Flipt.Client 0.5.0

Flipt Client C#

The flipt-client-csharp library contains the C# source code for the Flipt client-side evaluation client.

Installation

dotnet add package Flipt.Client

How Does It Work?

The flipt-client-csharp library is a wrapper around the flipt-engine-ffi library.

All evaluation happens within the SDK, using the shared library built from the flipt-engine-ffi library.

Because the evaluation happens within the SDK, the SDKs can be used in environments where the Flipt server is not available or reachable after the initial data is fetched.

Data Fetching

Upon instantiation, the flipt-client-csharp library will fetch the flag state from the Flipt server and store it in memory. This means that the first time you use the SDK, it will make a request to the Flipt server.

Polling (Default)

By default, the SDK will poll the Flipt server for new flag state at a regular interval. This interval can be configured using the FetchMode option when constructing a client. The default interval is 120 seconds.

Streaming (Flipt Cloud Only)

Flipt Cloud users can use the streaming fetch method to stream flag state changes from the Flipt server to the SDK.

When in streaming mode, the SDK will connect to the Flipt server and open a persistent connection that will remain open until the client is closed. The SDK will then receive flag state changes in real-time.

Retries

The SDK will automatically retry fetching (or initiating streaming) flag state if the client is unable to reach the Flipt server temporarily.

The SDK will retry up to 3 times with an exponential backoff interval between retries. The base delay is 1 second and the maximum delay is 30 seconds.

Retriable errors include:

• 429 Too Many Requests
• 502 Bad Gateway
• 503 Service Unavailable
• 504 Gateway Timeout
• Other potential transient network or DNS errors

Supported Architectures

This SDK currently supports the following OSes/architectures:

• Linux x86_64
• Linux arm64
• MacOS x86_64
• MacOS arm64
• Windows x86_64

Usage

In your C# code you can import this client and use it as so:

using Flipt.Client;

var options = new ClientOptions
  {
    Url = "http://localhost:8080",
    Authentication = new Authentication { ClientToken = "secret" }
  };

var client = new EvaluationClient("default", options);

var context = new Dictionary<string, string> { { "fizz", "buzz" } };
var response = client.EvaluateVariant("flag1", "someentity", context);

Initialization Arguments

The EvaluationClient constructor accepts two optional arguments:

• Namespace: The namespace to fetch flag state from. If not provided, the client will default to the default namespace.
• Options: An instance of the ClientOptions type that supports several options for the client. The structure is:
  • Url: The URL of the upstream Flipt instance. If not provided, the client will default to http://localhost:8080.
  • RequestTimeout: The timeout (in seconds) for total request time to the upstream Flipt instance. If not provided, the client will default to no timeout. Note: this only affects polling mode. Streaming mode will have no timeout set.
  • UpdateInterval: The interval (in seconds) in which to fetch new flag state. If not provided, the client will default to 120 seconds.
  • Authentication: The authentication strategy to use when communicating with the upstream Flipt instance. If not provided, the client will default to no authentication. See the Authentication section for more information.
  • Reference: The reference to use when fetching flag state. If not provided, reference will not be used.
  • FetchMode: The fetch mode to use when fetching flag state. If not provided, the client will default to polling.
  • ErrorStrategy: The error strategy to use when fetching flag state. If not provided, the client will default to Fail. See the Error Strategies section for more information.

Authentication

The EvaluationClient supports the following authentication strategies:

• No Authentication (default)
• Client Token Authentication
• JWT Authentication

Error Strategies

The EvaluationClient supports the following error strategies:

• Fail: The client will throw an error if the flag state cannot be fetched. This is the default behavior.
• Fallback: The client will maintain the last known good state and use that state for evaluation in case of an error.

Contributing

Contributions are welcome! Please feel free to open an issue or submit a Pull Request.

License

This project is licensed under the MIT License.