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  • Understanding linear linked list

    - by ArtWorkAD
    Hi, I have some problems understanding the linear linked list data structure. This is how I define a list element: class Node{ Object data; Node link; public Node(Object pData, Node pLink){ this.data = pData; this.link = pLink; } } To keep it simple we say that a list are linked nodes so we do not need to define a class list (recursion principle). My problem is that I am really confused in understanding how nodes are connected, more precisely the sequence of the nodes when we connect them. Node n1 = new Node(new Integer(2), null); Node n2 = new Node(new Integer(1), n1); What is link? Is it the previous or the next element? Any other suggestions to help me understanding this data structure?

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  • How to detect if breaking an edge will make a graph disjoint?

    - by the_graph_guy
    I have a graph that starts off with a single, root node. Nodes are added one by one to the graph. At node creation time, they have to be linked either to the root node, or to another node, by a single edge. Edges can also be created and deleted (one by one, between any two nodes). Nodes can be deleted one at a time. Node and edge creation, deletion operations can happen in any arbitrary order. OK, so here's my question: When an edge is deleted, is it possible do determine, in constant time (i.e. with an O(1) algorithm), if doing this will divide the graph into two disjoint subgraphs? If it will, then which side of the edge will the root node belong? I'm willing to maintain, within reasonable limits, any additional data structure that can facilitate the derivation of this information. Maybe it is not possible to do it in O(1), if so any pointers to literature will be appreciated.

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  • i need help to designe code in c++

    - by user344987
    ) Design and implement a Graph data structure. Use adjacency matrix to implement the unweighted graph edges. The Graph must support the following operations: 1.Constructor 2.Destructor 3.Copy constructor 4.A function to add an edge between two nodes in the graph 5.A display function that outputs all the edges of the graph 6.A function edge that accepts two nodes, the function returns true if there is an edge between the passed nodes, and returns false otherwise. B.(100 points) Depth first search and Breadth first search functions. C.(100 points) A function to output a spanning tree of the graph, use any algorithm you find appropriate, also, make the necessary changes on the data structure in A to implement your algorithm.

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  • Duplicate array but maintain pointer links

    - by St. John Johnson
    Suppose I have an array of nodes (objects). I need to create a duplicate of this array that I can modify without affecting the source array. But changing the nodes will affect the source nodes. Basically maintaining pointers to the objects instead of duplicating their values. // node(x, y) $array[0] = new node(15, 10); $array[1] = new node(30, -10); $array[2] = new node(-2, 49); // Some sort of copy system $array2 = $array; // Just to show modification to the array doesn't affect the source array array_pop($array2); if (count($array) == count($array2)) echo "Fail"; // Changing the node value should affect the source array $array2[0]->x = 30; if ($array2[0]->x == $array[0]->x) echo "Goal"; What would be the best way to do this?

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  • Is there a way to optimise finding text items on a page (not regex)

    - by Jeepstone
    After seeing several threads rubbishing the regexp method of finding a term to match within an HTML document, I've used the Simple HTML DOM PHP parser (http://simplehtmldom.sourceforge.net/) to get the bits of text I'm after, but I want to know if my code is optimal. It feels like I'm looping too many times. Is there a way to optimise the following loop? //Get the HTML and look at the text nodes $html = str_get_html($buffer); //First we match the <body> tag as we don't want to change the <head> items foreach($html->find('body') as $body) { //Then we get the text nodes, rather than any HTML foreach($body->find('text') as $text) { //Then we match each term foreach ($terms as $term) { //Match to the terms within the text nodes $text->outertext = str_replace($term, '<span class="highlight">'.$term.'</span>', $text->outertext); } } } For example, would it make a difference to determine check if I have any matches before I start the loop maybe?

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  • [.net] Treeview prevent Node collapse (weird problem)

    - by cssnoob
    Hey guyz! I have a .net 2.0 C# Project. I have a Treeview with 2 Nodes, each of them has many child nodes. When you click on a child node, a PDF is displayed in a webbrowser control depending on the properties of the node. Fine, but the problem is that when both Nodes are expanded, and I click on a child node, the other node gets collapsed! I don't have any code that collapses any node of the treeview, but somehow it happens! I also had a look at the BeforeCollapse Event, but somehow it doesn't fire, alltough the other node collapses! Can anyone imagine why this happens? I would be very grateful if anyone can teach me how to prevent this happening! Thank you very much!

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  • "[INS-30131] Initial setup required for the execution of installer validations failed." Encountering this error while installing Oracle database 12c. [on hold]

    - by user132992
    I am trying to install Oracle 12c database on my machine running Fedora 20. And I am encountering this problem: "[INS-30131] Initial setup required for the execution of installer validations failed." And when we see the details then it is like this: Cause - Failed to access the temporary location. Action - Ensure that the current user has required permissions to access the temporary location. Additional Information: - Framework setup check failed on all the nodes - Cause: Cause Of Problem Not Available   - Action: User Action Not Available Summary of the failed nodes fedora - Version of exectask could not be retrieved from node "fedora"   - Cause: Cause Of Problem Not Available   - Action: User Action Not Available To eliminate this error I have tried various measures including the change of permission of the tmp folder and restarting the computer but none is working. Plz someone help me out of this. Any kind of help will be appreciated...

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  • C++ FBX Animation Importer Using the FBX SDK

    - by Mike Sawayda
    Does anyone have any experience using the FBX SDK to load in animations. I got the meshes loaded in correctly with all of their verts, indices, UV's, and normals. I am just now trying to get the Animations working correctly. I have looked at the FBX SDK documentation with little help. If someone could just help me get started or point me in the right direction I would greatly appreciate it. I added some code so you can kinda get an idea of what I am doing. I should be able to place that code anywhere in the load FBX function and have it work. //GETTING ANIMAION DATA for(int i = 0; i < scene->GetSrcObjectCount<FbxAnimStack>(); ++i) { FbxAnimStack* lAnimStack = scene->GetSrcObject<FbxAnimStack>(i); FbxString stackName = "Animation Stack Name: "; stackName += lAnimStack->GetName(); string sStackName = stackName; int numLayers = lAnimStack->GetMemberCount<FbxAnimLayer>(); for(int j = 0; j < numLayers; ++j) { FbxAnimLayer* lAnimLayer = lAnimStack->GetMember<FbxAnimLayer>(j); FbxString layerName = "Animation Stack Name: "; layerName += lAnimLayer->GetName(); string sLayerName = layerName; queue<FbxNode*> nodes; FbxNode* tempNode = scene->GetRootNode(); while(tempNode != NULL) { FbxAnimCurve* lAnimCurve = tempNode->LclTranslation.GetCurve(lAnimLayer, FBXSDK_CURVENODE_COMPONENT_X); if(lAnimCurve != NULL) { //I know something needs to be done here but I dont know what. } for(int i = 0; i < tempNode->GetChildCount(false); ++i) { nodes.push(tempNode->GetChild(i)); } if(nodes.size() > 0) { tempNode = nodes.front(); nodes.pop(); } else { tempNode = NULL; } } } } Here is the full function bool FBXLoader::LoadFBX(ParentMeshObject* _parentMesh, char* _filePath, bool _hasTexture) { FbxManager* fbxManager = FbxManager::Create(); if(!fbxManager) { printf( "ERROR %s : %d failed creating FBX Manager!\n", __FILE__, __LINE__ ); } FbxIOSettings* ioSettings = FbxIOSettings::Create(fbxManager, IOSROOT); fbxManager->SetIOSettings(ioSettings); FbxString filePath = FbxGetApplicationDirectory(); fbxManager->LoadPluginsDirectory(filePath.Buffer()); FbxScene* scene = FbxScene::Create(fbxManager, ""); int fileMinor, fileRevision; int sdkMajor, sdkMinor, sdkRevision; int fileFormat; FbxManager::GetFileFormatVersion(sdkMajor, sdkMinor, sdkRevision); FbxImporter* importer = FbxImporter::Create(fbxManager, ""); if(!fbxManager->GetIOPluginRegistry()->DetectReaderFileFormat(_filePath, fileFormat)) { //Unrecognizable file format. Try to fall back on FbxImorter::eFBX_BINARY fileFormat = fbxManager->GetIOPluginRegistry()->FindReaderIDByDescription("FBX binary (*.fbx)"); } bool importStatus = importer->Initialize(_filePath, fileFormat, fbxManager->GetIOSettings()); importer->GetFileVersion(fileMinor, fileMinor, fileRevision); if(!importStatus) { printf( "ERROR %s : %d FbxImporter Initialize failed!\n", __FILE__, __LINE__ ); return false; } importStatus = importer->Import(scene); if(!importStatus) { printf( "ERROR %s : %d FbxImporter failed to import the file to the scene!\n", __FILE__, __LINE__ ); return false; } FbxAxisSystem sceneAxisSystem = scene->GetGlobalSettings().GetAxisSystem(); FbxAxisSystem axisSystem( FbxAxisSystem::eYAxis, FbxAxisSystem::eParityOdd, FbxAxisSystem::eLeftHanded ); if(sceneAxisSystem != axisSystem) { axisSystem.ConvertScene(scene); } TriangulateRecursive(scene->GetRootNode()); FbxArray<FbxMesh*> meshes; FillMeshArray(scene, meshes); unsigned short vertexCount = 0; unsigned short triangleCount = 0; unsigned short faceCount = 0; unsigned short materialCount = 0; int numberOfVertices = 0; for(int i = 0; i < meshes.GetCount(); ++i) { numberOfVertices += meshes[i]->GetPolygonVertexCount(); } Face face; vector<Face> faces; int indicesCount = 0; int ptrMove = 0; float wValue = 0.0f; if(!_hasTexture) { wValue = 1.0f; } for(int i = 0; i < meshes.GetCount(); ++i) { int vertexCount = 0; vertexCount = meshes[i]->GetControlPointsCount(); if(vertexCount == 0) continue; VertexType* vertices; vertices = new VertexType[vertexCount]; int triangleCount = meshes[i]->GetPolygonVertexCount() / 3; indicesCount = meshes[i]->GetPolygonVertexCount(); FbxVector4* fbxVerts = new FbxVector4[vertexCount]; int arrayIndex = 0; memcpy(fbxVerts, meshes[i]->GetControlPoints(), vertexCount * sizeof(FbxVector4)); for(int j = 0; j < triangleCount; ++j) { int index = 0; FbxVector4 fbxNorm(0, 0, 0, 0); FbxVector2 fbxUV(0, 0); bool texCoordFound = false; face.indices[0] = index = meshes[i]->GetPolygonVertex(j, 0); vertices[index].position.x = (float)fbxVerts[index][0]; vertices[index].position.y = (float)fbxVerts[index][1]; vertices[index].position.z = (float)fbxVerts[index][2]; vertices[index].position.w = wValue; meshes[i]->GetPolygonVertexNormal(j, 0, fbxNorm); vertices[index].normal.x = (float)fbxNorm[0]; vertices[index].normal.y = (float)fbxNorm[1]; vertices[index].normal.z = (float)fbxNorm[2]; texCoordFound = meshes[i]->GetPolygonVertexUV(j, 0, "map1", fbxUV); vertices[index].texture.x = (float)fbxUV[0]; vertices[index].texture.y = (float)fbxUV[1]; face.indices[1] = index = meshes[i]->GetPolygonVertex(j, 1); vertices[index].position.x = (float)fbxVerts[index][0]; vertices[index].position.y = (float)fbxVerts[index][1]; vertices[index].position.z = (float)fbxVerts[index][2]; vertices[index].position.w = wValue; meshes[i]->GetPolygonVertexNormal(j, 1, fbxNorm); vertices[index].normal.x = (float)fbxNorm[0]; vertices[index].normal.y = (float)fbxNorm[1]; vertices[index].normal.z = (float)fbxNorm[2]; texCoordFound = meshes[i]->GetPolygonVertexUV(j, 1, "map1", fbxUV); vertices[index].texture.x = (float)fbxUV[0]; vertices[index].texture.y = (float)fbxUV[1]; face.indices[2] = index = meshes[i]->GetPolygonVertex(j, 2); vertices[index].position.x = (float)fbxVerts[index][0]; vertices[index].position.y = (float)fbxVerts[index][1]; vertices[index].position.z = (float)fbxVerts[index][2]; vertices[index].position.w = wValue; meshes[i]->GetPolygonVertexNormal(j, 2, fbxNorm); vertices[index].normal.x = (float)fbxNorm[0]; vertices[index].normal.y = (float)fbxNorm[1]; vertices[index].normal.z = (float)fbxNorm[2]; texCoordFound = meshes[i]->GetPolygonVertexUV(j, 2, "map1", fbxUV); vertices[index].texture.x = (float)fbxUV[0]; vertices[index].texture.y = (float)fbxUV[1]; faces.push_back(face); } meshes[i]->Destroy(); meshes[i] = NULL; int indexCount = faces.size() * 3; unsigned long* indices = new unsigned long[faces.size() * 3]; int indicie = 0; for(unsigned int i = 0; i < faces.size(); ++i) { indices[indicie++] = faces[i].indices[0]; indices[indicie++] = faces[i].indices[1]; indices[indicie++] = faces[i].indices[2]; } faces.clear(); _parentMesh->AddChild(vertices, indices, vertexCount, indexCount); } return true; }

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  • SOA Suite Integration: Part 2: A basic BPEL process

    - by Anthony Shorten
    This is the next in the series about SOA Suite integration with Oracle Utilities Application Framework. One of the first scenarios I am going to illustrate in this series is building a basic BPEL process using Web Service calls to the Oracle Utilities Application Framework. The scenario is this. I will pass in the userid and the BPEL process will call our the AS-User Web Service we created in Part 1. This is just a basic test and illustrate how to import the Web Service into SOA Suite. To use this scenario, you will need access to Oracle SOA Suite, access to a copy of any Oracle Utilities Application Framework based product and Oracle JDeveloper (to build the process). First of all you need to start Oracle JDeveloper and create a new SOA Project to house the BPEL process in. For the purposes of this example I will call the project simpleBPEL and verify that SOA is part of the project. I will select "Composite with BPEL" to denote it as a BPEL process. I can also the same process to create a Mediator or OSB project (refer to the JDeveloper documentation on these technologies). For this example I will use BPEL 1.1 as my specification standard (BPEL 2.0 can also be used if desired). I give the individual BPEL process as simpleBPEL (you can use a different name but I wanted to keep the project and process the same for this example). I will also build a Synchronous BPEL Process as I want a response from the Web Service. I will leave the defaults to save time. I have no have a blank canvas to build my BPEL process against. Note: for simplicity I am going to use as much defaulting as possible. In fact I am not going to specify an input schema for the incoming call as I will use the basic single field used by BPEL as default. The first step is to import the AS-User Web Service into my BPEL project. To do this I use the standard Web Service BPEL component from the Component Palette to import the WSDL into the BPEL project. Now the tricky part (a joke), you drag and drop the component from the Palette onto the right side of the canvas in the Partner Links swim lane. This swim lane is reserved for Partner Links that have a Partner Role (i.e. being called rather than calling). When you drop the Web Service onto the canvas the Create Web Service wizard is invoked to ask for details of the Web Service. At this point you give the BPEL node a name. I have used the name RetrieveUser as a name. I placed the WSDL URL from the XAI Inbound Service screen in the WSDL URL. Once you specify the URL you can press the Find existing WSDL's button to load the information into BPEL from the call. You will notice the Port Type is prefilled with the port from the WSDL. I also suggest that you check copy wsdl and it's dependent artifacts into the project if you intending to work on the BPEL process offline. If you do not check this your target application must be accessible when you work on the BPEL process (that is not always convenient). Note: For the perceptive of you will notice that the URL specified in this example is different to the URL in the last post. The reason is for the demonstrations I shifted to a new server and did not redo all of the past screen captures. If you copy the WSDL into the project you will get an information screen about Localize Files. It is just a confirmation screen. The last confirmation screen is a summary of the partner link (the main tab is locked for editing at this stage). At this stage you have successfully imported the Web Service. To complete the setup of the Web Service you need to set the credentials for the Web Service to use. Refer to the past post on how to do that. Now to use the Web Service. To call the Web Service (as it is just imported not connected to the BPEL process yet), you must add an Invoke action to your BPEL Process. To do this, select Invoke action from the BPEL Constructs zone on the Component Palette and drop it on the edit nodes between the receiveInput and replyOutput nodes This will create an empty Invoke action. You will notice some connectors on the Invoke node. Grab the node closest to your Web Service and drag it to connect the Invoke to your Web Service. This instructs BPEL to use the Invoke to call the Web Service. Once the Invoke action is connected to the Web Service an Edit Invoke edit dialog is displayed. At this point I suggest you name the Invoke node. It is important to name the nodes straightaway and name them appropriately for you to trace the logic. I used InvokeUser as the name in this example. To complete the node configuration you must create Variables to hold the input and output for the call. To do this clock on Automatically Create Input Variable on the Edit Invoke dialog. You will be presented with a default variable name. It uses the node name (that is why it is important to name the node before hitting this button) as a prefix. You can name the variable anything but I usually take the default. Repeat the same for the output variable. You now have a completed node for invoking the service. You have a very basic BPEL process which contains an input, invoke and output node. It is not complete yet though. You need to tell the BPEL process how to pass data from the input to the invoke step and how to take the output from the service call and pass it back to the service. You need to now add an Assign node to assign the input to the Web Service. To do this select Assign activity from BPEL Constructs zone in the Component Palette. Drag and drop the Assign activity between the receiveInput and InvokeUser nodes as you want to pass data between these two nodes. You have now added a new Assign node to your BPEL process Double clicking the node allows you to specify the name of the node. I use AssignUser to describe that I am assigning user data. On the Copy Rules tab you can specify the mapping between the input variable InputVariable/payload/process/input string and the input variable for the Web Service call. We are passing data from the input to BPEL to the relevant input variable on the Web Service. This is simply drag and drop between the two data structures. In the example, I am using the input to pass to the user element in my Web Service as the user is the primary key for the object. The fields become linked (which means data from source will be copied to target). Almost there. You now need to process the output from the Web Service call to the outputVariable of the client call. I have decided to pass back one piece of data, the name associated with the user by concatenating the firstName and lastName elements from the Web Service call. To do this I will use a Transform as it is not just a matter of an Assign action. It is a concatenation operation. This also illustrates how you can use BPEL functionality to transform data from a Web Service call. As with the other components you drag and drop the Transform component to the appropriate place in the BPEL process. In this case we want to transform the output from the Web Service call so we want it after the InvokeUser action and the replyOutput action. The Transform component is actually part of the Oracle Extensions to the BPEL specification. Double clicking the Transform node will allow you to name the node.  In this example I used TransformName. To complete the transform I need to tell the product the source of the transformation and the target of the transform. In the example this is the InvokeUser output variable. I also named the mapper file to TransformName. By clicking the + or pencil icon next to the map I can create the map. The mapping screen is shows the source and target schemas for me to map across. As with the assign I can map the relevant elements. In my example, I first map the firstName from the Web Service to the result element. As I want to concatenate the names, I drop the concat function on the call line. I now attach the last name to the function to indicate the concatenation of the field. By default the names will be concatenated with no space. To make the name legible I add a space between the field by clicking the function and adding a space in the call. I now have a completed mapping. I can now save the whole project as my BPEL process is now complete. As you can see the following happens: We accept input from the client (the userid for the call) in the receiveInput step. We assign that value to the input parameters for the Web Service call in the AssignUser step. We invoke the Web Service call to retrieve the data from the product in the InvokeUser step. We take the output from the InvokeUser step and concatenate the names in the TransformName step. We pass back the data in the replyOutput step. At this point we can deploy the BPEL process to the SOA Suite server. I will not cover this aspect as it really all SOA Suite specific (it is all done via Oracle JDeveloper). Now we need to test the service in SOA Suite. We will use the Fusion Middleware Control test facility. I will assume that credentials have also been setup as per our previous post (else you will get a 401 error). You navigate to the deployed BPEL process within Fusion Middleware Control and select the Test Service option. Specify some test data on the payload at the bottom of the Test Service screen. In my case I am returning my own userid information. On the response tab you will see the result. It works. You can verify the steps using the Audit trace facility on individual calls. As you can see this is a basic BPEL but you get the idea of importing the Web Service is pretty straightforward. You can create more sophisticated BPEL processes using the full facilities in Oracle SOA Suite. I just showed you the basic principals.

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  • Solution 6 : Kill a Non-Clustered Process during Two-Node Cluster Failover

    - by StanleyGu
    Using Visual Studio 2008 and C#, I developed a windows service A and deployed it to two nodes of a windows server 2008 failover cluster. The service A is part of the failover cluster service, which means, when failover occurs at node1, the cluster service will failover the windows service A from node 1 to node 2. One of the tasks implemented by the windows service A is to start, monitor or kill a process B. The process B is installed to the two nodes but is not part of the failover cluster service. When a failover occurs at node1, the cluster service does not failover the process B from node 1 to node 2, and the process B continues running at node1. The requirement is: When failover occurs at node1, we want the process B running at node1 gets killed, but we do not want the process B be part of the failover cluster service. The first idea that pops up immediately is to put some code in an event handler triggered by the failover in the windows service A. The failover effect to the windows service A is similar to using the task manager to kill the process of the windows service A, but there is no event in windows service that can be triggered by killing the process of the window service. The events related to terminating a windows service are OnStop and OnShutDown, but killing the process of windows service A triggers neither of them. The OnStop event can only be triggered by stopping the windows service using Services Control Manager or Services Management Console. Apparently, the first idea is not feasible. The second idea that emerges is to put code into the OnStart event handler of the windows service A. When failover occurs at node 1, the windows service A is killed at node 1 and started at node 2. During the starting, the windows service A at node 2 kills the process B that is running at node 1. It is a workaround and works very well. The C# code implementation within the OnStart event handler is as following: 1.       Capture server names of the two nodes from App.config 2.       Determine server name of the remote node. 3.       Kill the process B running on the remote node. Check here for sample code.  

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  • design pattern advice: graph -> computation

    - by csetzkorn
    I have a domain model, persisted in a database, which represents a graph. A graph consists of nodes (e.g. NodeTypeA, NodeTypeB) which are connected via branches. The two generic elements (nodes and branches will have properties). A graph will be sent to a computation engine. To perform computations the engine has to be initialised like so (simplified pseudo code): Engine Engine = new Engine() ; Object ID1 = Engine.AddNodeTypeA(TypeA.Property1, TypeA.Property2, …, TypeA.Propertyn); Object ID2 = Engine.AddNodeTypeB(TypeB.Property1, TypeB.Property2, …, TypeB.Propertyn); Engine.AddBranch(ID1,ID2); Finally the computation is performed like this: Engine.DoSomeComputation(); I am just wondering, if there are any relevant design patterns out there, which help to achieve the above using good design principles. I hope this makes sense. Any feedback would be very much appreciated.

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  • Dynamically creating astar node map by triangular polygonal map

    - by jett
    My game's map format uses a bunch of triangles to make up the platforms and terrain in 2d. Right now I can set up a 2d array of nodes for the astar algorithm that basically is a bunch of rectangles across the maps x and y that can be set to "wall" if the a* algorithm should try to go around it. However I want a function in the map loader to create the node overlay if the nodes are not specified. I was thinking if more than n percent of the a* rectangle overlaid on map was filled by polygons I could mark that entry in the array as "wall". However I'm stuck on how to do this(or even start) where/when the triangles can be overlapping and also of variable size.

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  • SBUG Session: The Enterprise Cache

    - by EltonStoneman
    [Source: http://geekswithblogs.net/EltonStoneman] I did a session on "The Enterprise Cache" at the UK SOA/BPM User Group yesterday which generated some useful discussion. The proposal was for a dedicated caching layer which all app servers and service providers can hook into, sharing resources and common data. The architecture might end up like this: I'll update this post with a link to the slide deck once it's available. The next session will have Udi Dahan walking through nServiceBus, register on EventBrite if you want to come along. Synopsis Looked at the benefits and drawbacks of app-centric isolated caches, compared to an enterprise-wide shared cache running on dedicated nodes; Suggested issues and risks around caching including staleness of data, resource usage, performance and testing; Walked through a generic service cache implemented as a WCF behaviour – suitable for IIS- or BizTalk-hosted services - which I'll be releasing on CodePlex shortly; Listed common options for cache providers and their offerings. Discussion Cache usage. Different value propositions for utilising the cache: improved performance, isolation from underlying systems (e.g. service output caching can have a TTL large enough to cover downtime), reduced resource impact – CPU, memory, SQL and cost (e.g. caching results of paid-for services). Dedicated cache nodes. Preferred over in-host caching provided latency is acceptable. Depending on cache provider, can offer easy scalability and global replication so cache clients always use local nodes. Restriction of AppFabric Caching to Windows Server 2008 not viewed as a concern. Security. Limited security model in most cache providers. Options for securing cache content suggested as custom implementations. Obfuscating keys and serialized values may mean additional security is not needed. Depending on security requirements and architecture, can ensure cache servers only accessible to cache clients via IPsec. Staleness. Generally thought to be an overrated problem. Thinking in line with eventual consistency, that serving up stale data may not be a significant issue. Good technical arguments support this, although I suspect business users will be harder to persuade. Providers. Positive feedback for AppFabric Caching – speed, configurability and richness of the distributed model making it a good enterprise choice. .NET port of memcached well thought of for performance but lack of replication makes it less suitable for these shared scenarios. Replicated fork – repcached – untried and less active than memcached. NCache also well thought of, but Express version too limited for enterprise scenarios, and commercial versions look costly compared to AppFabric.

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  • Big Data – Operational Databases Supporting Big Data – RDBMS and NoSQL – Day 12 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned the importance of the Cloud in the Big Data Story. In this article we will understand the role of Operational Databases Supporting Big Data Story. Even though we keep on talking about Big Data architecture, it is extremely crucial to understand that Big Data system can’t just exist in the isolation of itself. There are many needs of the business can only be fully filled with the help of the operational databases. Just having a system which can analysis big data may not solve every single data problem. Real World Example Think about this way, you are using Facebook and you have just updated your information about the current relationship status. In the next few seconds the same information is also reflected in the timeline of your partner as well as a few of the immediate friends. After a while you will notice that the same information is now also available to your remote friends. Later on when someone searches for all the relationship changes with their friends your change of the relationship will also show up in the same list. Now here is the question – do you think Big Data architecture is doing every single of these changes? Do you think that the immediate reflection of your relationship changes with your family member is also because of the technology used in Big Data. Actually the answer is Facebook uses MySQL to do various updates in the timeline as well as various events we do on their homepage. It is really difficult to part from the operational databases in any real world business. Now we will see a few of the examples of the operational databases. Relational Databases (This blog post) NoSQL Databases (This blog post) Key-Value Pair Databases (Tomorrow’s post) Document Databases (Tomorrow’s post) Columnar Databases (The Day After’s post) Graph Databases (The Day After’s post) Spatial Databases (The Day After’s post) Relational Databases We have earlier discussed about the RDBMS role in the Big Data’s story in detail so we will not cover it extensively over here. Relational Database is pretty much everywhere in most of the businesses which are here for many years. The importance and existence of the relational database are always going to be there as long as there are meaningful structured data around. There are many different kinds of relational databases for example Oracle, SQL Server, MySQL and many others. If you are looking for Open Source and widely accepted database, I suggest to try MySQL as that has been very popular in the last few years. I also suggest you to try out PostgreSQL as well. Besides many other essential qualities PostgreeSQL have very interesting licensing policies. PostgreSQL licenses allow modifications and distribution of the application in open or closed (source) form. One can make any modifications and can keep it private as well as well contribute to the community. I believe this one quality makes it much more interesting to use as well it will play very important role in future. Nonrelational Databases (NOSQL) We have also covered Nonrelational Dabases in earlier blog posts. NoSQL actually stands for Not Only SQL Databases. There are plenty of NoSQL databases out in the market and selecting the right one is always very challenging. Here are few of the properties which are very essential to consider when selecting the right NoSQL database for operational purpose. Data and Query Model Persistence of Data and Design Eventual Consistency Scalability Though above all of the properties are interesting to have in any NoSQL database but the one which most attracts to me is Eventual Consistency. Eventual Consistency RDBMS uses ACID (Atomicity, Consistency, Isolation, Durability) as a key mechanism for ensuring the data consistency, whereas NonRelational DBMS uses BASE for the same purpose. Base stands for Basically Available, Soft state and Eventual consistency. Eventual consistency is widely deployed in distributed systems. It is a consistency model used in distributed computing which expects unexpected often. In large distributed system, there are always various nodes joining and various nodes being removed as they are often using commodity servers. This happens either intentionally or accidentally. Even though one or more nodes are down, it is expected that entire system still functions normally. Applications should be able to do various updates as well as retrieval of the data successfully without any issue. Additionally, this also means that system is expected to return the same updated data anytime from all the functioning nodes. Irrespective of when any node is joining the system, if it is marked to hold some data it should contain the same updated data eventually. As per Wikipedia - Eventual consistency is a consistency model used in distributed computing that informally guarantees that, if no new updates are made to a given data item, eventually all accesses to that item will return the last updated value. In other words -  Informally, if no additional updates are made to a given data item, all reads to that item will eventually return the same value. Tomorrow In tomorrow’s blog post we will discuss about various other Operational Databases supporting Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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  • PASS 13 Dispatches: moving to the cloud

    - by Tony Davis
    PASS Summit 13, Day 1 keynote by Quentin Clarke and we're hearing about “redefiniing mission critical in the cloud”. With a move to the Windows Azure cloud comes the promise of capacity on demand, automatic HA, backups, patching and so on, as well as passing responsibility to MS for managing hardware, upgrades and so on. However, for many databases and applications the best route to the cloud is not necessarily obvious. For most, the path of least resistance is IaaS – SQL Server in a Azure VM. It removes the hardware burden but you still have to manage your databases and implementing HA for SQL Server is your responsibility. Also, scaling up comes at quite a cost – the biggest VM (8 CPU cores, 56 GB RAM, 16 1TB drives with 500 IOPS each) weighs in at over over $4500 per month. With PaaS, in the form of Windows SQL Database, you get a “3-copies replica set” so HA comes out-of the box, and removes the majority of the administration burden, but you are moving your database into a very different environment. For a start, it's a shared environment, with other customers using the same compute nodes in the cluster, and potentially even sharing the same database (multi-tenancy). Unless you pay for SQL DB Premium edition, the resources available for your workload will depends on how nicely others “play” in the shared environment. You'll potentially need to do a lot of tuning, and application rewriting to avoid throttling issues, optimising application-database communication to deal with increased latency between the two, and so on. You'll need aggressive application caching. You'll also need retry logic and to deal with (expected) node failure and the need to reconnect. In Tuesday's PASS Summit pre-con from the SQLCAT team, they spent a lot of time covering some of the telemetric techniques (collect into Azure storage the necessary monitoring data) to perform capacity planning, work out the hotspots and bottlenecks in your cloud applications. Tools like WAD (Windows Azure Diagnostics), performance counters SQL Database DMVs, and others, will be essential. Of course, to truly exploit the vast horizontal scaling that is available from the existence of thousands of compute nodes, you'll also need to need to consider how to “shard” your data so Azure can move it between nodes at will. Finding the right path to the Cloud isn't easy, but it's coming. I spoke to people one year ago who saw no real benefit in trying to move their infrastructure and databases to the cloud, but now at their company, it's the conversation that won't go away. Tony.  

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  • A deque based on binary trees

    - by Greg Ros
    This is a simple immutable deque based on binary trees. What do you think about it? Does this kind of data structure, or possibly an improvement thereof, seem useful? How could I improve it, preferably without getting rid of its strengths? (Not in the sense of more operations, in the sense of different design) Does this sort of thing have a name? Red nodes are newly instantiated; blue ones are reused. Nodes aren't actually red or anything, it's just for emphasis.

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  • NoSQL Java API for MySQL Cluster: Questions & Answers

    - by Mat Keep
    The MySQL Cluster engineering team recently ran a live webinar, available now on-demand demonstrating the ClusterJ and ClusterJPA NoSQL APIs for MySQL Cluster, and how these can be used in building real-time, high scale Java-based services that require continuous availability. Attendees asked a number of great questions during the webinar, and I thought it would be useful to share those here, so others are also able to learn more about the Java NoSQL APIs. First, a little bit about why we developed these APIs and why they are interesting to Java developers. ClusterJ and Cluster JPA ClusterJ is a Java interface to MySQL Cluster that provides either a static or dynamic domain object model, similar to the data model used by JDO, JPA, and Hibernate. A simple API gives users extremely high performance for common operations: insert, delete, update, and query. ClusterJPA works with ClusterJ to extend functionality, including - Persistent classes - Relationships - Joins in queries - Lazy loading - Table and index creation from object model By eliminating data transformations via SQL, users get lower data access latency and higher throughput. In addition, Java developers have a more natural programming method to directly manage their data, with a complete, feature-rich solution for Object/Relational Mapping. As a result, the development of Java applications is simplified with faster development cycles resulting in accelerated time to market for new services. MySQL Cluster offers multiple NoSQL APIs alongside Java: - Memcached for a persistent, high performance, write-scalable Key/Value store, - HTTP/REST via an Apache module - C++ via the NDB API for the lowest absolute latency. Developers can use SQL as well as NoSQL APIs for access to the same data set via multiple query patterns – from simple Primary Key lookups or inserts to complex cross-shard JOINs using Adaptive Query Localization Marrying NoSQL and SQL access to an ACID-compliant database offers developers a number of benefits. MySQL Cluster’s distributed, shared-nothing architecture with auto-sharding and real time performance makes it a great fit for workloads requiring high volume OLTP. Users also get the added flexibility of being able to run real-time analytics across the same OLTP data set for real-time business insight. OK – hopefully you now have a better idea of why ClusterJ and JPA are available. Now, for the Q&A. Q & A Q. Why would I use Connector/J vs. ClusterJ? A. Partly it's a question of whether you prefer to work with SQL (Connector/J) or objects (ClusterJ). Performance of ClusterJ will be better as there is no need to pass through the MySQL Server. A ClusterJ operation can only act on a single table (e.g. no joins) - ClusterJPA extends that capability Q. Can I mix different APIs (ie ClusterJ, Connector/J) in our application for different query types? A. Yes. You can mix and match all of the API types, SQL, JDBC, ODBC, ClusterJ, Memcached, REST, C++. They all access the exact same data in the data nodes. Update through one API and new data is instantly visible to all of the others. Q. How many TCP connections would a SessionFactory instance create for a cluster of 8 data nodes? A. SessionFactory has a connection to the mgmd (management node) but otherwise is just a vehicle to create Sessions. Without using connection pooling, a SessionFactory will have one connection open with each data node. Using optional connection pooling allows multiple connections from the SessionFactory to increase throughput. Q. Can you give details of how Cluster J optimizes sharding to enhance performance of distributed query processing? A. Each data node in a cluster runs a Transaction Coordinator (TC), which begins and ends the transaction, but also serves as a resource to operate on the result rows. While an API node (such as a ClusterJ process) can send queries to any TC/data node, there are performance gains if the TC is where most of the result data is stored. ClusterJ computes the shard (partition) key to choose the data node where the row resides as the TC. Q. What happens if we perform two primary key lookups within the same transaction? Are they sent to the data node in one transaction? A. ClusterJ will send identical PK lookups to the same data node. Q. How is distributed query processing handled by MySQL Cluster ? A. If the data is split between data nodes then all of the information will be transparently combined and passed back to the application. The session will connect to a data node - typically by hashing the primary key - which then interacts with its neighboring nodes to collect the data needed to fulfil the query. Q. Can I use Foreign Keys with MySQL Cluster A. Support for Foreign Keys is included in the MySQL Cluster 7.3 Early Access release Summary The NoSQL Java APIs are packaged with MySQL Cluster, available for download here so feel free to take them for a spin today! Key Resources MySQL Cluster on-line demo  MySQL ClusterJ and JPA On-demand webinar  MySQL ClusterJ and JPA documentation MySQL ClusterJ and JPA whitepaper and tutorial

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  • Scene Graph Traversing Techniques

    - by Bunkai.Satori
    Scene Graph seems to be the most effective way of representing the game world. The game world usually tends to be as large as the memory and device can handle. In contrast, the screen of the device captures only a fraction of the Game World/Scene Graph. Ideally, I wish to process(update and render) only the visible game objects/nodes on per-frame basis. My question therefore is, how to traverse the scene graph so, that I will focus only on the game notes that are in the camera frustum? How to organize data so that I can easily focus only on the scene graph nodes visible to me? What are techniques to minimize scenegraph traversal time? Is there such way as more effective traversal, or do I have to traverse whole scene graph on per-frame basis?

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  • WebCenter Content shared folders for clustering

    - by Kyle Hatlestad
    When configuring a WebCenter Content (WCC) cluster, one of the things which makes it unique from some other WebLogic Server applications is its requirement for a shared file system.  This is actually not any different then 10g and previous versions of UCM when it ran directly on a JVM.  And while it is simple enough to say it needs a shared file system, there are some crucial details in how those directories are configured. And if they aren't followed, you may result in some unwanted behavior. This blog post will go into the details on how exactly the file systems should be split and what options are required. Beyond documents being stored on the file system and/or database and metadata being stored in the database along with other structured data, there is other information being read and written to on the file system.  Information such as user profile preferences, workflow item state information, metadata profiles, and other details are stored in files.  In addition, for certain processes within WCC, each of the nodes needs to know what the other nodes are doing so they don’t step on each other.  WCC keeps track of this through the use of lock files on the file system.  Because of this, each node of the WCC must have access to the same file system just as they have access to the same database. WCC uses its own locking mechanism using files, so it also needs to have access to those files without file attribute caching and without locking being done by the client (node).  If one of the nodes accesses a certain status file and it happens to be cached, that node might attempt to run a process which another node is already working on.  Or if a particular file is locked by one of the node clients, this could interfere with access by another node.  Unfortunately, when disabling file attribute caching on the file share, this can impact performance.  So it is important to only disable caching and locking on the particular folders which require it.  When configuring WebCenter Content after deploying the domain, it asks for 3 different directories: Content Server Instance Folder, Native File Repository Location, and Weblayout Folder.  And starting in PS5, it now asks for the User Profile Folder. Even if you plan on storing the content in the database, you still need to establish a Native File (Vault) and Weblayout directories.  These will be used for handling temporary files, cached files, and files used to deliver the UI. For these directories, the only folder which needs to have the file attribute caching and locking disabled is the ‘Content Server Instance Folder’.  So when establishing this share through NFS or a clustered file system, be sure to specify those options. For instance, if creating the share through NFS, use the ‘noac’ and ‘nolock’ options for the mount options. For the other directories, caching and locking should be enabled to provide best performance to those locations.   These directory path configurations are contained within the <domain dir>\ucm\cs\bin\intradoc.cfg file: #Server System PropertiesIDC_Id=UCM_server1 #Server Directory Variables IdcHomeDir=/u01/fmw/Oracle_ECM1/ucm/idc/ FmwDomainConfigDir=/u01/fmw/user_projects/domains/base_domain/config/fmwconfig/ AppServerJavaHome=/u01/jdk/jdk1.6.0_22/jre/ AppServerJavaUse64Bit=true IntradocDir=/mnt/share_no_cache/base_domain/ucm/cs/ VaultDir=/mnt/share_with_cache/ucm/cs/vault/ WeblayoutDir=/mnt/share_with_cache/ucm/cs/weblayout/ #Server Classpath variables #Additional Variables #NOTE: UserProfilesDir is only available in PS5 – 11.1.1.6.0UserProfilesDir=/mnt/share_with_cache/ucm/cs/data/users/profiles/ In addition to these folder configurations, it’s also recommended to move node-specific folders to local disk to avoid unnecessary traffic to the shared directory.  So on each node, go to <domain dir>\ucm\cs\bin\intradoc.cfg and add these additional configuration entries: VaultTempDir=<domain dir>/ucm/<cs>/vault/~temp/ TraceDirectory=<domain dir>/servers/<UCM_serverN>/logs/EventDirectory=<domain dir>/servers/<UCM_serverN>/logs/event/ And of course, don’t forget the cluster-specific configuration values to add as well.  These can be added through Admin Server -> General Configuration -> Additional Configuration Variables or directly in the <IntradocDir>/config/config.cfg file: ArchiverDoLocks=true DisableSharedCacheChecking=true ServiceAllowRetry=true    (use only with Oracle RAC Database)PublishLockTimeout=300000  (time can vary depending on publishing time and number of nodes) For additional information and details on clustering configuration, I highly recommend reviewing document [1209496.1] on the support site.  In addition, there is a great step-by-step guide on setting up a WebCenter Content cluster [1359930.1].

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  • What are graphs in laymen's terms

    - by Justin984
    What are graphs, in computer science, and what are they used for? In laymen's terms preferably. I have read the definition on Wikipedia: In computer science, a graph is an abstract data type that is meant to implement the graph and hypergraph concepts from mathematics. A graph data structure consists of a finite (and possibly mutable) set of ordered pairs, called edges or arcs, of certain entities called nodes or vertices. As in mathematics, an edge (x,y) is said to point or go from x to y. The nodes may be part of the graph structure, or may be external entities represented by integer indices or references. but I'm looking for a less formal, easier to understand definition.

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  • Database-as-a-Service on Exadata Cloud

    - by Gagan Chawla
    Note – Oracle Enterprise Manager 12c DBaaS is platform agnostic and is designed to work on Exadata/non-Exadata, physical/virtual, Oracle/non Oracle platforms and it’s not a mandatory requirement to use Exadata as the base platform. Database-as-a-Service (DBaaS) is an important trend these days and the top business drivers motivating customers towards private database cloud model include constant pressure to reduce IT Costs and Complexity, and also to be able to improve Agility and Quality of Service. The first step many enterprises take in their journey towards cloud computing is to move to a consolidated and standardized environment and Exadata being already a proven best-in-class popular consolidation platform, we are seeing now more and more customers starting to evolve from Exadata based platform into an agile self service driven private database cloud using Oracle Enterprise Manager 12c. Together Exadata Database Machine and Enterprise Manager 12c provides industry’s most comprehensive and integrated solution to transform from a typical silo’ed environment into enterprise class database cloud with self service, rapid elasticity and pay-per-use capabilities.   In today’s post, I’ll list down the important steps to enable DBaaS on Exadata using Enterprise Manager 12c. These steps are chalked down based on a recent DBaaS implementation from a real customer engagement - Project Planning - First step involves defining the scope of implementation, mapping functional requirements and objectives to use cases, defining high availability, network, security requirements, and delivering the project plan. In a Cloud project you plan around technology, business and processes all together so ensure you engage your actual end users and stakeholders early on in the project right from the scoping and planning stage. Setup your EM 12c Cloud Control Site – Once the project plan approval and sign off from stakeholders is achieved, refer to EM 12c Install guide and these are some important tips to follow during the site setup phase - Review the new EM 12c Sizing paper before you get started with install Cloud, Chargeback and Trending, Exadata plug ins should be selected to deploy during install Refer to EM 12c Administrator’s guide for High Availability, Security, Network/Firewall best practices and options Your management and managed infrastructure should not be combined i.e. EM 12c repository should not be hosted on same Exadata where target Database Cloud is to be setup Setup Roles and Users – Cloud Administrator (EM_CLOUD_ADMINISTRATOR), Self Service Administrator (EM_SSA_ADMINISTRATOR), Self Service User (EM_SSA_USER) are the important roles required for cloud lifecycle management. Roles and users are managed by Super Administrator via Setup menu –> Security option. For Self Service/SSA users custom role(s) based on EM_SSA_USER should be created and EM_USER, PUBLIC roles should be revoked during SSA user account creation. Configure Software Library – Cloud Administrator logs in and in this step configures software library via Enterprise menu –> provisioning and patching option and the storage location is OMS shared filesystem. Software Library is the centralized repository that stores all software entities and is often termed as ‘local store’. Setup Self Update – Self Update is one of the most innovative and cool new features in EM 12c framework. Self update can be accessed via Setup -> Extensibility option by Super Administrator and is the unified delivery mechanism to get all new and updated entities (Agent software, plug ins, connectors, gold images, provisioning bundles etc) in EM 12c. Deploy Agents on all Compute nodes, and discover Exadata targets – Refer to Exadata discovery cookbook for detailed walkthrough to ensure successful discovery of Exadata targets. Configure Privilege Delegation Settings – This step involves deployment of privilege setting template on all the nodes by Super Administrator via Setup menu -> Security option with the option to define whether to use sudo or powerbroker for all provisioning and patching operations. Provision Grid Infrastructure with RAC Database on Compute Nodes – Software is provisioned in this step via a provisioning profile using EM 12c database provisioning. In case of Exadata, Grid Infrastructure and RAC Database software is already deployed on compute nodes via OneCommand from Oracle, so SSA Administrator just needs to discover Oracle Homes and Listener as EM targets. Databases will be created as and when users request for databases from cloud. Customize Create Database Deployment Procedure – the actual database creation steps are "templatized" in this step by Self Service Administrator and the newly saved deployment procedure will be used during service template creation in next step. This is an important step and make sure you have locked all the required variables marked as locked as ‘Y’ in this table. Setup Self Service Portal – This step involves setting up of zones, user quotas, service templates, chargeback plan. The SSA portal is setup by Self Service Administrator via Setup menu -> Cloud -> Database option and following guided workflow. Refer to DBaaS cookbook for details. You also have an option to customize SSA login page via steps documented in EM 12c Cloud Administrator’s guide Final Checks – Define and document process guidelines for SSA users and administrators. Get your SSA users trained on Self Service Portal features and overall DBaaS model and SSA administrators should be familiar with Self Service Portal setup pieces, EM 12c database lifecycle management capabilities and overall EM 12c monitoring framework. GO LIVE – Announce rollout of Database-as-a-Service to your SSA users. Users can login to the Self Service Portal and request/monitor/view their databases in Exadata based database cloud. Congratulations! You just delivered a successful database cloud implementation project! In future posts, we will cover these additional useful topics around database cloud – DBaaS Implementation tips and tricks – right from setup to self service to managing the cloud lifecycle ‘How to’ enable real production databases copies in DBaaS with rapid provisioning in database cloud Case study of a customer who recently achieved success with their transformational journey from traditional silo’ed environment on to Exadata based database cloud using Enterprise Manager 12c. More Information – Podcast on Database as a Service using Oracle Enterprise Manager 12c Oracle Enterprise Manager 12c Installation and Administration guide, Cloud Administration guide DBaaS Cookbook Exadata Discovery Cookbook Screenwatch: Private Database Cloud: Set Up the Cloud Self-Service Portal Screenwatch: Private Database Cloud: Use the Cloud Self-Service Portal Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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  • Maven Integrated View for NetBeans IDE

    - by Geertjan
    Started working on an oft-heard request from Kirk Pepperdine for an integrated view for multimodule builds for Maven projects in NetBeans IDE, as explained here. I suddenly had some kind of brainwave and solved all the remaining problems I had, by delegating to the LogicalViewProvider's node, instead of the project's node, which means I inherit all the icons, actions, package nodes, and anything else that was originally defined within the original project, in this case for the open source JAnnocessor project: Above, you can see that the Maven submodules can either be edited in-line, i.e., within the parent project, or separately, by opening them in the traditional NetBeans way. Get the module here: http://plugins.netbeans.org/plugin/45180/?show=true Some people out there might be interested in how this is achieved. First, hide the original ModulesNodeFactory in the layer. Then create the following class, which creates what you see in the screenshot above: import java.util.ArrayList; import java.util.List; import javax.swing.event.ChangeListener; import org.netbeans.api.project.Project; import org.netbeans.spi.project.SubprojectProvider; import org.netbeans.spi.project.ui.LogicalViewProvider; import org.netbeans.spi.project.ui.support.NodeFactory; import org.netbeans.spi.project.ui.support.NodeList; import org.openide.nodes.FilterNode; import org.openide.nodes.Node; @NodeFactory.Registration(projectType = "org-netbeans-modules-maven", position = 400) public class ModulesNodeFactory2 implements NodeFactory { @Override public NodeList<?> createNodes(Project prjct) { return new MavenModulesNodeList(prjct); } private class MavenModulesNodeList implements NodeList<Project> { private final Project project; public MavenModulesNodeList(Project prjct) { this.project = prjct; } @Override public List<Project> keys() { return new ArrayList<Project>( project.getLookup(). lookup(SubprojectProvider.class).getSubprojects()); } @Override public Node node(final Project project) { Node node = project.getLookup().lookup(LogicalViewProvider.class).createLogicalView(); return new FilterNode(node, new FilterNode.Children(node)); } @Override public void addChangeListener(ChangeListener cl) { } @Override public void removeChangeListener(ChangeListener cl) { } @Override public void addNotify() { } @Override public void removeNotify() { } } } Considering that there's only about 5 actual statements above, it's pretty amazing how much can be achieved with so little code. The NetBeans APIs really are very cool. Hope you like it, Kirk!

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  • Use CSS Selectors with HtmlUnit

    - by kerry
    HtmlUnit is a great library for performing web integration tests in Java.  But sometimes node traversal can be somewhat cumbersome. Fear not fellow automated tester (good for you!).  I found a great little project on Github that will allow you to query your document for elements via css selectors similar to jQuery. The project is located at https://github.com/chrsan/css-selectors.  You can use Maven to build it, or download 1.0.2 here.  Beware.  I will not be updating this link so I suggest you download the latest code. In any case, you can use it like so: // from HtmlUnit getting started final WebClient webClient = new WebClient(); final HtmlPage page = webClient.getPage("http://htmlunit.sourceforge.net"); final DOMNodeSelector cssSelector = new DOMNodeSelector(page.getDocumentElement()); final Set elements = cssSelector.querySelectorAll("div.section h2"); final Node first = elements.iterator().next(); assertThat(first.getTextContent(), equalTo("HtmlUnit")); The only problem here is that the querySelectAll returns a Set<Node>.  Not HtmlElement like we may want in some cases.   However, if you were to reflect on the Set, you would find that it is indeed a Set of HtmlElement objects. Typically, I like to create a base class for my web tests.  Just for fun, I am using the $ method similar to jQuery. public class WebTestBase { protected WebClient webClient; protected HtmlPage htmlPage; protected void goTo(final String url){ return (HtmlPage)webClient.getPage(url); } protected List $(final String cssSelector) { final DOMNodeSelector cssSelector = new DOMNodeSelector(htmlPage.getDocumentElement()); final Set nodes = cssSelector.querySelectorAll("div.section h2"); // for some reason Set cannot be cast to Set? final List elements = new ArrayList(nodes.size()); for (final Node node : nodes) { elements.add((HtmlElement)node); } return elements; } } Now we can write tests like this: public class LoginWebTest extends WebTestBase { @Test public void login_page_has_instructions() throws Exception { goTo(baseUrl + "/login") assertThat( $("p.instructions").size(), equalTo(1) ); } }

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  • Connectify Dispatch: Link All Your Network Connections into a Super Pipeline

    - by Jason Fitzpatrick
    Connectify Dispatch is a network management tool that takes all the connections around you–Ethernet, Wi-Fi nodes, even 3G/4G cellular connections–and combines them into one giant data pipeline. At its most simple, Connectify Dispatch takes all the network inputs available to your computer (be those connections hard-line Ethernet, Wi-Fi nodes, or cellular connections) and merges the separate data connections seamlessly into one master connection. If any of the connections should falter (like your 3G reception goes out), Connectify automatically shifts the data to other available networks without any interruption. In addition you can specify which network Connectify should favor with connection prioritization; perfect for using your cellular connection without breaking through your data cap for the month right away. Hit up the link below to read more about Connectify Dispatch and the companion app Connectify Hotspot. Connectify Dispatch Secure Yourself by Using Two-Step Verification on These 16 Web Services How to Fix a Stuck Pixel on an LCD Monitor How to Factory Reset Your Android Phone or Tablet When It Won’t Boot

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  • Big Data – Buzz Words: What is HDFS – Day 8 of 21

    - by Pinal Dave
    In yesterday’s blog post we learned what is MapReduce. In this article we will take a quick look at one of the four most important buzz words which goes around Big Data – HDFS. What is HDFS ? HDFS stands for Hadoop Distributed File System and it is a primary storage system used by Hadoop. It provides high performance access to data across Hadoop clusters. It is usually deployed on low-cost commodity hardware. In commodity hardware deployment server failures are very common. Due to the same reason HDFS is built to have high fault tolerance. The data transfer rate between compute nodes in HDFS is very high, which leads to reduced risk of failure. HDFS creates smaller pieces of the big data and distributes it on different nodes. It also copies each smaller piece to multiple times on different nodes. Hence when any node with the data crashes the system is automatically able to use the data from a different node and continue the process. This is the key feature of the HDFS system. Architecture of HDFS The architecture of the HDFS is master/slave architecture. An HDFS cluster always consists of single NameNode. This single NameNode is a master server and it manages the file system as well regulates access to various files. In additional to NameNode there are multiple DataNodes. There is always one DataNode for each data server. In HDFS a big file is split into one or more blocks and those blocks are stored in a set of DataNodes. The primary task of the NameNode is to open, close or rename files and directory and regulate access to the file system, whereas the primary task of the DataNode is read and write to the file systems. DataNode is also responsible for the creation, deletion or replication of the data based on the instruction from NameNode. In reality, NameNode and DataNode are software designed to run on commodity machine build in Java language. Visual Representation of HDFS Architecture Let us understand how HDFS works with the help of the diagram. Client APP or HDFS Client connects to NameSpace as well as DataNode. Client App access to the DataNode is regulated by NameSpace Node. NameSpace Node allows Client App to connect to the DataNode based by allowing the connection to the DataNode directly. A big data file is divided into multiple data blocks (let us assume that those data chunks are A,B,C and D. Client App will later on write data blocks directly to the DataNode. Client App does not have to directly write to all the node. It just has to write to any one of the node and NameNode will decide on which other DataNode it will have to replicate the data. In our example Client App directly writes to DataNode 1 and detained 3. However, data chunks are automatically replicated to other nodes. All the information like in which DataNode which data block is placed is written back to NameNode. High Availability During Disaster Now as multiple DataNode have same data blocks in the case of any DataNode which faces the disaster, the entire process will continue as other DataNode will assume the role to serve the specific data block which was on the failed node. This system provides very high tolerance to disaster and provides high availability. If you notice there is only single NameNode in our architecture. If that node fails our entire Hadoop Application will stop performing as it is a single node where we store all the metadata. As this node is very critical, it is usually replicated on another clustered as well as on another data rack. Though, that replicated node is not operational in architecture, it has all the necessary data to perform the task of the NameNode in the case of the NameNode fails. The entire Hadoop architecture is built to function smoothly even there are node failures or hardware malfunction. It is built on the simple concept that data is so big it is impossible to have come up with a single piece of the hardware which can manage it properly. We need lots of commodity (cheap) hardware to manage our big data and hardware failure is part of the commodity servers. To reduce the impact of hardware failure Hadoop architecture is built to overcome the limitation of the non-functioning hardware. Tomorrow In tomorrow’s blog post we will discuss the importance of the relational database in Big Data. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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