# \[Alpha] Go feature server

## Overview

The Go feature server is an HTTP/gRPC endpoint that serves features. It is written in Go.

## Configuration of `feature_store.yaml`

The current Go feature server needs a Python based feature Transformation service support. Please refer to the following code as an example:

```
# -*- coding: utf-8 -*-
from feast.feature_store import FeatureStore


def main():
    # Init the Feature Store
    store = FeatureStore(repo_path="./feature_repo/")

    # Start the feature transformation server
    # default port is 6569
    store.serve_transformations(6569)

if __name__ == "__main__":
    main()
```

At the same time, we need to configure the `feature_store.yaml` as following:

```
...
entity_key_serialization_version: 3
feature_server:
    type: local
    transformation_service_endpoint: "localhost:6569"
...
```

## Supported APIs

Here is the list of supported APIs:

| Method |          API         |                  Comment                  |
| :----: | :------------------: | :---------------------------------------: |
|  POST  | /get-online-features | Retrieve features of one or many entities |
|   GET  |        /health       |      Status of the Go Feature Server      |

## OTEL based Observability

The Go feature server support [OTEL](https://opentelemetry.io/) based Observabilities. To enable it, we need to set the global env `ENABLE_OTEL_TRACING` to `"true"` (as a string type!) in the container or your local OS.

```
export ENABLE_OTEL_TRACING='true'
```

There are example OTEL infra setup under the `/go/infra/docker/otel` folder.

## Demo

Please check the Reference\[2] for a local demo of Go feature server. If you want to see a real world example of applying Go feature server in Production, please check Reference\[1].

## Reference

1. [Expedia Group's Go Feature Server Implementation (in Production)](https://github.com/EXPEbdodla/feast)
2. [A Go Feature server demo from Feast](https://github.com/feast-dev/feast-credit-score-local-tutorial)


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