25 research outputs found
Efficient state-based CRDTs by delta-mutation
CRDTs are distributed data types that make eventual consistency of a distributed object possible and non ad-hoc. Specifically, state-based CRDTs ensure convergence through disseminating the entire state, that may be large, and merging it to other replicas; whereas operation-based CRDTs disseminate operations (i.e., small states) assuming an exactly-once reliable dissemination layer. We introduce Delta State Conflict-Free Replicated Datatypes (δ-CRDT) that can achieve the best of both worlds: small messages with an incremental nature, disseminated over unreliable communication channels. This is achieved by defining δ-mutators to return a delta-state, typically with a much smaller size than the full state, that is joined to both: local and remote states. We introduce the δ-CRDT framework, and we explain it through establishing a correspondence to current state-based CRDTs. In addition, we present an anti-entropy algorithm that ensures causal consistency, and two δ-CRDT specifications of well-known replicated datatypes.This work is co-financed by the North Portugal Regional Operational Programme (ON.2, O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF), within project NORTE07-0124-FEDER-000058; and by EU FP7 SyncFree project (609551)
Achlys : Towards a framework for distributed storage and generic computing applications for wireless IoT edge networks with Lasp on GRiSP
Internet of Things (IoT) has gained substantial attention over the past
years. And the main discussion has been how to process the amount of data that
it generates which has lead to the edge computing paradigm. Wether it is called
fog1, edge or mist, the principle remains that cloud services must become
available closer to clients. This documents presents ongoing work on future
edge systems that are built to provide steadfast IoT services to users by
bringing storage and processing power closer to peripheral parts of networks.
Designing such infrastructures is becoming much more challenging as the number
of IoT devices keeps growing. Production grade deployments have to meet very
high performance requirements, and end-to-end solutions involve significant
investments. In this paper, we aim at providing a solution to extend the range
of the edge model to the very farthest nodes in the network. Specifically, we
focus on providing reliable storage and computation capabilities immediately on
wireless IoT sensor nodes. This extended edge model will allow end users to
manage their IoT ecosystem without forcibly relying on gateways or Internet
provider solutions. In this document, we introduce Achlys, a prototype
implementation of an edge node that is a concrete port of the Lasp programming
library on the GRiSP Erlang embedded system. This way, we aim at addressing the
need for a general purpose edge that is both resilient and consistent in terms
of storage and network. Finally, we study example use cases that could take
advantage of integrating the Achlys framework and discuss future work for the
latter.Comment: 7 page
Replicated Data Types
International audienceA CRDT is an abstract data type that implements some familiar object, such as a counter, a set or a sequence. Internally, a CRDT is replicated, to provide reliability, availability. A CRDT supports concurrent updates, and encapsulates some strategy that provably ensures that replicas of the CRDT will converge despite this concurrency
Replicated Data Types
International audienceA CRDT is an abstract data type that implements some familiar object, such as a counter, a set or a sequence. Internally, a CRDT is replicated, to provide reliability, availability. A CRDT supports concurrent updates, and encapsulates some strategy that provably ensures that replicas of the CRDT will converge despite this concurrency
Delta state replicated data types
Conflict-free Replicated Data Types (CRDTs) are distributed data types that make eventual consistency of a distributed object possible and non ad-hoc. Specifically, state-based CRDTs ensure convergence through disseminating the entire state, that may be large, and merging it to other replicas. We introduce Delta State Conflict-Free Replicated Data Types (delta-CRDT) that can achieve the best of both operation-based and state-based CRDTs: small messages with an incremental nature, as in operation-based CRDTs, disseminated over unreliable communication channels, as in traditional state-based CRDTs. This is achieved by defining delta-mutators to return a delta-state, typically with a much smaller size than the full state, that to be joined with both local and remote states. We introduce the delta-CRDT framework, and we explain it through establishing a correspondence to current state-based CRDTs. In addition, we present an anti-entropy algorithm for eventual convergence, and another one that ensures causal consistency. Finally, we introduce several delta-CRDT specifications of both well-known replicated datatypes and novel datatypes, including a generic map composition. (C) 2017 Elsevier Inc. All rights reserved.The work presented was partially supported by EU FP7 SyncFree project (609551), EU H2020 LightKone project (732505), and SMILES line in project TEC4Growth (NORTE-01-0145-FEDER-000020)