gTC: gRPC Traffic Controller

gRPC Traffic Controller (or gTC) is a Kubernetes controller that allows through a manifest to describe routing configuration between gRPC clients and servers. It provides configuration to the clients using the gRPC xDS service discovery integration available in all major gRPC implemetations.

Some of the gRPC features supported by gTC:

• Traffic Splitting and Routing
• Weighted Load Balancing
• Circuit breaking
• Retries
• Fault injection
• Locality Fallback
• Hash Ring Load Balancing
• Topology Aware Routing, if a destination service has TAR enabled, gTC will serve the hinted endpoints with a higher priority.

Some features I wish to add:

• Prometheus Metrics
• Integration of SPIFFE and SPIRE, for both TLS and RBAC.

Documentation

Please refer to the official website.

Usage Examples

See the example setup.

Current Status

xDS features implemented in gRPC are listed here, this table tracks their support in gTC.

gRFC	Status
A27	Supported (except LRS)
A28	Supported
A29	TODO
A31	Supported: MaxStreamDuration on routes and HTTPConnManager.
A32	Supported: Cluster MaxRequests
A33	Supported: delay and abort injection
A36	TODO
A39	Supported filters at listener, route and backend level
A40	TODO, Not directly related but it highlight the need of supporting CSDS on gTC's end?
A41	TODO
A42	Supported: Route Hash Policies and LB Policy on backend
A44	Supported, both on route and listener

• I indend to suport xDS enabled gRPC servers, yet it might require a slight API change, or even a new CRD. More thinking is needed here.
• LRS server side is left out of scope at the moment, though it could be an interesting thing to elaborate (expose load metrics?) I am unsure of what to do with for now.

Getting Started

Required Tools

• go1.21
• k3d
• ko
• helm
• kubectl

Running the development environment

For the first time you need to install the code generation tools

make install_code_generator install_controller_tools

Then you can run

make dev

This command:

1. Creates a k3d cluster
2. Installs the gTC controller
3. Deploy an example server
4. Deploys an example client.

From there you can run a few example commands

make client_shell_0 CMD='/ko-app/client -period=100ms --addr xds:///echo-server/basic  "hello there"'
make client_shell_0 CMD='/ko-app/client -premium -period=100ms --addr xds:///echo-server/abort-fault-injection-backend-override  "hello there"'

Feel free to try out all the examples available

If you wish to run the test suite

make test