When a 3D model is transmitted over a lossy network, some model information may inevitably be missing. Under such situation, one may not be able to visualize the receiving model unless the lost model information has b...When a 3D model is transmitted over a lossy network, some model information may inevitably be missing. Under such situation, one may not be able to visualize the receiving model unless the lost model information has been retransmitted. Progressive model transmission offers an alternative to avoid the ＂all or nothing situation＂ by allowing a model to be visualized with a degraded quality when only part of the model data has been received. Unfortunately, in case some model refinement information is missing, one may still need to wait for such information to be retransmitted before the model can be rendered with a desired visual quality. To address this problem, we have developed a novel error resilient packetization scheme. We first construct a Non-Redundant Directed Acyclic Graph to encode the dependencies among the vertex splits of a progressive mesh. A special Global Graph Equipartition Packing Algorithm is then applied to partitioning this graph into several equal size sub-graphs, which is packed as packets. The packing algorithm comprises two main phases： initial partition phase and global refinement phase. Experimental results demonstrate that the proposed scheme can minimize the dependencies between packets. Hence, it reduces the delay in rendering 3D models with proper quality at the clients.展开更多
The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raf...The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and fault-tolerance.However,it is non-trivial to replicate IMDB because high transaction rate has brought new challenges.First,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes.Second,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap.Third,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often happen.In this case,the performance would be significantly affected because the follower node falls into the long-duration exception handling process(e.g.,fetch lost logs from the leader).To this end,we build QuorumX,an efficient and stable quorum-based replication framework for IMDB under heavy OLTP workloads.QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings.Further,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs.We further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication performance.Our evaluation results with the YCSB,TPC-C and a realistic microbenchmark demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication and could always provide a stable service with data consistency and a low-level visibility gap.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No. 60533080the National Research Foundation for Doctoral Program of Higher Education of China Under Grant No. 20060335111.
文摘When a 3D model is transmitted over a lossy network, some model information may inevitably be missing. Under such situation, one may not be able to visualize the receiving model unless the lost model information has been retransmitted. Progressive model transmission offers an alternative to avoid the ＂all or nothing situation＂ by allowing a model to be visualized with a degraded quality when only part of the model data has been received. Unfortunately, in case some model refinement information is missing, one may still need to wait for such information to be retransmitted before the model can be rendered with a desired visual quality. To address this problem, we have developed a novel error resilient packetization scheme. We first construct a Non-Redundant Directed Acyclic Graph to encode the dependencies among the vertex splits of a progressive mesh. A special Global Graph Equipartition Packing Algorithm is then applied to partitioning this graph into several equal size sub-graphs, which is packed as packets. The packing algorithm comprises two main phases： initial partition phase and global refinement phase. Experimental results demonstrate that the proposed scheme can minimize the dependencies between packets. Hence, it reduces the delay in rendering 3D models with proper quality at the clients.
基金This work was partially supported by National Key R&D Program of China(2018YFB1003404)NSFC(Grant Nos.61972149,61977026)ECNU Academic Innovation Promotion Program for Excellent Doctoral Students.
文摘The modern in-memory database(IMDB)can support highly concurrent on-line transaction processing(OLTP)workloads and generate massive transactional logs per second.Quorum-based replication protocols such as Paxos or Raft have been widely used in the distributed databases to offer higher availability and fault-tolerance.However,it is non-trivial to replicate IMDB because high transaction rate has brought new challenges.First,the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes.Second,followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap.Third,modern databases are often built with a cluster of commodity machines connected by low configuration networks,in which the network anomalies often happen.In this case,the performance would be significantly affected because the follower node falls into the long-duration exception handling process(e.g.,fetch lost logs from the leader).To this end,we build QuorumX,an efficient and stable quorum-based replication framework for IMDB under heavy OLTP workloads.QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings.Further,we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs.We further carefully design the process for the follower node in order to alleviate the influence of the unreliable network on the replication performance.Our evaluation results with the YCSB,TPC-C and a realistic microbenchmark demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication and could always provide a stable service with data consistency and a low-level visibility gap.
