Explain the concept of achieving consensus between distributed system nodes.

Consensus among distributed nodes is the process where multiple independent nodes of a system agree on a single decision or state, despite possible failures, delays, or unreliable messages.

Main tasks of consensus:

• Ensure data consistency among nodes.
• Ensure system fault tolerance.

Examples of consensus algorithms:

• Paxos
• Raft
• Zab

In general, a consensus algorithm allows nodes to propose a value, exchange messages, and reach a single decision that will be accepted by all correct nodes.

For example, in a data replication system, to keep all copies identical, nodes must agree on which operation to apply next. If one node fails or the network is unstable, the consensus algorithm guarantees that the remaining nodes will not diverge in their state.

In Go, such algorithms are often implemented for distributed systems using channels and goroutines for message exchange and synchronization.