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  • how to manage a multi user server on linux?

    - by user1175942
    I'm working on a university project, where I have Tomcat as a web server, and I want to create a multi user environment on top of linux, so every user that logs into my website has his own credentials, and he can access only his own data (files and folders...). The main issue is that the purpose of the website is executing code on the server-side, so I must have a good (reasonable) protection against malicious code. (a user destroying his own user is fine by me) I thought that defining a linux-user for every website-user is the best solution - it isolates each user from the other, and I can define each one's permissions. Can I create users in linux using shell commands? Can I configure max quota/memory/cpu for a user? Anyone has another idea for managing that kind of multi-user environment?

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  • Lock-free multi-threading is for real threading experts...

    - by vdhant
    I was reading through an answer that Jon Skeet gave to a question and in it he mentioned this: As far as I'm concerned, lock-free multi-threading is for real threading experts, of which I'm not one. Its not the first time that I have heard this, but I find very few people talking about how you actually do it if you are interested in learning how to write lock-free multi-threading code. So my question is besides learning all you can about threading, etc where do you start trying to learn to specifically write lock-free multi-threading code and what are some good resources. Cheers

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  • is it possible to create a multi-project template that references n number of existing projects and

    - by jcollum
    The situation: I need to create about 40+ solutions that all reference 3 projects and have one project that is unique to each one. I'd like to create a multi-project template that does this, but from what I've read it looks like it's very difficult or impossible (related SO question, but doesn't answer). I want my solution to look like this (names changed of course): These three are used by all solutions created under this "family": MyCompany.Extensions MyCompany.MyProject.Tests.Shared MyCompany.MyProject.Scripts This one is the one that makes the solution unique, 123, 124, 125 etc: MyCompany.MyProject.Tests.Unit123 Is it possible to set up a multi-project template that will generate this structure? References: MSDN Create Multi Project Templates

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  • Adding a mini admin to a webpage.

    - by DADU
    Hello Picture this: you are creating a little module that people can incorporate into their website easily, for example, a little contact form. It would consist of a PHP file that outputs some HTML, a Javascript file (ajax etc.), a CSS file and a CSS skin. Now the person who doesn't know much about coding wants to integrate it on a webpage (website/index.php). We could do this with three rules of code: <link rel="stylesheet" href="module/css/module.css" /> <script src="module/js/module.js"></script> <?php require_once 'module/module.php'; ?> There's no doubt this part is questionable, right? Now when we want to add an admin for this little module, there are two options: Accessing the admin via an extra URL like website/module/admin.php and after authentication, displaying a page where the person can do all the settings. The person then goes back to index.php to see the results. Enabling the admin via an extra URL like website/module/admin.php and after authentication, redirecting back to index.php. The person can now edit the module directly (HTML5 contenteditable) and see changes live, on the webpage where everybody else will see it when the person saves the changes. Option 2 has a couple of advantages: The person doesn't have to toggle between admin and index.php. The person can see directly how it's looking at the webpage it's integrated in. The person probably feels like the module is more part of the webpage/website. Of course option 2 has some disadvantages too: Not everything works well editing it inline. The person would need to have an HTML5 compliant browser. Probably some more I can't think of right now. Now I have a few concerns that's I can't seem to see a clear answer to. How would we let the person integrate the admin on their webpage? The admin files only need to be included in index.php if the person has choosen to edit the module via the url (website/module/admin.php). But how can we do this if we have a admin.css file that belongs in the head section, an admin.php file that goes into the body, and another admin.js file that's included at the end of the body? How would we know the file that admin.php needs to redirect back to, after authentication? index.php could be any webpage with any name. Any real life website/web apps examples using this principle are welcome too. If there's something unclear, I am glad to add additional info.

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  • Mixing Forms and Token Authentication in a single ASP.NET Application (the Details)

    - by Your DisplayName here!
    The scenario described in my last post works because of the design around HTTP modules in ASP.NET. Authentication related modules (like Forms authentication and WIF WS-Fed/Sessions) typically subscribe to three events in the pipeline – AuthenticateRequest/PostAuthenticateRequest for pre-processing and EndRequest for post-processing (like making redirects to a login page). In the pre-processing stage it is the modules’ job to determine the identity of the client based on incoming HTTP details (like a header, cookie, form post) and set HttpContext.User and Thread.CurrentPrincipal. The actual page (in the ExecuteHandler event) “sees” the identity that the last module has set. So in our case there are three modules in effect: FormsAuthenticationModule (AuthenticateRequest, EndRequest) WSFederationAuthenticationModule (AuthenticateRequest, PostAuthenticateRequest, EndRequest) SessionAuthenticationModule (AuthenticateRequest, PostAuthenticateRequest) So let’s have a look at the different scenario we have when mixing Forms auth and WS-Federation. Anoymous request to unprotected resource This is the easiest case. Since there is no WIF session cookie or a FormsAuth cookie, these modules do nothing. The WSFed module creates an anonymous ClaimsPrincipal and calls the registered ClaimsAuthenticationManager (if any) to transform it. The result (by default an anonymous ClaimsPrincipal) gets set. Anonymous request to FormsAuth protected resource This is the scenario where an anonymous user tries to access a FormsAuth protected resource for the first time. The principal is anonymous and before the page gets rendered, the Authorize attribute kicks in. The attribute determines that the user needs authentication and therefor sets a 401 status code and ends the request. Now execution jumps to the EndRequest event, where the FormsAuth module takes over. The module then converts the 401 to a redirect (302) to the forms login page. If authentication is successful, the login page sets the FormsAuth cookie.   FormsAuth authenticated request to a FormsAuth protected resource Now a FormsAuth cookie is present, which gets validated by the FormsAuth module. This cookie gets turned into a GenericPrincipal/FormsIdentity combination. The WS-Fed module turns the principal into a ClaimsPrincipal and calls the registered ClaimsAuthenticationManager. The outcome of that gets set on the context. Anonymous request to STS protected resource This time the anonymous user tries to access an STS protected resource (a controller decorated with the RequireTokenAuthentication attribute). The attribute determines that the user needs STS authentication by checking the authentication type on the current principal. If this is not Federation, the redirect to the STS will be made. After successful authentication at the STS, the STS posts the token back to the application (using WS-Federation syntax). Postback from STS authentication After the postback, the WS-Fed module finds the token response and validates the contained token. If successful, the token gets transformed by the ClaimsAuthenticationManager, and the outcome is a) stored in a session cookie, and b) set on the context. STS authenticated request to an STS protected resource This time the WIF Session authentication module kicks in because it can find the previously issued session cookie. The module re-hydrates the ClaimsPrincipal from the cookie and sets it.     FormsAuth and STS authenticated request to a protected resource This is kind of an odd case – e.g. the user first authenticated using Forms and after that using the STS. This time the FormsAuth module does its work, and then afterwards the session module stomps over the context with the session principal. In other words, the STS identity wins.   What about roles? A common way to set roles in ASP.NET is to use the role manager feature. There is a corresponding HTTP module for that (RoleManagerModule) that handles PostAuthenticateRequest. Does this collide with the above combinations? No it doesn’t! When the WS-Fed module turns existing principals into a ClaimsPrincipal (like it did with the FormsIdentity), it also checks for RolePrincipal (which is the principal type created by role manager), and turns the roles in role claims. Nice! But as you can see in the last scenario above, this might result in unnecessary work, so I would rather recommend consolidating all role work (and other claims transformations) into the ClaimsAuthenticationManager. In there you can check for the authentication type of the incoming principal and act accordingly. HTH

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  • Capturing stdout from an imported module in wxpython and sending it to a textctrl, without blocking the GUI

    - by splafe
    There are alot of very similar questions to this but I can't find one that applies specifically to what I'm trying to do. I have a simulation (written in SimPy) that I'm writing a GUI for, the main output of the simulation is text - to the console from 'print' statements. Now, I thought the simplest way would be to create a seperate module GUI.py, and import my simulation program into it: import osi_model I want all the print statements to be captured by the GUI and appear inside a Textctrl, which there's countless examples of on here, along these lines: class MyFrame(wx.Frame): def __init__(self, *args, **kwds): <general frame initialisation stuff..> redir=RedirectText(self.txtCtrl_1) sys.stdout=redir class RedirectText: def __init__(self,aWxTextCtrl): self.out=aWxTextCtrl def write(self,string): self.out.WriteText(string) I am also starting my simulation from a 'Go' button: def go_btn_click(self, event): print 'GO' self.RT = threading.Thread(target=osi_model.RunThis()) self.RT.start() This all works fine, and the output from the simulation module is captured by the TextCtrl, except the GUI locks up and becomes unresponsive - I still need it to be accessible (at the very minimum to have a 'Stop' button). I'm not sure if this is a botched attempt at creating a new thread that I've done here, but I assume a new thread will be needed at some stage in this process. People suggest using wx.CallAfter, but I'm not sure how to go about this considering the imported module doesn't know about wx, and also I can't realistically go through the entire simulation architecture and change all the print statements to wx.CallAfter, and any attempt to capture the shell from inside the imported simulation program leads to the program crashing. Does anybody have any ideas about how I can best achieve this? So all I really need is for all console text to be captured by a TextCtrl while the GUI remains responsive, and all text is solely coming from an imported module. (Also, secondary question regarding a Stop button - is it bad form to just kill the simulation thread?). Thanks, Duncan

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  • j_security_check to SSO in different module under Oracle App Server?

    - by thebearinboulder
    I have an existing j2ee application running on Oracle App Server. It is targeted towards paying customers so the content is secured and a SSO module properly intercepts all requests for secured content. Now the company is adding a unbranded public-facing module with a number of unsecured pages. At one point the user is expected to register for a free account and log in to proceed further. Think doctors adding a public-facing site with information for potential patients, or lawyers adding a public-facing site with information for potential clients. There's some information on the session and the usual approach would be to authenticate the user, persist the session information using the now-known user id, invalidate the existing session (to prevent certain types of attacks), the reload the session information before returning to the user. I can't just persist it under the session id since that's about to change. The glitch is that the existing application already has an SSO module and I get a 404 error every time I try to direct to j_security_check. I've tried that, /sso/j_security_check, even http://localhost/sso/j_security_check, all without success. I noticed that an earlier question said that tomcat requires access to a secured page before j_security_check is even visible. I don't know if that's the case with Oracle AS. Ideas? Or is the best approach to continue arguing that we have a different user base so it would be better to handle authentication in our own module anyway?

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  • Zend Framework - How do make a hierarchy without it being a module?

    - by Josh
    Here is my specific issue. I want to make an api level which then under that you can select which method you will use. For example: test.com/api/rest test.com/api/xmlprc Currently I have api mapping to a module directory. I then setup a route to make it a rest route. test.com/api is a rest route, but I would rather have it be test.com/api/rest. This would allow me later to add others. In Bootstrap.php: $front = Zend_Controller_Front::getInstance(); $router = $front->getRouter(); $route = new Zend_Controller_Router_Route( 'api/:module/:controller/:id/*', array('module' =>'default') ); $router-addRoute('api', $route); $restRoute = new Zend_Rest_Route($front, array(), array( 'rest' )); $router-addRoute('rest', $restRoute); return $router; In application.ini: resources.frontController.moduleDirectory = APPLICATION_PATH "/modules" I know it will involve routes, but sometimes I find the Zend Framework documentation to be a little hard to follow. When I go to test.com/rest/controller/ it works how it should, but if I go to test.com/api/rest/ it tells me that my module is api and controller is rest.

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  • How can I use io.StringIO() with the csv module?

    - by Tim Pietzcker
    I tried to backport a Python 3 program to 2.7, and I'm stuck with a strange problem: >>> import io >>> import csv >>> output = io.StringIO() >>> output.write("Hello!") # Fail: io.StringIO expects Unicode Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' >>> output.write(u"Hello!") # This works as expected. 6L >>> writer = csv.writer(output) # Now let's try this with the csv module: >>> csvdata = [u"Hello", u"Goodbye"] # Look ma, all Unicode! (?) >>> writer.writerow(csvdata) # Sadly, no. Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unicode argument expected, got 'str' According to the docs, io.StringIO() returns an in-memory stream for Unicode text. It works correctly when I try and feed it a Unicode string manually. Why does it fail in conjunction with the csv module, even if all the strings being written are Unicode strings? Where does the str come from that causes the Exception? (I do know that I can use StringIO.StringIO() instead, but I'm wondering what's wrong with io.StringIO() in this scenario)

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  • Configure a wireless network that accepts any WPA2-PSK network key

    - by Michel
    I recently bought a UART WiFi module ( this one ) and configured it with right SSID but wrong password( and I don't know what it is ). The problem is that I can't reset this module to its manufacture settings and I can't connect to this module via serial port to configure it with some wire or cable. But I'm sure that my module is trying to connect my access point but with wrong network key ( because in logs of my access point I can see my module that trying to connect but it can't ) So, I wonder to know is there any way to create or configure a network (using some access point or something else) based on WPA2 Personal security that accepts any WPA2-PSK passwords ? Or is there any other solution for this problem ? If no, is there anyway to see what password this module using to connect to that network ? ( If yes, then I can change password of my network to that password and access to this module's admin panel ) I tried create an open network ( without any security key ) but my module just searches for WPA2 based networks ( I think ).

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  • How to tell X.org to reload input device module? (Working around suspend-to-ram crash on Acer laptop

    - by Vi
    When X.org boots up, Synaptics touchpad works well. But when I remove the module it falls back to /dev/input/mice and don't use normal driver even when touchpad is available again. Xorg.0.log: ... (II) XINPUT: Adding extended input device "Synaptics Touchpad" (type: TOUCHPAD) (--) Synaptics Touchpad: touchpad found # { rmmod psmouse && echo mem /sys/power/state && modprobe psmouse; } (WW) : No Device specified, looking for one... (II) : Setting Device option to "/dev/input/mice" ... How to tell X.org to try it's InputDevice again (without restarting X server)? P.S. rmmod psmouse is needed to prevent crashing of Acer Extensa 5220 when resuming from suspend-to-ram. Update: Found answer myself: Doing xinput set-int-prop "Synaptics Touchpad" "Device Enabled" 8 1 after reloading the kernel module reloads touchpad. Now suspend-to-ram works OK.

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  • How to tell X.org to reload input device module?

    - by Vi
    When X.org boots up, Synaptics touchpad works well. But when I remove the module it falls back to /dev/input/mice and don't use normal driver even when touchpad is available again. Xorg.0.log: ... (II) XINPUT: Adding extended input device "Synaptics Touchpad" (type: TOUCHPAD) (--) Synaptics Touchpad: touchpad found # { rmmod psmouse && echo mem /sys/power/state && modprobe psmouse; } (WW) : No Device specified, looking for one... (II) : Setting Device option to "/dev/input/mice" ... How to tell X.org to try it's InputDevice again (without restarting X server)? P.S. rmmod psmouse is needed to prevent crashing of Acer Extensa 5220 when resuming from suspend-to-ram. Update: Found answer myself: Doing xinput set-int-prop "Synaptics Touchpad" "Device Enabled" 8 1 after reloading the kernel module reloads touchpad. Now suspend-to-ram works OK.

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  • How to extend a file definition from an existing module in the node?

    - by c33s
    I use an older version of the example42 mysql module, which defines the mysql.conf file but not its content. Mmy goal is to just include the mysql module and add a content definition in the node. class mysql { ... file { "mysql.conf": path => "${mysql::params::configfile}", mode => "${mysql::params::configfile_mode}", owner => "${mysql::params::configfile_owner}", group => "${mysql::params::configfile_group}", ensure => present, require => Package["mysql"], notify => Service["mysql"], } ... } node xyz { include mysql File["mysql.conf"] { content => template("mymodule/mysql.conf.erb")} } The above code produces a "Only subclasses can override parameters" What is the correct way to just add a content definition to an existing file definition?

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  • Unable to uninstall maas completely

    - by user210844
    I'm not able to uninstall MAAS sudo apt-get purge maas ; sudo apt-get autoremove Reading package lists... Done Building dependency tree Reading state information... Done Package 'maas' is not installed, so not removed 0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Setting up maas-region-controller (1.2+bzr1373+dfsg-0ubuntu1) ... Considering dependency proxy for proxy_http: Module proxy already enabled Module proxy_http already enabled Module expires already enabled Module wsgi already enabled sed: -e expression #1, char 91: unterminated `s' command dpkg: error processing maas-region-controller (--configure): subprocess installed post-installation script returned error exit status 1 No apport report written because MaxReports is reached already dpkg: dependency problems prevent configuration of maas-dns: maas-dns depends on maas-region-controller (= 1.2+bzr1373+dfsg-0ubuntu1); however: Package maas-region-controller is not configured yet. dpkg: error processing maas-dns (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already Errors were encountered while processing: maas-region-controller maas-dns E: Sub-process /usr/bin/dpkg returned an error code (1) Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded. 2 not fully installed or removed. After this operation, 0 B of additional disk space will be used. Setting up maas-region-controller (1.2+bzr1373+dfsg-0ubuntu1) ... Considering dependency proxy for proxy_http: Module proxy already enabled Module proxy_http already enabled Module expires already enabled Module wsgi already enabled sed: -e expression #1, char 91: unterminated `s' command dpkg: error processing maas-region-controller (--configure): subprocess installed post-installation script returned error exit status 1 No apport report written because MaxReports is reached already dpkg: dependency problems prevent configuration of maas-dns: maas-dns depends on maas-region-controller (= 1.2+bzr1373+dfsg-0ubuntu1); however: Package maas-region-controller is not configured yet. dpkg: error processing maas-dns (--configure): dependency problems - leaving unconfigured No apport report written because MaxReports is reached already Errors were encountered while processing: maas-region-controller maas-dns E: Sub-process /usr/bin/dpkg returned an error code (1)

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  • What's the difference between General Ledger Transfer Program, Create Accounting and Submit Accounting?

    - by Oracle_EBS
    In Release 12, the General Ledger Transfer Program is no longer used. Use Create Accounting or Submit Accounting instead. Submit Accounting spawns the Revenue Recognition Process. The Create Accounting program does not. So if you create transactions with rules, then you would want to run Submit Accounting Process to spawn Revenue Recognition to create the distribution rows, which Create Accounting is then spawned to process to the GL. Create Accounting Submit Accounting Short Name for Concurrent Program XLAACCPB ARACCPB Specific to Receivables No Yes Runs Revenue Recognition automatically No Yes Can be run real-time for one Transaction/Receipt at a time Yes No Spawns the following Programs 1) XLAACCPB module: Create Accounting 2) XLAACCUP module: Accounting Program 3) GLLEZL module: Journal Import 1) ARTERRPM module: Revenue Recognition Master Program 2) ARTERRPW module: Revenue Recognition with parallel workers - could be numerous 3) ARREVSWP - Revenue Contingency Analyzer 4) XLAACCPB module: Create Accounting 5) XLAACCUP module: Accounting Program 5) GLLEZL module: Journal Import Keep in mind, Reports owned by application 'Subledger Accounting' cannot be seen when running the report from Receivables responsibility. You may want to request your sysadmin to attach the following SLA reports/programs to your AR responsibility as you will need these for your AR closing process: XLAPEXRPT : Subledger Period Close Exception Report - shows transactions in status final, incomplete and unprocessed. XLAGLTRN : Transfer Journal Entries to GL - transfers transactions in final status and manually created transactions to GL To add reports/programs owned by application 'Subledger Accounting' (Subledger Period Close Exception Report and Transfer Journal Entries to GL_ Add to the request group as follows: Let's use Subledger Accounting Report XLATBRPT: Open Account Balances Listing Report as an example. Responsibility: System Administrator Navigation: Security > Responsibility > Define Query the name of your Receivables Responsibility and note the Request Group (ie. Receivables All) Navigation: Security > Responsibility > Request Query the Request Group Go to Request Zone and Click on Add Record Enter the following: Type: Program Name: Open Account Balances Listing Save Responsibility: Receivables Manager Navigation: Control > Requests > Run In the list of values you should now see 'Open Account Balances Listing' report References: Note: 748999.1 How to add reports for application subledger accounting to receivables responsibiilty Note: 759534.1 R12 ARGLTP General Ledger Transfer Program Errors Out Note: 1121944.1 Understanding and Troubleshooting Revenue Recognition in Oracle Receivables

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  • How to turn on/off code modules?

    - by Safran Ali
    I am trying to run multiple sites using single code base and code base consist of the following module (i.e. classes) User module Q & A module Faq module and each class works on MVC pattern i.e. it consist of Entity class Helper class (i.e. static class) View (i.e. pages and controls) and let's say I have 2 sites site1.com and site2.com. And I am trying to achieve following functionality site1.com can have User, Q & A and Faq module up and running site2.com can have User and Q & A module live while Faq module is switched off but it can be turned-on if needed, so my query here is what is the best way to achieve such functionality Do I introduce a flag bit that I check on every page and control belonging to that module? It's more like CMS where you can turn on/off different features. I am trying to get my head around it, please provide me with an example or point out if I am taking the wrong approach.

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  • ASMLib

    - by wcoekaer
    Oracle ASMlib on Linux has been a topic of discussion a number of times since it was released way back when in 2004. There is a lot of confusion around it and certainly a lot of misinformation out there for no good reason. Let me try to give a bit of history around Oracle ASMLib. Oracle ASMLib was introduced at the time Oracle released Oracle Database 10g R1. 10gR1 introduced a very cool important new features called Oracle ASM (Automatic Storage Management). A very simplistic description would be that this is a very sophisticated volume manager for Oracle data. Give your devices directly to the ASM instance and we manage the storage for you, clustered, highly available, redundant, performance, etc, etc... We recommend using Oracle ASM for all database deployments, single instance or clustered (RAC). The ASM instance manages the storage and every Oracle server process opens and operates on the storage devices like it would open and operate on regular datafiles or raw devices. So by default since 10gR1 up to today, we do not interact differently with ASM managed block devices than we did before with a datafile being mapped to a raw device. All of this is without ASMLib, so ignore that one for now. Standard Oracle on any platform that we support (Linux, Windows, Solaris, AIX, ...) does it the exact same way. You start an ASM instance, it handles storage management, all the database instances use and open that storage and read/write from/to it. There are no extra pieces of software needed, including on Linux. ASM is fully functional and selfcontained without any other components. In order for the admin to provide a raw device to ASM or to the database, it has to have persistent device naming. If you booted up a server where a raw disk was named /dev/sdf and you give it to ASM (or even just creating a tablespace without asm on that device with datafile '/dev/sdf') and next time you boot up and that device is now /dev/sdg, you end up with an error. Just like you can't just change datafile names, you can't change device filenames without telling the database, or ASM. persistent device naming on Linux, especially back in those days ways to say it bluntly, a nightmare. In fact there were a number of issues (dating back to 2004) : Linux async IO wasn't pretty persistent device naming including permissions (had to be owned by oracle and the dba group) was very, very difficult to manage system resource usage in terms of open file descriptors So given the above, we tried to find a way to make this easier on the admins, in many ways, similar to why we started working on OCFS a few years earlier - how can we make life easier for the admins on Linux. A feature of Oracle ASM is the ability for third parties to write an extension using what's called ASMLib. It is possible for any third party OS or storage vendor to write a library using a specific Oracle defined interface that gets used by the ASM instance and by the database instance when available. This interface offered 2 components : Define an IO interface - allow any IO to the devices to go through ASMLib Define device discovery - implement an external way of discovering, labeling devices to provide to ASM and the Oracle database instance This is similar to a library that a number of companies have implemented over many years called libODM (Oracle Disk Manager). ODM was specified many years before we introduced ASM and allowed third party vendors to implement their own IO routines so that the database would use this library if installed and make use of the library open/read/write/close,.. routines instead of the standard OS interfaces. PolyServe back in the day used this to optimize their storage solution, Veritas used (and I believe still uses) this for their filesystem. It basically allowed, in particular, filesystem vendors to write libraries that could optimize access to their storage or filesystem.. so ASMLib was not something new, it was basically based on the same model. You have libodm for just database access, you have libasm for asm/database access. Since this library interface existed, we decided to do a reference implementation on Linux. We wrote an ASMLib for Linux that could be used on any Linux platform and other vendors could see how this worked and potentially implement their own solution. As I mentioned earlier, ASMLib and ODMLib are libraries for third party extensions. ASMLib for Linux, since it was a reference implementation implemented both interfaces, the storage discovery part and the IO part. There are 2 components : Oracle ASMLib - the userspace library with config tools (a shared object and some scripts) oracleasm.ko - a kernel module that implements the asm device for /dev/oracleasm/* The userspace library is a binary-only module since it links with and contains Oracle header files but is generic, we only have one asm library for the various Linux platforms. This library is opened by Oracle ASM and by Oracle database processes and this library interacts with the OS through the asm device (/dev/asm). It can install on Oracle Linux, on SuSE SLES, on Red Hat RHEL,.. The library itself doesn't actually care much about the OS version, the kernel module and device cares. The support tools are simple scripts that allow the admin to label devices and scan for disks and devices. This way you can say create an ASM disk label foo on, currently /dev/sdf... So if /dev/sdf disappears and next time is /dev/sdg, we just scan for the label foo and we discover it as /dev/sdg and life goes on without any worry. Also, when the database needs access to the device, we don't have to worry about file permissions or anything it will be taken care of. So it's a convenience thing. The kernel module oracleasm.ko is a Linux kernel module/device driver. It implements a device /dev/oracleasm/* and any and all IO goes through ASMLib - /dev/oracleasm. This kernel module is obviously a very specific Oracle related device driver but it was released under the GPL v2 so anyone could easily build it for their Linux distribution kernels. Advantages for using ASMLib : A good async IO interface for the database, the entire IO interface is based on an optimal ASYNC model for performance A single file descriptor per Oracle process, not one per device or datafile per process reducing # of open filehandles overhead Device scanning and labeling built-in so you do not have to worry about messing with udev or devlabel, permissions or the likes which can be very complex and error prone. Just like with OCFS and OCFS2, each kernel version (major or minor) has to get a new version of the device drivers. We started out building the oracleasm kernel module rpms for many distributions, SLES (in fact in the early days still even for this thing called United Linux) and RHEL. The driver didn't make sense to get pushed into upstream Linux because it's unique and specific to the Oracle database. As it takes a huge effort in terms of build infrastructure and QA and release management to build kernel modules for every architecture, every linux distribution and every major and minor version we worked with the vendors to get them to add this tiny kernel module to their infrastructure. (60k source code file). The folks at SuSE understood this was good for them and their customers and us and added it to SLES. So every build coming from SuSE for SLES contains the oracleasm.ko module. We weren't as successful with other vendors so for quite some time we continued to build it for RHEL and of course as we introduced Oracle Linux end of 2006 also for Oracle Linux. With Oracle Linux it became easy for us because we just added the code to our build system and as we churned out Oracle Linux kernels whether it was for a public release or for customers that needed a one off fix where they also used asmlib, we didn't have to do any extra work it was just all nicely integrated. With the introduction of Oracle Linux's Unbreakable Enterprise Kernel and our interest in being able to exploit ASMLib more, we started working on a very exciting project called Data Integrity. Oracle (Martin Petersen in particular) worked for many years with the T10 standards committee and storage vendors and implemented Linux kernel support for DIF/DIX, data protection in the Linux kernel, note to those that wonder, yes it's all in mainline Linux and under the GPL. This basically gave us all the features in the Linux kernel to checksum a data block, send it to the storage adapter, which can then validate that block and checksum in firmware before it sends it over the wire to the storage array, which can then do another checksum and to the actual DISK which does a final validation before writing the block to the physical media. So what was missing was the ability for a userspace application (read: Oracle RDBMS) to write a block which then has a checksum and validation all the way down to the disk. application to disk. Because we have ASMLib we had an entry into the Linux kernel and Martin added support in ASMLib (kernel driver + userspace) for this functionality. Now, this is all based on relatively current Linux kernels, the oracleasm kernel module depends on the main kernel to have support for it so we can make use of it. Thanks to UEK and us having the ability to ship a more modern, current version of the Linux kernel we were able to introduce this feature into ASMLib for Linux from Oracle. This combined with the fact that we build the asm kernel module when we build every single UEK kernel allowed us to continue improving ASMLib and provide it to our customers. So today, we (Oracle) provide Oracle ASMLib for Oracle Linux and in particular on the Unbreakable Enterprise Kernel. We did the build/testing/delivery of ASMLib for RHEL until RHEL5 but since RHEL6 decided that it was too much effort for us to also maintain all the build and test environments for RHEL and we did not have the ability to use the latest kernel features to introduce the Data Integrity features and we didn't want to end up with multiple versions of asmlib as maintained by us. SuSE SLES still builds and comes with the oracleasm module and they do all the work and RHAT it certainly welcome to do the same. They don't have to rebuild the userspace library, it's really about the kernel module. And finally to re-iterate a few important things : Oracle ASM does not in any way require ASMLib to function completely. ASMlib is a small set of extensions, in particular to make device management easier but there are no extra features exposed through Oracle ASM with ASMLib enabled or disabled. Often customers confuse ASMLib with ASM. again, ASM exists on every Oracle supported OS and on every supported Linux OS, SLES, RHEL, OL withoutASMLib Oracle ASMLib userspace is available for OTN and the kernel module is shipped along with OL/UEK for every build and by SuSE for SLES for every of their builds ASMLib kernel module was built by us for RHEL4 and RHEL5 but we do not build it for RHEL6, nor for the OL6 RHCK kernel. Only for UEK ASMLib for Linux is/was a reference implementation for any third party vendor to be able to offer, if they want to, their own version for their own OS or storage ASMLib as provided by Oracle for Linux continues to be enhanced and evolve and for the kernel module we use UEK as the base OS kernel hope this helps.

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  • What alternatives do I have if I want a distributed multi-master database?

    - by Jonas
    I will build a system where I want to reduce single-point-of-failures, and I need a database. Is there any (free) relational database systems that can handle multi-master setups good (i.e where it is easy to add and remove nodes) or is it better to go with a NoSQL-database? As what I have understood, a key-value store will handle this better. What database system do you recommend for a multi-master (cluster) setup?

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  • Are Multi-column Primary Keys in MySQL a optimisation problem?

    - by David
    Been looking into using multi-column primary keys and as performance is extremely important with the size of traffic and database I need to know if there is anything to consider before I start throwing out the unique ID method on many of my tables and start using mulit column primary keys. So, what are the performance/optimisation pros/cons to using multi column primary keys versus a basic single column, auto-inc primary key?

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  • Python: Multi list comprehension, is there such an unwieldy beast of prey ?

    - by bandana
    consider the following python 'code'. it demonstrates the concept of a multi-list comprehension: start = ['a', 'b', 'c'] middle = ['r', 'a', 'a'] finish = ['t', 'r', 't'] l = [s.upper() + m + f for s in start, m in middle, e in finish] >>> print l ['Art', 'Bar', 'Cat'] Alas, the above code does not work in python. What would be a good approximation of multi-list comprehension in python? Please discuss what happens when the lists have different lengths.

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