jm + exactly-once-delivery   3

Exactly-once Support in Apache Kafka – Jay Kreps
If you’re one of the people who think [exactly-once support is impossible], I’d ask you to take an actual look at what we actually know to be possible and impossible, and what has been built in Kafka, and hopefully come to a more informed opinion. So let’s address this in two parts. First, is exactly-once a theoretical impossibility? Second, how does Kafka support it.
exactly-once-delivery  distributed  kafka  distcomp  jay-kreps  coding  broadcast 
16 days ago by jm
You Cannot Have Exactly-Once Delivery
Cut out and keep:
Within the context of a distributed system, you cannot have exactly-once message delivery. Web browser and server? Distributed. Server and database? Distributed. Server and message queue? Distributed. You cannot have exactly-once delivery semantics in any of these situations.
distributed  distcomp  exactly-once-delivery  networking  outages  network-partitions  byzantine-generals  reference 
march 2015 by jm
Exactly-Once Delivery May Not Be What You Want
An extremely good explanation from Marc Brooker that exactly-once delivery in a distributed system is very hard.
And so on. There's always a place to slot in one more turtle. The bad news is that I'm not aware of a nice solution to the general problem for all side effects, and I suspect that no such solution exists. On the bright side, there are some very nice solutions that work really well in practice. The simplest is idempotence. This is a very simple idea: we make the tasks have the same effect no matter how many times they are executed.
architecture  messaging  queues  exactly-once-delivery  reliability  fault-tolerance  distcomp  marc-brooker 
november 2014 by jm

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