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  • [JAVA] Activity Stream- Producing X amount of objects in a panel on app load

    - by Matthew De'Loughry
    Hi guys, Just wondering if you could help wanting to produce an activity stream in Java, the idea was to have a JLabel and text area followed by a divider be displayed on a screen and then repeated X amount of times according to what data was in a database. What I was wondering is how could I possibly repeat the placing the jlabel, text area, and diveder on the screen above the last rendered objects on the fly and all displayed correctly no matter the size of the text area of each set of object sort of like the image below. Hope I made it clear as I could thanks

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  • Deleting dynamic array of char in C++.

    - by anonymous
    I have this class, with the atribute 'word' class Node { char *word; Inside the Node constructor, I do this asignation: word = new char[strlen(someword)]; In the destructor of the Node class, I try to delete the contents pointed by word: delete []word; I obtain the next message after executing the programs: "Heap block at 003E4F48 modified at 003E4F51 past requested size of 1" What am I not doing well?

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  • Function to get the font and calculate the width of the string not working on first instance

    - by user3627265
    I'm trying to calculate the width of the string based on the font style and size. The user will provide the string, the font style and the font size, and then after giving all the data the user will hit the submit button and the function will trigger. Basically this script works but only when the submit button is hit twice or the font is selected twice,. I mean if you selec DNBlock as a font, it will not work for first time, but the second time you hit submit, it will then work. I'm not sure where is the problem here, but when I used the default font style like Arial, times new roman etc it works perfectly fine. Any Idea on this? I suspected that the font style is not being rendered by the script or something. Correct me if I'm wrong. Thanks //Repeat String String.prototype.repeat = function( num ) { return new Array( num + 1 ).join( this ); } //Calculate the width of string String.prototype.textWidth = function() { var fntStyle = document.getElementById("fntStyle").value; if(fntStyle == "1") { var fs = "DNBlock"; } else if(fntStyle == "2") { var fs = "DNBlockDotted"; } else if(fntStyle == "3") { var fs = "DNCursiveClassic"; } else if(fntStyle == "4") { var fs = "DNCursiveDotted"; } else if(fntStyle == "5") { var fs = "FoundationCursiveDots-Regul"; } var f = document.getElementById("fntSize").value.concat('px ', fs), o = $('<div>' + this + '</div>') .css({'position': 'absolute', 'float': 'left', 'white-space': 'nowrap', 'visibility': 'hidden', 'font': f}) .appendTo($('body')), w = o.width(); o.remove(); return w; } //Trigger the event $("#handwriting_gen").submit(function () { var rptNO = parseInt($('#rptNO').val()); $("[name='txtLine[]']").each(function(){ alert(this.value.repeat(rptNO).textWidth()); if(this.value.repeat(rptNO).textWidth() > 1000) { $(this).focus(); $(this).css({"background-color":"#f6d9d4"}).siblings('span.errorMsg').text('Text is too long.'); event.preventDefault(); } }); });

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  • Creating Java Dialogs

    - by mike_hornbeck
    What would be the easiest way for creating a dialog: - in one window I'm giving data for envelope addressing, also set font type from list of sizes - when clicked OK, in the same window or in next window I get preview of how the envelope would look like with the given names, and used selected font size It should look similarly to this : Should I use Jdialog ? Or will JOptionPane will be enough ? The next step will be to choose color of font and background so I must keep that in mind.

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  • how to see the optimized code in c

    - by sganesh
    I can examine the optimization using profiler, size of the executable file and time to take for the execution. I can get the result of the optimization. But I have these questions, How to get the optimized C code. Which algorithm or method used by C to optimize a code. Thanks in advance.

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  • Present a default window layout on startup in Windows 7

    - by sipickles
    Hello, I have a Win7 PC in use as part of an experiment control system. The experiment in question uses 4 windows simultaneously, and I would like to find away to open, position and size these 4 windows with a script. The script would run at start up, so that the newly booted PC presents the user with the four windows as default. Obviously I can use a batch file in the startup folder to open windows and run applications, but is there a way to specify the layout of these windows? Many thanks Si

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  • Storing Images

    - by Mike
    Hello All, How to Store Large size Images into iPhone Application? Images are taken from UIImagePickerController but saving into Database and retrieving from Database crash the application.

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  • Including huge string in our c++ programs ?

    - by Xinus
    I am trying to include huge string in my c++ programs, Its size is 20598617 characters , I am using #define to achieve it. I have a header file which contains this statement #define "<huge string containing 20598617 characterd>" When I try to compile the program I get error as fatal error C1060: compiler is out of heap space I tried following command line options with no success /Zm200 /Zm1000 /Zm2000 How can I make successful compilation of this program? Platform: Windows 7

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  • Width of Repeating Backgrounds

    - by tdskate
    Hello. What's best, a repeating background of 100px wide so that the actual file doesn't need to be redrawn 1000X times in width, or a 1px file that probably has smaller file size, but the browser will need to redraw it a lot more. Thanks.

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  • accessing a vector from the back

    - by Faken
    Is there a way to access an element on a vector starting from the back? I want to access the second last element.currently I'm using the following to achieve that: myVector[myVector.size() - 2] but this seems slow and clunky, is there a better way?

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  • Resize image to 100% height of a div and keep aspect ratio

    - by belovah
    Here is a quick sketch. I would like to achieve that images in the gallery div will be 100% of the height of the gallery div and keep the aspect ratio AND that images would resize as you would change the size of browser. Is this possible? Any help would be much appreciated. Here is what I made so far: www.nulaena.si/photob/.

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  • Accessing Text Input Field Data

    - by 01010011
    Hi, Using CodeIgniter, how do I access and display text entered into an input field on a view file (see code below) from my controller file? // input_view.php $input_data = array('name' => 'search_field', 'size' => '70'); echo form_input($input_data);

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  • mysql like issue on partial match

    - by ubercooluk
    Im having a mysql query like this SELECT group_name FROM t_groups WHERE group_name LIKE '%PCB%'; The results are group_name ------------ PCB Full size PCB Another query, SELECT group_name FROM t_groups WHERE group_name LIKE '%PCB-123%'; group_name ----------- PCB-123 How can i use a query that will show all the three results ?,I mean i need to get all the results that starts or contains PCB

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  • Scrolling an HTML 5 page using JQuery

    - by nikolaosk
    In this post I will show you how to use JQuery to scroll through an HTML 5 page.I had to help a friend of mine to implement this functionality and I thought it would be a good idea to write a post.I will not use any JQuery scrollbar plugin,I will just use the very popular JQuery Library. Please download the library (minified version) from http://jquery.com/download.Please find here all my posts regarding JQuery.Also have a look at my posts regarding HTML 5.In order to be absolutely clear this is not (and could not be) a detailed tutorial on HTML 5. There are other great resources for that.Navigate to the excellent interactive tutorials of W3School.Another excellent resource is HTML 5 Doctor.Two very nice sites that show you what features and specifications are implemented by various browsers and their versions are http://caniuse.com/ and http://html5test.com/. At this times Chrome seems to support most of HTML 5 specifications.Another excellent way to find out if the browser supports HTML 5 and CSS 3 features is to use the Javascript lightweight library Modernizr.In this hands-on example I will be using Expression Web 4.0.This application is not a free application. You can use any HTML editor you like.You can use Visual Studio 2012 Express edition. You can download it here. Let me move on to the actual example.This is the sample HTML 5 page<!DOCTYPE html><html lang="en">  <head>    <title>Liverpool Legends</title>        <meta http-equiv="Content-Type" content="text/html;charset=utf-8" >        <link rel="stylesheet" type="text/css" href="style.css">        <script type="text/javascript" src="jquery-1.8.2.min.js"> </script>     <script type="text/javascript" src="scroll.js">     </script>       </head>  <body>    <header>        <h1>Liverpool Legends</h1>    </header>        <div id="main">        <table>        <caption>Liverpool Players</caption>        <thead>            <tr>                <th>Name</th>                <th>Photo</th>                <th>Position</th>                <th>Age</th>                <th>Scroll</th>            </tr>        </thead>        <tfoot class="footnote">            <tr>                <td colspan="4">We will add more photos soon</td>            </tr>        </tfoot>    <tbody>        <tr class="maintop">        <td>Alan Hansen</td>            <td>            <figure>            <img src="images\Alan-hansen-large.jpg" alt="Alan Hansen">            <figcaption>The best Liverpool Defender <a href="http://en.wikipedia.org/wiki/Alan_Hansen">Alan Hansen</a></figcaption>            </figure>            </td>            <td>Defender</td>            <td>57</td>            <td class="top">Middle</td>        </tr>        <tr>        <td>Graeme Souness</td>            <td>            <figure>            <img src="images\graeme-souness-large.jpg" alt="Graeme Souness">            <figcaption>Souness was the captain of the successful Liverpool team of the early 1980s <a href="http://en.wikipedia.org/wiki/Graeme_Souness">Graeme Souness</a></figcaption>            </figure>            </td>            <td>MidFielder</td>            <td>59</td>        </tr>        <tr>        <td>Ian Rush</td>            <td>            <figure>            <img src="images\ian-rush-large.jpg" alt="Ian Rush">            <figcaption>The deadliest Liverpool Striker <a href="http://it.wikipedia.org/wiki/Ian_Rush">Ian Rush</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>51</td>        </tr>        <tr class="mainmiddle">        <td>John Barnes</td>            <td>            <figure>            <img src="images\john-barnes-large.jpg" alt="John Barnes">            <figcaption>The best Liverpool Defender <a href="http://en.wikipedia.org/wiki/John_Barnes_(footballer)">John Barnes</a></figcaption>            </figure>            </td>            <td>MidFielder</td>            <td>49</td>            <td class="middle">Bottom</td>        </tr>                <tr>        <td>Kenny Dalglish</td>            <td>            <figure>            <img src="images\kenny-dalglish-large.jpg" alt="Kenny Dalglish">            <figcaption>King Kenny <a href="http://en.wikipedia.org/wiki/Kenny_Dalglish">Kenny Dalglish</a></figcaption>            </figure>            </td>            <td>Midfielder</td>            <td>61</td>        </tr>        <tr>            <td>Michael Owen</td>            <td>            <figure>            <img src="images\michael-owen-large.jpg" alt="Michael Owen">            <figcaption>Michael was Liverpool's top goal scorer from 1997–2004 <a href="http://www.michaelowen.com/">Michael Owen</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>33</td>        </tr>        <tr>            <td>Robbie Fowler</td>            <td>            <figure>            <img src="images\robbie-fowler-large.jpg" alt="Robbie Fowler">            <figcaption>Fowler scored 183 goals in total for Liverpool <a href="http://en.wikipedia.org/wiki/Robbie_Fowler">Robbie Fowler</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>38</td>        </tr>        <tr class="mainbottom">            <td>Steven Gerrard</td>            <td>            <figure>            <img src="images\steven-gerrard-large.jpg" alt="Steven Gerrard">            <figcaption>Liverpool's captain <a href="http://en.wikipedia.org/wiki/Steven_Gerrard">Steven Gerrard</a></figcaption>            </figure>            </td>            <td>Midfielder</td>            <td>32</td>            <td class="bottom">Top</td>        </tr>    </tbody></table>          </div>            <footer>        <p>All Rights Reserved</p>      </footer>     </body>  </html>  The markup is very easy to follow and understand. You do not have to type all the code,simply copy and paste it.For those that you are not familiar with HTML 5, please take a closer look at the new tags/elements introduced with HTML 5.When I view the HTML 5 page with Firefox I see the following result. I have also an external stylesheet (style.css). body{background-color:#efefef;}h1{font-size:2.3em;}table { border-collapse: collapse;font-family: Futura, Arial, sans-serif; }caption { font-size: 1.2em; margin: 1em auto; }th, td {padding: .65em; }th, thead { background: #000; color: #fff; border: 1px solid #000; }tr:nth-child(odd) { background: #ccc; }tr:nth-child(even) { background: #404040; }td { border-right: 1px solid #777; }table { border: 1px solid #777;  }.top, .middle, .bottom {    cursor: pointer;    font-size: 22px;    font-weight: bold;    text-align: center;}.footnote{text-align:center;font-family:Tahoma;color:#EB7515;}a{color:#22577a;text-decoration:none;}     a:hover {color:#125949; text-decoration:none;}  footer{background-color:#505050;width:1150px;}These are just simple CSS Rules that style the various HTML 5 tags,classes. The jQuery code that makes it all possible resides inside the scroll.js file.Make sure you type everything correctly.$(document).ready(function() {                 $('.top').click(function(){                     $('html, body').animate({                         scrollTop: $(".mainmiddle").offset().top                     },4000 );                  });                 $('.middle').click(function(){                     $('html, body').animate({                         scrollTop: $(".mainbottom").offset().top                     },4000);                  });                     $('.bottom').click(function(){                     $('html, body').animate({                         scrollTop: $(".maintop").offset().top                     },4000);                  }); });  Let me explain what I am doing here.When I click on the Middle word (  $('.top').click(function(){ ) this relates to the top class that is clicked.Then we declare the elements that we want to participate in the scrolling. In this case is html,body ( $('html, body').animate).These elements will be part of the vertical scrolling.In the next line of code we simply move (navigate) to the element (class mainmiddle that is attached to a tr element.)      scrollTop: $(".mainmiddle").offset().top  Make sure you type all the code correctly and try it for yourself. I have tested this solution will all 4-5 major browsers.Hope it helps!!!

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  • Diving into OpenStack Network Architecture - Part 2 - Basic Use Cases

    - by Ronen Kofman
      rkofman Normal rkofman 4 138 2014-06-05T03:38:00Z 2014-06-05T05:04:00Z 3 2735 15596 Oracle Corporation 129 36 18295 12.00 Clean Clean false false false false EN-US X-NONE HE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi; mso-bidi-language:AR-SA;} In the previous post we reviewed several network components including Open vSwitch, Network Namespaces, Linux Bridges and veth pairs. In this post we will take three simple use cases and see how those basic components come together to create a complete SDN solution in OpenStack. With those three use cases we will review almost the entire network setup and see how all the pieces work together. The use cases we will use are: 1.       Create network – what happens when we create network and how can we create multiple isolated networks 2.       Launch a VM – once we have networks we can launch VMs and connect them to networks. 3.       DHCP request from a VM – OpenStack can automatically assign IP addresses to VMs. This is done through local DHCP service controlled by OpenStack Neutron. We will see how this service runs and how does a DHCP request and response look like. In this post we will show connectivity, we will see how packets get from point A to point B. We first focus on how a configured deployment looks like and only later we will discuss how and when the configuration is created. Personally I found it very valuable to see the actual interfaces and how they connect to each other through examples and hands on experiments. After the end game is clear and we know how the connectivity works, in a later post, we will take a step back and explain how Neutron configures the components to be able to provide such connectivity.  We are going to get pretty technical shortly and I recommend trying these examples on your own deployment or using the Oracle OpenStack Tech Preview. Understanding these three use cases thoroughly and how to look at them will be very helpful when trying to debug a deployment in case something does not work. Use case #1: Create Network Create network is a simple operation it can be performed from the GUI or command line. When we create a network in OpenStack the network is only available to the tenant who created it or it could be defined as “shared” and then it can be used by all tenants. A network can have multiple subnets but for this demonstration purpose and for simplicity we will assume that each network has exactly one subnet. Creating a network from the command line will look like this: # neutron net-create net1 Created a new network: +---------------------------+--------------------------------------+ | Field                     | Value                                | +---------------------------+--------------------------------------+ | admin_state_up            | True                                 | | id                        | 5f833617-6179-4797-b7c0-7d420d84040c | | name                      | net1                                 | | provider:network_type     | vlan                                 | | provider:physical_network | default                              | | provider:segmentation_id  | 1000                                 | | shared                    | False                                | | status                    | ACTIVE                               | | subnets                   |                                      | | tenant_id                 | 9796e5145ee546508939cd49ad59d51f     | +---------------------------+--------------------------------------+ Creating a subnet for this network will look like this: # neutron subnet-create net1 10.10.10.0/24 Created a new subnet: +------------------+------------------------------------------------+ | Field            | Value                                          | +------------------+------------------------------------------------+ | allocation_pools | {"start": "10.10.10.2", "end": "10.10.10.254"} | | cidr             | 10.10.10.0/24                                  | | dns_nameservers  |                                                | | enable_dhcp      | True                                           | | gateway_ip       | 10.10.10.1                                     | | host_routes      |                                                | | id               | 2d7a0a58-0674-439a-ad23-d6471aaae9bc           | | ip_version       | 4                                              | | name             |                                                | | network_id       | 5f833617-6179-4797-b7c0-7d420d84040c           | | tenant_id        | 9796e5145ee546508939cd49ad59d51f               | +------------------+------------------------------------------------+ We now have a network and a subnet, on the network topology view this looks like this: Now let’s dive in and see what happened under the hood. Looking at the control node we will discover that a new namespace was created: # ip netns list qdhcp-5f833617-6179-4797-b7c0-7d420d84040c   The name of the namespace is qdhcp-<network id> (see above), let’s look into the namespace and see what’s in it: # ip netns exec qdhcp-5f833617-6179-4797-b7c0-7d420d84040c ip addr 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00     inet 127.0.0.1/8 scope host lo     inet6 ::1/128 scope host        valid_lft forever preferred_lft forever 12: tap26c9b807-7c: <BROADCAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN     link/ether fa:16:3e:1d:5c:81 brd ff:ff:ff:ff:ff:ff     inet 10.10.10.3/24 brd 10.10.10.255 scope global tap26c9b807-7c     inet6 fe80::f816:3eff:fe1d:5c81/64 scope link        valid_lft forever preferred_lft forever   We see two interfaces in the namespace, one is the loopback and the other one is an interface called “tap26c9b807-7c”. This interface has the IP address of 10.10.10.3 and it will also serve dhcp requests in a way we will see later. Let’s trace the connectivity of the “tap26c9b807-7c” interface from the namespace.  First stop is OVS, we see that the interface connects to bridge  “br-int” on OVS: # ovs-vsctl show 8a069c7c-ea05-4375-93e2-b9fc9e4b3ca1     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2"                 type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"     Bridge br-ex         Port br-ex             Interface br-ex                 type: internal     Bridge br-int         Port "int-br-eth2"             Interface "int-br-eth2"         Port "tap26c9b807-7c"             tag: 1             Interface "tap26c9b807-7c"                 type: internal         Port br-int             Interface br-int                 type: internal     ovs_version: "1.11.0"   In the picture above we have a veth pair which has two ends called “int-br-eth2” and "phy-br-eth2", this veth pair is used to connect two bridge in OVS "br-eth2" and "br-int". In the previous post we explained how to check the veth connectivity using the ethtool command. It shows that the two are indeed a pair: # ethtool -S int-br-eth2 NIC statistics:      peer_ifindex: 10 . .   #ip link . . 10: phy-br-eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 . . Note that “phy-br-eth2” is connected to a bridge called "br-eth2" and one of this bridge's interfaces is the physical link eth2. This means that the network which we have just created has created a namespace which is connected to the physical interface eth2. eth2 is the “VM network” the physical interface where all the virtual machines connect to where all the VMs are connected. About network isolation: OpenStack supports creation of multiple isolated networks and can use several mechanisms to isolate the networks from one another. The isolation mechanism can be VLANs, VxLANs or GRE tunnels, this is configured as part of the initial setup in our deployment we use VLANs. When using VLAN tagging as an isolation mechanism a VLAN tag is allocated by Neutron from a pre-defined VLAN tags pool and assigned to the newly created network. By provisioning VLAN tags to the networks Neutron allows creation of multiple isolated networks on the same physical link.  The big difference between this and other platforms is that the user does not have to deal with allocating and managing VLANs to networks. The VLAN allocation and provisioning is handled by Neutron which keeps track of the VLAN tags, and responsible for allocating and reclaiming VLAN tags. In the example above net1 has the VLAN tag 1000, this means that whenever a VM is created and connected to this network the packets from that VM will have to be tagged with VLAN tag 1000 to go on this particular network. This is true for namespace as well, if we would like to connect a namespace to a particular network we have to make sure that the packets to and from the namespace are correctly tagged when they reach the VM network. In the example above we see that the namespace interface “tap26c9b807-7c” has vlan tag 1 assigned to it, if we examine OVS we see that it has flows which modify VLAN tag 1 to VLAN tag 1000 when a packet goes to the VM network on eth2 and vice versa. We can see this using the dump-flows command on OVS for packets going to the VM network we see the modification done on br-eth2: #  ovs-ofctl dump-flows br-eth2 NXST_FLOW reply (xid=0x4):  cookie=0x0, duration=18669.401s, table=0, n_packets=857, n_bytes=163350, idle_age=25, priority=4,in_port=2,dl_vlan=1 actions=mod_vlan_vid:1000,NORMAL  cookie=0x0, duration=165108.226s, table=0, n_packets=14, n_bytes=1000, idle_age=5343, hard_age=65534, priority=2,in_port=2 actions=drop  cookie=0x0, duration=165109.813s, table=0, n_packets=1671, n_bytes=213304, idle_age=25, hard_age=65534, priority=1 actions=NORMAL   For packets coming from the interface to the namespace we see the following modification: #  ovs-ofctl dump-flows br-int NXST_FLOW reply (xid=0x4):  cookie=0x0, duration=18690.876s, table=0, n_packets=1610, n_bytes=210752, idle_age=1, priority=3,in_port=1,dl_vlan=1000 actions=mod_vlan_vid:1,NORMAL  cookie=0x0, duration=165130.01s, table=0, n_packets=75, n_bytes=3686, idle_age=4212, hard_age=65534, priority=2,in_port=1 actions=drop  cookie=0x0, duration=165131.96s, table=0, n_packets=863, n_bytes=160727, idle_age=1, hard_age=65534, priority=1 actions=NORMAL   To summarize we can see that when a user creates a network Neutron creates a namespace and this namespace is connected through OVS to the “VM network”. OVS also takes care of tagging the packets from the namespace to the VM network with the correct VLAN tag and knows to modify the VLAN for packets coming from VM network to the namespace. Now let’s see what happens when a VM is launched and how it is connected to the “VM network”. Use case #2: Launch a VM Launching a VM can be done from Horizon or from the command line this is how we do it from Horizon: Attach the network: And Launch Once the virtual machine is up and running we can see the associated IP using the nova list command : # nova list +--------------------------------------+--------------+--------+------------+-------------+-----------------+ | ID                                   | Name         | Status | Task State | Power State | Networks        | +--------------------------------------+--------------+--------+------------+-------------+-----------------+ | 3707ac87-4f5d-4349-b7ed-3a673f55e5e1 | Oracle Linux | ACTIVE | None       | Running     | net1=10.10.10.2 | +--------------------------------------+--------------+--------+------------+-------------+-----------------+ The nova list command shows us that the VM is running and that the IP 10.10.10.2 is assigned to this VM. Let’s trace the connectivity from the VM to VM network on eth2 starting with the VM definition file. The configuration files of the VM including the virtual disk(s), in case of ephemeral storage, are stored on the compute node at/var/lib/nova/instances/<instance-id>/. Looking into the VM definition file ,libvirt.xml,  we see that the VM is connected to an interface called “tap53903a95-82” which is connected to a Linux bridge called “qbr53903a95-82”: <interface type="bridge">       <mac address="fa:16:3e:fe:c7:87"/>       <source bridge="qbr53903a95-82"/>       <target dev="tap53903a95-82"/>     </interface>   Looking at the bridge using the brctl show command we see this: # brctl show bridge name     bridge id               STP enabled     interfaces qbr53903a95-82          8000.7e7f3282b836       no              qvb53903a95-82                                                         tap53903a95-82    The bridge has two interfaces, one connected to the VM (“tap53903a95-82 “) and another one ( “qvb53903a95-82”) connected to “br-int” bridge on OVS: # ovs-vsctl show 83c42f80-77e9-46c8-8560-7697d76de51c     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2"                 type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"     Bridge br-int         Port br-int             Interface br-int                 type: internal         Port "int-br-eth2"             Interface "int-br-eth2"         Port "qvo53903a95-82"             tag: 3             Interface "qvo53903a95-82"     ovs_version: "1.11.0"   As we showed earlier “br-int” is connected to “br-eth2” on OVS using the veth pair int-br-eth2,phy-br-eth2 and br-eth2 is connected to the physical interface eth2. The whole flow end to end looks like this: VM è tap53903a95-82 (virtual interface)è qbr53903a95-82 (Linux bridge) è qvb53903a95-82 (interface connected from Linux bridge to OVS bridge br-int) è int-br-eth2 (veth one end) è phy-br-eth2 (veth the other end) è eth2 physical interface. The purpose of the Linux Bridge connecting to the VM is to allow security group enforcement with iptables. Security groups are enforced at the edge point which are the interface of the VM, since iptables nnot be applied to OVS bridges we use Linux bridge to apply them. In the future we hope to see this Linux Bridge going away rules.  VLAN tags: As we discussed in the first use case net1 is using VLAN tag 1000, looking at OVS above we see that qvo41f1ebcf-7c is tagged with VLAN tag 3. The modification from VLAN tag 3 to 1000 as we go to the physical network is done by OVS  as part of the packet flow of br-eth2 in the same way we showed before. To summarize, when a VM is launched it is connected to the VM network through a chain of elements as described here. During the packet from VM to the network and back the VLAN tag is modified. Use case #3: Serving a DHCP request coming from the virtual machine In the previous use cases we have shown that both the namespace called dhcp-<some id> and the VM end up connecting to the physical interface eth2  on their respective nodes, both will tag their packets with VLAN tag 1000.We saw that the namespace has an interface with IP of 10.10.10.3. Since the VM and the namespace are connected to each other and have interfaces on the same subnet they can ping each other, in this picture we see a ping from the VM which was assigned 10.10.10.2 to the namespace: The fact that they are connected and can ping each other can become very handy when something doesn’t work right and we need to isolate the problem. In such case knowing that we should be able to ping from the VM to the namespace and back can be used to trace the disconnect using tcpdump or other monitoring tools. To serve DHCP requests coming from VMs on the network Neutron uses a Linux tool called “dnsmasq”,this is a lightweight DNS and DHCP service you can read more about it here. If we look at the dnsmasq on the control node with the ps command we see this: dnsmasq --no-hosts --no-resolv --strict-order --bind-interfaces --interface=tap26c9b807-7c --except-interface=lo --pid-file=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/pid --dhcp-hostsfile=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/host --dhcp-optsfile=/var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/opts --leasefile-ro --dhcp-range=tag0,10.10.10.0,static,120s --dhcp-lease-max=256 --conf-file= --domain=openstacklocal The service connects to the tap interface in the namespace (“--interface=tap26c9b807-7c”), If we look at the hosts file we see this: # cat  /var/lib/neutron/dhcp/5f833617-6179-4797-b7c0-7d420d84040c/host fa:16:3e:fe:c7:87,host-10-10-10-2.openstacklocal,10.10.10.2   If you look at the console output above you can see the MAC address fa:16:3e:fe:c7:87 which is the VM MAC. This MAC address is mapped to IP 10.10.10.2 and so when a DHCP request comes with this MAC dnsmasq will return the 10.10.10.2.If we look into the namespace at the time we initiate a DHCP request from the VM (this can be done by simply restarting the network service in the VM) we see the following: # ip netns exec qdhcp-5f833617-6179-4797-b7c0-7d420d84040c tcpdump -n 19:27:12.191280 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP, Request from fa:16:3e:fe:c7:87, length 310 19:27:12.191666 IP 10.10.10.3.bootps > 10.10.10.2.bootpc: BOOTP/DHCP, Reply, length 325   To summarize, the DHCP service is handled by dnsmasq which is configured by Neutron to listen to the interface in the DHCP namespace. Neutron also configures dnsmasq with the combination of MAC and IP so when a DHCP request comes along it will receive the assigned IP. Summary In this post we relied on the components described in the previous post and saw how network connectivity is achieved using three simple use cases. These use cases gave a good view of the entire network stack and helped understand how an end to end connection is being made between a VM on a compute node and the DHCP namespace on the control node. One conclusion we can draw from what we saw here is that if we launch a VM and it is able to perform a DHCP request and receive a correct IP then there is reason to believe that the network is working as expected. We saw that a packet has to travel through a long list of components before reaching its destination and if it has done so successfully this means that many components are functioning properly. In the next post we will look at some more sophisticated services Neutron supports and see how they work. We will see that while there are some more components involved for the most part the concepts are the same. @RonenKofman

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  • Nginx + Nagios : 502 Bad gateway

    - by MrROY
    I have a fully new install nagios, but I can't access to it. Here's my Nginx config: server{ listen 80; server_name 61.148.45.10; # blahblah # Nagios Monitoring location /nagios3/ { proxy_pass http://127.0.0.1:80; } } Nagios is installed step by step(From this Linode guide): sudo apt-get install -y nagios3 Then I try to visit http://ip-address/nagios3/, but it shows 502 bad gateway. How do I deal with this ? This is my /var/log/syslog: Oct 25 14:18:17 my-server nagios3: SERVICE ALERT: localhost;Disk Space;WARNING;SOFT;1;DISK WARNING - free space: /boot 43 MB (20% inode=99%): Oct 25 14:19:07 my-server nagios3: SERVICE ALERT: localhost;HTTP;WARNING;SOFT;1;HTTP WARNING: HTTP/1.1 403 Forbidden - 319 bytes in 0.000 second response time Oct 25 14:19:17 my-server nagios3: SERVICE ALERT: localhost;Disk Space;WARNING;SOFT;2;DISK WARNING - free space: /boot 43 MB (20% inode=99%): Oct 25 14:20:07 my-server nagios3: SERVICE ALERT: localhost;HTTP;WARNING;SOFT;2;HTTP WARNING: HTTP/1.1 403 Forbidden - 319 bytes in 0.000 second response time Oct 25 14:20:17 my-server nagios3: SERVICE ALERT: localhost;Disk Space;WARNING;SOFT;3;DISK WARNING - free space: /boot 43 MB (20% inode=99%): Oct 25 14:21:07 my-server nagios3: SERVICE ALERT: localhost;HTTP;WARNING;SOFT;3;HTTP WARNING: HTTP/1.1 403 Forbidden - 319 bytes in 0.000 second response time Oct 25 14:21:17 my-server nagios3: SERVICE ALERT: localhost;Disk Space;WARNING;HARD;4;DISK WARNING - free space: /boot 43 MB (20% inode=99%): Oct 25 14:21:17 my-server nagios3: SERVICE NOTIFICATION: root;localhost;Disk Space;WARNING;notify-service-by-email;DISK WARNING - free space: /boot 43 MB (20% inode=99%): Oct 25 14:21:17 my-server postfix/pickup[24474]: 4F89F394034C: uid=109 from=<nagios> Oct 25 14:21:17 my-server postfix/cleanup[27756]: 4F89F394034C: message-id=<20131025062117.4F89F394034C@my-server> Oct 25 14:21:17 my-server postfix/qmgr[24475]: 4F89F394034C: from=<nagios@[email protected]>, size=594, nrcpt=1 (queue active) Oct 25 14:21:17 my-server postfix/local[27758]: 4F89F394034C: to=<root@localhost>, relay=local, delay=0.15, delays=0.11/0/0/0.04, dsn=2.0.0, status=sent (delivered to mailbox) Oct 25 14:21:17 my-server postfix/qmgr[24475]: 4F89F394034C: removed Oct 25 14:22:07 my-server nagios3: SERVICE ALERT: localhost;HTTP;WARNING;HARD;4;HTTP WARNING: HTTP/1.1 403 Forbidden - 319 bytes in 0.000 second response time Oct 25 14:22:07 my-server nagios3: SERVICE NOTIFICATION: root;localhost;HTTP;WARNING;notify-service-by-email;HTTP WARNING: HTTP/1.1 403 Forbidden - 319 bytes in 0.000 second response time Oct 25 14:22:07 my-server postfix/pickup[24474]: 219CA3940381: uid=109 from=<nagios> Oct 25 14:22:07 my-server postfix/cleanup[27756]: 219CA3940381: message-id=<20131025062207.219CA3940381@my-server> Oct 25 14:22:07 my-server postfix/qmgr[24475]: 219CA3940381: from=<nagios@[email protected]>, size=605, nrcpt=1 (queue active) Oct 25 14:22:07 my-server postfix/local[27758]: 219CA3940381: to=<root@localhost>, relay=local, delay=0.12, delays=0.07/0/0/0.05, dsn=2.0.0, status=sent (delivered to mailbox) Oct 25 14:22:07 my-server postfix/qmgr[24475]: 219CA3940381: removed Oct 25 14:39:01 my-server CRON[28242]: (root) CMD ( [ -x /usr/lib/php5/maxlifetime ] && [ -d /var/lib/php5 ] && find /var/lib/php5/ -depth -mindepth 1 -maxdepth 1 -type f -cmin +$(/usr/lib/php5/maxlifetime) ! -execdir fuser -s {} 2>/dev/null \; -delete) And there're lot of 127.0.0.1 visit in nginx log, but I actually visit from a external ip: 127.0.0.1 - - [25/Oct/2013:14:21:02 +0800] "GET /nagios3/ HTTP/1.0" 502 575 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/3 0.0.1599.69 Safari/537.36" 127.0.0.1 - - [25/Oct/2013:14:21:02 +0800] "GET /nagios3/ HTTP/1.0" 502 575 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/3 0.0.1599.69 Safari/537.36" 127.0.0.1 - - [25/Oct/2013:14:21:02 +0800] "GET /nagios3/ HTTP/1.0" 502 575 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/3 0.0.1599.69 Safari/537.36"

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