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Questions tagged [paxos]

Paxos is a family of protocols for a network of unreliable processors to agree on a result.

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Programming language to choose for implementing distributed message passing algorithms

Basically, I would want to implement the following algorithms and analyze how the system built using these algorithms behave under different conditions. Gossip protocol Multiple paxos Consistent hashing My interest here is in these algorithms. I…
user855
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Why is it legit to use no-op to fill gaps between paxos events?

I am learning Paxos algorithm (http://research.microsoft.com/en-us/um/people/lamport/pubs/paxos-simple.pdf) and there is one point I do not understand. We know that events follow a timely order, and it happens when, say, events 1-5 and 10 are…
OneZero
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In Paxos, can an Acceptor accept a different value after it has already accepted one?

In Multi-Paxos algorithm, consider this message flow from the viewpoint of an acceptor: receive: Prepare(N) reply: Promise(N, null) receive: Accept!(N, V1) reply: Accepted(N, V1) receive: Accept!(N+1, V2) reply: ? What should the acceptor's reaction…
Sergej Koščejev
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Leader election for paxos-based replicated key value store

I am going to implement a key value store with multi Paxos. I would have several nodes, one of which is the primary node. This primary node receive update requests and replicate values to slave nodes. My question is how the primary node (or leader)…
yuefengz
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avoiding overuse of consensus protocols in a distributed system

I'm new to distributed systems, and I'm reading about "simple Paxos". It creates a lot of chatter and I'm thinking about performance implications. Let's say you're building a globally-distributed database, with several small-ish clusters located in…
Dan
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How does a consensus algorithm guarantee consistency?

How does a consensus algorithm like Paxos "guarantee safety (freedom from inconsistency)" when two generals prove the "impossibility of designing algorithms to safely agree"? When I consider the simplest case of getting two servers to either (1)…
Witness Protection ID 44583292
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Clarifications regarding Paxos and the paper Paxos Made Simple

I read the paper named "Paxos made simple" but still got some confusions: What does the "instances of paxos algorithm" refers to? does each instance indicate there is an input/command from external clients? and the paxos algorithm for each instance…
rayeaster
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How do replicas coming back online in PAXOS or RAFT catch up?

In consensus algorithms like for example PAXOS and RAFT, a value is proposed, and if a quorum agrees, it's written durably to the data store. What happens to the participants that were unavailable at the time of the quorum? How do they eventually…
Markus Jevring
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RabbitMQ - parallel processing with strict ordering guarantees

In HappyFunPizzaCorp we have a POS system which generates two events: new_order event and payment event. Both events contain a pizza order_id key for cross referencing. Both events are sent to an exchange TheExchange. new_order events are always…
Nick Hristov
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What is the proper behaviour for a Paxos agent in this scenario?

I'm looking into Paxos and I'm confused about how the algorithm should behave in this contrived example. I hope the diagram below explains the scenario. A few points: Each agent acts as a proposer/acceptor/learner Prepare messages have form…
Allen George
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Difference between 2PC (2 phase commit) and 2 PL (2 phase locking)

What is the difference between the two? The protocol on the surface looks different, but I would like to understand what is really different between the two and why they are not equivalent.
user855
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consensus algorithm: what will happen if an odd cluster becomes even because of a node failure?

Consensus algorithm (e.g. raft) requires the cluster contains an odd number of nodes to avoid the split-brain problem. Say I have a cluster of 5 nodes, what will happen if only one node fails? The cluster has 4 nodes now, which breaks the odd…
zx_wing
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why does paxos proposalId need to be unique

could anyone tell me why the proposal Id needs to be unique in Paxos? I think the reason why this the proposalId needs to be unique is that we need to use it to reject the old proposal and sort the max vote. So if we make the phase one: acceptor…
terry
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Why Paxos is design in two phases

Why Paxos requires two phases(prepare/promise + accept/accepted) instead of a single one? That is, using only prepare/promise portion, if the proposer has heard back from a majority of acceptors, that value is choose. What is the problem, does it…
Jacky1205
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Paxos phase 2a message loss

The figure below is the message flow of basic Paxos, in the phase 2a, the Leader chooses value Vn for its proposal1 and sends Accept!(1,Vn) to every acceptor. My question is: what if two of theses three messages get lost? I mean only Acceptor 1 (not…
HuangJie
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