Questions about the challenges of solving problems with multiple cooperating but separate agents.
Questions tagged [distributed-systems]
411 questions
17
votes
5 answers
External consistency vs linearizability
In Spanner, TrueTime & The CAP Theorem, Eric Brewer writes:
One subtle thing about Spanner is that it gets serializability from
locks, but it gets external consistency (similar to linearizability) from TrueTime [emphasis added].
What is the…
Lorin Hochstein
- 281
- 2
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8
votes
1 answer
Consensus problem of distributed systems
I just started reading about distributed systems for the first time ever. There is a fairly slick proof of the impossibility of consensus in an asynchronous model using some combinatorial topology. On the other hand, there are multiple consensus…
eof
- 121
- 2
7
votes
1 answer
Does location transparency imply access transparency?
In distributed systems theory, I have found the definition that a distributed system requires, among others, location and access transparency.
I was wondering if location transparency does not already include access transparency.
Wikipedia defines…
helm
- 173
- 4
7
votes
2 answers
Theoretical foundations of robust and distributed services
I have the notion of a social network which is robust against malicious attacks from the outside. My vision is a system that is structurally built up as a distributed network of equal servers that operate on the same data and offer the identical…
tsh
- 171
- 3
5
votes
2 answers
Why is Two-Phase Commit (2PC) blocking?
Can anyone let me know, why 2PC is blocking when the coordinator fails? Is it because the cohorts don't employ timeout concept in 2PC?
Good reference: Analysis and Verification of Two-Phase Commit & Three-Phase Commit Protocols, by Muhammad…
KGhatak
- 229
- 4
- 15
5
votes
1 answer
Confusion about example in Raft consensus paper
In part (c) of Figure 8 in this paper http://ramcloud.stanford.edu/raft.pdf, I am confused how S1 knows that the current term is 4 when it restarts and is elected leader.
Here is the sequence as I currently understand it:
S1 is elected leader for…
Bryan Glazer
- 53
- 4
4
votes
0 answers
Is there any theory behind GraphQL?
GraphQL is a query language for your API, and a server-side runtime for executing queries by using a type system you define for your data.
Source: http://graphql.org/learn/
So GraphQL allows a server to implement a HTTP-endpoint that accepts…
Thomas Eizinger
- 141
- 2
4
votes
1 answer
Paxos: Accepting Proposals With Different Values and Consensus in Paxos
I have a number of questions about Paxos which I can't answer in full confidence from reading the paper (Paxos Made Simple).
My questions are loosely based around the following quote:
In Paxos, a value is chosen when a single proposal with that…
George Robinson
- 353
- 4
- 9
3
votes
2 answers
Sequential History in Herlihy and Wing's Linearizability paper
I've been reading Herlihy and Wing's paper Linearizability: A Correctness Condition for Concurrent Objects (ACM Transactions on Programming Languages and Systems, 12(3):463–492, 1990; PDF) and there's one piece of the paper that is a fairly small…
maths
- 133
- 4
3
votes
1 answer
Contamination in Atomic Broadcast in crash stop failure model
I'm reading several papers about different broadcast algorithms. Most of them are designed for crash stop model but they also consider contamination scenarios.
For example for a Causal Atomic Broadcast when a faulty process
fails to delivers…
Majid Azimi
- 205
- 1
- 7
3
votes
1 answer
Is per-record timeline consistency is somehow equivalent to causal consistency?
What I understand about per-record timeline consistency is:
For a specific primary key all the insert/update/delete operations should
be read in the same order by all replicas.
Since all modifications to a specific primary key are causally…
Majid Azimi
- 205
- 1
- 7
3
votes
1 answer
Why does the proposer sends an accept request with the same value it got from the acceptor?
In the second phase of the paxos algorithm, the proposer issues an accept request with the number n and the value v it got from the acceptor, if the acceptor has already chosen a value previously. My questions is why the proposer is doing this?…
fluter
- 131
- 2
3
votes
1 answer
Can we say that Zookeeper updates are ACD (ACID without the I)?
Zookeeper is based on the Zab (which is slightly different to Paxos) system.
We can do Atomic locks on top of a Zookeeper cluster.
Zookeeper provides eventual consistency.
Zookeeper provides durability.
(I'm aware that Zookeeper sacrifices…
hawkeye
- 1,199
- 8
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3
votes
1 answer
Paxos: Instances, Rounds, Phases
In the paper, Paxos Made Simple, Lamport describes a round of Paxos as two phases: a $prepare$ phase, and an $accept$ phase. An instance of Paxos can have multiple rounds. Can a round have multiple proposers make proposals, or is it strictly one…
George Robinson
- 353
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- 9
3
votes
1 answer
Paxos: Responding to Reordered Prepare Requests
In the paper, Paxos Made Simple, a proposer asks an acceptor to respond to a prepare request with:
A promise never to again accept a proposal numbered less than n, and the proposal with the highest number less than n that it has…
George Robinson
- 353
- 4
- 9