Cloud CDN

1. Cloud CDN

Next, let's discuss content delivery network or CDN, which caches content nearer to users. We'll also talk about CDN Interconnect, which lets select third party content delivery network or CDN providers establish direct interconnect links at edge locations in the Google network. Cloud CDN caches content at the edges of the Google network. This caching provides faster content delivery to users while reducing transmission costs. Content can be cached at CDN nodes as shown on the map. There are over 90 of these cache sites spread across metropolitan areas in Asia Pacific, the Americas, and AMIA. For an updated list, see the cache locations in the Google Cloud documentation. For Cloud CDN performance measured by Stexis, please see the reports on the Citrix website. When setting up the back end service of an application load balancer, you can enable Cloud CDN with a checkbox. Using cache modes, you can control the factors that determine whether Cloud CDN caches your content. Cloud CDN offers three cache modes. The cache modes define how responses are cached, whether Cloud CDN respects cache directives sent by the origin, and how cache TTLs are applied. The available cache modes are USE_ORIGIN_HEADERS, CACHE_ALL_STATIC, and FORCE_CACHE_ALL. USE_ORIGIN_HEADERS mode requires origin responses to set valid cache directives and valid caching headers. CACHE_ALL_STATIC mode automatically caches static content that doesn't have the no store private or no cache directive. Origin responses that set valid caching directives are also cached. FORCE_CACHE_ALL mode unconditionally caches responses, overriding any cache directive set by the origin. If you use a shared back-end with this mode configured, ensure that you don't cache private per user content, such as dynamic HTML or API responses. Let's walk through the Cloud CDN response flow with this diagram. In this example, the application load balancer has two types of back-ends. There are managed VM instance groups in the US central one and Asia East one regions, and there's a Cloud storage bucket in US East one. A URL map decides which back-end to send the content to. The Cloud storage bucket could be used to serve static content, and the instance groups could handle PHP traffic. When a user in San Francisco is the first to access content, the cache site in San Francisco sees that it can't fulfill the request. This situation is called a cache miss. If content is in a nearby cache, Cloud CDN might attempt to get the content from it. For example, if a user in Los Angeles has already accessed the content. Otherwise, the request is forwarded to the application load balancer, which in turn forwards the request to one of your back-ends. Depending on the content that is being served, the request will be forwarded to the US Central One Instance Group or the US East one storage bucket. If the content from the back end is cacheable, the cache site in San Francisco can store it for future requests. In other words, if another user requests the same content in San Francisco, the cache site might now be able to serve that content. This approach shortens the round trip time and saves the origin server from having to process the request. This is called a cache hit. For more information on what content can be cached, please refer to caching overview in the Google Cloud documentation. Each Cloud CDN request is automatically logged within Google Cloud. These logs will indicate a cache hit or cache miss status for each HTTP request of the load balancer. You will explore such logs in the next lab. Cache modes, let you control how content is cached. CDN Interconnect lets select third party content delivery network providers establish direct interconnect links at edge locations in the Google Edge network. These connections let you direct your traffic from your VPC networks to a CDN provider network. For a complete list of CDN providers, refer to the CDN Interconnect overview in the Google Cloud documentation. CDN Interconnect lets you connect directly to select CDN providers from Google Cloud. Your network traffic that egresses from Google Cloud through one of these links benefits from the direct connectivity to supported CDN providers. CDN Interconnect reduces your Cloud CDN cache population costs. If you have a high volume of egress traffic, consider using CDN Interconnect. You can use the CDN interconnect links between Google Cloud and selected providers to automatically optimize the egress traffic and save money. If you're populating the Cloud CDN cache locations with large data files from Google Cloud, this optimization can be especially helpful. Frequent content updates are another typical CDN Interconnect use case. Cloud workloads that frequently update data stored in Cloud CDN cache locations benefit from using CDN Interconnect. The direct link to the Cloud CDN provider reduces latency. Ingress traffic is free for all regions. Egress traffic rates apply only to data that leaves compute engine or Cloud storage. Egress charges for CDN interconnect appear on the invoice as compute engine network egress via carrier peering network. The special pricing for your traffic that egress from Google Cloud to a CDN provider is automatic. Google works with approved CDN partners and supported locations to accept provider IP addresses. Any data that you send to your allow listed CDN provider from Google Cloud is charged at the reduced price. This reduced price applies only to IPv4 traffic. It does not apply to IPv6 traffic. Intra-region pricing for CDN Interconnect applies only to intra-region egress traffic that is sent to Google Approved CDN providers at specific locations. CDN Interconnect does not require any configuration or integration with Cloud load balancing. If your CDN provider is already part of the program, you don't need to do anything. Traffic from supported Google Cloud locations to your CDN provider automatically benefits from the direct connection and reduced pricing. Work with your supported CDN provider to learn what locations are supported. Your supported CDN service provider can also help you correctly configure your deployment to use intra-region egress routes, which costs less than intra-region egress traffic.

2. Let's practice!

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