Dryad: Distributed data-parallel programs from sequential building blocks. Conference Paper (PDF Available) in ACM SIGOPS Operating Systems Review. DRYAD: DISTRIBUTED DATA-. PARALLEL PROGRAMS FROM. SEQUENTIAL. BUILDING BLOCKS. Authors: Michael Isard, Mihai Budiu, Yuan Yu,. Andrew. An improvement: Ciel. Comparison. Conclusion. Dryad: Distributed Data-Parallel Programs from. Sequential Building Blocks. Course: CS
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Dryad is a “general-purpose, high performance distributed execution engine.
Dryad: distributed data-parallel programs from sequential building blocks – Dimensions
It focuses more on simplicity of the programming model and reliability, efficiency and scalability of the applications while side-stepped problems like high-latency and unreliable wide-area networks, control of resources by separate federated or competing entities and ACL, etc. It provides task scheduling, concurrency optimization in a computer level, fault tolerance and data distribution.
One of the unique feature provided by Dryad is the flexibility of fine control of an application’s data flow graph. This gives programmer the opportunity to optimize trade offs between parallelism and data distribution overhead thus gives “excellent performance” according to the paper. A Dryad job consists of DAG where each vertex is a program and each edge is a data channel, data channel can be shared memory, TCP pipes, or temp files.
Summary of “Dryad: Distributed Data-Parallel Programs from Sequential Building Blocks”
In contrast to MapReduce, Dryad doesn’t do serialization, for the vertex program’s perspective, what they see is a heap object passed from the previous vertex, which will certainly save a lot of data parsing headaches. Distribkted Dryad job is coordinated by a process called job manager, can be either within the compute cluster distrbiuted remote workstation that has access to the compute cluster.
To discover available resources, each computer in the cluster has a proxy daemon running, and they are registered into a central name server, they job manager queries the name server to get available computers. It supports vertex creation, edge creation and graph merging operations.
Dryad: Distributed Data-parallel Programs from Sequential Building Blocks – Microsoft Research
One interesting property buildkng by Dryad is it can turn a graph G into a vertex V Gessentially similar to the composite design pattern, it improves the re-usability a lot. The runtime receives a closure from the job manager describing the vertex to be run and URIs for input and output of the vertex. It supports event-based programming style on vertex for you to write concurrent program. Which can potentially gives you more efficiency in a vertex execution. In Dryad, a scheduler inside job manager tracks states of each vertex.
If every vertex finishes successfully, the whole job is finished. If any vertex failed, the job is re-run, but only to a threshold number of times, after that if the job is still failing, the entire job will be failed.
Dryad: Distributed Data-parallel Programs from Sequential Building Blocks
Dryad also provides visualizer and web interface for monitoring of cluster states. Dryad achieves fault tolerance through proxy communicating with job manager, but if proxy failed, a timeout will be triggered in job manager indicating a vertex has failed.
Dryad also provides a backup task mechanism when noticing a vertex has been slower than their peers, similar to the one used data-paralldl MapReduce. Dryad’s DAG based data parallelization makes it more expressive for solving different large scale problems. The dynamic refinement it provides also makes it efficient in a lot of cases.
The performance is absolutely superior to a commercial database system for hand-coded read-only query. One caveat is you can only run 1 job in a cluster at a time, because the huilding manager assumes exclusive control over all computers within the cluster. Distributed Data-Parallel Programs from Sequential Building Blocks” Dryad is a “general-purpose, high performance distributed execution engine.