How can you handle network partitions in distributed systems?

2 The PACELC model

The CAP theorem is a simplified way of looking at the trade-offs in distributed systems. A more nuanced model is the PACELC model, which states that if there is a partition (P), how does the system trade-off between availability (A) and consistency (C); else (E), when the system is running normally, how does it trade-off between latency (L) and consistency (C). The PACELC model helps you understand the performance and consistency implications of your design choices in different scenarios.

3 The BASE approach

One way to handle network partitions is to adopt the BASE approach, which stands for basically available, soft state, eventual consistency. This approach sacrifices strong consistency for high availability and low latency, and relies on asynchronous replication and reconciliation to achieve eventual consistency. The BASE approach is suitable for applications that can tolerate some inconsistency, such as social media, e-commerce, or analytics.

4 The CRDT technique

Another way to handle network partitions is to use the CRDT technique, which stands for conflict-free replicated data type. This technique allows multiple replicas of the same data to be updated independently and concurrently, without coordination, and to converge to the same state eventually. The CRDT technique ensures that the replicas are mathematically guaranteed to be conflict-free, and avoids the need for complex resolution algorithms. The CRDT technique is suitable for applications that need to support collaborative editing, synchronization, or offline access.

5 The quorum system

A third way to handle network partitions is to use the quorum system, which is a set of rules that determines how many nodes need to agree on a read or write operation. The quorum system can help you balance between consistency and availability, depending on how you set the quorum size and distribution. The quorum system can also help you tolerate node failures, as long as a majority of nodes are reachable. The quorum system is suitable for applications that need to maintain strong consistency, such as banking, voting, or inventory management.

6 The fallback strategy

A final way to handle network partitions is to use the fallback strategy, which is a plan that defines how the system should behave when a network partition is detected. The fallback strategy can involve switching to a different mode of operation, such as degraded service, read-only mode, or local caching. The fallback strategy can also involve notifying the users, logging the events, or triggering alerts. The fallback strategy is suitable for applications that need to preserve user experience, data integrity, or security.