Syndicate is a scalable software-defined storage system. It gives users the ability to manage data consistency guarantees, dataflow processing logic, and administrative and trust boundaries in an end-to-end fashion, across a dynamic set of existing services. By doing so, Syndicate can safely combine multiple existing cloud services into a coherent storage medium, and remain resilient to individual service outages, API changes, and cost changes. Applications using Syndicate do not need to evolve in lock-step with the cloud services they leverage, and application developers can mix and match services to find their cost/performance sweet spots.

A Syndicate deployment is comprised of users, volumes, and gateways:

• A user represents an administrative domain, and incorporates the notion of a set of hosts under the control of a single principal. For example, you are the user of your personal devices, while Google is the user of their datacenters.
• A volume is not only a collection of files and directories, but also represents a trust domain. Volumes intersect one or more administrative domains, and incorporate the set of hosts that process I/O requests on its data. Additionally, a volume defines what kinds of I/O requests may occur at each intersection point.
• A gateway is a service at the intersection between a user and a volume, which processes I/O requests. It can be as small as a single process on a single host, or as large as a fleet of datacenters. A user instantiates one or more gateways in a volume to access its data, and a user defines exactly how the gateway handles I/O requests from other gateways. There are three gateway flavors:
  • User Gateways: These are gateways that interact with the user's applications. User gateways coordinate to maintain each file's consistency and control how file data flows throughout the system.
  • Replica Gateways: These are gateways that take data from user gateways, and make it persistent. They serve it back upon request. They don't coordinate I/O, but instead operate on immutable, globally-unique chunks of data.
  • Acquisition Gateways: These are gateways that map data from external sources as files and directories within the volume. They are read-only.

Gateways discover one another and bootstrap coordination via an untrusted PaaS-hosted Metadata Service. The current implementation is compatible with Google AppEngine and AppScale.

The code for Syndicate is split into individual repositories under the syndicate-storage organization. The main Syndicate components are:

• Syndicate Core: Contains libsyndicate, libsyndicate-ug, the Syndicate Metadata Service, the Syndicate Python package (including cloud service drivers), and all the protocol definitions.
• Syndicate UG tools: Contains a set of command-line client tools that interact with Syndicate files and directories.
• Syndicatefs: FUSE filesystem client to Syndicate volumes.
• Syndicate RG: Syndicate replica gateway--a gateway that persists data on behalf of other gateways and serves it back on request.
• Syndicate AG: Syndicate acquisition gateway--a gateway that exposes data in existing services as files and directories in a Syndicate volume.
• Syndicate Automount: Syndicate automount service--a network service for provisioning and managing Syndicate gateways at scale.

The code in this repository is legacy, and preserved here for posterity. Do not use it; use the code in the individual repositories above.