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• I make this for balancing paranthesis of equation but i think it is wrong check and correct it

  - by muhammadlodhi

  int main(){ char i,input[30],close,open; for(i=0;i<='.';i++){ printf("enter equation"); scanf("%c",input[i]); if(input[i]=='(') input++; input[i]=open; else if(input[i]==')') input[i]--; input[i]=close; else if(open[i]==close[i]) { printf("paranthesis are balance"); } else printf("paranthesis are not balance"); } getch(); return 0; }

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• Load Balance and Parallel Performance

  Load balancing an application workload among threads is critical to performance. However, achieving perfect load balance is non-trivial, and it depends on the parallelism within the application, workload, the number of threads, load balancing policy, and the threading implementation.

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• Implementing a Linux-HA based clustering setup on Windows

  - by Alex

  I have a (tried and tested) setup involving: 2x Load balancing nodes on a floating IP via Heartbeat, load balancing 2 tomcat servers. 2x Tomcat servers 2x Galera Cluster MySQL servers synchronously replicating (+1 arbitrator node) All are evenly spread across 2 physical nodes. Now, I have to somehow get the same functionality on Windows Server (2008? I think) nodes .... running under Xen virtualization. There is no possibility to use Linux for any of the nodes. I count two main problems: No Linux-HA hearbeat daemon for the load balancing No Galera synchronous replication for MySQL I freely admit to having nearly no Windows knowledge when it comes to clustering. Is there a way to closely mimic the setup I have described or is it a total write-off?

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• Disaster Recovery Example

  Previously, I use to work for a small internet company that sells dental plans online. Our primary focus concerning disaster prevention and recovery is on our corporate website and private intranet site. We had a multiphase disaster recovery plan that includes data redundancy, load balancing, and off-site monitoring. Data redundancy is a key aspect of our disaster recovery plan. The first phase of this is to replicate our data to multiple database servers and schedule daily backups of the databases that are stored off site. The next phase is the file replication of data amongst our web servers that are also backed up daily by our collocation. In addition to the files located on the server, files are also stored locally on development machines, and again backed up using version control software. Load balancing is another key aspect of our disaster recovery plan. Load balancing offers many benefits for our system, better performance, load distribution and increased availability. With our servers behind a load balancer our system has the ability to accept multiple requests simultaneously because the load is split between multiple servers. Plus if one server is slow or experiencing a failure the traffic is diverted amongst the other servers connected to the load balancer allowing the server to get back online. The final key to our disaster recovery plan is off-site monitoring that notifies all IT staff of any outages or errors on the main website encountered by the monitor. Messages are sent by email, voicemail, and SMS. According to Disasterrecovery.org, disaster recovery planning is the way companies successfully manage crises with minimal cost and effort and maximum speed compared to others that are forced to make decision out of desperation when disasters occur. In addition Sun Guard stated in 2009 that the first step in disaster recovery planning is to analyze company risks and factor in fixed costs for things like hardware, software, staffing and utilities, as well as indirect costs, such as floor space, power protection, physical and information security, and management. Also availability requirements need to be determined per application and system as well as the strategies for recovery.

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• Instructions on how to configure a WebLogic Cluster and use it with Oracle Http Server

  - by Laurent Goldsztejn

  On October 17th I delivered a webcast on WebLogic Clustering that included a demo with Apache as the proxy server.  I realized that many steps are needed to set up the configuration I used during the demo.  The purpose of this article is to go through these steps to show how quickly and easily one can define a new cluster and then proxy requests via an Oracle Http Server (OHS). The domain configuration wizard offers the option to create a cluster.  The administration console or WLST, the Weblogic scripting tool can also be used to define a new cluster.  It can be created at any time but the servers that will participate in it cannot be in a running state. Cluster Creation using the configuration wizard Network and architecture requirements need to be considered while choosing between unicast and multicast. Multicast Vs. Unicast with WebLogic Clustering is of great help to make the best decision between the two messaging modes.  In addition, Configure Cluster offers details on each single field displayed above. After this initial configuration page, individual servers could be assigned to this newly created cluster although servers can be added later to the cluster.  What is not recommended is for the Admin server to participate in a cluster as the main purpose of the Admin server is to perform the bulk of the processing for the domain.  Servers need to stop before being assigned to a cluster.  There is also no minimum number of servers that have to participate in the cluster. At this point the configuration should be done and the cluster created successfully.  This can easily be verified from the console. Each clustered managed server can be launched to join the cluster.   At startup the following messages should be logged for each clustered managed server: <Notice> <WeblogicServer> <BEA-000365> <Server state changed to STARTING> <Notice> <Cluster> <BEA-000197> <Listening for announcements from cluster using messaging_mode cluster messaging> <Notice> <Cluster> <BEA-000133> <Waiting to synchronize with other running members of cluster_name>  It's time to try sending requests to the cluster and we will do this with the help of Oracle Http Server to play the role of a proxy server to demonstrate load balancing.  Proxy Server configuration  The first step is to download Weblogic Server Web Server Plugin that will enhance the web server by handling requests aimed at being sent to the Weblogic cluster.  For our test Oracle Http Server (OHS) will be used.  However plug-ins are also available for Apache Http server, Microsoft Internet Information Server (IIS), Oracle iPlanet Webserver or even WebLogic Server with the HttpClusterServlet. Once OHS is installed on the system, the configuration file, mod_wl_ohs.conf, will need to be altered to include Weblogic proxy specifics. First of all, add the following directive to instruct Apache to load the Weblogic shared object module extracted from the plugins file just downloaded. LoadModule weblogic_module modules/mod_wl_ohs.so and then create an IfModule directive to encapsulate the following location block so that proxy will be enabled by path (each request including /wls will be directed directly to the WebLogic Cluster).  You could also proxy requests by MIME type using MatchExpression in the Location block. <IfModule weblogic_module> <Location /wls>    SetHandler weblogic-handler    PathTrim /wls    WebLogicCluster MS1_URL:port,MS2_URL:port    Debug ON    WLLogFile        c:/tmp/global_proxy.log     WLTempDir        "c:/myTemp"    DebugConfigInfo  On </Location> </IfModule> SetHandler specifies the handler for the plug-in module  PathTrim will instruct the plug-in to trim /w ls from the URL before forwarding the request to the cluster. The list of WebLogic Servers defined in WeblogicCluster could contain a mixed set of clustered and single servers.  However, the dynamic list returned for this parameter will only contain valid clustered servers and may contain more servers if not all clustered servers are listed in WeblogicCluster. Testing proxy and load balancing It's time to start OHS web server which should at this point be configured correctly to proxy requests to the clustered servers.  By default round-robin is the load balancing strategy set by WebLogic. Testing the load balancing can be easily done by disabling cookies on your browser given that a request containing a cookie attempts to connect to the primary server. If that attempt fails, the plug-in attempts to make a connection to the next available server in the list in a round-robin fashion.  With cookies enabled, you could use two different browsers to test the load balancing with a JSP page that contains the following: <%@ page contentType="text/html; charset=iso-8859-1" language="java"  %>  <%  String path = request.getContextPath();   String getProtocol=request.getScheme();   String getDomain=request.getServerName();   String getPort=Integer.toString(request.getLocalPort());   String getPath = getProtocol+"://"+getDomain+":"+getPort+path+"/"; %> <html> <body> Receiving Server <%=getPath%> </body> </html>  Assuming that you name the JSP page Test.jsp and the webapp that contains it TestApp, your browsers should open the following URL: http://localhost/wls/TestApp/Test.jsp  Each browser should connect to a different clustered server and this simple JSP should confirm that.  The webapp that contains the JSP needs to be deployed to the cluster. You can also verify that the load is correctly balanced by looking at the proxy log file.  Each request generates a set of log entries that starts with : timestamp ================New Request: Each request is associated with a primary server and a secondary server if one is available.  For our test request, the following entries should appear in the log as well:Using Uri /wls/TestApp/Test.jsp After trimming path: '/TestApp/Test.jsp' The final request string is '/TestApp/Test.jsp' If an exception occurs, it should also be logged in the proxy log file with the prefix:timestamp *******Exception type   WeblogicBridgeConfig DebugConfigInfo enables runtime statistics and the production of configuration information.  For security purposes, this parameter should be turned off in production. http://webserver_host:port/path/xyz.jsp?__WebLogicBridgeConfig will display a proxy bridge page detailing the plugin configuration followed by runtime statistics which could help in diagnosing issues along with the analyzing of the proxy log file.  In our example the url would be: http://localhost/wls/TestApp/Test.jsp?__WebLogicBridgeConfig  Here is how the top section of the screen can look like: The bottom part of the page contains runtime statistics, here is a snippet of it (unrelated with the previous JSP example).   This entire plugin configuration should be very similar with other web servers, what varies is the name of the proxy server configuration file. So, as you can see, it only takes a few minutes to configure a Weblogic cluster and get servers to join it. 

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• WCF Keep Alive: Whether to disable keepAliveEnabled

  - by Lijo

  I have a WCF web service hosted in a load balanced environment. I do not need any WCF session related functionality in the service. QUESTION What are the scenarios in which performances will be best if keepAliveEnabled = false keepAliveEnabled = true Reference From Load Balancing By default, the BasicHttpBinding sends a connection HTTP header in messages with a Keep-Alive value, which enables clients to establish persistent connections to the services that support them. This configuration offers enhanced throughput because previously established connections can be reused to send subsequent messages to the same server. However, connection reuse may cause clients to become strongly associated to a specific server within the load-balanced farm, which reduces the effectiveness of round-robin load balancing. If this behavior is undesirable, HTTP Keep-Alive can be disabled on the server using the KeepAliveEnabled property with a CustomBinding or user-defined Binding.

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• Sticky connection and HTTPS support for HAProxy

  - by Saif

  Hi Mates, We have 2 HTTP Load balancer with HAproxy and heartbeat. There are 4 apache nodes in this cluster. It's doing round robin load balancing. The HTTP cluster working fine. We are having problem with our portal because it uses SSO. We need sticky connection support in our HAproxy. Also we need load balancing for HTTPS traffic. Here's our HAproxy conf file. global # to have these messages end up in /var/log/haproxy.log you will # need to: # # 1) configure syslog to accept network log events. This is done # by adding the '-r' option to the SYSLOGD_OPTIONS in # /etc/sysconfig/syslog # # 2) configure local2 events to go to the /var/log/haproxy.log # file. A line like the following can be added to # /etc/sysconfig/syslog # # local2.* /var/log/haproxy.log # log 127.0.0.1 local0 log 127.0.0.1 local1 notice chroot /var/lib/haproxy pidfile /var/run/haproxy.pid maxconn 4000 user haproxy group haproxy daemon # turn on stats unix socket stats socket /var/lib/haproxy/stats #--------------------------------------------------------------------- # common defaults that all the 'listen' and 'backend' sections will # use if not designated in their block #--------------------------------------------------------------------- defaults mode http log global option httplog option dontlognull option http-server-close option forwardfor except 127.0.0.0/8 option redispatch retries 3 timeout http-request 10s timeout queue 1m timeout connect 10s timeout client 1m timeout server 1m timeout http-keep-alive 10s timeout check 10s maxconn 3000 #--------------------------------------------------------------------- # main frontend which proxys to the backends #--------------------------------------------------------------------- frontend main *:5000 acl url_static path_beg -i /static /images /javascript /stylesheets acl url_static path_end -i .jpg .gif .png .css .js use_backend static if url_static default_backend app #--------------------------------------------------------------------- # static backend for serving up images, stylesheets and such #--------------------------------------------------------------------- backend static balance roundrobin server static 127.0.0.1:4331 check #--------------------------------------------------------------------- # round robin balancing between the various backends #--------------------------------------------------------------------- backend app listen ha-http 10.190.1.28:80 mode http stats enable stats auth admin:xxxxxx balance roundrobin cookie JSESSIONID prefix option httpclose option forwardfor option httpchk HEAD /haproxy.txt HTTP/1.0 server apache1 portal-04:80 cookie A check server apache2 im-01:80 cookie B check server apache3 im-02:80 cookie B check server apache4 im-03:80 cookie B check Please advice. Thanks for your help in advance.

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• Sticky connection and HTTPS support for HAProxy

  - by Saif

  We have 2 HTTP Load balancer with HAproxy and heartbeat. There are 4 apache nodes in this cluster. It's doing round robin load balancing. The HTTP cluster working fine. We are having problem with our portal because it uses SSO. We need sticky connection support in our HAproxy. Also we need load balancing for HTTPS traffic. Here's our HAproxy conf file. global # to have these messages end up in /var/log/haproxy.log you will # need to: # # 1) configure syslog to accept network log events. This is done # by adding the '-r' option to the SYSLOGD_OPTIONS in # /etc/sysconfig/syslog # # 2) configure local2 events to go to the /var/log/haproxy.log # file. A line like the following can be added to # /etc/sysconfig/syslog # # local2.* /var/log/haproxy.log # log 127.0.0.1 local0 log 127.0.0.1 local1 notice chroot /var/lib/haproxy pidfile /var/run/haproxy.pid maxconn 4000 user haproxy group haproxy daemon # turn on stats unix socket stats socket /var/lib/haproxy/stats #--------------------------------------------------------------------- # common defaults that all the 'listen' and 'backend' sections will # use if not designated in their block #--------------------------------------------------------------------- defaults mode http log global option httplog option dontlognull option http-server-close option forwardfor except 127.0.0.0/8 option redispatch retries 3 timeout http-request 10s timeout queue 1m timeout connect 10s timeout client 1m timeout server 1m timeout http-keep-alive 10s timeout check 10s maxconn 3000 #--------------------------------------------------------------------- # main frontend which proxys to the backends #--------------------------------------------------------------------- frontend main *:5000 acl url_static path_beg -i /static /images /javascript /stylesheets acl url_static path_end -i .jpg .gif .png .css .js use_backend static if url_static default_backend app #--------------------------------------------------------------------- # static backend for serving up images, stylesheets and such #--------------------------------------------------------------------- backend static balance roundrobin server static 127.0.0.1:4331 check #--------------------------------------------------------------------- # round robin balancing between the various backends #--------------------------------------------------------------------- backend app listen ha-http 10.190.1.28:80 mode http stats enable stats auth admin:xxxxxx balance roundrobin cookie JSESSIONID prefix option httpclose option forwardfor option httpchk HEAD /haproxy.txt HTTP/1.0 server apache1 portal-04:80 cookie A check server apache2 im-01:80 cookie B check server apache3 im-02:80 cookie B check server apache4 im-03:80 cookie B check Please advice. Thanks for your help in advance.

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• Forwarding HTTP Request with Direct Server Return

  - by Daniel Crabtree

  I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything. Thanks.

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• ArchBeat Top 10 for December 2-8, 2012

  - by Bob Rhubart

  The Top 10 most-clicked items shared on the OTN ArchBeat Facebook page for the week of December 2-8, 2012 Configure Oracle SOA JMSAdatper to Work with WLS JMS Topics Another of the four posts published on Dec 4 by the Fusion Middleware A-Team blogger identified as "fip" illlustrates "how to configure the JMS Topic, the JmsAdapter connection factory, as well as the composite so that the JMS Topic messages will be evenly distributed to same composite running off different SOA cluster nodes without causing duplication." Web Service Example - Part 3: Asynchronous Part 3 in this series from the Oracle ADF Mobile blog looks at "firing the web service asynchronously and then filling in the UI when it completes." Denis says, "This can be useful when you have data on the device in a local store and want to show that to the user while the application uses lazy loading from a web service to load more data." Advanced Oracle SOA Suite Oracle Open World 2012 SOA Presentations Oracle SOA & BPM Partner Community blogger Juergen Kress shares a list of 13 SOA presentations delivered or moderated by Oracle SOA Product Management at OOW12 in San Francisco. Oracle WebLogic Server WLS Domain Browser My colleague Jeff Davies, a frequent speaker at OTN Architect Day events and a genuinely nice guy, emailed me last night with this message: "I just came across this app on Google Play. It allows WebLogic administrators to browse WLS 12c domain information. I installed it on my phone and tried it out. Works very fast." I'm an iPhone guy, but I'm perfectly comfortable taking Jeff at his word. The app is called WLS Domain Browser. Follow the link for more info from the Google Play site. Retrieve Performance Data from SOA Infrastructure Database Another of the four blog posts published on Dec 4 by very busy Oracle Fusion Middleware A-Team member "fip," this one offers "examples of some basic SQL queries you can run against the infrastructure database of Oracle SOA Suite 11G to acquire the performance statistics for a given period of time." How to Achieve OC4J RMI Load Balancing "Having returned from a customer who faced challenges with OC4J RMI load balancing, I felt there is still some confusion in the field [about] how OC4J RMI load balancing works," says the Oracle Fusion Middleware A-Team member known only as "fip." "Hence I decide to dust off an old tech note that I wrote a few years back and share it with the general public." From XaaS to Java EE – Which damn cloud is right for me in 2012? Oracle ACE Director Markus Eisele wrestles with a timely technical issue and shares his observations on several of the alternatives. Exalogic 2.0.1 Tea Break Snippets - Creating a ModifyJeOS VirtualBox "One of the main advantages of this is that Templates can be created away from the Exalogic Environment," explains The Old Toxophilist. (BTW: I had to look it up: a toxophilist is one who collects bows and arrows.) ADF Mobile - Implementing Reusable Mobile Architecture "Reusability was always a strong part of ADF," says Oracle ACE Director Andrejus Baranovskis. "The same high reusability level is supported now in ADF Mobile." The objective of this post is "to prove technically that [the] reusable architecture concept works for ADF Mobile." Using BPEL Performance Statistics to Diagnose Performance Bottlenecks Someone had a busy day… This post, one of four published on DeC 4 by a member of the Oracle Fusion Middleware A-Team identified only as "fip," offers details on how to "enable, retrieve and interpret the performance statistics, before the future versions provides a more pleasant user experience." Thought for the Day "If you're afraid to change something it is clearly poorly designed." — Martin Fowler Source: SoftwareQuotes.com

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• You Probably Already Have a “Private Cloud”

  - by BuckWoody

  I’ve mentioned before that I’m not a fan of the word “Cloud”. It’s too marketing-oriented, gimmicky and non-specific. A better definition (in many cases) is “Distributed Computing”. That means that some or all of the computing functions are handled somewhere other than under your specific control. But there is a current use of the word “Cloud” that does not necessarily mean that the computing is done somewhere else. In fact, it’s a vector of Cloud Computing that can better be termed “Utility Computing”. This has to do with the provisioning of a computing resource. That means the setup, configuration, management, balancing and so on that is needed so that a user – which might actually be a developer – can do some computing work. To that person, the resource is just “there” and works like they expect, like the phone system or any other utility. The interesting thing is, you can do this yourself. In fact, you probably already have been, or are now. It’s got a cool new trendy term – “Private Cloud”, but the fact is, if you have your setup automated, the HA and DR handled, balancing and performance tuning done, and a process wrapped around it all, you can call yourself a “Cloud Provider”. A good example here is your E-Mail system. your users – pretty much your whole company – just logs into e-mail and expects it to work. To them, you are the “Cloud” provider. On your side, the more you automate and provision the system, the more you act like a Cloud Provider. Another example is a database server. In this case, the “end user” is usually the development team, or perhaps your SharePoint group and so on. The data professionals configure, monitor, tune and balance the system all the time. The more this is automated, the more you’re acting like a Cloud Provider. Lots of companies help you do this in your own data centers, from VMWare to IBM and many others. Microsoft's offering in this is based around System Center – they have a “cloud in a box” provisioning system that’s actually pretty slick. The most difficult part of operating a Private Cloud is probably the scale factor. In the case of Windows and SQL Azure, we handle this in multiple ways – and we're happy to share how we do it. It’s not magic, and the algorithms for balancing (like the one we started with called Paxos) are well known. The key is the knowledge, infrastructure and people. Sure, you can do this yourself, and in many cases such as top-secret or private systems, you probably should. But there are times where you should evaluate using Azure or other vendors, or even multiple vendors to spread your risk. All of this should be based on client need, not on what you know how to do already. So congrats on your new role as a “Cloud Provider”. If you have an E-mail system or a database platform, you can just put that right on your resume.

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• Binary Search Tree for specific intent

  - by Luís Guilherme

  We all know there are plenty of self-balancing binary search trees (BST), being the most famous the Red-Black and the AVL. It might be useful to take a look at AA-trees and scapegoat trees too. I want to do deletions insertions and searches, like any other BST. However, it will be common to delete all values in a given range, or deleting whole subtrees. So: I want to insert, search, remove values in O(log n) (balanced tree). I would like to delete a subtree, keeping the whole tree balanced, in O(log n) (worst-case or amortized) It might be useful to delete several values in a row, before balancing the tree I will most often insert 2 values at once, however this is not a rule (just a tip in case there is a tree data structure that takes this into account) Is there a variant of AVL or RB that helps me on this? Scapegoat-trees look more like this, but would also need some changes, anyone who has got experience on them can share some thougts? More precisely, which balancing procedure and/or removal procedure would help me keep this actions time-efficient?

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• Forwarding HTTP Request with Direct Server Return

  - by Daniel Crabtree

  I have servers spread across several data centers, each storing different files. I want users to be able to access the files on all servers through a single domain and have the individual servers return the files directly to the users. The following shows a simple example: 1) The user's browser requests http://www.example.com/files/file1.zip 2) Request goes to server A, based on the DNS A record for example.com. 3) Server A analyzes the request and works out that /files/file1.zip is stored on server B. 4) Server A forwards the request to server B. 5) Server B returns file1.zip directly to the user without going through server A. Note: steps 4 and 5 must be transparent to the user and cannot involve sending a redirect to the user as that would violate the requirement of a single domain. From my research, what I want to achieve is called "Direct Server Return" and it is a common setup for load balancing. It is also sometimes called a half reverse proxy. For step 4, it sounds like I need to do MAC Address Translation and then pass the request back onto the network and for servers outside the network of server A tunneling will be required. For step 5, I simply need to configure server B, as per the real servers in a load balancing setup. Namely, server B should have server A's IP address on the loopback interface and it should not answer any ARP requests for that IP address. My problem is how to actually achieve step 4? I have found plenty of hardware and software that can do this for simple load balancing at layer 4, but these solutions fall short and cannot handle the kind of custom routing I require. It seems like I will need to roll my own solution. Ideally, I would like to do the routing / forwarding at the web server level, i.e. in PHP or C# / ASP.net. However, I am open to doing it at a lower level such as Apache or IIS, or at an even lower level, i.e. a custom proxy service in front of everything.

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• Sonicwall SSL VPN Login : I need help with a NetExtender initialization error.

  - by jacke672

  I receive the error message: "Server is busy now, please try it later!" after logging into our Sonicwall successfully and attempting to initialize NetExtender for the "virtual office" function. It was set up yesterday and I am able to log in without any issues, but I keep getting hung up on the installation and/or initialization of NetExtender. I have attempted to connect remotely on XP and 7 using both FireFox and IE. I am using a Sonicwall NSA-240 with load balancing active (1 ISP and 2 different connections)- I have tried turning off load balancing and disabling the secondary connection but still receive the same error. I've been in contact with SonicWall support but I haven't heard from them as of yet so I'm asking the Server Fault community in the meantime... Does anyone have any ideas as per what could be the issue? Thanks -Jack

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• Load-balancer options

  - by toolkit

  I am looking at a number of possible options for load-balancing. So far, I am constrained to the following options: DNS server load-balancer, balancing to a cluster of tomcat servers, with terracotta for session replication. Pros - don't have to buy new kit. Cons - DNS lb can keep directing to a broken server. Hardware load-balancer, direct to cluster of tomcat servers. Pros - could have second box for failover lb. Cons - expense. Apache server load-balancer. Pros - apache's lb polls for broken servers. Cons - apache server is single point of failure, plus need to buy another server. Are there any other options I should consider? Thanks. Update: Thanks for all the answers so far +1's all round. Not accepting an answer yet, to keep more ideas coming.

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• CentOS Failover Cluster - SIOCADDRT: No such process (when adding a loopback)

  - by Steve Rolfe

  I'm trying to configure two web servers for a load balancing server. The load balancing aspect works fine (it sees both server, kills 'em if it needs to, and seems to direct traffic fine). The only issue is with the servers looping: /etc/sysconfig/network-scripts/ifcfg-lo:0 DEVICE=lo:0 IPADDR=<Virtual IP> NETMASK=255.255.255.255 ONBOOT=yes NAME=loopback Everytime I try a "service network restart" I get a SIOCADDRT: No such process when loading the loopback interface. Anyone have an idea what's causing this?

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• Hot new GlassFish 3.1 bits released today

  - by pieter.humphrey

  Java EE 6 developers will wake up this morning and be able to experience a new, major release of the Oracle GlassFish Server and the companion GlassFish Server 3.1, Open Source Edition.  This release extends Java EE 6 Reference Implementation New Application Development Capabilities, Centralized Administration and High Availability Features.  IDE tool support will include NetBeans and Eclipse  (update center link is here), as well as the next release of Oracle Enterprise Pack for Eclipse will be updated to include the new GlassFish 3.1 Server Plug-in. Developers will be interested in the vastly improved OSGi support in GlassFish 3.1, as well as other developer friendly-features: - Enables hybrid application development Easily utilize OSGi services from Java EE Applications Easily utilize Java EE services from OSGi services - Updates the Apache Felix runtime to 3.0.6, including the Apache Gogo shell - OSGi Web Console integrated with GlassFish Admin Console (requires Update Center download, community supported) - Extends GlassFish Server 3.0 ActiveRedeploy feature to include Stateful EJBs. When applications are re-deployed, GlassFish maintains HTTP session and EJB state, enabling rapid iterative development - Application-scoped resources enable developers to limit the scope of resources to a deployed application - JDBC statement leak detection and reclaim automatically monitors, logs, and reclaims database cursors when applications fail to do so - Full EJB feature support in Embedded API Technorati Tags: OTN,Java EE6,Glassfish,Eclipse,Developer,OSGi,NetBeans,Oracle Enterprise Pack for Eclipse,clustering,high availablity,load balancing,failover,Oracle WebLogic Server del.icio.us Tags: OTN,Java EE6,Glassfish,Eclipse,Developer,OSGi,NetBeans,Oracle Enterprise Pack for Eclipse,clustering,high availablity,load balancing,failover,Oracle WebLogic Server

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• A Cautionary Tale About Multi-Source JNDI Configuration

  - by scott.s.nelson(at)oracle.com

  Here's a bit of fun with WebLogic JDBC configurations.  I ran into this issue after reading that p13nDataSource and cgDataSource-NonXA should not be configured as multi-source. There were some issues changing them to use the basic JDBC connection string and when rolling back to the bad configuration the server went "Boom".  Since one purpose behind this blog is to share lessons learned, I just had to post this. If you write your descriptors manually (as opposed to generating them using the WLS console) and put a comma-separated list of JNDI addresses like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool,contentDataSource, contentVersioningDataSource,portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0,portalDataSource-rac1</data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params> so long as the first address resolves, it will still work. Sort of.  If you call this connection to do an update, only one node of the RAC instance is updated. Other wonderful side-effects include the server refusing to start sometimes. The proper way to list the JNDI sources is one per node, like this: <jdbc-data-source-params> <jndi-name>weblogic.jdbc.jts.commercePool</jndi-name> <jndi-name>contentDataSource</jndi-name> <jndi-name>contentVersioningDataSource</jndi-name> <jndi-name>portalFrameworkPool</jndi-name> <algorithm-type>Load-Balancing</algorithm-type> <data-source-list>portalDataSource-rac0, portalDataSource-rac1, portalDataSource-rac2 </data-source-list> <failover-request-if-busy>false</failover-request-if-busy> </jdbc-data-source-params>(Props to Sandeep Seshan for locating the root cause)

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• HAProxy NGInx SSL setup

  - by Niclas

  I've been looking around different setups for a server cluster supporting SSL and I would like to benchmark my idea with you. Requirements: All servers in the cluster should be under the same full domain name. (http and https) Routing to subsystems is done on URI matching in HA proxy. All URIs have support for SSL support. Wish: Centralizing routing rules ---<----http-----<-- | | Inet -->HA--+---https--->NGInx_SSL_1..N | | +---http---> Apache_1..M | +---http---> NodeJS Idea: Configure HA to route all SSL traffic (mode=tcp,algorithm=Source) to an NGInx cluster turning https traffic into http. Re-pass the http traffic from NGInx to the HA for normal load-balancing which performs load balancing based on HA config. My question is simply: Is this the best way to to configure based on requirements above?

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• Oracle Traffic Director – download and check out new cool features in 11.1.1.7.0 by Frances Zhao

  - by JuergenKress

  As Oracle's strategic layer-7 software load balancer product, Oracle Traffic Direct is fast, reliable, secure, easy-to-use and scalable; that you can deploy as the reliable entry point for all TCP, HTTP and HTTPS traffic to application servers and web servers in your network. The latest release Oracle Traffic Director 11.1.1.7.0 is available for ExaLogic and Database Appliance! For download and details please visit the Traffic Director OTN website. It this release, we have introduced some major new functionality and improvements. Web application firewall. Oracle Traffic Director supports web application firewalls. A web application firewall (WAF) is a filter or server plugin that applies a set of rules, called rule sets, to an HTTP request. Using a web application firewall, users can inspect traffic and deny requests to protect back-end applications from CSRF vulnerabilities and common attacks such as cross-site scripting. WebSocket Connections. Oracle Traffic Director handles WebSocket connections by default. WebSocket connections are long-lived and allow support for live content, games in real-time, video chatting, and so on. Support for LDAP/T3 Load Balancing. Oracle Traffic Director now supports basic LDAP/T3 load balancing at layer 7, where requests are handled as generic TCP connections for traffic tunneling. It works in full-NAT mode. Please download and try it out. For more information, check out the data sheet and the documentation. For regular information become a member in the WebLogic Partner Community please visit: http://www.oracle.com/partners/goto/wls-emea ( OPN account required). If you need support with your account please contact the Oracle Partner Business Center. Blog Twitter LinkedIn Mix Forum Wiki Technorati Tags: traffic director,WebLogic Community,Oracle,OPN,Jürgen Kress

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• Want to SASL/TLS authentication

  - by Naval

  I want to send mail from remote client from my server(centos 5 and 64 bit) for this i need to sasl auth but i have no idea about it what changes i have to make in my server and client here I want to make things more clear my server's hostname/Ip is = test02.s80.in/176.67.172.209 now i want to authenticat remote client vps2.smail.info and vps1.smail.info to deliver mail .. so plz help me if any systematic way to do sasl/tls authentication for these clients... i am using DNS load-balancing(round-robin) mx record lookup technique for load balancing..

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• Cheapest High Available Web Server [closed]

  - by xyz

  I would like to create a high-available setup (e.g. a small cluster) for a webserver, i.e. it will run Apache, PHP and MySQL. There will be between 2-8 small websites running with only very little traffic and workload. High availability is however very important. I don't want to be dependent on 1 datacenter, so there must be a minimum of 2 servers placed in different datacenters, and if one server goes down, the user must experience no or only a minimum of downtime - and no data loss. I have considered Amazon AWS using their Elastic Load Balancing, since it is possible to buy 2 EC2 instances in 2 availability zones and set up load balancing and RDS (Multi-AZ). However this seems rather expensive. Using the AWS price calculator http://calculator.s3.amazonaws.com/calc5.html it totals to 185$/month the first year (including the free tier). Are my calculations incorrect or is there a cheaper way to make this HA setup? Best regards

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• How to setup Wordpress High Availability

  - by Ketam

  I have installed Galera Cluster on 3 cluster + 1 management. I wanted to make it like this, Server1: Home (www.domain.com) Server2: For BBpress/Forum (Forum Tab Menu will forward to forum.domain.com) Server3: BuddyPress Activity (Social Tab Menu will forward to social.domain.com) The purpose I am doing this is to distribute my resource and load balancing each other at same time. However, I have difficulty to setup Apache Load-Balancing/mod_proxy/clustering or any suitable to have high availability WordPress. Any best suggestion/solution to make high availability WordPress? Or how to? And another question is I tried to copy whole WordPress files & folders to Server2 connecting to local database (same data inside since it is already on Galera Cluster) but the page blank. Any advice? OS: Centos 6.2 Thanks in advanced.

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• Haproxy Slow Reload in DB Mode

  - by com

  Recently I started using great tool for load balancing - Haproxy. There is only one disturbing thing that I cannot figure out how to deal with it. We use haproxy for load balancing mysql traffic. When there is a lot of traffic and many connection it takes ages for haproxy to reload (~ 30 min), with less traffic it doest reload within 1 min. I do reload with: service haproxy reload Of course if I need to do an urgent change in configuration I expect haproxy to do reload very fast. Killing haproxy instances waiting for disconnection causes to disconnection of msyql connections. It looks like that I made mistake in settings of haproxy or in settings of application. If you know how to solve this please help me. Thanks!

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• The Interaction between Three-Tier Client/Server Model and Three-Tier Application Architecture Model

  The three-tier client/server model is a network architectural approach currently used in modern networking. This approach divides a network in to three distinct components. Three-Tier Client/Server Model Components Client Component Server Component Database Component The Client Component of the network typically represents any device on the network. A basic example of this would be computer or another network/web enabled devices that are connected to a network. Network clients request resources on the network, and are usually equipped with a user interface for the presentation of the data returned from the Server Component. This process is done through the use of various software clients, and example of this can be seen through the use of a web browser client. The web browser request information from the Server Component located on the network and then renders the results for the user to process. The Server Components of the network return data based on specific client request back to the requesting client.  Server Components also inherit the attributes of a Client Component in that they are a device on the network and that they can also request information from other Server Components. However what differentiates a Client Component from a Server Component is that a Server Component response to requests from devices on the network. An example of a Server Component can be seen in a web server. A web server listens for new requests and then interprets the request, processes the web pages, and then returns the processed data back to the web browser client so that it may render the data for the user to interpret. The Database Component of the network returns unprocessed data from databases or other resources. This component also inherits attributes from the Server Component in that it is a device on a network, it can request information from other server components and database components, and it also listens for new requests so that it can return data when needed. The three-tier client/server model is very similar to the three-tier application architecture model, and in fact the layers can be mapped to one another. Three-Tier Application Architecture Model Presentation Layer/Logic Business Layer/Logic Data Layer/Logic The Presentation Layer including its underlying logic is very similar to the Client Component of the three-tiered model. The Presentation Layer focuses on interpreting the data returned by the Business Layer as well as presents the data back to the user.  Both the Presentation Layer and the Client Component focus primarily on the user and their experience. This allows for segments of the Business Layer to be distributable and interchangeable because the Presentation Layer is not directly integrated in with Business Layer. The Presentation Layer does not care where the data comes from as long as it is in the proper format. This allows for the Presentation Layer and Business Layer to be stored on one or more different servers so that it can provide a higher availability to clients requesting data. A good example of this is a web site that uses load balancing. When a web site decides to take on the task of load balancing they must obtain a network device that sits in front of a one or machines in order to distribute the request across multiple servers. When a user comes in through the load balanced device they are redirected to a specific server based on a few factors. Common Load Balancing Factors Current Server Availability Current Server Response Time Current Server Priority The Business Layer and corresponding logic are business rules applied to data prior to it being sent to the Presentation Layer. These rules are used to manipulate the data coming from the Data Access Layer, in addition to validating any data prior to being stored in the Data Access Layer. A good example of this would be when a user is trying to create multiple accounts under one email address. The Business Layer logic can prevent duplicate accounts by enforcing a unique email for every new account before the data is even stored in the Data Access Layer. The Server Component can be directly tied to this layer in that the server typically stores and process the Business Layer before it is returned to the end-user via the Presentation Layer. In addition the Server Component can also run automated process through the Business Layer on the data in the Data Access Layer so that additional business analysis can be derived from the data that has been already collected. The Data Layer and its logic are responsible for storing information so that it can be easily retrieved. Typical in most modern applications data is stored in a database management system however data can also be in the form of files stored on a file server. In addition a database can take on one of several forms. Common Database Formats XML File Pipe Delimited File Tab Delimited File Comma Delimited File (CSV) Plain Text File Microsoft Access Microsoft SQL Server MySql Oracle Sybase The Database component of the Networking model can be directly tied to the Data Layer because this is where the Data Layer obtains the data to return back the Business Layer. The Database Component basically allows for a place on the network to store data for future use. This enables applications to save data when they can and then quickly recall the saved data as needed so that the application does not have to worry about storing the data in memory. This prevents overhead that could be created when an application must retain all data in memory. As you can see the Three-Tier Client/Server Networking Model and the Three-Tiered Application Architecture Model rely very heavily on one another to function especially if different aspects of an application are distributed across an entire network. The use of various servers and database servers are wonderful when an application has a need to distribute work across the network. Network Components and Application Layers Interaction Database components will store all data needed for the Data Access Layer to manipulate and return to the Business Layer Server Component executes the Business Layer that manipulates data so that it can be returned to the Presentation Layer Client Component hosts the Presentation Layer that  interprets the data and present it to the user

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