{"id":16860,"date":"2021-10-15T09:06:48","date_gmt":"2021-10-15T13:06:48","guid":{"rendered":"https:\/\/www.eginnovations.com\/blog\/?p=16860"},"modified":"2025-01-17T06:12:42","modified_gmt":"2025-01-17T11:12:42","slug":"gslb-on-netscaler","status":"publish","type":"post","link":"https:\/\/www.eginnovations.com\/blog\/gslb-on-netscaler\/","title":{"rendered":"GSLB on NetScaler"},"content":{"rendered":"<div class=\"inner_content\">\n<h2><span class=\"ez-toc-section\" id=\"Customer_Corner_-_How_to_set_up_alerting_for_web_servers_in_an_activepassive_set-up\"><\/span>Customer Corner &#8211; How to set up alerting for web servers in an active\/passive set-up<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>This blog post is the first in a series highlighting actual questions asked to eG Enterprise during customer support calls and our answers to those.<\/p>\n<p>At first, it appeared that this customer had a simple active\/passive web server set-up to provide failover resilience. However, it transpired that they were using Citrix ADC\u2019s (was NetScaler) GSLB (Global Server Load Balancing) features. This is a perfect use case to leverage eG Enterprise\u2019s conditional metric aggregation technologies to alert them when a certain percentage of sites were down vs. individual servers in an environment designed for redundancy and failover.<\/p>\n<p style=\"margin-bottom: 10px;\"><strong>Q &#8211; \u201cI have two web servers in an active\/passive set-up. In eG Enterprise, how do I configure to get alerted only if both web servers go down?\u201d<\/strong><\/p>\n<p><strong>A &#8211;<\/strong> For any active\/passive set-up, we recommend that you do the following:<\/p>\n<ul>\n<li>Configure both the web servers for monitoring.<\/li>\n<li>Configure the website hosted on the web servers to be monitored by using an external agent (i.e., <u>not by<\/u> the agents installed locally on the web servers).<\/li>\n<li>Configure minor priority for alerts from individual servers and critical priority for the alert associated to the website.<\/li>\n<\/ul>\n<p>This configuration will ensure that you get minor alerts when one server goes down, but critical alerts when both web servers go down and the website is unavailable.<\/p>\n<p style=\"margin-bottom: 10px;\"><strong>Q &#8211; In my case, a service from each web server is a GSLB site on NetScaler. How can I get alerts when a certain portion of the sites go down?<\/strong><\/p>\n<p><strong>A &#8211;<\/strong> Metric aggregation is an immensely powerful capability, which you can apply to many of the eG Enterprise components to customize your insights for your own needs \u2013 for example, in dashboards, topology, etc., and for getting alerted when more than XX% servers\/users have issues rather than alerts for individual servers\/users.<\/p>\n<p>You can use <a href=\"https:\/\/www.eginnovations.com\/documentation\/Admin\/Conditional-Aggregation.htm\">conditional metric aggregation<\/a> to customize alerting in any way you want. Using this feature, you can group objects and raise alerts on thresholds for the group rather than for the individual server\/user, etc. Standard metric aggregation allows you to aggregate metrics. For instance, when you create an aggregate test to report the average CPU usage of a Windows server farm comprising four Windows servers. If three out of the four servers register a CPU usage of 40% each, and one server registers 80%, then the average CPU usage for that farm will be 50%. This seemingly low aggregated CPU usage value does not reveal the fact that a single Windows server is seeing more than 80% of CPU resources.<\/p>\n<p>To allow administrators greater flexibility and visibility into the health of the target infrastructure, eG Enterprise offers Conditional Aggregation as well as Standard Aggregation. This is most useful when administrators only want to know the count or percentage of components that fulfill a defined condition or conditions. For instance, administrators may just want to know how many Windows servers are consuming over 80% of the CPU resources. So, in your case, you could raise a minor alert when more than 25% of the sites go down, a major alert when 50% are down, and a critical alert when more than 75% of the sites go down, etc.<\/p>\n<p>For more information, check out <a href=\"https:\/\/www.eginnovations.com\/documentation\/Admin\/Metric-Aggregation.htm\">https:\/\/www.eginnovations.com\/documentation\/Admin\/Metric-Aggregation.htm<\/a> or <a href=\"https:\/\/www.eginnovations.com\/company\/contact-us\">reach out to us<\/a> for a discussion. You might also like to check out our quick how-to-videos: <a href=\"https:\/\/www.youtube.com\/watch?v=oOEVTA3V4ZQ\">Understanding and Modifying Thresholds<\/a> and <a href=\"https:\/\/www.youtube.com\/watch?v=4PnZYmg1aS4\">Creating Group Thresholds<\/a>.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"More_about_GSLB\"><\/span>More about GSLB<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>In this \u00a0call, the customer was using GSLB (Global Server Load Balancing), <a href=\"https:\/\/docs.citrix.com\/en-us\/citrix-adc\/current-release\/global-server-load-balancing.html\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Global Server Load Balancing | Citrix ADC 13.0<\/a>. Citrix\u2019s partner, rhipe, has an overview of \u201c<a href=\"https:\/\/www.rhipe.com\/citrix-netscaler-series-part-8\/\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">A GSLB active-passive load balancing example<\/a>\u201d available. Citrix ADC\u2019s GSLB features are often seen outside of VDI use cases for the delivery of applications via web applications server technologies, such as Apache TomCat, IBM WebSphere, and Oracle WebLogic.<\/p>\n<p>GSLB also has a key role in many hybrid cloud scenarios. For example, \u00a0when using AWS Outposts \u2013 see more: <a href=\"https:\/\/www.citrix.com\/blogs\/2020\/12\/16\/application-delivery-in-hybrid-cloud-with-citrix-adc-and-aws\/\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Application delivery in hybrid cloud with Citrix ADC and AWS | Citrix Blogs<\/a><\/p>\n<p>Carl Stalhood has a great blog of resources around GSLB for Citrix ADC (formally NetScaler), <a href=\"https:\/\/www.carlstalhood.com\/global-server-load-balancing-gslb-citrix-adc\/\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Global Server Load Balancing (GSLB) \u2013 Citrix ADC \u2013 Carl Stalhood<\/a>, and Bas van Kaam has <a href=\"https:\/\/www.basvankaam.com\/2015\/10\/20\/citrix-netscaler-the-basics-continued-part-five-global-server-load-balancing\/\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">a must read article that includes a comprehensive explanation of the underlying technology<\/a> and architecture.<\/p>\n<p>Christiaan Brinkhoff has a great blog detailing a disaster recovery scenario leveraging GSLB &#8211; <a href=\"https:\/\/www.mycugc.org\/blogs\/cugc-blogs\/2017\/08\/09\/use-netscaler-global-server-load-balancing-to-reco\" target=\"_blank\" rel=\"nofollow noopener noreferrer\">Use NetScaler Global Server Load Balancing to Recover your Citrix XenApp or XenDesktop environment on Microsoft Azure<\/a>.<\/p>\n<p>You can read the details of the metrics, logs, and signals that eG Enterprise collects around GSLB on Citrix ADC here:<\/p>\n<ul>\n<li><a href=\"https:\/\/www.eginnovations.com\/documentation\/Citrix-ADC-VPX-MPX\/GSLB-Domains-Test.htm\">GSLB Domains Test<\/a><\/li>\n<li><a href=\"https:\/\/www.eginnovations.com\/documentation\/Citrix-ADC-VPX-MPX\/GSLB-Sites-Test.htm\">GSLB Sites Test<\/a><\/li>\n<li><a href=\"https:\/\/www.eginnovations.com\/documentation\/Citrix-ADC-VPX-MPX\/GSLB-Services-Test.htm\">GSLB Services Test<\/a><\/li>\n<li><a href=\"https:\/\/www.eginnovations.com\/documentation\/Citrix-ADC-VPX-MPX\/GSLB-Virtual-Servers-Test.htm\">GSLB Virtual Servers Test<\/a><\/li>\n<\/ul>\n<p>And details of our Citrix ADC\/NetScaler support are available here: <a href=\"https:\/\/www.eginnovations.com\/supported-technologies\/citrix-monitoring\/netscaler-monitoring\">Citrix NetScaler Performance Monitoring from eG Innovations<\/a>.<\/p>\n<div class=\"link_list_style\" style=\"margin: 0px auto 20px; padding: 1px 20px 10px;\">\n<h3><span class=\"ez-toc-section\" id=\"What_is_GSLB\"><\/span>What is GSLB?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Global Server Load Balancing (GSLB) is used to manage and control the traffic flow between two (or more) separate physical locations (data centers) that are often geographically dispersed. This can be for either load balancing purposes, or high availability, or fault tolerance, or disaster recovery, etc. The mechanism behind GSLB is based on Microsoft DNS<\/p>\n<p>GSLB can manage disaster situations or network outages where users of one data center can be redirected to other data centers for seamless user experience and business continuity.<\/p>\n<p>The GSLB feature is included with the Citrix ADC Advance and Premium edition licenses. The Citrix ADC option license is supported with the Standard edition<\/p>\n<\/div>\n<p>In the figure below, Site 1 is an active site and Site 2 is a passive site, which has the same configuration as that of Site 1.<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" class=\"aligncenter size-full wp-image-16863\" src=\"https:\/\/www.eginnovations.com\/blog\/wp-content\/uploads\/2021\/10\/gslb-netscaler.jpg?nores\" alt=\"GSLB in Netscaler\" width=\"840\" height=\"500\" border=\"0\" \/><br \/>\nIf Site 1 goes <strong>down<\/strong>, Site 2 becomes operational.<\/p>\n<p>When the client sends a DNS request, the request can land in any of the two sites. However, the services are selected only from the active site (Site 1) as long as it is <strong>up<\/strong>.<\/p>\n<p>Services from the passive site (Site 2) are selected only if the active site (Site 1) is <strong>down<\/strong>.<\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Customer Corner &#8211; How to set up alerting for web servers in an active\/passive set-up This blog post is the first in a series highlighting actual questions asked to eG Enterprise during customer support calls and our answers to those. At first, it appeared that this customer had a simple active\/passive web server set-up to [&hellip;]<\/p>\n","protected":false},"author":30,"featured_media":16861,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"_lmt_disableupdate":"no","_lmt_disable":"","footnotes":""},"categories":[8],"tags":[411,82,410],"class_list":["post-16860","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-citrix-monitoring","tag-citrix-adc","tag-citrix-performance","tag-netscaler"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v24.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>GSLB on NetScaler<\/title>\n<meta name=\"description\" content=\"GSLB is a premium enterprise feature of NetScaler. 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