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Unleash Edge

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This document was generated from the README in the Unleash Edge GitHub repository.

Unleash Edge

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Warning: Unleash Edge requires Unleash v4.15.0 or higher

Unleash Edge is the successor to the Unleash Proxy.

Unleash Edge sits between the Unleash API and your SDKs and provides a cached read-replica of your Unleash instance. This means you can scale up your Unleash instance to thousands of connected SDKs without increasing the number of requests you make to your Unleash instance.

Unleash Edge offers two important features:

  • Performance: Unleash Edge caches in memory and can run close to your end-users. A single instance can handle tens to hundreds of thousands of requests per second.
  • Resilience: Unleash Edge is designed to survive restarts and operate properly even if you lose connection to your Unleash server.

Unleash Edge is built to help you scale Unleash.

  • If you're looking for the easiest way to connect your client SDKs you can check out our Frontend API.
  • If you're looking to learn how to scale your own feature flag system why not check out our recommendations for building and scaling feature flags

Migrating to Edge from the Proxy​

For more info on migrating, check out the migration guide that details the differences between Edge and the Proxy and how to achieve similar behavior in Edge.

Quickstart​

Running Edge in Docker with our recommended setup:

docker run -it -p 3063:3063 -e STRICT=true -e UPSTREAM_URL=<yourunleashinstance> -e TOKENS=<yourclienttoken> unleashorg/unleash-edge:<mostrecentversion> edge

Edge behaviors​

As of version 19.2.0, Unleash Edge now supports two behaviors when running in edge mode: strict and dynamic. We recommend adopting the new strict behavior, while dynamic remains as a legacy option that will be deprecated and removed in a future release.

For legacy reasons, dynamic behavior is still the default. However, a warning will be logged at startup to indicate its deprecation.

Please note that these behaviors are mutually exclusive.

Strict behavior​

If started with the --strict flag or the STRICT environment variable, Edge now starts with strict behavior and must be given tokens at startup.

Edge will refuse requests from SDKs that have a wider or different access scope than the initial tokens. Specifically, this means incoming requests must have a token that exactly matches the environment and is bound to a project or projects specified in that token.

E.g. If you start with one wildcard token with access to the development environment *:development.<somelongrandomstring> and your clients use various tokens with access to specific projects in the development environment, Edge will filter features to only grant access to the narrower scope.

Dynamic behavior​

With dynamic behavior, Edge behaves as it has since v1.0.0. Any new client tokens are validated against upstream and if found to be valid, a refresh job will be configured with the minimum set of tokens that are able to fetch all projects and environments Edge has seen. Set with --dynamic or the DYNAMIC environment variable. (19.2.0 / July 4th 2024): We're looking to deprecate this behavior. If you need this behavior, reach out to us on Slack, the final decision has not been made yet. In 19.2.0 this behavior is still the default, but Edge will log that you should make a choice between dynamic or strict behavior. When dynamic behavior is selected (by default or by choice), Edge will print a warning about the planned deprecation.

Deploying​

See our page on Deploying Edge

Getting Unleash Edge​

Unleash Edge is distributed as a binary and as a docker image.

Binary​

  • The binary is downloadable from our Releases page.
  • We're currently building for linux x86_64, windows x86_64, darwin (OS X) x86_64 and darwin (OS X) aarch64 (M1/M2 macs)

Docker​

  • The docker image gets uploaded to dockerhub and Github Package registry.
  • For dockerhub use the coordinates unleashorg/unleash-edge:<version>.
  • For Github package registry use the coordinates ghpr.io/unleash/unleash-edge:<version>
  • If you'd like to live on the edge (sic) you can use the tag edge. This is built from HEAD on each commit
  • When running the docker image, the same CLI arguments that's available when running the binary is available to your docker run command. To start successfully you will need to decide which mode you're running in.
    • If running in edge mode your command should be
      • docker run -p 3063:3063 -e UPSTREAM_URL=<YOUR_UNLEASH_INSTANCE> unleashorg/unleash-edge:<version> edge
    • If running in offline mode you will need to provide a volume containing your feature toggles file. An example is available inside the examples folder. To use this, you can use the command
      • docker run -v ./examples:/edge/data -p 3063:3063 -e BOOTSTRAP_FILE=/edge/data/features.json -e TOKENS='my-secret-123,another-secret-789' unleashorg/unleash-edge:<version> offline

Cargo/Rust​

If you have the Rust toolchain installed you can build a binary for the platform you're running by cloning this repo and running cargo build --release. This will give you an unleash-edge binary in ./target/release

Concepts​

See our page on Edge concepts

Metrics​

❗ Note: For Edge to correctly register SDK usage metrics, your Unleash instance must be v5.9.0 or newer. ! Note: If you're daisy chaining you will need at least Edge 17.0.0 upstream of any Edge 19.0.0 to preserve metrics.

Since Edge is designed to avoid overloading its upstream, Edge gathers and accumulates usage metrics from SDKs for a set interval (METRICS_INTERVAL_SECONDS) before posting a batch upstream. This reduces load on Unleash instances down to a single call every interval, instead of every single client posting to Unleash for updating metrics. Unleash instances running on versions older than 4.22 are not able to handle the batch format posted by Edge, which means you won't see any metrics from clients connected to an Edge instance until you're able to update to 4.22 or newer.

Compatibility​

Unleash Edge adheres to Semantic Versioning (SemVer) on the API and CLI layers. If you're using Unleash Edge as a library in your projects, be cautious, internal codebase changes, which might occur in any version release (including minor and patch versions), could potentially break your implementation.

Performance​

See our page on [Edge benchmarking][Benchmarking](https://github.com/Unleash/unleash-edge/blob/main/./docs/benchmarking.md)

Debugging​

You can adjust the RUST_LOG environment variable to see more verbose log output. For example, in order to get logs originating directly from Edge but not its dependencies, you can raise the default log level from error to warning and set Edge to debug, like this:

RUST_LOG="warn,unleash_edge=debug" ./unleash-edge #<command>

See more about available logging and log levels at https://docs.rs/env_logger/latest/env_logger/#enabling-logging

Troubleshooting​

Missing metrics in upstream server​

Possible reasons​

  • Old Edge version. In order to guarantee metrics on newer Unleash versions, you will need to be using Edge v17.0.0 or newer
  • Old SDK clients. We've noticed that some clients, particularly early Python (1.x branch) as well as earlier .NET SDKs (we recommend you use 4.1.5 or newer) struggle to post metrics with the strict headers Edge requires.

Development​

See our Contributors guide as well as our development-guide

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