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• Translate an IQueryable instance to LINQ syntax in a string

  - by James Dunne

  I would like to find out if anyone has existing work surrounding formatting an IQueryable instance back into a LINQ C# syntax inside a string. It'd be a nice-to-have feature for an internal LINQ-to-SQL auditing framework I'm building. Once my framework gets the IQueryable instance from a data repository method, I'd like to output something like: This LINQ query: from ce in db.EiClassEnrollment join c in db.EiCourse on ce.CourseID equals c.CourseID join cl in db.EiClass on ce.ClassID equals cl.ClassID join t in db.EiTerm on ce.TermID equals t.TermID join st in db.EiStaff on cl.Instructor equals st.StaffID where (ce.StudentID == studentID) && (ce.TermID == termID) && (cl.Campus == campusID) select new { ce, cl, t, c, st }; Generates the following LINQ-to-SQL query: DECLARE @p0 int; DECLARE @p1 int; DECLARE @p2 int; SET @p0 = 777; SET @p1 = 778; SET @p2 = 779; SELECT [t0].[ClassEnrollmentID], ..., [t4].[Name] FROM [dbo].[ei_ClassEnrollment] AS [t0] INNER JOIN [dbo].[ei_Course] AS [t1] ON [t0].[CourseID] = [t1].[CourseID] INNER JOIN [dbo].[ei_Class] AS [t2] ON [t0].[ClassID] = [t2].[ClassID] INNER JOIN [dbo].[ei_Term] AS [t3] ON [t0].[TermID] = [t3].[TermID] INNER JOIN [dbo].[ei_Staff] AS [t4] ON [t2].[Instructor] = [t4].[StaffID] WHERE ([t0].[StudentID] = @p0) AND ([t0].[TermID] = @p1) AND ([t2].[Campus] = @p2) I already have the SQL output working as you can see. I just need to find a way to get the IQueryable to translate into a string representing its original LINQ syntax (with an acceptable translation loss). I'm not afraid of writing it myself, but I'd like to see if anyone else has done this first.

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• How to do a back-reference on Google AppEngine?

  - by jCuga

  I'm trying to access an object that is linked to by a db.ReferenceProperty in Google app engine. Here's the model's code: class InquiryQuestion(db.Model): inquiry_ref = db.ReferenceProperty(reference_class=GiftInquiry, required=True, collection_name="inquiry_ref") And I am trying to access it in the following way: linkedObject = question.inquiry_ref and then linkedKey = linkedObject.key but it's not working. Can anyone please help?

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• Dataset Binding stored procedures update/insert/delete

  - by Jin

  Hi all, I am currently having a problem since the DB has been changed. I am using Datasets for a c# application, and there is a user management system. For the security issues, our current DB design is like user log into app. DB returns a session ID On use of any other stored procedures, a session ID must be specified. BUT, the DB didn't request session ID before. since I am using the datasets, I used update/insert/delete stored procedures with "TableAdaptor Configuration Wizard". Bind Commands to Existing Stored Procedures (choose stored procedures to call and specify any reuiqred parameters) Now, it seems like I have to specify session ID for Insert/Update/Delete stored procedures. How do I specify session ID parameter here? It seems like I have to pick one return parameter variable from a select statement. Thanks,

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• Application Role and access second database

  - by lszk

  I have written a script to create an audit trails to my database in a second one db. So far I had no problems during tests on my dev machine from SQL Server Management Studio. Problems started to occurs when I first tried to test my triggers from my application by modyfing data in it. Using profiler I found out, that my audit trails db is not visible in sys.databases, so here lies the problem. The application using an Application Role, so as I found on MSDN, that's why I can't get access to other db on the server. I'm not a DBA. I have no experience with properly settings the security stuff, so please guide me, how can I set the setting for guest account (according to MSDN) to get access to this db? I need to have a record for this database in sys.databases and I need to be able to insert data in this database in all tables. No select, update or delete I need.

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• Get next key-value pair in an object

  - by captainclam

  So, given a key, I want to find the next property in an object. Then, I want to return the value of the NEXT property. I can not rely on the keys to be ordered or sequential (they're uuids). Please see below for trivial example of what I want: var db ={ a: 1, b: 2, c: 3 } var next = function(db, key) { // ??? } next(db, 'a'); // I want 2 next(db, 'b'); // I want 3 I also want a prev() function, but I'm sure it will be the same solution. This seems like such a trivial problem but I can't for the life of me figure out how to do it. Happy for the solution to use underscore.js or be written in coffeescript :)

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• Is fetching data from database a get-method thing?

  - by theva

  I have a small class that I call Viewer. This class is supposed to view the proper layout of each page or something like that... I have a method called getFirstPage, when called the user of this method will get a setting value for which page is currently set as the first page. I have some code here, I think it works but I am not really shure that I have done it the right way: class Viewer { private $db; private $user; private $firstPage; function __construct($db, $user) { $this->db = $db; if(isset($user)) { $this->user = $user; } else { $this->user = 'default'; } } function getFistPage() { $std = $db->prepare("SELECT firstPage FROM settings WHERE user = ':user'"); $std->execute(array(':user' => $user)); $result = $std->fetch(); $this->firstPage = $result['firstPage']; return $this->firstPage; } } My get method is fetching the setting from databse (so far so good?). The problem is that then I have to use this get method to set the private variable firstPage. It seems like I should have a set method to do this, but I cannot really have a set method that just fetch some setting from database, right? Because the user of this object should be able to assume that there already is a setting defined in the object... How should I do that?

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• How to Merge two databases in one in MS SQL Server 2008?

  - by SzamDev

  Hi I have 2 PCs, each one of them has MS SQL Server 2008 installed on it and there is a database with data in it. I need a way that I can move data in my DB from this MS SQL Server to another one (another PC which has the same DB) move data from one PC to another one - There is one proplem, the ID column, because each DB in my 2 PCs has data in it so this column counts from 1,2,3,....... ( data will be conflict with other data in my DB ) Is there any way to solve my proplem and move data successfully?

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• Is existed web markup languages with possibility insert sql query?

  - by MercurieVV

  Actually what I want - simple DB with simple User Interface. Like MS Access, but for web and it can be without Dragn n Drop, but described with markup language. For example if I want to create list report, then i need to write something like: <table query="SELECT * from mytable"></table> It needed for simple data applications. In that kind application no programming logic required. Just working with DB. Changing DB data and showing it.

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• Any Way to Use a Join in a Lambda Where() on a Table<>?

  - by lush

  I'm in my first couple of days using Linq in C#, and I'm curious to know if there is a more concise way of writing the following. MyEntities db = new MyEntities(ConnString); var q = from a in db.TableA join b in db.TableB on a.SomeFieldID equals b.SomeFieldID where (a.UserID == CurrentUser && b.MyField == Convert.ToInt32(MyDropDownList.SelectedValue)) select new { a, b }; if(q.Any()) { //snip } I know that if I were to want to check the existence of a value in the field of a single table, I could just use the following: if(db.TableA.Where(u => u.UserID == CurrentUser).Any()) { //snip } But I'm curious to know if there is a way to do the lambda technique, but where it would satisfy the first technique's conditions across those two tables. Sorry for any mistakes or clarity, I'll edit as necessary. Thanks in advance.

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• Displaying Data from a Join in Codeigniter

  - by Brad

  I am using a simple join to pull data from two databases. This is the join in the model function com_control(){ $this->db->select('*'); $this->db->from('comments'); $this->db->join('posts', 'comments.entry_id = posts.id'); $query = $this->db->get(); return $query->result; } My desired method of display is going to be in a table so I am starting out to use like this foreach($comm_control as $row){ $this->table->add_row( $row->entry_id, $row->comments.id, $row->comment, $row->title ); }//end of foreach My problem is the display of data from comments.id. What is the proper format to add the comment.id into the table rows? I need the ID from both tables for display, edit and delete further on in the table. The only display I get at this time for "comment.id" is the word id. The Any help would be appreciated.

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• Both sql LAST_INSERT_ID() and PHP insert_id return 0

  - by jakubplus

  I've been searching google a lot for this issue and really found nothing. People just keep copying MySQL documentation on last_insert_id and nothing else. I've got an issue regarding last_insert_id, because for both situations (php & sql) it returns 0. YES: I've set a PRIMARY & UNIQUE field with AUTO_INCREMENT value YES: i've done some inserting before NO: Making double query with INSERT AND SELECT LAST... doesn't work. I've created a class Db for maintaining connection & query: class Db { public function connect() { $db = new mysqli('','','','',''); ... return $db; } public function insert() { $this->connect()->query("INSERT INTO bla bla..."); return $this->connect()->insert_id; } } And it doesn't work.

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• Cannot insert into SQLite database through php PDO

  - by user323941

  Pls help see what is wrong.... (I test the db connection is fine) <?php $user_name=$_POST['user_name']; $password=$_POST['password']; $dbh=new PDO('sqlite:./db/user.db') or die("fail to connect db"); try{ $stmt = $dbh->prepare("INSERT INTO user_info VALUES (?, ?)"); $stmt->bindParam(1, $a); $stmt->bindParam(2, $b); $a=$user_name; $b=$password; $stmt->execute(); } catch(PDOException $e) {echo $e->getMessage();} ?>

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• If I can't use datacontext in a static

  - by Richard77

  Hello, I've got this public static class MyClassHelper { DataContex db = new DataContext(); public static Type MyMethod() { //Do Something with db // such as db.myTable } } I'm getting the following error: "An object reference is required for the non-static field, method or property..." Is there anyway to get around this? How about this. I've an object that contains only integers, which is fine for all the internal functionings as it allows me to link tables. But occasionaly, I need to display some information to the user. That's why, I'd like to create a static method so it would read the integer, look up in the DB, and display a name instead of a number. I want it to be a static method so that I can use it in my View template. Thanks for helping

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• get value from database based on array in codeigniter

  - by Developer

  I have an array $user = array([0]=>1 [1]=>2 [2]=>3) which contains id's of certain users. I need to get the countries of these users from database. foreach($userid as $user){ $this->db->select('country'); $this->db->where('user_id',$user); $this->db->from('company'); $usercountry = $this->db->get(); $count = $usercountry->row(); $country = $count->country; } Suppose user1 has country ES, user2 has IN, user3 has US, user4 has UK. then if array contains 1,2,3. Then i need to get the countries ES,IN,US.

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• Resolve property at runtime. C#

  - by user1031381

  I have some class which have some code public IEnumerable<TypeOne> TypeOne { get { if (db != null) { var col = db.Select<TypeOne>(); if (col.Count > 0) return col; } return db2.TypeOne; } } public IEnumerable<TypeTwo> TypeTwo { get { if (db != null) { var col = db.Select<TypeTwo>(); if (col.Count > 0) return col; } return db2.TypeTwo; } } So as You can see there is a lot of duplicated Code and there are same property name and item type of enumerable. I want to call some property of object like "obj.MyProp". And MyProp must be resolved at runtime with some generic or non-generic method. Is it possible?

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• iOS AS3 AIR local storage

  - by Kere Puki

  I am developing an app which requires a SQL DB on the device. I am using the File.applicationStorageDirectory and folder.resolvePath to add a new DB. When debugging the app it all looks like it executes correctly and I am able to successfully create a new table. I haven't gone too far with inserting and reading records however I just wanted to ask, when I re-run the app does the existing DB file get replaced with a new empty one? If so do I need to check if the file exists etc. How can I look at the DB on the device (iOS at this stage)? Thanks

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• LINQ to SQL, how to write a method which checks if a row exists when we have multiple tables

  - by Beles

  Hi, I'm trying to write a method in C# which can take as parameter a tabletype, column and a columnvalue and check if the got a row with a with value the method looks like: public object GetRecordFromDatabase(Type tabletype, string columnname, string columnvalue) I'm using LINQ to SQL and need to to this in a generic way so I don't need to write each table I got in the DB. I have been doing this so far for each table, but with more than 70 of these it becomes cumbersome and boring to do. Is there a way to generate the following code dynamically, And swap out the hardcoded tablenames with the values from the parameterlist? In this example I have a table in the DB named tbl_nation, which the DataContext pluralizes to tbl_nations, and I'm checking the column for the value if (DB.tbl_nations.Count(c => c.code.Equals(columnvalue)) == 1) { return DB.tbl_nations.Single(c => c.code.Equals(columnvalue)); }

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• This query show me with this active record

  - by New Kid

  I am having trouble getting two tables and passing them to controller: IN A MODEL: function get_all_entries() { $query = $this->db->get('entry'); return $query->result(); $this->db->select('entry_id , count(comment_id) as total_comment'); $this->db->group_by('entry_id'); $comment = $this->db->get('comment'); return $comment->result(); } IN A CONTROLLER: $data['query'] = $this->blog_model->get_all_entries(); $this->load->view('blog/index',$data); How do I return $query and $comment variables to controller? I think I am doing it wrong.

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• Can SQLite file copied successfully on the data folder of an unrooted android device ?

  - by student

  I know that in order to access the data folder on the device, it needs to be rooted. However, if I just want to copy the database from my assets folder to the data folder on my device, will the copying process works on an unrooted phone? The following is my Database Helper class. From logcat, I can verify that the methods call to copyDataBase(), createDataBase() and openDataBase() are returned successfully. However, I got this error message android.database.sqlite.SQLiteException: no such table: TABLE_NAME: when my application is executing rawQuery. I'm suspecting the database file is not copied successfully (cannot be too sure as I do not have access to data folder), yet the method call to copyDatabase() are not throwing any exception. What could it be? Thanks. ps: My device is still unrooted, I hope it is not the main cause of the error. public DatabaseHelper(Context context) { super(context, DB_NAME, null, 1); this.myContext = context; } public void createDataBase() throws IOException{ boolean dbExist = checkDataBase(); String s = new Boolean(dbExist).toString(); Log.d("dbExist", s ); if(dbExist){ //do nothing - database already exist Log.d("createdatabase","DB exists so do nothing"); }else{ this.getReadableDatabase(); try { copyDataBase(); Log.d("copydatabase","Successful return frm method call!"); } catch (IOException e) { throw new Error("Error copying database"); } } } private boolean checkDataBase(){ File dbFile = new File(DB_PATH + DB_NAME); return dbFile.exists(); } private void copyDataBase() throws IOException{ //Open your local db as the input stream InputStream myInput = null; myInput = myContext.getAssets().open(DB_NAME); Log.d("copydatabase","InputStream successful!"); // Path to the just created empty db String outFileName = DB_PATH + DB_NAME; //Open the empty db as the output stream OutputStream myOutput = new FileOutputStream(outFileName); //transfer bytes from the inputfile to the outputfile byte[] buffer = new byte[1024]; int length; while ((length = myInput.read(buffer))>0){ myOutput.write(buffer, 0, length); } //Close the streams myOutput.flush(); myOutput.close(); myInput.close(); } public void openDataBase() throws SQLException{ //Open the database String myPath = DB_PATH + DB_NAME; myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READONLY); } /* @Override public synchronized void close() { if(myDataBase != null) myDataBase.close(); super.close(); }*/ public void close() { // NOTE: openHelper must now be a member of CallDataHelper; // you currently have it as a local in your constructor if (myDataBase != null) { myDataBase.close(); } } @Override public void onCreate(SQLiteDatabase db) { } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { } }

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• Is it possible to set path of database for delayed job in rails?

  - by WitchOfCloud

  Now, I am developing with mailing system with delayed_jobs gem. When I ran on developing environment, it operated well. But, after deploying application on server, it is not acted. This is my database.yml development: adapter: sqlite3 database: db/development.sqlite3 pool: 5 timeout: 5000 test: adapter: sqlite3 database: db/test.sqlite3 pool: 5 timeout: 5000 production: adapter: sqlite3 database: /var/www/service/shared/db/production.sqlite3 pool: 5 timeout: 5000 I checked queue(in /var/www/...) and it act well. Also, I started delayed_jobs(rake jobs:work). So, I think that problem is delayed_job crawl db/development.sqlite3 How can solve this problem?

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• Path Inclusion/Global variable not working?

  - by Dan LaManna

  Simply put, my config file includes my database class, and the config file has in it: global $db; $db = new database(DB_HOST, DB_NAME, DB_USER, DB_PASS); That file is root/config.php Moving on to root/functions/func.newpage.php doesn't have any includes/requires, and uses $db-classfunction since the file I'm working with: root/newpage.php - requires the config file, as well as func.newpage.php. However I still come up with: Undefined variable db. Anything you guys are seeing I'm not? Thanks! Let me know if more details are needed.

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• Begin the Clone Wars Have!

  - by Antony Reynolds

  Creating a New Virtual Machine from an Existing Virtual Disk In previous posts I described how I set up an OEL6 machine under VirtualBox that can run an 11gR2 database and FMW 11.1.1.5.  That is great if you want the DB and FMW running in the same virtual image and it has served me well for some proof of concepts and also for some testing of different JVMs.  However I also wanted to run some testing of FMW with the database running on a separate physical machine.  So in this post I will show how to take a VirtualBox image and create a new image based on the disks from that original image. What are my Options? There is more than one way to skin a cat, or in this case to create two separate VMs that can run on different hardware.  Some of the options include: Create new virtual disk images for each new VM. Clone the existing disk images and point the new VM at the cloned images. Point the new VM at the existing snapshots. #1 is too much like hard work, install OEL twice, install a database again, install FMW again, run RCU again!  Life is too short! #2 is probably the safest way of doing things.  VirtualBox allows you to clone a disk image for use in a separate machine.  However this of course duplicates the disk and means that it is now occupying 3 times the space, once for the original disk and twice more for the two clones I would need. #3 is the most space efficient way of doing things.  It does mean however that I can only run the new “cloned” images if I have access to the original image because that is where the base snapshots reside.  However this is not a problem for me as long as I remember to keep all threee images together.  So this is the approach we will follow. Snapshot, What Snapshot? As we are going to create new virtual machines based on existing snapshots we need to figure out which snapshot to use.  We do this by opening the “Media Manager” from within VirtualBox and moving the mouse over the snapshot images until we find the snapshots we want – the snapshot name is identified in the “Attached to:” comment.  In my case I wanted the FMW installed snapshot because that had a database configured for FMW alongside the FMW software.  I made a note of the filename of that snapshot (actually I just noted the first 5 characters as that was all that was needed to uniquely identify the snapshot file). When we create the new machines we will point them at the snapshot filename we have just checked. Network or NotWork? Because we want the two new machines to communicate with each other when hosted in different physical machines we can’t use the default NAT networking mode without a lot of hassle.  But at the same time we need them to have fixed IP addresses relative to each other so that they can see each other whilst also being able to see the outside world. To achieve all these requirements I created two network adapters for each machine.  Adapter 1 was a standard NAT mapping.  This will allow each machine to get a dynamic IP address (10.0.2.15 by default) that can be used to access the external world through the VBox provided NAT gateway.  This is the same as the existing configuration. The second adapter I created as a bridged adapter.  This gives the virtual machine direct access to the host network card and by using fixed IP addresses each machine can see the other.  It is important to choose fixed IP addresses that are not routable across your internal network so you don’t get any clashes with other machines on your network.  Of course you could always get proper fixed IP addresses from your network people, but I have serveral people using my images and as long as I don’t have two instances of the same VM on the same network segment this is easier and avoids reconfiguring the network every time someone wants a copy of my VM.  If it is available I would suggest using the 10.0.3.* network as 10.0.2.* is the default NAT network.  You can check availability by pinging 10.0.3.1 and 10.0.3.2 from your host machine.  If it times out then you are probably safe to use that. Creating the New VMs Now that I had collected the data that I needed I went ahead and created the new VMs. When asked for a “Boot Hard Disk” I used the “Choose a virtual hard disk file…” link to find the snapshot I had previously selected and set that to be the existing hard disk.  I chose the previously existing SOA 11.1.1.5 install for both the new DB and FMW machines because that snapshot had the database with the RCU completed that I wanted for my DB machine and it had the SOA software installed which I wanted for my FMW machine. After the initial creation of the virtual machine go into the network setting section and enable a second adapter which will be bridged.  Make a note of the MAC addresses (the last four digits should be sufficient) of the two adapters so that you can later set the bridged adapter to use fixed IP and the NAT adapter to use DHCP. We are now ready to start the VMs and reconfigure Linux. Reconfiguring Linux Because I now have two new machines I need to change their network configuration.  In particular I need to change the hostname, update the hosts file and change the network settings. Changing the Hostname I renamed both hosts by running the hostname command as root: hostname vboxfmw.oracle.com I also edited the /etc/sysconfig file and set the correct hostname in there. HOSTNAME=vboxfmw.oracle.com Changing the Network Settings I needed to change the network configuration to give the bridged network a fixed IP address.  I first explicitly set the MAC addresses of the two adapters, because the order of the virtual adapters in the VirtualBox Manager is not necessarily the same as the order of the adapters in the guest OS.  So I went in to the System->Preferences->Network Connections screen and explicitly set the “Device MAC address” for the two adapters. Having correctly mapped the Linux adapters to the VirtualBox adapters I then set the Bridged adapter to use fixed IP addressing rather than DHCP.  There is no need for additional routing or default gateways because we expect the two machine to be on the same LAN segment. Updating the Hosts File Having renamed the machines and reconfigured the network I then updated the /etc/hosts file to refer to the new machine name add a new line to the hosts file to provide an additional IP address for my server (the new fixed IP address) add a new line for the fixed IP address of the other virtual machine 10.0.3.101      vboxdb.oracle.com       vboxdb  # Added by NetworkManager 10.0.2.15       vboxdb.oracle.com       vboxdb  # Added by NetworkManager 10.0.3.102      vboxfmw.oracle.com      vboxfmw # Added by NetworkManager 127.0.0.1       localhost.localdomain   localhost ::1     vboxdb.oracle.com       vboxdb  localhost6.localdomain6 localhost6 To make sure everything takes effect I restarted the server. Reconfiguring the Database on the DB Machine Because we changed the hostname the listener and the EM console no longer start so I need to modify the listener.ora to use the new hostname and I also need to rebuild the EM configuration because it also relies on the hostname. I edited the $ORACLE_HOME/network/admin/listener.ora and changed the listening address to the new hostname:       (ADDRESS = (PROTOCOL = TCP)(HOST = vboxdb.oracle.com)(PORT = 1521)) After changing the listener.ora I was able to start the listener using: lsnrctl start I also had to reconfigure the EM database control.  I first deconfigured it using the command: emca -deconfig dbcontrol db -repos drop This drops the repository and removes any existing registered dbcontrols. I then re-configured it using the following command: emca -config dbcontrol db -repos create This creates the EM repository and then configures and starts dbcontrol. Now my database machine is ready so I can close it down and take a snapshot. Disabling the Database on the FMW Machine I set up the database to start automatically by creating a service called “dbora”.  On the FMW machine I do not need the database running so I can prevent it auto-starting by running the following command: chkconfig –del dbora Note that because I am using a snapshot it is not a waste of disk space to have the DB installed but not used.  As long as I don’t run it, it won’t cost me anything. I can now close the FMW machine down and take a snapshot. Creating a New Domain The FMW machine is now ready to create a new domain.  When creating the domain I can point it at the second machine which is running the database.  I can potentially run these machines on two separate physical machines as long as I have the original virtual machine available to both of the physical machines. Gotchas in Snapshotting VirtualBox does not support the concept of linked machines in a network like some virtualization technologies so when creating a snapshot it is a good idea to shut both VMs down and then take a snapshot on both of them.  This is because we want to keep the database in sync with the middleware.  One way to make sure that this happens would be to place all the domain configuration files on the database server via an NFS share, this would mean that all we would need to snapshot would be the database machine because that would hold all the state and configuration. The Sky’s the Limit We have covered a simple case of having just two machines.  I have a more complicated configuration in which two machine run a RAC database off the same base OS image, and two more machines run a SOA cluster based on the same OS image.  Just remember what machine holds state and what are the consequences of taking a snapshot.

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• Clustering Basics and Challenges

  - by Karoly Vegh

  For upcoming posts it seemed to be a good idea to dedicate some time for cluster basic concepts and theory. This post misses a lot of details that would explode the articlesize, should you have questions, do not hesitate to ask them in the comments.  The goal here is to get some concepts straight. I can't promise to give you an overall complete definitions of cluster, cluster agent, quorum, voting, fencing, split brain condition, so the following is more of an explanation. Here we go. -------- Cluster, HA, failover, switchover, scalability -------- An attempted definition of a Cluster: A cluster is a set (2+) server nodes dedicated to keep application services alive, communicating through the cluster software/framework with eachother, test and probe health status of servernodes/services and with quorum based decisions and with switchover/failover techniques keep the application services running on them available. That is, should a node that runs a service unexpectedly lose functionality/connection, the other ones would take over the and run the services, so that availability is guaranteed. To provide availability while strictly sticking to a consistent clusterconfiguration is the main goal of a cluster.  At this point we have to add that this defines a HA-cluster, a High-Availability cluster, where the clusternodes are planned to run the services in an active-standby, or failover fashion. An example could be a single instance database. Some applications can be run in a distributed or scalable fashion. In the latter case instances of the application run actively on separate clusternodes serving servicerequests simultaneously. An example for this version could be a webserver that forwards connection requests to many backend servers in a round-robin way. Or a database running in active-active RAC setup.  -------- Cluster arhitecture, interconnect, topologies -------- Now, what is a cluster made of? Servers, right. These servers (the clusternodes) need to communicate. This of course happens over the network, usually over dedicated network interfaces interconnecting all the clusternodes. These connection are called interconnects.How many clusternodes are in a cluster? There are different cluster topologies. The most simple one is a clustered pair topology, involving only two clusternodes:  There are several more topologies, clicking the image above will take you to the relevant documentation. Also, to answer the question Solaris Cluster allows you to run up to 16 servers in a cluster. Where shall these clusternodes be placed? A very important question. The right answer is: It depends on what you plan to achieve with the cluster. Do you plan to avoid only a server outage? Then you can place them right next to eachother in the datacenter. Do you need to avoid DataCenter outage? In that case of course you should place them at least in different fire zones. Or in two geographically distant DataCenters to avoid disasters like floods, large-scale fires or power outages. We call this a stretched- or campus cluster, the clusternodes being several kilometers away from eachother. To cover really large distances, you probably need to move to a GeoCluster, which is a different kind of animal.  What is a geocluster? A Geographic Cluster in Solaris Cluster terms is actually a metacluster between two, separate (locally-HA) clusters.  -------- Cluster resource types, agents, resources, resource groups -------- So how does the cluster manage my applications? The cluster needs to start, stop and probe your applications. If you application runs, the cluster needs to check regularly if the application state is healthy, does it respond over the network, does it have all the processes running, etc. This is called probing. If the cluster deems the application is in a faulty state, then it can try to restart it locally or decide to switch (stop on node A, start on node B) the service. Starting, stopping and probing are the three actions that a cluster agent does. There are many different kinds of agents included in Solaris Cluster, but you can build your own too. Examples are an agent that manages (mounts, moves) ZFS filesystems, or the Oracle DB HA agent that cares about the database, or an agent that moves a floating IP address between nodes. There are lots of other agents included for Apache, Tomcat, MySQL, Oracle DB, Oracle Weblogic, Zones, LDoms, NFS, DNS, etc.We also need to clarify the difference between a cluster resource and the cluster resource group.A cluster resource is something that is managed by a cluster agent. Cluster resource types are included in Solaris cluster (see above, e.g. HAStoragePlus, HA-Oracle, LogicalHost). You can group cluster resources into cluster resourcegroups, and switch these groups together from one node to another. To stick to the example above, to move an Oracle DB service from one node to another, you have to switch the group between nodes, and the agents of the cluster resources in the group will do the following:  On node A Shut down the DB Unconfigure the LogicalHost IP the DB Listener listens on unmount the filesystem   Then, on node B: mount the FS configure the IP  startup the DB -------- Voting, Quorum, Split Brain Condition, Fencing, Amnesia -------- How do the clusternodes agree upon their action? How do they decide which node runs what services? Another important question. Running a cluster is a strictly democratic thing.Every node has votes, and you need the majority of votes to have the deciding power. Now, this is usually no problem, clusternodes think very much all alike. Still, every action needs to be governed upon in a productive system, and has to be agreed upon. Agreeing is easy as long as the clusternodes all behave and talk to eachother over the interconnect. But if the interconnect is gone/down, this all gets tricky and confusing. Clusternodes think like this: "My job is to run these services. The other node does not answer my interconnect communication, it must be down. I'd better take control and run the services!". The problem is, as I have already mentioned, clusternodes very much think alike. If the interconnect is gone, they all assume the other node is down, and they all want to mount the data backend, enable the IP and run the database. Double IPs, double mounts, double DB instances - now that is trouble. Also, in a 2-node cluster they both have only 50% of the votes, that is, they themselves alone are not allowed to run a cluster.  This is where you need a quorum device. According to Wikipedia, the "requirement for a quorum is protection against totally unrepresentative action in the name of the body by an unduly small number of persons.". They need additional votes to run the cluster. For this requirement a 2-node cluster needs a quorum device or a quorum server. If the interconnect is gone, (this is what we call a split brain condition) both nodes start to race and try to reserve the quorum device to themselves. They do this, because the quorum device bears an additional vote, that could ensure majority (50% +1). The one that manages to lock the quorum device (e.g. if it's an FC LUN, it SCSI reserves it) wins the right to build/run a cluster, the other one - realizing he was late - panics/reboots to ensure the cluster config stays consistent.  Losing the interconnect isn't only endangering the availability of services, but it also endangers the cluster configuration consistence. Just imagine node A being down and during that the cluster configuration changes. Now node B goes down, and node A comes up. It isn't uptodate about the cluster configuration's changes so it will refuse to start a cluster, since that would lead to cluster amnesia, that is the cluster had some changes, but now runs with an older cluster configuration repository state, that is it's like it forgot about the changes.  Also, to ensure application data consistence, the clusternode that wins the race makes sure that a server that isn't part of or can't currently join the cluster can access the devices. This procedure is called fencing. This usually happens to storage LUNs via SCSI reservation.  Now, another important question: Where do I place the quorum disk?  Imagine having two sites, two separate datacenters, one in the north of the city and the other one in the south part of it. You run a stretched cluster in the clustered pair topology. Where do you place the quorum disk/server? If you put it into the north DC, and that gets hit by a meteor, you lose one clusternode, which isn't a problem, but you also lose your quorum, and the south clusternode can't keep the cluster running lacking the votes. This problem can't be solved with two sites and a campus cluster. You will need a third site to either place the quorum server to, or a third clusternode. Otherwise, lacking majority, if you lose the site that had your quorum, you lose the cluster. Okay, we covered the very basics. We haven't talked about virtualization support, CCR, ClusterFilesystems, DID devices, affinities, storage-replication, management tools, upgrade procedures - should those be interesting for you, let me know in the comments, along with any other questions. Given enough demand I'd be glad to write a followup post too. Now I really want to move on to the second part in the series: ClusterInstallation.  Oh, as for additional source of information, I recommend the documentation: http://docs.oracle.com/cd/E23623_01/index.html, and the OTN Oracle Solaris Cluster site: http://www.oracle.com/technetwork/server-storage/solaris-cluster/index.html

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• Manage SQL Server Connectivity through Windows Azure Virtual Machines Remote PowerShell

  - by SQLOS Team

  Manage SQL Server Connectivity through Windows Azure Virtual Machines Remote PowerShell Blog This blog post comes from Khalid Mouss, Senior Program Manager in Microsoft SQL Server. Overview The goal of this blog is to demonstrate how we can automate through PowerShell connecting multiple SQL Server deployments in Windows Azure Virtual Machines. We would configure TCP port that we would open (and close) though Windows firewall from a remote PowerShell session to the Virtual Machine (VM). This will demonstrate how to take the advantage of the remote PowerShell support in Windows Azure Virtual Machines to automate the steps required to connect SQL Server in the same cloud service and in different cloud services.  Scenario 1: VMs connected through the same Cloud Service 2 Virtual machines configured in the same cloud service. Both VMs running different SQL Server instances on them. Both VMs configured with remote PowerShell turned on to be able to run PS and other commands directly into them remotely in order to re-configure them to allow incoming SQL connections from a remote VM or on premise machine(s). Note: RDP (Remote Desktop Protocol) is kept configured in both VMs by default to be able to remote connect to them and check the connections to SQL instances for demo purposes only; but not actually required. Step 1 – Provision VMs and Configure Ports   Provision VM1; named DemoVM1 as follows (see examples screenshots below if using the portal):   Provision VM2 (DemoVM2) with PowerShell Remoting enabled and connected to DemoVM1 above (see examples screenshots below if using the portal): After provisioning of the 2 VMs above, here is the default port configurations for example: Step2 – Verify / Confirm the TCP port used by the database Engine By the default, the port will be configured to be 1433 – this can be changed to a different port number if desired.   1. RDP to each of the VMs created below – this will also ensure the VMs complete SysPrep(ing) and complete configuration 2. Go to SQL Server Configuration Manager -> SQL Server Network Configuration -> Protocols for <SQL instance> -> TCP/IP - > IP Addresses   3. Confirm the port number used by SQL Server Engine; in this case 1433 4. Update from Windows Authentication to Mixed mode   5.       Restart SQL Server service for the change to take effect 6.       Repeat steps 3., 4., and 5. For the second VM: DemoVM2 Step 3 – Remote Powershell to DemoVM1 Enter-PSSession -ComputerName condemo.cloudapp.net -Port 61503 -Credential <username> -UseSSL -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) Your will then be prompted to enter the password. Step 4 – Open 1433 port in the Windows firewall netsh advfirewall firewall add rule name="DemoVM1Port" dir=in localport=1433 protocol=TCP action=allow Output: netsh advfirewall firewall show rule name=DemoVM1Port Rule Name:                            DemoVM1Port ---------------------------------------------------------------------- Enabled:                              Yes Direction:                            In Profiles:                             Domain,Private,Public Grouping:                             LocalIP:                              Any RemoteIP:                             Any Protocol:                             TCP LocalPort:                            1433 RemotePort:                           Any Edge traversal:                       No Action:                               Allow Ok. Step 5 – Now connect from DemoVM2 to DB instance in DemoVM1 Step 6 – Close port 1433 in the Windows firewall netsh advfirewall firewall delete rule name=DemoVM1Port Output: Deleted 1 rule(s). Ok. netsh advfirewall firewall show  rule name=DemoVM1Port No rules match the specified criteria.   Step 7 – Try to connect from DemoVM2 to DB Instance in DemoVM1  Because port 1433 has been closed (in step 6) in the Windows Firewall in VM1 machine, we can longer connect from VM3 remotely to VM1. Scenario 2: VMs provisioned in different Cloud Services 2 Virtual machines configured in different cloud services. Both VMs running different SQL Server instances on them. Both VMs configured with remote PowerShell turned on to be able to run PS and other commands directly into them remotely in order to re-configure them to allow incoming SQL connections from a remote VM or on on-premise machine(s). Note: RDP (Remote Desktop Protocol) is kept configured in both VMs by default to be able to remote connect to them and check the connections to SQL instances for demo purposes only; but not actually needed. Step 1 – Provision new VM3 Provision VM3; named DemoVM3 as follows (see examples screenshots below if using the portal): After provisioning is complete, here is the default port configurations: Step 2 – Add public port to VM1 connect to from VM3’s DB instance Since VM3 and VM1 are not connected in the same cloud service, we will need to specify the full DNS address while connecting between the machines which includes the public port. We shall add a public port 57000 in this case that is linked to private port 1433 which will be used later to connect to the DB instance. Step 3 – Remote Powershell to DemoVM1 Enter-PSSession -ComputerName condemo.cloudapp.net -Port 61503 -Credential <UserName> -UseSSL -SessionOption (New-PSSessionOption -SkipCACheck -SkipCNCheck) You will then be prompted to enter the password.   Step 4 – Open 1433 port in the Windows firewall netsh advfirewall firewall add rule name="DemoVM1Port" dir=in localport=1433 protocol=TCP action=allow Output: Ok. netsh advfirewall firewall show rule name=DemoVM1Port Rule Name:                            DemoVM1Port ---------------------------------------------------------------------- Enabled:                              Yes Direction:                            In Profiles:                             Domain,Private,Public Grouping:                             LocalIP:                              Any RemoteIP:                             Any Protocol:                             TCP LocalPort:                            1433 RemotePort:                           Any Edge traversal:                       No Action:                               Allow Ok.   Step 5 – Now connect from DemoVM3 to DB instance in DemoVM1 RDP into VM3, launch SSM and Connect to VM1’s DB instance as follows. You must specify the full server name using the DNS address and public port number configured above. Step 6 – Close port 1433 in the Windows firewall netsh advfirewall firewall delete rule name=DemoVM1Port   Output: Deleted 1 rule(s). Ok. netsh advfirewall firewall show  rule name=DemoVM1Port No rules match the specified criteria.  Step 7 – Try to connect from DemoVM2 to DB Instance in DemoVM1  Because port 1433 has been closed (in step 6) in the Windows Firewall in VM1 machine, we can no longer connect from VM3 remotely to VM1. Conclusion Through the new support for remote PowerShell in Windows Azure Virtual Machines, one can script and automate many Virtual Machine and SQL management tasks. In this blog, we have demonstrated, how to start a remote PowerShell session, re-configure Virtual Machine firewall to allow (or disallow) SQL Server connections. References SQL Server in Windows Azure Virtual Machines   Originally posted at http://blogs.msdn.com/b/sqlosteam/

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• Capistrano asks for SSH password when deploying from local machine to server

  - by GhostRider

  When I try to ssh to a server, I'm able to do it as my id_rsa.pub key is added to the authorized keys in the server. Now when I try to deploy my code via Capistrano to the server from my local project folder, the server asks for a password. I'm unable to understand what could be the issue if I'm able to ssh and unable to deploy to the same server. $ cap deploy:setup "no seed data" triggering start callbacks for `deploy:setup' * 13:42:18 == Currently executing `multistage:ensure' *** Defaulting to `development' * 13:42:18 == Currently executing `development' * 13:42:18 == Currently executing `deploy:setup' triggering before callbacks for `deploy:setup' * 13:42:18 == Currently executing `db:configure_mongoid' * executing "mkdir -p /home/deploy/apps/development/flyingbird/shared/config" servers: ["dev1.noob.com", "176.9.24.217"] Password: Cap script: # gem install capistrano capistrano-ext capistrano_colors begin; require 'capistrano_colors'; rescue LoadError; end require "bundler/capistrano" # RVM bootstrap # $:.unshift(File.expand_path('./lib', ENV['rvm_path'])) require 'rvm/capistrano' set :rvm_ruby_string, 'ruby-1.9.2-p290' set :rvm_type, :user # or :user # Application setup default_run_options[:pty] = true # allow pseudo-terminals ssh_options[:forward_agent] = true # forward SSH keys (this will use your SSH key to get the code from git repository) ssh_options[:port] = 22 set :ip, "dev1.noob.com" set :application, "flyingbird" set :repository, "repo-path" set :scm, :git set :branch, fetch(:branch, "master") set :deploy_via, :remote_cache set :rails_env, "production" set :use_sudo, false set :scm_username, "user" set :user, "user1" set(:database_username) { application } set(:production_database) { application + "_production" } set(:staging_database) { application + "_staging" } set(:development_database) { application + "_development" } role :web, ip # Your HTTP server, Apache/etc role :app, ip # This may be the same as your `Web` server role :db, ip, :primary => true # This is where Rails migrations will run # Use multi-staging require "capistrano/ext/multistage" set :stages, ["development", "staging", "production"] set :default_stage, rails_env before "deploy:setup", "db:configure_mongoid" # Uncomment if you use any of these databases after "deploy:update_code", "db:symlink_mongoid" after "deploy:update_code", "uploads:configure_shared" after "uploads:configure_shared", "uploads:symlink" after 'deploy:update_code', 'bundler:symlink_bundled_gems' after 'deploy:update_code', 'bundler:install' after "deploy:update_code", "rvm:trust_rvmrc" # Use this to update crontab if you use 'whenever' gem # after "deploy:symlink", "deploy:update_crontab" if ARGV.include?("seed_data") after "deploy", "db:seed" else p "no seed data" end #Custom tasks to handle resque and redis restart before "deploy", "deploy:stop_workers" after "deploy", "deploy:restart_redis" after "deploy", "deploy:start_workers" after "deploy", "deploy:cleanup" 'Create symlink for public uploads' namespace :uploads do task :symlink do run <<-CMD rm -rf #{release_path}/public/uploads && mkdir -p #{release_path}/public && ln -nfs #{shared_path}/public/uploads #{release_path}/public/uploads CMD end task :configure_shared do run "mkdir -p #{shared_path}/public" run "mkdir -p #{shared_path}/public/uploads" end end namespace :rvm do desc 'Trust rvmrc file' task :trust_rvmrc do run "rvm rvmrc trust #{current_release}" end end namespace :db do desc "Create mongoid.yml in shared path" task :configure_mongoid do db_config = <<-EOF defaults: &defaults host: localhost production: <<: *defaults database: #{production_database} staging: <<: *defaults database: #{staging_database} EOF run "mkdir -p #{shared_path}/config" put db_config, "#{shared_path}/config/mongoid.yml" end desc "Make symlink for mongoid.yml" task :symlink_mongoid do run "ln -nfs #{shared_path}/config/mongoid.yml #{release_path}/config/mongoid.yml" end desc "Fill the database with seed data" task :seed do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake db:seed" end end namespace :bundler do desc "Symlink bundled gems on each release" task :symlink_bundled_gems, :roles => :app do run "mkdir -p #{shared_path}/bundled_gems" run "ln -nfs #{shared_path}/bundled_gems #{release_path}/vendor/bundle" end desc "Install bundled gems " task :install, :roles => :app do run "cd #{release_path} && bundle install --deployment" end end namespace :deploy do task :start, :roles => :app do run "touch #{current_path}/tmp/restart.txt" end desc "Restart the app" task :restart, :roles => :app do run "touch #{current_path}/tmp/restart.txt" end desc "Start the workers" task :stop_workers do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake resque:stop_workers" end desc "Restart Redis server" task :restart_redis do "/etc/init.d/redis-server restart" end desc "Start the workers" task :start_workers do run "cd #{current_path}; RAILS_ENV=#{default_stage} bundle exec rake resque:start_workers" end end

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