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• Apache2 mod_proxy to remote Tomcat7 - slow response

  - by 12N

  Been stuck with this one for a few days. Will try to provide as much information as possible, but please feel free to ask for extra detail. I have 2 VMs behind a NAT, 192.168.0.100 and 192.168.0.102, both running Ubuntu 11.04 x64. The first one is mapped to the exterior and is our webserver, has one Apache/2.2.17 install with several vhosts to serve static content, and there's also mod_jk for load balancing. The second one has a tomcat 7 install with several J2EE REST webservices but no apache - requests are expected to be passed directly from .100 apache to .102 tomcat. It is my intention to prepare a tomcat clustered environment. My problem: Requests reach to 192.168.0.100 with no trouble whatsoever, but then take about... 100 seconds for data to actually arrive to .102 - by that time apache has already timeouted, but tomcat receives and processes the request pretty normally. This happens both when using mod_jk, mod_proxy, or mod_ajp_proxy. No idea why, since there are no firewalls in either of the machines, both are pingable - more than that, there are NFS shares active working like a charm - and a mod_proxy experience shown that requests originating directly from .100 are processed normally. Also, to add insult to injury, a similar environment is set up at our office network. Everything works perfectly. -_- The only difference? We have no ip translation at the office and do everything by internal addresses - dunno if that's relevant in any way. Some configs: Apache vhost: <VirtualHost *:80> ServerAdmin webmaster@localhost DocumentRoot /var/www/ ServerName www.example.com ProxyRequests Off <Proxy *> Options Indexes FollowSymLinks MultiViews AllowOverride all Order allow,deny allow from all </Proxy> ProxyPass /bork http://192.168.0.102:8080/bork ProxyPassReverse /bork http://192.168.0.102:8080/bork LogLevel debug CustomLog ${APACHE_LOG_DIR}/api_access.log combined ErrorLog ${APACHE_LOG_DIR}/api_error.log </VirtualHost> Tomcat connectors <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" enableLookups="false" redirectPort="8443" protocol="AJP/1.3" /> And a debug log from apache, from a test using mod_proxy_ajp. The behavior is pretty much the same in mod_proxy, at least regarding the delay. Please note that tomcat eventually receives and processes the request, more or less when the log starts being updated again: [Sun May 06 14:40:33 2012] [debug] proxy_util.c(1506): [client 188.81.234.2] proxy: ajp: found worker ajp://192.168.0.102:8008/bork for ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap [Sun May 06 14:40:33 2012] [debug] mod_proxy.c(1015): Running scheme ajp handler (attempt 0) [Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(661): proxy: AJP: serving URL ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap [Sun May 06 14:40:33 2012] [debug] proxy_util.c(2011): proxy: AJP: has acquired connection for (192.168.0.102) [Sun May 06 14:40:33 2012] [debug] proxy_util.c(2067): proxy: connecting ajp://192.168.0.102:8008/bork/SSOIdentityProviderSoap to 192.168.0.102:8008 [Sun May 06 14:40:33 2012] [debug] proxy_util.c(2193): proxy: connected /bork/SSOIdentityProviderSoap to 192.168.0.102:8008 [Sun May 06 14:40:33 2012] [debug] proxy_util.c(2444): proxy: AJP: fam 2 socket created to connect to 192.168.0.102 [Sun May 06 14:40:33 2012] [debug] ajp_header.c(224): Into ajp_marshal_into_msgb [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[0] [Accept-Encoding] = [gzip,deflate] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[1] [Content-Type] = [text/xml;charset=UTF-8] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[2] [SOAPAction] = [""] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[3] [User-Agent] = [Jakarta Commons-HttpClient/3.1] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[4] [Host] = [www.example.com] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(290): ajp_marshal_into_msgb: Header[5] [Content-Length] = [520] [Sun May 06 14:40:33 2012] [debug] ajp_header.c(450): ajp_marshal_into_msgb: Done [Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(267): proxy: APR_BUCKET_IS_EOS [Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(272): proxy: data to read (max 8186 at 4) [Sun May 06 14:40:33 2012] [debug] mod_proxy_ajp.c(287): proxy: got 520 bytes of data [Sun May 06 14:40:33 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 06 [Sun May 06 14:40:33 2012] [debug] ajp_header.c(697): ajp_parse_type: got 06 [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 2 in child 5916 for worker ajp://192.168.0.100:8008/coding [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.100:8008/coding already initialized [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5916 for (192.168.0.100) [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5916 for worker http://192.168.0.102:8080 [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5916 for (192.168.0.102) [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5916 for worker ajp://192.168.0.102:8008/bork [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized [Sun May 06 14:40:37 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5916 for (192.168.0.102) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5918 for (192.168.0.100) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5918 for worker http://192.168.0.102:8080 [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5918 for (192.168.0.102) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5918 for worker ajp://192.168.0.102:8008/bork [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5918 for (192.168.0.102) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 2 in child 5917 for worker ajp://192.168.0.100:8008/coding [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.100:8008/coding already initialized [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 2 in child 5917 for (192.168.0.100) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 3 in child 5917 for worker http://192.168.0.102:8080 [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker http://192.168.0.102:8080 already initialized [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 3 in child 5917 for (192.168.0.102) [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1818): proxy: grabbed scoreboard slot 4 in child 5917 for worker ajp://192.168.0.102:8008/bork [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1837): proxy: worker ajp://192.168.0.102:8008/bork already initialized [Sun May 06 14:40:38 2012] [debug] proxy_util.c(1934): proxy: initialized single connection worker 4 in child 5917 for (192.168.0.102) [Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 04 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 04 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(516): ajp_unmarshal_response: status = 200 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(537): ajp_unmarshal_response: Number of headers is = 1 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(599): ajp_unmarshal_response: Header[0] [Content-Type] = [text/xml;charset=utf-8] [Sun May 06 14:42:09 2012] [debug] ajp_header.c(609): ajp_unmarshal_response: ap_set_content_type done [Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 03 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 03 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 03 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 03 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(687): ajp_read_header: ajp_ilink_received 05 [Sun May 06 14:42:09 2012] [debug] ajp_header.c(697): ajp_parse_type: got 05 [Sun May 06 14:42:09 2012] [debug] mod_deflate.c(615): [client 188.81.234.2] Zlib: Compressed 447 to 255 : URL /bork/SSOIdentityProviderSoap [Sun May 06 14:42:09 2012] [debug] mod_proxy_ajp.c(570): proxy: got response from (null) (192.168.0.102) [Sun May 06 14:42:09 2012] [debug] proxy_util.c(2029): proxy: AJP: has released connection for (192.168.0.102) [Sun May 06 14:42:09 2012] [info] [client 188.81.234.2] Request body read timeout Was wondering if any one could provide some advice, perhaps even point out any hideous, horrible configuration error? thanks in advance!

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• Post build events using ROBOCOPY instead of XCOPY

  - by Vizioz Limited

  I don't know about you, but for a long time I have used XCOPY statements in my Visual Studio post build events to copy my Umbraco files from the project folders to the local version of the website associated with the project.For the last few months we have been building a website framework for a client, who has subsequently sold the site to 5 clients, each with a different skin and some variations in their functional requirements.So, we now have a single source solutions, that builds and copies the site files into 5 seperate local websites, which enables us to easily test them all, what we had found was that this process was starting to slow up our build process and was reaching 30-45 seconds on a high spec Quad core machine (and slower on others)Today I asked Colin to create seperate Solution Configurations within Visual Studio so that while we were developing we could target a single site, and when we wanted to test all sites, we could target "ALL" and the Post Build script would then copy the files to all sites.This worked well, and with a couple of other optimisations, our build was now taking about 10 seconds for a single site.Then Colin came across ROBOCOPY and suggested that maybe this would be a suitable alternative to XCOPY, well, I had not heard of it.. (shock horror some of you shout, some I am sure like me, are also wondering what it is!)ROBOCOPY is new in Windows Vista & Windows 7 (you can also download it for XP & Windows 2003) and it has a lot of additional features, the two that were most interesting to us were:/MIR = Mirror a folder tree/XD = Exclude Directories/NP = No Progress (i.e. it does not give you a chart of it's results, which just fills up your Output window!)So, we set about implementing ROBOCOPY, we decided to use the /MIR switch on all folders that we knew were always stored in our project folders:- images- css- masterpages- xsltAnd for other files we just used the straight robocopy functionality.We also decided to exclude all the .SVN directories using the /XD switch and finally we added the /NP switch as mentioned above.The beauty of all of this, is the /MIR functionality, as this means that only files that have changed will be copied across which greatly speeds up the process, especially on the images folders which previously copied across on every build, now, if we add a new image to the project it will be copied across automatically and then never again, unless we change it of course!The build time now for all sites is approximately 4 seconds and for a single site, 2 seconds, I would highly recommend the time to make the same optimisations to your build processes if you have not done so already.

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• Best Practices - updated: which domain types should be used to run applications

  - by jsavit

  This post is one of a series of "best practices" notes for Oracle VM Server for SPARC (formerly named Logical Domains). This is an updated and enlarged version of the post on this topic originally posted October 2012. One frequent question "what type of domain should I use to run applications?" There used to be a simple answer: "run applications in guest domains in almost all cases", but now there are more things to consider. Enhancements to Oracle VM Server for SPARC and introduction of systems like the current SPARC servers including the T4 and T5 systems, the Oracle SuperCluster T5-8 and Oracle SuperCluster M6-32 provide scale and performance much higher than the original servers that ran domains. Single-CPU performance, I/O capacity, memory sizes, are much larger now, and far more demanding applications are now being hosted in logical domains. The general advice continues to be "use guest domains in almost all cases", meaning, "use virtual I/O rather than physical I/O", unless there is a specific reason to use the other domain types. The sections below will discuss the criteria for choosing between domain types. Review: division of labor and types of domain Oracle VM Server for SPARC offloads management and I/O functionality from the hypervisor to domains (also called virtual machines), providing a modern alternative to older VM architectures that use a "thick", monolithic hypervisor. This permits a simpler hypervisor design, which enhances reliability, and security. It also reduces single points of failure by assigning responsibilities to multiple system components, further improving reliability and security. Oracle VM Server for SPARC defines the following types of domain, each with their own roles: Control domain - management control point for the server, runs the logical domain daemon and constraints engine, and is used to configure domains and manage resources. The control domain is the first domain to boot on a power-up, is always an I/O domain, and is usually a service domain as well. It doesn't have to be, but there's no reason to not leverage it for virtual I/O services. There is one control domain per T-series system, and one per Physical Domain (PDom) on an M5-32 or M6-32 system. M5 and M6 systems can be physically domained, with logical domains within the physical ones. I/O domain - a domain that has been assigned physical I/O devices. The devices may be one more more PCIe root complexes (in which case the domain is also called a root complex domain). The domain has native access to all the devices on the assigned PCIe buses. The devices can be any device type supported by Solaris on the hardware platform. a SR-IOV (Single-Root I/O Virtualization) function. SR-IOV lets a physical device (also called a physical function) or PF) be subdivided into multiple virtual functions (VFs) which can be individually assigned directly to domains. SR-IOV devices currently can be Ethernet or InfiniBand devices. direct I/O ownership of one or more PCI devices residing in a PCIe bus slot. The domain has direct access to the individual devices An I/O domain has native performance and functionality for the devices it owns, unmediated by any virtualization layer. It may also have virtual devices. Service domain - a domain that provides virtual network and disk devices to guest domains. The services are defined by commands that are run in the control domain. It usually is an I/O domain as well, in order for it to have devices to virtualize and serve out. Guest domain - a domain whose devices are all virtual rather than physical: virtual network and disk devices provided by one or more service domains. In common practice, this is where applications are run. Device considerations Consider the following when choosing between virtual devices and physical devices: Virtual devices provide the best flexibility - they can be dynamically added to and removed from a running domain, and you can have a large number of them up to a per-domain device limit. Virtual devices are compatible with live migration - domains that exclusively have virtual devices can be live migrated between servers supporting domains. On the other hand: Physical devices provide the best performance - in fact, native "bare metal" performance. Virtual devices approach physical device throughput and latency, especially with virtual network devices that can now saturate 10GbE links, but physical devices are still faster. Physical I/O devices do not add load to service domains - all the I/O goes directly from the I/O domain to the device, while virtual I/O goes through service domains, which must be provided sufficient CPU and memory capacity. Physical I/O devices can be other than network and disk - we virtualize network, disk, and serial console, but physical devices can be the wide range of attachable certified devices, including things like tape and CDROM/DVD devices. In some cases the lines are now blurred: virtual devices have better performance than previously: starting with Oracle VM Server for SPARC 3.1 there is near-native virtual network performance. There is more flexibility with physical devices than before: SR-IOV devices can now be dynamically reconfigured on domains. Tradeoffs one used to have to make are now relaxed: you can often have the flexibility of virtual I/O with performance that previously required physical I/O. You can have the performance and isolation of SR-IOV with the ability to dynamically reconfigure it, just like with virtual devices. Typical deployment A service domain is generally also an I/O domain: otherwise it wouldn't have access to physical device "backends" to offer to its clients. Similarly, an I/O domain is also typically a service domain in order to leverage the available PCI buses. Control domains must be I/O domains, because they boot up first on the server and require physical I/O. It's typical for the control domain to also be a service domain too so it doesn't "waste" the I/O resources it uses. A simple configuration consists of a control domain that is also the one I/O and service domain, and some number of guest domains using virtual I/O. In production, customers typically use multiple domains with I/O and service roles to eliminate single points of failure, as described in Availability Best Practices - Avoiding Single Points of Failure . Guest domains have virtual disk and virtual devices provisioned from more than one service domain, so failure of a service domain or I/O path or device does not result in an application outage. This also permits "rolling upgrades" in which service domains are upgraded one at a time while their guests continue to operate without disruption. (It should be noted that resiliency to I/O device failures can also be provided by the single control domain, using multi-path I/O) In this type of deployment, control, I/O, and service domains are used for virtualization infrastructure, while applications run in guest domains. Changing application deployment patterns The above model has been widely and successfully used, but more configuration options are available now. Servers got bigger than the original T2000 class machines with 2 I/O buses, so there is more I/O capacity that can be used for applications. Increased server capacity made it attractive to run more vertically-scaled applications, such as databases, with higher resource requirements than the "light" applications originally seen. This made it attractive to run applications in I/O domains so they could get bare-metal native I/O performance. This is leveraged by the Oracle SuperCluster engineered systems mentioned previously. In those engineered systems, I/O domains are used for high performance applications with native I/O performance for disk and network and optimized access to the Infiniband fabric. Another technical enhancement is Single Root I/O Virtualization (SR-IOV), which make it possible to give domains direct connections and native I/O performance for selected I/O devices. Not all I/O domains own PCI complexes, and there are increasingly more I/O domains that are not service domains. They use their I/O connectivity for performance for their own applications. However, there are some limitations and considerations: at this time, a domain using physical I/O cannot be live-migrated to another server. There is also a need to plan for security and introducing unneeded dependencies: if an I/O domain is also a service domain providing virtual I/O to guests, it has the ability to affect the correct operation of its client guest domains. This is even more relevant for the control domain. where the ldm command must be protected from unauthorized (or even mistaken) use that would affect other domains. As a general rule, running applications in the service domain or the control domain should be avoided. For reference, an excellent guide to secure deployment of domains by Stefan Hinker is at Secure Deployment of Oracle VM Server for SPARC. To recap: Guest domains with virtual I/O still provide the greatest operational flexibility, including features like live migration. They should be considered the default domain type to use unless there is a specific requirement that mandates an I/O domain. I/O domains can be used for applications with the highest performance requirements. Single Root I/O Virtualization (SR-IOV) makes this more attractive by giving direct I/O access to more domains, and by permitting dynamic reconfiguration of SR-IOV devices. Today's larger systems provide multiple PCIe buses - for example, 16 buses on the T5-8 - making it possible to configure multiple I/O domains each owning their own bus. Service domains should in general not be used for applications, because compromised security in the domain, or an outage, can affect domains that depend on it. This concern can be mitigated by providing guests' their virtual I/O from more than one service domain, so interruption of service in one service domain does not cause an application outage. The control domain should in general not be used to run applications, for the same reason. Oracle SuperCluster uses the control domain for applications, but it is an exception. It's not a general purpose environment; it's an engineered system with specifically configured applications and optimization for optimal performance. These are recommended "best practices" based on conversations with a number of Oracle architects. Keep in mind that "one size does not fit all", so you should evaluate these practices in the context of your own requirements. Summary Higher capacity servers that run Oracle VM Server for SPARC are attractive for applications with the most demanding resource requirements. New deployment models permit native I/O performance for demanding applications by running them in I/O domains with direct access to their devices. This is leveraged in SPARC SuperCluster, and can be leveraged in T-series servers to provision high-performance applications running in domains. Carefully planned, this can be used to provide peak performance for critical applications. That said, the improved virtual device performance in Oracle VM Server means that the default choice should still be guest domains with virtual I/O.

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• Combine multiple unix commands into one output

  - by Ben McCormack

  I need to search our mail logs for a specific e-mail address. We keep a current file named maillog as well as a week's worth of .bz2 files in the same folder. Currently, I'm running the following commands to search for the file: grep [email protected] maillog bzgrep [email protected] *.bz2 Is there a way combine the grep and bzgrep commands into a single output? That way, I could pipe the combined results to a single e-mail or a single file.

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• multiple webapps in tomcat -- what is the optimal architecture?

  - by rvdb

  I am maintaining a growing base of mainly Cocoon-2.1-based web applications [http://cocoon.apache.org/2.1/], deployed in a Tomcat servlet container [http://tomcat.apache.org/], and proxied with an Apache http server [http://httpd.apache.org/docs/2.2/]. I am conceptually struggling with the best way to deploy multiple web applications in Tomcat. Since I'm not a Java programmer and we don't have any sysadmin staff I have to figure out myself what is the most sensible way to do this. My setup has evolved through 2 scenarios and I'm considering a third for maximal separation of the distinct webapps. [1] 1 Tomcat instance, 1 Cocoon instance, multiple webapps -tomcat |_ webapps |_ webapp1 |_ webapp2 |_ webapp[n] |_ WEB-INF (with Cocoon libs) This was my first approach: just drop all web applications inside a single Cocoon webapps folder inside a single Tomcat container. This seemed to run fine, I did not encounter any memory issues. However, this poses a maintainability drawback, as some Cocoon components are subject to updates, which often affect the webapp coding. Hence, updating Cocoon becomes unwieldy: since all webapps share the same pool of Cocoon components, updating one of them would require the code in all web applications to be updated simultaneously. In order to isolate the web applications, I moved to the second scenario. [2] 1 Tomcat instance, each webapp in its dedicated Cocoon environment -tomcat |_ webapps |_ webapp1 | |_ WEB-INF (with Cocoon libs) |_ webapp1 | |_ WEB-INF (with Cocoon libs) |_ webapp[n] |_ WEB-INF (with Cocoon libs) This approach separates all webapps into their own Cocoon environment, run inside a single Tomcat container. In theory, this works fine: all webapps can be updated independently. However, this soon results in PermGenSpace errors. It seemed that I could manage the problem by increasing memory allocation for Tomcat, but I realise this isn't a structural solution, and that overloading a single Tomcat in this way is prone to future memory errors. This set me thinking about the third scenario. [3] multiple Tomcat instances, each with a single webapp in its dedicated Cocoon environment -tomcat |_ webapps |_ webapp1 |_ WEB-INF (with Cocoon libs) -tomcat |_ webapps |_ webapp2 |_ WEB-INF (with Cocoon libs) -tomcat |_ webapps |_ webapp[n] |_ WEB-INF (with Cocoon libs) I haven't tried this approach, but am thinking of the $CATALINA_BASE variable. A single Tomcat distribution can be multiply instanciated with different $CATALINA_BASE environments, each pointing to a Cocoon instance with its own webapp. I wonder whether such an approach could avoid the structural memory-related problems of approach [2], or will the same issues apply? On the other hand, this approach would complicate management of the Apache http frontend, as it will require the AJP connectors of the different Tomcat instances to be listening at different ports. Hence, Apache's worker configuration has to be updated and reloaded whenever a new webapp (in its own Tomcat instance) is added. And there seems no way to reload worker.properties without restarting the entire Apache http server. Is there perhaps another / more dynamic way of 'modularizing' multiple Tomcat-served webapps, or can one of these scenarios be refined? Any thoughts, suggestions, advice much appreciated. Ron

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• 2 (or 3 or 4...) websites in IIS, pointing to same ASP.NET application IIS

  - by billfredtom

  I wish to maintain a single a single code base (ASP.NET app) setup at c:\inetpub\wwwroot\myApp, and point several IIS websites at this single code base. Will this be an issue? Will IIS see this as a conflict in resource allocation? Reasons why I want to do it: Each IIS website can then have it's own IP, SSL cert, etc. Each IIS website can have it's own ISAPI filters installed for friendly URLs, etc. Easier to maintain the code base by having single point of deployment

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• 14 WordPress Photo Blog & Portfolio Themes

  - by Aditi

  The best thing you can do to preserve your memories is to capture them. Photographs can help you relive all those sweet moments you had with your special someone or the ones closest to you. With the sudden explosion in the number of blogs on blogosphere it was quite obvious that many bloggers would like to share their most cherished memories on their blog. We saw blogs full of images along with the intricate details and now we are presenting you some WordPress themes to help you showcase your photography or make a photo blog so that you can share those small delights you captured with your special ones, no matter where they are. These WordPress photo blog themes are not just limited for personal use as some of them have been designed especially for professional use. Graphix Price: $69 Single & $149 Developer Package | DownLoad DeepFocus Price: $39 Package | DownLoad ReCapture Price: $50 or $75 Package | DownLoad PhotoGraphic Price: $50 or $75 Package | DownLoad PhotoLand Price: $39 Single & $99 Developer Package | DownLoad SimplePress Perfect Theme for showcasing your Portfolio, very simple & easy to navigate. Lots of Features. Price: $39 Single & $99 Developer Package | DownLoad ePhoto Price: $39 Single & $99 Developer Package | DownLoad Outline Price: $50 or $75 Package | DownLoad Gallery The theme features a simple options panel for easy setup, automatic resizing & cropping for thumbnails, and 5 colour styles. Price: $49 | DownLoad eGallery eGallery is one of the best theme to showcase your images. It has some features which you don’t see in any other themes of this kind. It’s particularly nice if you want to encourage social interaction as readers can rate and comment on your images. It is compatible with all major web browsers. Price: $39 | DownLoad Photoblog Price: $49 | DownLoad Ultra Web Studio Price: $30 | DownLoad Showtime Ultimate WordPress Theme for you to create your web portfolio, 3 different styles. Price: $40 | DownLoad Boomerang Price: $35 | DownLoad Related posts:6 PhotoBlog Portfolio WordPress Themes Wootube WordPress Video Blog Theme 7 Portfolio WordPress Themes

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• Oracle Access Manager 11.1.2 Certified with E-Business Suite 12

  - by Elke Phelps (Oracle Development)

  I am happy to announce that Oracle Access Manager 11gR2 (11.1.2) is now certified with E-Business Suite Releases 12.0.6 and 12.1. If you are implementing single sign-on for the first time, or are an existing Oracle Access Manager user, you may integrate with Oracle Access Manager 11gR2 using Oracle Access Manager WebGate and Oracle E-Business Suite AccessGate. Supported Architecture and Release Versions Oracle Access Manager 11.1.2 Oracle E-Business Suite Release 12.0.6, 12.1.1+ Oracle Identity Management 11.1.1.5, 11.1.1.6 Oracle Internet Directory 11.1.1.6 Oracle WebLogic Server 10.3.0.5+ What's New In This Oracle Access Manager 11gR2 Integration? Simplified integration: We've simplified the instructions and cut the number of pages, while adding clarity to the steps. Automation of configuration steps:  We've automated some of the required configuration steps. This is the first phase of automation and diagnostics that are part of our roadmap for this integration. Use of default OAM Login page: We are reducing the required troubleshooting by delivering the default OAM Login page for the integration. A custom login page can still be created by using Oracle Access Manager. Use of the Detached Credential collector in a Demilitarized Zone: We have certified the Detached Credential collector as part of a DMZ configuration. This will enhance the security of the underlying Oracle Access Manager and E-Business Suite components, which will now be required only within a company's intranet.   Choosing the Right Architecture Our previously published blog article and support note with single sign-on recommended and certified integration paths has been updated to include Oracle Access Manager 11gR2: Overview of Single Sign-On Integration Options for Oracle E-Business Suite (Note 1388152.1) Other References Integrate with Oracle Access Manager 11gR2 (11.1.2) using Oracle E-Business Suite AccessGate (Note 1484024.1) Overview of Single Sign-On Integration Options for Oracle E-Business Suite (Note 1388152.1) Related Articles Understanding Options for Integrating Oracle Access Manager with E-Business Suite Why Does E-Business Suite Integration with OAM Require Oracle Internet Directory? In-Depth: Using Third-Party Identity Managers with E-Business Suite Release 12

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• Implications of using many USB web cameras

  - by Martin

  I'm looking into connecting multiple low resolution USB webcams to a single computer. What implications might this have on performance? How does, for example, four 320x240 cameras fare against a single 640x480 camera? I'm not well versed in the architecture of the USB interface, what are the performance caveats? By performance I mean how would it affect the time to read the image data from multiple cameras compared to a single one.

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• Multi-level wildcard (catch-all) DNS setup *.*.domain.com => one IP/CNAME

  - by Jan Rovner

  It is well known that it is possible to configure a DNS server to do a "catch-all" resolving on a single subdomain level, such as *.example.com. IN A x.x.x.x, so that anything.example.com maps to a single IP/CNAME. However, I need to set up an at least "level-2" wildcard sub-subdomain catch-all wildcard system so that any.thing.example.com or better, item.of.any.level.under.example.com will be resolved to a single IP. Has anyone got this working?

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• Easily Close All Tabs in Google Chrome

  - by Asian Angel

  Do you find yourself with a lot of tabs open but dread closing all but one manually? Now you can close all of your tabs with a single click, and have just one ready to go with the Close all Tabs extension. Before We all find ourselves with a lot of tabs open sooner or later. That is not so bad until we realize that we need to close all of them and get back to work. A person could open a new tab and manually close the rest or close the entire window and restart Chrome. But a single click solution would be a lot more convenient. After There it is…the single click solution. Just click the Toolbar Button and BOOM! One fresh window with a single new tab page showing. Now if you could only take the rest of the day off… Conclusion The Close all Tabs extension may not be something that everyone would use, but if you are tired of manually closing all of those tabs then you will definitely like it. Links Download the Close all Tabs extension (Google Chrome Extensions) Similar Articles Productive Geek Tips Focused New Tabs Quick-Fix for Google ChromeVisually Browse Through Your Open Tabs in Google ChromeMake Google Chrome Open with Pinned TabsStupid Geek Tricks: Compare Your Browser’s Memory Usage with Google ChromeEasily Control a Large Amount of Tabs in Google Chrome TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Acronis Online Backup DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows Fun with 47 charts and graphs Tomorrow is Mother’s Day Check the Average Speed of YouTube Videos You’ve Watched OutlookStatView Scans and Displays General Usage Statistics How to Add Exceptions to the Windows Firewall Office 2010 reviewed in depth by Ed Bott

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• Configuring a Unified Communications Certificate for many virtual hosts running in Jetty

  - by rrc7cz

  I have a single IP with Jetty serving up X sites on port 80. Basically you can sign up for our service, then point your domain www.mycompany.com to that IP, and Jetty will serve up your custom site. I would like to add SSL support for all sites. To simplify things, I've looked at getting a single Unified Communications Certificate to plug into Jetty and have it work for all sites. Is this possible? Has anyone done this before? Does Jetty only support traditional, single-domain certs? What issues might I run in to compared to a single-domain cert?

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• DAS vs SAN storage for serving 2 to 4 nodes

  - by Luke404

  We currently have 4 Linux nodes with local storage, arranged in two active/passive pairs with storage mirrored using DRBD, running virtual machines (actually using Xen Hypervisor) for typical hosting workloads (mail, web, a couple VPS, etc.). We're approaching the (presumed) maximum IOPS of those servers, and we're planning to migrate to an external storage solution with two active nodes, with capacity for up to four active nodes. Since we're an all-Dell shop I've done some research and found the MD3200 / MD3200i products should be the ones we're looking for. We are pretty sure we won't be attaching more than 4 hosts on a single storage and I'm wondering if there is any clear advantage for one or the other. In theory I should be able to attach 4 SAS hosts to a single MD3200 (single links on a single controller MD3200, or dual redundant SAS links from each host to a dual-controller MD3200), or 4 iSCSI hosts to a single MD3200i (directly on its 4 GigE ports without any switch, again with dual links for the dual controller option). Both setups should let us implement live VM migration since all hosts can access all the LUNs at the same time, and also some shared filesystem like GFS2 or OCFS2. Also, both setups should allow full redundancy of the whole system (assuming dual controllers in the storage). One difference I can see is that the DAS solution is actually limited to 4 hosts while the iSCSI one should be able to grow to more hosts (adding two GigE switches to the mix). One point for the iSCSI solution is that it would allow us to start out with our current nodes and upgrade them at a later time (we can't add other SAS controllers, but they already have 4 GigE ports each). With the right (iSCSI|SAS) controllers I should be able to connect diskless nodes and boot them off the external storage which I think is a good thing (get rid of any local storage). On the other hand, I would have thought the SAS one to be cheaper but it seems like an MD3200 actually costs a little less than an MD3200i (?) (please note: I've used Dell gear in my examples since that's what we're looking for but I assume the same goes with other vendors) I would like to know if my assumptions above are correct, and if I'm missing any important difference between the two setups.

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• How print multiple independent pages in one print job?

  - by C.W.Holeman II

  How can I combine multiple single page prints into a single print job? For example, using Firefox on Linux one can print a web page such that each sheet of paper has four pages printed upon it. I would like to combine several separate web pages so that for example, web-page-a, web-page-b and web-page-c (each less than one print page long) are printed on a single sheet of paper. I would like to do this without having to use some for of image editor to combine them.

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• Producer-consumer pattern with consumer restrictions

  - by Dan

  I have a processing problem that I am thinking is a classic producer-consumer problem with the two added wrinkles that there may be a variable number of producers and there is the restriction that no more than one item per producer may be consumed at any one time. I will generally have 50-100 producers and as many consumers as CPU cores on the server. I want to maximize the throughput of the consumers while ensuring that there are never more than one work item in process from any single producer. This is more complicated than the classic producer-consumer problem which I think assumes a single producer and no restriction on which work items may be in progress at any one time. I think the problem of multiple producers is relatively easily solved by enqueuing all work items on a single work queue protected by a critical section. I think the restriction on simultaneously processing work items from any single producer is harder because I cannot think of any solution that does not require each consumer to notify some kind of work dispatcher that a particular work item has been completed so as to lift the restriction on work items from that producer. In other words, if Consumer2 has just completed WorkItem42 from Producer53, there needs to be some kind of callback or notification from Consumer2 to a work dispatcher to allow the work dispatcher to release the next work item from Producer53 to the next available consumer (whether Consumer2 or otherwise). Am I overlooking something simple here? Is there a known pattern for this problem? I would appreciate any pointers.

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• Microsoft Outlook: show multi-day appointments as boxes in calendar day and week view

  - by Bernd

  I would like to show appointments spanning several days the same way as appintments within a single day. Single day appointments are shown with a white or colored box, covering the day horizontally. Multi-day appointments are shown in the day/week header and are indicated blue or purple on the left side of a day. This happens even if a multi-day appointment is not an all-day appointment (i.e. checkbox is off) and I have a start and end time. I frequently have a hard time seeing appointment overlaps wenn acceping single day appointments. Therefore I am looking for multi-day appointments shown the same way as single day appointments. I am on Outlook 2003.

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• Should the syntax for disabling code differ from that of normal comments?

  - by deltreme

  For several reasons during development I sometimes comment out code. As I am chaotic and sometimes in a hurry, some of these make it to source control. I also use comments to clarify blocks of code. For instance: MyClass MyFunction() { (...) // return null; // TODO: dummy for now return obj; } Even though it "works" and alot of people do it this way, it annoys me that you cannot automatically distinguish commented-out code from "real" comments that clarify code: it adds noise when trying to read code you cannot search for commented-out code for for instance an on-commit hook in source control. Some languages support multiple single-line comment styles - for instance in PHP you can either use // or # for a single-line comment - and developers can agree on using one of these for commented-out code: # return null; // TODO: dummy for now return obj; Other languages - like C# which I am using today - have one style for single-line comments (right? I wish I was wrong). I have also seen examples of "commenting-out" code using compiler directives, which is great for large blocks of code, but a bit overkill for single lines as two new lines are required for the directive: #if compile_commented_out return null; // TODO: dummy for now #endif return obj; So as commenting-out code happens in every(?) language, shouldn't "disabled code" get its own syntax in language specifications? Are the pro's (separation of comments / disabled code, editors / source control acting on them) good enough and the cons ("shouldn't do commenting-out anyway", not a functional part of a language, potential IDE lag (thanks Thomas)) worth sacrificing? Edit I realise the example I used is silly; the dummy code could easily be removed as it is replaced by the actual code.

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• Sprite transparency not effected libGDX

  - by Aon GoltzCrank

  I am making a game using libGDX and Tween Universal Engine. My problem is as follows: I have 2 screens so fars, a splash screen with the logo, and a second one which is the main menu. In the splash screen I use a SpriteBatch and a Sprite with the Texture of the image I want (which goes through some scaling.) Now I use the Tween engine, along with a created SpriteAccessor to control the alpha of the sprite. I fade the picture in, then fade it out, then change it to the next screen. In the next screen I have a single sprite, and a single, 3 slot, sprite array. In this screen I also use the tween engine, I fade the single sprite into the screen (it's the background image) then I try to, using the same method, (Tween.to) to change the alpah of the sprite array (each sprite by itself.), I first set it to 0 using Tween.set, then using the method I change it. This didn't work, after some tests I tried setting the alpha of a single sprite from the array to 0, and that didn't work. It's like the program is ignoring the alpha value, I even printed out the alpha value, it saying 0, but the sprite is visible. How can I fix this, or why might it be caused?

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• How to keep background requests in sequence

  - by Jason Lewis

  I'm faced with implementing interfaces for some rather archaic systems, for handling online deposits to stored value accounts (think campus card accounts for students). Here's my dilemma: stage 1 of the process involves passing the user off to a thrid-party site for the credit card transaction, like old-school PayPal. Step two involves using a proprietary protocol for communicating with a legacy system for conducting the actual deposit. Step two requires that each transaction have a unique sequence number, and that the requests' seqnums are in order. Since we're logging each transaction in Postgres, my first thought was to take a number from a sequence in the DB, guaranteeing uniqueness. But since we're dealing with web requests that might come in near-simultaneously, and since latency with the return from the off-ste payment processor is beyond our control, there's always the chance for a race condition in the order of requests passed back to the proprietary system, and if the seqnums are out of order, the request fails silently (brilliant, right?). I thought about enqueuing the requests in Redis and using Resque workers to process them (single worker, single process, so they are processed in order), but we need to be able to give the user feedback as to whether the transaction was processed successfully, so this seems less feasible to me. I've tried to make this application handle concurrency well (as much as possible for a Ruby on Rails app), but now we're in a situation where we have to interact with a system that is designed to be single process, single threaded, and sequential. If it at least gave an "out of order" error, I could just increment (or take the next value off the sequence), but it's designed to fail silently in the event of ANY error. We are handling timeouts in a way that blocks on I/O, but since the application uses multiple workers (Unicorn), that's no guarantee. Any ideas/suggestions would be appreciated.

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• Excel: Change all cells with one character to something else

  - by Allan

  Is there a formula I can use that will change all cells with one character to something else? For example, I have cells with single letters and no matter what the letter is I want that cell to contain the word Member. More Info: I get spreadsheets that contain, up to 40,000 rows. Column B will have names in the cells. Every once in a while a column will just have an initial instead of a full name. I'm looking for a way to change every single cell containing only one single character to the word "Member." The cells that need to change could be any letter but no matter what that letter is, if it's just a single letter in a cell, it needs to change to the word "Member."

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• Is it possible to use bittorrent for a fileserver

  - by sris

  I would like to set up a file server that is searchable, preferable via the web. I'm wondering if it would be possible to achieve this using the bittorrent protocol and have a single client sharing every single torrent on the server. I guess I could use some available tracker solution for the webinterface or write one myself. My concerns are the if there are any limits to the number of torrents a single client can share since this may potentially be 10k torrents. The number of downloading clients is very small, only myself and my relatives. The idea is to have a single place to host everything from vacation photos to musical creations. Is there any other options for this kind of file server. It should also be easy to upload files to the server.

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• Multiple domains for different products?

  - by alexandertr

  I have a website with software applications. Is it good for SEO to choose one keyword rich domain name for each of our software products or should we stick to a single domain? From a user's perspective I think it would be easier to remember a domain that is keyword rich as the user will instantly know what this product is for. But I have read articles that the latest trend in SEO is to stick to one domain for all of your products and invest on this single domain website. Is that true? What do you advise? Should I register a separate domain for each of our products or should I use only one single domain? Should I do a 301 redirect with a .htaccess to a single domain? And what about the sitemaps? Should I register all sites in Google Webmaster Tools and post a separate sitemap for each one of them? should my main site sitemap include all pages or should separate domains have their own sitemaps?

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• Efficiency of iterators and alternatives? [migrated]

  - by user48037

  I have the following code for my game tiles: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { for (it = gameTiles[x][y].tiles.begin() ; it != gameTiles[x][y].tiles.end(); ++it) {}}} tiles is: struct Game_Tile { // More specific object types will be added here eventually vector<GameObject_Tile*> tiles; }; My problem is that if I change the vector to just be a single GameObject_Tile* instead and remove the iterator line in the loop I go from about 200fps to 450fps. Some context: The vector/pointer only contains one object in both scenarios. I will eventually need to store multiple, but for testing I just set it to a single pointer. The loop goes through 2,300 objects each frame and draws them. I would like to point out that if I remove the Draw (not seen int he example) method, I gain about 30 frames in both scenarios, the issue is the iteration. So I am wondering why having this as a vector being looped through by an iterator (to get at a single object) is costing me over 200 frames when compared to it being a single pointer? The 200+ frames faster code is: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { //gameTiles[x][y].tiles is used as a pointer here instead of using *it }} tiles is: struct Game_Tile { // More specific object types will be added here eventually GameObject_Tile* tiles; };

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• Content Being Echoed Below Footer in Category Post Template

  - by poindexter

  I have created a category template in Wordpress for all posts that are in the 'blog' category. The file name is single-blog.php. There is some conditional code in single.php that checks whether the post is in the 'blog' category and if it is it redirects it to single-blog.php. That seems to be working fine. The problem is that on all the individual 'blog' categorized posts the post title and content are echoed below the footer of the page. I do not know why they are showing up and I haven't been able to stop it or hide it. The Loop is getting closed on the template page, but I'm wondering if the Loop from single.php is somehow also being sent over. You can view an example of the problem here: http://69.20.59.228/2010/03/test-blog-post/ Please let me know if you have any suggestions. I am posting two sections of code below. The first is the conditional call in single.php. The second is the code from the single-blog.php (the category post template). the conditional call in single.php. <?php $post = $wp_query->post; if (in_category('blog')) { include(TEMPLATEPATH.'/single-blog.php'); }?> code from the single-blog.php (the category post template) <?php get_header(); ?> <?php get_sidebar(); ?> <p><h2>The IQNavigator Blog</h2></p> <em><a href="/category/blog">Blog Home</a></em> | <em><a href="/category/blog/feed/">Subscribe via RSS</a></em><p><br></br></p> <?php if (have_posts()) : while (have_posts()) : the_post(); ?> <div <?php post_class() ?> id="post-<?php the_ID(); ?>"> <h1 class="pagetitle"><?php the_title(); ?></h1> <!-- <p class="details">Posted <?php the_time('l, F jS, Y') ?> at <?php the_time() ?></p> --> <div class="entry"> <?php the_content('<p class="serif">Read the rest of this entry &raquo;</p>'); ?> <?php wp_link_pages(array('before' => '<p><strong>Pages:</strong> ', 'after' => '</p>', 'next_or_number' => 'number')); ?> <?php the_tags( '<p>Tags: ', ', ', '</p>'); ?> <p class="postmetadata alt"> <small> -----<br> Posted <?php /* This is commented, because it requires a little adjusting sometimes. You'll need to download this plugin, and follow the instructions: http://binarybonsai.com/wordpress/time-since/ */ /* $entry_datetime = abs(strtotime($post->post_date) - (60*120)); echo time_since($entry_datetime); echo ' ago'; */ ?> on <?php the_time('l, F jS, Y') ?>, filed under <?php the_category(', ') ?>. Follow any responses to this entry through the <?php post_comments_feed_link('RSS'); ?> feed. <?php if ( comments_open() && pings_open() ) { // Both Comments and Pings are open ?> <a href="#respond">Leave your own comment</a>, or <a href="<?php trackback_url(); ?>" rel="trackback">trackback</a> from your own site. <?php } elseif ( !comments_open() && pings_open() ) { // Only Pings are Open ?> Responses are currently closed, but you can <a href="<?php trackback_url(); ?> " rel="trackback">trackback</a> from your own site. <?php } elseif ( comments_open() && !pings_open() ) { // Comments are open, Pings are not ?> You can skip to the end and leave a response. Pinging is currently not allowed. <?php } elseif ( !comments_open() && !pings_open() ) { // Neither Comments, nor Pings are open ?> Both comments and pings are currently closed. <?php } edit_post_link('Edit this entry','','.'); ?> </small> </p> <?php the_tags( '<p>Tagged: ', ', ', '</p>'); ?> </div> </div> <?php comments_template(); ?> <?php endwhile; else: ?> <p>Sorry, no posts matched your criteria.</p> <?php endif; ?> <?php get_footer(); ?>

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• How to Achieve OC4J RMI Load Balancing

  - by fip

  This is an old, Oracle SOA and OC4J 10G topic. In fact this is not even a SOA topic per se. Questions of RMI load balancing arise when you developed custom web applications accessing human tasks running off a remote SOA 10G cluster. Having returned from a customer who faced challenges with OC4J RMI load balancing, I felt there is still some confusions in the field how OC4J RMI load balancing work. Hence I decide to dust off an old tech note that I wrote a few years back and share it with the general public. Here is the tech note: Overview A typical use case in Oracle SOA is that you are building web based, custom human tasks UI that will interact with the task services housed in a remote BPEL 10G cluster. Or, in a more generic way, you are just building a web based application in Java that needs to interact with the EJBs in a remote OC4J cluster. In either case, you are talking to an OC4J cluster as RMI client. Then immediately you must ask yourself the following questions: 1. How do I make sure that the web application, as an RMI client, even distribute its load against all the nodes in the remote OC4J cluster? 2. How do I make sure that the web application, as an RMI client, is resilient to the node failures in the remote OC4J cluster, so that in the unlikely case when one of the remote OC4J nodes fail, my web application will continue to function? That is the topic of how to achieve load balancing with OC4J RMI client. Solutions You need to configure and code RMI load balancing in two places: 1. Provider URL can be specified with a comma separated list of URLs, so that the initial lookup will land to one of the available URLs. 2. Choose a proper value for the oracle.j2ee.rmi.loadBalance property, which, along side with the PROVIDER_URL property, is one of the JNDI properties passed to the JNDI lookup.(http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI) More details below: About the PROVIDER_URL The JNDI property java.name.provider.url's job is, when the client looks up for a new context at the very first time in the client session, to provide a list of RMI context The value of the JNDI property java.name.provider.url goes by the format of a single URL, or a comma separate list of URLs. A single URL. For example: opmn:ormi://host1:6003:oc4j_instance1/appName1 A comma separated list of multiple URLs. For examples:  opmn:ormi://host1:6003:oc4j_instanc1/appName, opmn:ormi://host2:6003:oc4j_instance1/appName, opmn:ormi://host3:6003:oc4j_instance1/appName When the client looks up for a new Context the very first time in the client session, it sends a query against the OPMN referenced by the provider URL. The OPMN host and port specifies the destination of such query, and the OC4J instance name and appName are actually the “where clause” of the query. When the PROVIDER URL reference a single OPMN server Let's consider the case when the provider url only reference a single OPMN server of the destination cluster. In this case, that single OPMN server receives the query and returns a list of the qualified Contexts from all OC4Js within the cluster, even though there is a single OPMN server in the provider URL. A context represent a particular starting point at a particular server for subsequent object lookup. For example, if the URL is opmn:ormi://host1:6003:oc4j_instance1/appName, then, OPMN will return the following contexts: appName on oc4j_instance1 on host1 appName on oc4j_instance1 on host2, appName on oc4j_instance1 on host3,  (provided that host1, host2, host3 are all in the same cluster) Please note that One OPMN will be sufficient to find the list of all contexts from the entire cluster that satisfy the JNDI lookup query. You can do an experiment by shutting down appName on host1, and observe that OPMN on host1 will still be able to return you appname on host2 and appName on host3. When the PROVIDER URL reference a comma separated list of multiple OPMN servers When the JNDI propery java.naming.provider.url references a comma separated list of multiple URLs, the lookup will return the exact same things as with the single OPMN server: a list of qualified Contexts from the cluster. The purpose of having multiple OPMN servers is to provide high availability in the initial context creation, such that if OPMN at host1 is unavailable, client will try the lookup via OPMN on host2, and so on. After the initial lookup returns and cache a list of contexts, the JNDI URL(s) are no longer used in the same client session. That explains why removing the 3rd URL from the list of JNDI URLs will not stop the client from getting the EJB on the 3rd server. About the oracle.j2ee.rmi.loadBalance Property After the client acquires the list of contexts, it will cache it at the client side as “list of available RMI contexts”.  This list includes all the servers in the destination cluster. This list will stay in the cache until the client session (JVM) ends. The RMI load balancing against the destination cluster is happening at the client side, as the client is switching between the members of the list. Whether and how often the client will fresh the Context from the list of Context is based on the value of the  oracle.j2ee.rmi.loadBalance. The documentation at http://docs.oracle.com/cd/B31017_01/web.1013/b28958/rmi.htm#BABDGFBI list all the available values for the oracle.j2ee.rmi.loadBalance. Value Description client If specified, the client interacts with the OC4J process that was initially chosen at the first lookup for the entire conversation. context Used for a Web client (servlet or JSP) that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be returned each time InitialContext() is invoked. lookup Used for a standalone client that will access EJBs in a clustered OC4J environment. If specified, a new Context object for a randomly-selected OC4J instance will be created each time the client calls Context.lookup(). Please note the regardless of the setting of oracle.j2ee.rmi.loadBalance property, the “refresh” only occurs at the client. The client can only choose from the "list of available context" that was returned and cached from the very first lookup. That is, the client will merely get a new Context object from the “list of available RMI contexts” from the cache at the client side. The client will NOT go to the OPMN server again to get the list. That also implies that if you are adding a node to the server cluster AFTER the client’s initial lookup, the client would not know it because neither the server nor the client will initiate a refresh of the “list of available servers” to reflect the new node. About High Availability (i.e. Resilience Against Node Failure of Remote OC4J Cluster) What we have discussed above is about load balancing. Let's also discuss high availability. This is how the High Availability works in RMI: when the client use the context but get an exception such as socket is closed, it knows that the server referenced by that Context is problematic and will try to get another unused Context from the “list of available contexts”. Again, this list is the list that was returned and cached at the very first lookup in the entire client session.

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