Consistency Analysis Inwards Bloom: A Calm Together With Collected Approach

This operate from CIDR11 aims to render theoretical foundations for correctness nether eventual consistency, in addition to identifies "order independence" (independence of plan execution from temporal nondeterminism) equally a sufficient status for eventual consistency.

CALM (consistency in addition to logical monotonicity) regulation states that monotonic programs guarantee lodge independence, in addition to hence, eventual consistency. A monotonic plan is 1 where whatever truthful contestation remains to last truthful equally novel axioms arrive. In contrast, inwards a non-monotonic program, novel input tin drive the before output to last revoked. A monotonic plan guarantees eventual consistency, whereas non-monotonicity requires the purpose of coordination logic.

To simplify the employment of identifying monotonic in addition to nonmonotonic plan segments, this operate proposes using plan analysis inwards a declarative language, Bloom. In Bloom, monotonicity of a plan is examined via uncomplicated syntactic checks. Selection, join, in addition to projection operators are monotonic, whereas aggregation in addition to negation operators are nonmonotonic in addition to are flagged equally "points of order" inwards the program. Coordination logic needs to last introduced at these points of lodge to gain consistency.

Bloom is implemented inwards Ruby equally a domain specific language, called Bud. The newspaper presents 2 illustration studies, a key-value store in addition to a shopping cart implementation, to demonstrate the to a higher house concepts. Bloom's alpha release was out a twain days ago. Congratulations to the Bloom team! I am certain they volition have useful feedback equally the linguistic communication gets used for edifice things.

Our related operate on CALM principle

I tried to intend of an analogue to the monotonicity belongings inwards the context of guarded-command languages. I think, monotonicity belongings corresponds to the guards beingness "stable" (closed nether plan actions) inwards a guarded-command program. If all guards of a plan are stable, so the plan is monotonic. For a guard that refers to the nation at other processes, usually nosotros would take away synchronization in addition to atomicity to evaluate the guard in addition to execute the contestation at the same step. But for actions amongst stable guards, nosotros don't take away that; nosotros tin evaluate the guard at 1 pace in addition to execute the contestation at a after pace amongst several other actions from other processes executing inwards betwixt without take away for synchronization.

We had inwards fact noticed this equally a squeamish belongings a twelvemonth ago, in addition to published a newspaper on this amongst around generalizations of the stable property: Slow is Fast for Wireless Sensor Networks inwards the presence of Message Losses

This operate on guarded-command languages tin render an imperative option to declarative languages for realizing the CALM principle. Declarative programs are hard to master copy for many developers (count me here) in addition to may last difficult[different] to seek out in addition to debug. Imperative programs convey an wages inwards this regard.

Concluding remarks

I intend this is a promising administration to pursue. As Barbara Liskov mentioned in her ACM Turing Award Lecture (SOSP'09), "The Power of Abstraction", the adjacent breakthrough for distributed computing volition nigh probable last led past times novel programming languages/abstractions.

I gauge the adjacent interesting query for this operate is: What are the rules of thumbs for writing programs amongst less synchronization points?

Exercise questions

Are map, cut primitives inwards Bloom monotonic? What does this imply for map-reduce chain programs?

Can yous reconstruct whatever of the analysis for the provided programs?

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