what is distributed
A distributed system is a system composed of a group of computer nodes that communicate through a network and coordinate their work to complete a common task.
Purpose
The emergence of distributed systems is to use cheap and ordinary machines to complete computing and storage tasks that cannot be completed by a single computer. Its purpose is to use more machines to process more data.
The benefits of distribution (what problems are solved)
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Solve the stand-alone performance bottleneck problem
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The cost performance of stand-alone expansion is getting lower and lower, and the expansion has an upper critical point, while distributed can use multiple cheap servers to solve performance problems
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Solve system high availability problems
bring about problems
The problems caused by distribution are mainly caused by resource isolation and network problems.
Since process resources cannot access each other's resources, the following problems arise:
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Resource mutual exclusion needs distributed locks to solve
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Transaction problems are solved by distributed transactions
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Distributed buffer instead of native buffer
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Distributed messages instead of local message queues
There are also some problems caused by the network, because the network is unreliable, so it will happen:
- network communication failed
- Network Partition/Split Brain Problem
CAP theorem
CAP theorem, also known as Brewer's theorem, points out that for a distributed computing system, it is impossible to satisfy the following three points at the same time:
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Consistence (equivalent to all