associated host identifiers are kept in a priority queue. When a scheduled recovery event arises in the simulation for a particular strain s in a particular host, the program searches through carriage of that host to find the Infection whose recT matches the recovery time (double recoverTime). (For reasons that aren't worth going into, it's not as expedient for me to use recT as the key to InfectionMap; the strain s is more useful, and coinfections with the same strain are possible.) assert( carriage.size() > 0 ); pair<InfectionMap::iterator,InfectionMap::iterator> ret = carriage.equal_range( s ); InfectionMap::iterator it; for ( it = ret.first; it != ret.second; it++ ) { if ( ((*it).second).recT == recoverTime ) { // produces seg fault carriage.erase( it ); } } I get a "Program received signal EXC_BAD_ACCESS, Could not access memory. Reason: KERN_INVALID_ADDRESS at address..." on the line specified above. The recoverTime is fine, and the assert(...) in the code is not tripped. As I said, this seg fault appears 'randomly' after thousands of successful recovery events. How would you go about figuring out what's going on? I'd love ideas about what could be wrong and how I can further investigate the problem. Update I added a new assert and a check just inside the for loop: assert( carriage.size() > 0 ); assert( carriage.count( s ) > 0 ); pair<InfectionMap::iterator,InfectionMap::iterator> ret = carriage.equal_range( s ); InfectionMap::iterator it; cout << "carriage.count(" << s << ")=" << carriage.count(s) << endl; for ( it = ret.first; it != ret.second; it++ ) { cout << "(*it).first=" << (*it).first << endl; // error here if ( ((*it).second).recT == recoverTime ) { carriage.erase( it ); } } The EXC_BAD_ACCESS error now appears at the (*it).first call, again after many thousands of successful recoveries. Can anyone give me tips on how to figure out how this problem arises? I'm trying to use gdb. Frame 0 from the backtrace reads "#0 0x0000000100001d50 in Host::recover (this=0x100530d80, s=0, recoverTime=635.91148029170529) at Host.cpp:317" I'm not sure what useful information I can extract here. Update 2 I added a break; after the carriage.erase(it). This works, but I have no idea why (e.g., why it would remove the seg fault at (*it).first.

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