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Page downgrade
In a big promotion or some special circumstances, some pages occupy some scarce service resources, and in an emergency, it can be downgraded as a whole to save the commander.
Page fragment downgrade
For example, the merchant part of the product detail page needs to be downgraded at this time because the data is wrong;
Page asynchronous request degradation
For example, there are asynchronous loading requests for recommendation information/delivery to, etc. on the product detail page. If the information is slow in response or there is a problem with the back-end service, it can be downgraded;
Service function degradation
For example, when rendering the product details page, you need to call some less important services: related categories, hot lists, etc., and these services are not directly obtained under abnormal conditions, that is, they can be downgraded;
Read downgrade
For example, in the multi-level cache mode, if there is a problem with the back-end service, it can be downgraded to a read-only cache. This method is suitable for scenarios that do not require high read consistency;
Write downgrade
For example, if you want to buy in a flash, we can only update the Cache, and then deduct the inventory to the DB asynchronously and synchronously to ensure final consistency. At this time, the DB can be downgraded to the Cache.
Reptile downgrade
In the event of a big promotion, crawler traffic can be directed to static pages or returned to empty data, thereby protecting scarce back-end resources.
Automatic switch downgrade
Automatic degradation is based on system load, resource usage, SLA and other indicators.
Downgrade over time
When the accessed database/http service/remote call response is slow or the response is slow for a long time, and the service is not a core service, it can be automatically downgraded after timeout; for example, there are recommended content/evaluation on the product detail page, but the recommended content/evaluation is temporarily unavailable The display will not have a great impact on the user's shopping process; this kind of service can be downgraded over time. If it is to call someone else's remote service, define a maximum service response time with the other party, and if it expires, it will be automatically degraded.