How to briefly describe the principle of CAP
Today, I will talk to you about how to briefly describe the principle of CAP, which may not be well understood by many people. in order to make you understand better, the editor has summarized the following contents for you. I hope you can get something according to this article.
In a distributed system (a collection of nodes that connect to each other and share data), when it comes to read and write operations, only two of the three are guaranteed: Consistence, Availability, and Partition Tolerance.
The following explanations are C, A, P respectively.
Consistency: for the specified client, the read operation ensures that the latest write results can be returned.
Availability: non-failed nodes return reasonable responses (not errors and timeouts) within a reasonable period of time.
Partition fault tolerance: when there is a network partition, the system can continue to "perform its duties".
CAP principle
When a network partition failure occurs, we either cancel the operation so that the data is constant, but the system is not available, or we continue to write data, but the consistency of the data is not guaranteed.
For a distributed system, network failure is bound to occur, that is, partition tolerance must be guaranteed, so availability and consistency must be one of the two.
When the network partition fails, that is, when the network is unavailable, if consistency is selected, the system may return an error code or simply time out, that is, the system is unavailable. If usability is selected, the system can always return a piece of data, but there is no guarantee that the data is up-to-date.
Therefore, with regard to the principle of CAP, it is more accurate to say that under the premise that distributed systems must meet the tolerance of partitions, availability and consistency cannot be satisfied at the same time.
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