Paxos

Setting Analogy Straight :

Let's say you and your friends want to decide on something, like what game to play. But here's the catch: you all have different ideas and you need to come to an agreement.

Now, let's say you're the leader and you want to make sure everyone agrees on the same game. You might start by suggesting a game, let's say "Hide and Seek." You ask your friends if they agree, and if they all say "Yes," then that's the game you'll play.

But what if not everyone agrees? Let's say one of your friends suggests playing "Tag" instead. Now, there's a disagreement. What do you do?

This is where Paxos comes in. Paxos is like a special system that helps you and your friends reach an agreement. It has a few steps:

1. Propose: You, as the leader, propose a game. Let's say you suggest "Hide and Seek" again.
2. Accept or Reject: Your friends consider your proposal. If they all agree, then the game is chosen, and you start playing "Hide and Seek."
3. If there's a disagreement, you need to negotiate. You ask your friends what games they suggest, and they each suggest their own games.
4. Iteration: You go through multiple rounds of proposing and suggesting games until eventually, you find a game that everyone can agree on. It might take a few tries, but eventually, you'll reach a consensus.

Paxos helps you and your friends communicate and decide on the best game to play, even when there are different opinions. It ensures that everyone has a chance to speak and be heard, and that a decision is made that everyone can be happy with.

So, Paxos is like a special method to help you and your friends agree on something by proposing ideas, discussing them, and finding a solution that works for everyone.

Ok !

The Paxos algorithm is a way for a group of computers to reach a consensus or agree on something, even if some of the computers may fail or have unreliable communication. It's commonly used in distributed systems, where multiple computers work together to achieve a common goal.

Let's break down the Paxos algorithm into its main components:

1. Proposal Phase: In this phase, a computer called the "proposer" suggests a value or a decision to the other computers, known as "acceptors." The proposer sends a message called a "prepare" to the acceptors, asking them to promise not to accept any proposals with a lower number. The acceptors respond with their promises.
2. Acceptance Phase: If the proposer receives promises from the majority of acceptors, it can proceed to the acceptance phase. The proposer sends a message called an "accept" to the acceptors, including the proposed value. The acceptors, upon receiving this message, check if they have made promises to higher-numbered proposals. If not, they accept the proposal and notify the proposer.
3. Learning Phase: Once the proposer receives acknowledgments from the majority of acceptors, it knows that the proposal has been accepted. The proposer sends a message called "learn" to all the computers, informing them of the agreed-upon value.

By following these steps, the Paxos algorithm ensures that a consensus is reached among the computers, even in the presence of failures or unreliable communication. It guarantees that the agreed-upon value is chosen by a majority and that once a value is chosen, all correct computers will eventually learn about it.

The Paxos algorithm can be quite complex and involves additional details to handle different scenarios, such as handling competing proposals and dealing with failed or slow computers. However, the basic idea is to have a proposal phase, an acceptance phase, and a learning phase to achieve consensus among the participating computers.