Google Inc.

Michael James Boyer Epstein

Alexander Lloyd

Wilson Cheng-Yi Hsieh

Peter H Hochschild

Robert Edman Felderman

Sean Quinlan

Eric Hugh Veach

Jeffrey Adgate Dean

Sanjay Ghemawat

Andrew Fikes

Yasushi Saito

Sebastian Kanthak

Michal Piotr Szymaniak

Christopher Scott Taylor

Chris Jorgen Taylor

Abhishek Sheopory

The subject matter described herein provides techniques to ensure that queries of a distributed database observe a consistent read of the database without locking or logging. In this regard, next-write timestamps uniquely identify a set of write transactions whose updates can be observed by reads. By publishing the next-write timestamps from within an extendable time lease and tracking a 'safe timestamp,' the database queries can be executed without logging read operations or blocking future write transactions, and clients issuing the queries at the “safe timestamp” observe a consistent view of the database as it exists on or before that timestamp. Aspects of this disclosure also provide for extensions, done cheaply and without the need for logging, to the range of timestamps at which read transactions can be executed.

Time reservations for ensuring consistent reads in a distributed database without logging

The present technology proposes techniques for generating globally coherent timestamps. This technology may allow distributed systems to causally order transactions without incurring various types of communication delays inherent in explicit synchronization. By globally deploying a number of time masters that are based on various types of time references, the time masters may serve as primary time references. Through an interactive interface, the techniques may track, calculate and record data relative to each time master thus providing the distributed systems with causal timestamps.

Generating globally coherent timestamps

The present technology proposes techniques for ensuring globally consistent transactions. This technology may allow distributed systems to ensure the causal order of read and write transactions across different partitions of a distributed database. By assigning causally generated timestamps to the transactions based on one or more globally coherent time services, the timestamps can be used to preserve and represent the causal order of the transactions in the distributed system. In this regard, certain transactions may wait for a period of time after choosing a timestamp in order to delay the start of any second transaction that might depend on it. The wait may ensure that the effects of the first transaction are not made visible until its timestamp is guaranteed to be in the past. This may ensure that a consistent snapshot of the distributed database can be determined for any past timestamp.

Ensuring globally consistent transactions

The subject matter described herein provides techniques to ensure that queries of a distributed database observe a consistent read of the database without locking or logging. In this regard, next-write timestamps uniquely identify a set of write transactions whose updates can be observed by reads. By publishing the next-write timestamps from within an extendable time lease and tracking a 'safe timestamp,' the database queries can be executed without logging read operations or blocking future write transactions, and clients issuing the queries at the 'safe timestamp' observe a consistent view of the database as it exists on or before that timestamp. Aspects of this disclosure also provide for extensions, done cheaply and without the need for logging, to the range of timestamps at which read transactions can be executed.

A system, computer-readable storage medium storing at least one program, and a computer-implemented method for identifying a storage group in a distributed storage system into which data is to be stored is presented. A data structure including information relating to storage groups in a distributed storage system is maintained, where a respective entry in the data structure for a respective storage group includes placement metrics for the respective storage group. A request to identify a storage group into which data is to be stored is received from a computer system. The data structure is used to determine an identifier for a storage group whose placement metrics satisfy a selection criterion. The identifier for the storage group whose placement metrics satisfy the selection criterion is returned to the computer system.

Storing and moving data in a distributed storage system

Growing community of inventors

Brooklyn, NY, United States of America

Michael James Boyer Epstein