Large amount of private cache6/7/2023 If clients send byte range requests with the Accept-Encoding header that leads to the Origin responding with different content lengths, then Azure Front Door will return a 503 error. Azure Front Door requires the content-length values to be the same for any GET HTTP request. Range requests may be compressed into different sizes. If the origin uses Chunked Transfer Encoding (CTE) to send compressed data to the Azure Front Door PoP, then response sizes greater than 8 MB aren't supported. The resulting item is returned with a Transfer-Encoding: chunked response header. Afterward, the compressed file is served from the cache. When a request for an asset specifies compression and the request results in a cache miss, Azure Front Door (classic) does compression of the asset directly on the POP server. If a request supports gzip and Brotli compression, Brotli compression takes precedence. These profiles support the following compression encodings: The current list is:Īdditionally, the file must also be between 1 KB and 8 MB in size, inclusive. Currently, Front Door (classic) doesn't allow this list to be changed. ![]() In order for a file to be eligible for compression, caching must be enabled and the file must be of a MIME type to be eligible for compression. If your origin doesn't send the correct response headers with valid values, Azure Front Door doesn't cache the response, and you might see inconsistent behavior.Īzure Front Door (classic) can dynamically compress content on the edge, resulting in a smaller and faster response time to your clients. Also, the Content-Range response header must be present, and must match the actual length of the content that your origin returns. ![]() The response must use HTTP status code 206. When your origin responds to a request with a Range header, it must respond in one of the following ways: If the origin doesn't support byte-range requests, or if it doesn't handle range requests correctly, then this optimization isn't effective. This optimization relies on the origin's ability to support byte-range requests. If the chunks aren't all cached, pre-fetching is used to request chunks from the origin. ![]() Subsequent requests for the file or byte ranges are served from the cache. For more information on the byte-range request, read RFC 7233.įront Door caches any chunks as they're received so the entire file doesn't need to be cached on the Front Door cache. This process continues until the entire file gets downloaded (if requested) or the client closes the connection. This pre-fetch ensures that the content stays one chunk ahead of the user, which reduces latency. Front Door then pre-fetches the next chunk in parallel. After receiving a full file request or byte-range file request, the Azure Front Door environment requests the file from the origin in chunks of 8 MB.Īfter the chunk arrives at the Azure Front Door environment, it's cached and immediately served to the user. When a large file is requested, Front Door retrieves smaller pieces of the file from the origin. If caching is enabled, Front Door uses a technique called object chunking. Delivery of large filesĪzure Front Door delivers large files without a cap on file size. All other request methods are always proxied through the network. Only requests that use the GET request method are cacheable. As a result, you might still see some traffic reach your origin, even if you served cached responses. ![]() If no cached response is available, the request is forwarded to the origin.Įach Front Door edge site manages its own cache, and requests might be served by different edge sites. Caching helps to reduce the amount of traffic sent to your origin server. When caching is configured on your route, the edge site that receives each request checks its cache for a valid response. Azure Front Door is a modern content delivery network (CDN), with dynamic site acceleration and load balancing capabilities.
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