RTable ("Replicated Table") is a library that provides synchronous geo-replication capability over the Azure Table service. The library is self-contained and has no service dependencies, making it an excellent tool for disaster recovery and business continuity scenarios on Azure.

RTable provides synchronous geo-replication for Azure tables, thereby enabling zero-RPO availability and disaster recovery in the event of Azure table failures. Clients continue to benefit from the amazing scale, lower cost and manageability of Azure storage while gaining disaster tolerance. The protocol is optimized for read-latency – which is the same as for a regular Azure table read. In addition, recovery actions, such as re-introducing a replica, do not impact read or write availability. The protocol runs entirely from client-side and does not require any external service. Customers control the number and location of regions for replication. For more detailed documentaton, refer to the docs folder.

Latest: See a talk on RTable at Facebook's Networking@Scale

https://www.youtube.com/watch?v=ktXYnSvHbZ4&feature=share

• Synchronous geo-replication over Azure tables to enable zero RPO availability and disaster recovery.
• Very minimal change needed to an existing Azure table client. Many existing tools, such as, storage explorer, continue to work without any change.
• Read latency same as without replication.
• No external service is required.

• Increased write latency. The latency depends on the locations chosen.
• Write latency increases linearly with the number of replicas. Since the underlying Azure tables are highly durable, the main design goal of the protocol was to provide availability in the event of temporary Azure table outages. It is best suited for replication across two or three regions.
• The protocol runs on the client side. So any changes to the protocol will require clients to update the library.

The RTable protocol provides strong consistency and as such is best suited for applications that need zero RPO recovery. The protocol favors Consistency and Partition Tolerance in the CAP theorem. Table operations may experience failure in the event of an Azure table failure until the faulty replica is taken out of rotation. Our goal is to limit this unavailability period to be less than five minutes.

To get started, clone the repo and build using msbuild or Visual Studio.

The RTable library has the following build dependencies (NuGet packages):

• Azure storage library: WindowsAzure.Storage.4.3.0 (and its own dependencies)
• JSON.NET: Newtonsoft.Json.5.0.8
• Configuration: Microsoft.WindowsAzure.ConfigurationManager.1.8.0.0
• NUnit Framework
• FiddlerCore

The dependent packages will be automatically downloaded using NuGet.

A comprehensive suite of tests can be found under the Test folder. To run unit tests:

1. Build the entire solution including Tests.csproj
2. Go to folder: test\bin
3. Update the RTableTestConfiguration.xml to update the storage account names and keys (replace the ******). You need three storage accounts.
4. Download nunit.Runners package
5. Run nunit-console.exe test\bin\Microsoft.Azure.Toolkit.Replication.Test.dll to run all tests

At this time, the RTable library is only being released as a source download. To use the component, a developer will need to build it themselves.

In the future, as the library matures, a great experience, including published NuGet packages, will appear. Thanks for your patience.

The Microsoft Azure Storage Service supports creating accounts with geo-replication enabled. The replication provided by the service works with a paired region and is an excellent choice for replication.

However, the replication does not happen as quickly. When zero RPO is preferred, this library can help make that happen.

A component initially built for use by the Azure Network software engineering team at Microsoft, rtable is a replication library that provides strong consistency and is easy to use, built on top of the existing Azure Table experience you may be familiar with from the Azure Storage SDK.

Please feel free to open bugs and issues on GitHub.

For information about contributing to Azure open source projects, see the general guidance, including the legal CLA requirement, here: http://azure.github.io/guidelines.html#cla

azure-rtable ver. 0.9

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