Traffic management
1. Traffic management
Traffic management is key to ensuring optimal network performance and user experience. In this section, we'll delve into a real world use case and its implementation. Bola, a Cloud network engineer at Cymbal Corporation, is responsible for maintaining their video streaming platform. The website accesses the Cymbal store infrastructure using Cloud load balancing. To optimize performance and costs, they want to route user traffic to different server backends based on the requested video quality. For example, 4K versus HD. What should Bola do? Bola can benefit from traffic management. Traffic management provides enhanced features to route load balancer traffic based on criteria that you specify. With traffic management, you can; implement traffic steering based on HTTPS parameters, such as the host, path, headers, and other request parameters. Perform request-based and response-based actions, such as redirects and header transformations, and use traffic policies to fine tune load balancing behavior, such as retry policies, request mirroring, and cross origin resource sharing or cores. The traffic features that are available can vary per load balancer. Check the Google Cloud documentation for details. For example, traffic management overview for a classic application load balancer, traffic management overview for global external application load balancers, and traffic management overview for regional external application load balancers. Recall that in addition to traffic management, Cloud load balancing offers backend services like health checks, session affinity, balancing mode, and capacity scaling. These load balancers support traffic management. Global external Application Load Balancer, Global classic Application Load Balancer, Internal Application Load Balancer, and the Regional external Application Load Balancer. Other load balancers have access to only traffic features available in backend services, such as balancing mode and session affinity. Not all load balancers support all traffic management features. For a complete list of traffic management features supported for each load balancer, refer to the routing and traffic management in the Google Cloud documentation. The URL map contains rules that define the criteria to use to route incoming traffic to a backend service or a backend bucket. Traffic management features are configured in a URL map. In other words, the load balancer uses the URL map to determine where to route incoming traffic. When you configure routing, you can choose between the following modes; simple host and path rule or advanced host path and route rule. Each URL map can contain only one mode or the other mode. A request is first evaluated based on the host rule. If the domain matches a defined host rule, the system uses its associated path matcher to further refine routing. Each host rule consists of a list of one or more hosts and a single path matcher. If no host rules are defined, the request is routed to the default service. The request path is compared against available path rules with the longest, most specific match taking priority. Path rules are evaluated on a longest path matches first basis. You can specify the path rules in any order. Once the best match is found, the request is sent to the corresponding backend service. If no specific host and path rules apply, the request is handled by the default backend service. This setup allows you to create custom routing rules like sending video related requests to a dedicated service while directing general traffic to a different backend. Going back to the scenario, Bola can use the URL map to distribute traffic. The host rule is cymbal.com, which means any host other than cymbal.com, for example, cymbal.org or cymbal.net are directed to the default service. Once the host name cymbal.com matches, the URL is matched for a path rule. The default backend service is video site. Requests with the exact URL path video-hd are directed to the video HD backend service. Requests with the exact URL path video-4k are directed to the video-4k backend service. On this slide, you see a URL map that routes video traffic to the example we covered in the previous slides. This example is shown by using a YAML file. You can also use the Google Cloud Console to configure URL maps. Let's look at how this example works. Default service. The default service defines a service where traffic should be routed when no matching URL is found. You must specify a default service or a backend bucket. The host rules defines a list of host names that are processed by this rule. In this example, there's only one item in the list, which means that only one host rule is defined. This host rule contains an asterisk. The asterisk is a wildcard, which matches all hosts. To see where to find the matching logic to use, look at the value of path matcher. For this host rule, pathMatcher is set to pathmap. Here's a path matchers list, which contains a list of path matching rules. The only element in this list is path map. Each match rule defines logic to process the traffic that is sent to the backend service. In this example, there are two sets of paths. One paths list defines valid URL paths for the video hd. The other paths list defines valid URL paths for the video 4K. If the URL contains a match for one of these paths lists, the load balancer routes the traffic to the corresponding service. If the traffic contains a path that matches none of the paths lists, then it's sent to the default backend video site. In other words, the traffic is sent to the service denoted by pathmatchers/defaultservice. For additional details, refer to the documentation. The advanced routing mode can choose a rule based on a defined priority and includes additional configuration options. Instead of path rules, advanced routing uses route rules. Each URL map can include either simple or advanced rules, but not both. This URL map contains rules that route 95% of the traffic to Service A, and 5% of the traffic is routed to Service B. The example shows a YAML implementation of an advanced routing mode. You can also use the Google Cloud Console to configure URL maps. Let's look at how this example works. When no matching host rule is found, the default service defines a service to use. The field default service is required. The host rules works the same way for simple routing mode. As in the previous example, this host rule uses the asterisk to match all hosts. Because path matcher is set to matcher 1, /pathMatchers/matcher1 defines the matching logic. /pathMatchers/matcher1 contains a list of route rules. The route rules contain a list of one or more match rules and a route action. When URL satisfy the match rules, their traffic is processed by the route action. In this example, there's only one item in match rules. Where prefix match equals an empty string, the prefix match condition matches the URL path prefix, URLs that start with the same string match. In the example, the prefix match is the empty string, which matches all URLs. In other words, all URLs trigger this match rule, and the route action is applied. The route action defines how the traffic is routed. In the example, the route action is set to weightedBackendServices. Weighted backend services is a list of backend services. A weight value is specified for each backend service, representing a percentage of the total traffic. Ninety-five percent of the traffic is sent to Service A, and 5% of the traffic is sent to Service B. The route action can also define traffic policies such as retry policies and cores. For a complete list of route action values, refer to the Google Cloud documentation for the load balancer that you're using. In this example, you might notice that there are two default service key value pairs. One default service is associated with the host rules and the other is associated with the route rules. If there's no matching host rule, the first default service is used. If there's no matching route rule, the second default service is used. Not all load balancers support all traffic management features. For a complete list of traffic management features supported for each load balancer, refer to routing and traffic management in the Google Cloud documentation. Wild cards are supported, but only after a forward slash. For example, /video/* is valid and /video* is invalid. Rule matching does not use regular expressions or substring matching. For example, /videos/hd* does not match /videos/hd-pdq, because -pdq is a substring and also because it comes after the forward slash. /video/* matches /video/hd-pdq. You can also use Gemini to learn more. One trick to get better responses is to assign Gemini a role. Prime the model to assume a specific role, also known as a persona. Adding a role is not always necessary, but can enforce a certain level of expertise when generating a response. Improve performance, and tailor's communication style. This technique is particularly useful for getting the model to perform highly technical tasks or enforcing specific communication styles. The example on the slide shows a sample prompt where Gemini assumes the role of a Google Cloud technical support engineer.2. Let's practice!
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