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Centro de ayuda/ Object Storage Service/ Guía del usuario/ Vuelta a la fuente/ Overview

Actualización más reciente 2024-09-18 GMT+08:00

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Overview

When a client does not access the requested data in OBS, the 404 error is returned. However, OBS provides the back-to-source function to help you obtain the requested data from its source site if it is not found in OBS.

Back-to-Source by Mirroring

If a mirroring back-to-source rule is configured for an OBS bucket and the requested data is not found in the bucket, the system will retrieve the data, when the back-to-source rule applies to the data, from the origin server, upload it to the bucket, and then return it to the requesting client. This process does not interrupt services. Therefore, you can use this function to seamlessly migrate data from the origin server to OBS, or migrate services to OBS without being sensed by users, at low costs. Figura 1 illustrates the mirroring back-to-source process.

Figura 1 Back-to-source by mirroring

Limitations and Constraints

Back to source is currently available only in the following regions: AP-Singapore, CN East-Shanghai1, CN North-Beijing4, CN-Hong Kong, AP-Bangkok, CN South-Guangzhou, and AP-Jakarta.
Anonymous users cannot configure mirroring back-to-source rules for a bucket.

Parallel file systems do not support mirroring back-to-source rules.
A mirroring back-to-source rule is not compatible with the static website hosting function. Specifically, if a 404 error occurs when objects are downloaded from an OBS hosted static website domain, it does not trigger the mirroring back-to-source process.
The bucket, to which a back-to-source rule is configured, cannot be specified as the source site.
Currently, mirroring back to source from private buckets is supported for only some cloud vendors.
The origin server cannot transfer data in Transfer-Encoding: chunked mode. That is, the response to the request for downloading an object from the origin server must contain the Content-Length header to specify the size of the source object.
An object cannot match two different mirroring back-to-source rules.
Only buckets of version 3.0 or later support the mirroring back-to-source function.
A mirroring back-to-source rule takes effect five minutes later after any change to the rule.
A maximum of 10 mirroring back-to-source rules can be configured for a bucket.
The mirroring back-to-source function is offered for free.