how to solve this inconsistency problem in distributed systems?

To ensure that shared resources are accessed in a consistent order by consistency, there are several consistency models that can be used in distributed systems. These models define the level of consistency that is guaranteed for shared resources in the presence of concurrent access by multiple processes.

What is the Consistency Model?

A consistency model is a set of rules or guidelines that determine how a distributed system should behave in terms of the ordering and visibility of updates made to shared data.

In a distributed system, where multiple nodes can access and modify the same data, it’s important to ensure that all nodes have a consistent view of the data to avoid conflicts and inconsistencies. A consistency model defines the level of consistency required for the system and specifies the mechanisms used to achieve it.

Different consistency models offer different trade-offs between consistency and performance, and they may prioritize factors such as availability, partition tolerance, or the level of coordination required between nodes.

Following are the different kinds of consistency models:

Eventual Consistency

• Weakest form of consistency.
• This ensures high availability and returns the same value for READ requests.
• One popular example is Cassandra – ( NoSQL, highly available ).

Causal Consistency

• Has consistency stronger than eventual consistency.
• Preserves the order of casually-related(dependent) operations.
• So, that’s why it does not ensure the ordering of operations that are non-causal.
• One example is Comment replies.

Sequential Consistency

• Stronger than causal consistency.
• Doesn’t ensure writes are visible instantaneously or in the same order as according to some global block.
• One example is that of facebook posts of friends (sequential for a particular friend, but not for overall)

Strict Consistency/ Linearizability

• This is the strongest consistency model.
• All read requests are consistent as they get the latest write value
• One popular example is password update of someone’s bank account.

Why to use sequential consistency as a consistency model in distributive systems?

Every concurrent execution of a program should ensure that the results of the execution are to be in some sequential order. It provides an intuitive model of how the distributed systems should behave, which makes it easier for users to understand and reason about the behavior of the system.