gRPC Load Balancer

grpc_load_balancer is a Python package that allows you to easily configure and manage separate gRPC server and client instances using a metrics-based load balancing approach. This is useful when you have multiple services running and want to distribute the load efficiently among them. The package includes a connection forwarder, a metrics-based server finder, and a configuration loader. It implemetns the following design:

Features

• Forward connections from clients to gRPC servers.
• Use Prometheus metrics to select the best server to handle a request.
• Configure and manage gRPC server finder using environment variables.

Installation

You can install grpc_load_balancer using pip:

pip install grpc_load_balancer

Install promethus-client:

pip install prometheus-client

Usage

Configuring and running a gRPC server

Here's a simple example of how to use grpc_load_balancer with a gRPC server and prometeus-client:

Import the required modules:

import grpc
from grpc_load_balancer import GrpcConnnectionForwarder
from prometheus_client import start_http_server, Gauge

Initialize your gRPC server(s)

    grpc_server = create_example_grpc_server() # implement this function yourself
    connection_counter = Gauge('connections_num', 'Number of connections forwarded')
    forwarder = GrpcConnnectionForwarder(
        grpc_server, callback=lambda value: connection_counter.set(value)
    )
    start_http_server(prometheus_port)
    # forwarder_port - port to listen connections from gRPC clients

    # Note this call is blocking
    forwarder.serve(host="0.0.0.0", port=forwarder_port)

    # If you want to run the server in a separate thread, and want to stop it later, use the forwarder.stop() method
    

Configuring and running a gRPC client

Import the required modules:

import grpc
from grpc_load_balancer import EnvConfigLoader, MetricsBasedServerFinder

Initialize the configuration loader

# This is example how your environment variables can look like
# os.environ['LB_METRICS_NAME'] = 'connections_num'
# os.environ['LB_HOST1_HOST'] = 'localhost'
# os.environ['LB_HOST1_PORT'] = '20000'
# os.environ['LB_HOST1_METRICS_PORT'] = '20001'
# os.environ['LB_HOST2_HOST'] = 'localhost'
# os.environ['LB_HOST2_PORT'] = '30000'
# os.environ['LB_HOST2_METRICS_PORT'] = '30001'

env_config_loader = EnvConfigLoader(prefix="LB")

Initialize the server finder, find the best server and connect to it

    metrics_based_server_finder = env_config_loader.init_metrics_based_server_finder()
    best_host = metrics_based_server_finder.fetch_metrics()
    channel = grpc.insecure_channel(f"{best_host[0]}:{best_host[1]}")
    client = create_example_grpc_client(channel) # implement this function yourself
    # Use the client to send requests to the server

Troubleshooting

If you have any problems with grpc_load_balancer, please open an issue on GitHub. Also, you can check tests/test_grpc_load_balancer.py for more information.

Contributing

We welcome contributions to grpc_load_balancer. If you find a bug or want to propose a new feature, please open a GitHub issue or submit a pull request.

License

This project is licensed under the MIT License. See LICENSE for details.