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Linkerd2 Development Guide

🎈 Welcome to the Linkerd2 development guide! 👋

This document will help you build and run Linkerd2 from source. More information about testing from source can be found in the TEST.md guide.

Table of contents

Repo layout

Linkerd2 is primarily written in Rust, Go, and React. At its core is a high-performance data plane written in Rust. The control plane components are written in Go. The dashboard UI is a React application.

Control Plane (Go/React)

  • cli: Command-line linkerd utility, view and drive the control plane.
  • controller
    • destination: Accepts requests from proxy instances and serves service discovery information.
    • public-api: Accepts requests from API clients such as cli and web, provides access to and control of the Linkerd2 service mesh.
    • tap: Provides a live pipeline of requests.
  • web: Provides a UI dashboard to view and drive the control plane. This component is written in Go and React.

Data Plane (Rust)

  • linkerd2-proxy: Rust source code for the proxy lives in the linkerd2-proxy repo.
  • linkerd2-proxy-api: Protobuf definitions for the data plane APIs live in the linkerd2-proxy-api repo.

Components

Linkerd2 Components

linkerd2_components digraph G { rankdir=LR; 
node [style=filled, shape=rect];

"cli" [color=lightblue];
"destination" [color=lightblue];
"public-api" [color=lightblue];
"tap" [color=lightblue];
"web" [color=lightblue];

"proxy" [color=orange];

"cli" -> "public-api";

"web" -> "public-api";
"web" -> "grafana";

"public-api" -> "tap";
"public-api" -> "kubernetes api";
"public-api" -> "prometheus";

"tap" -> "kubernetes api";
"tap" -> "proxy";

"proxy" -> "destination";

"destination" -> "kubernetes api";

"grafana" -> "prometheus";
"prometheus" -> "kubernetes api";
"prometheus" -> "proxy";

} linkerd2_components

Development configurations

Depending on use case, there are several configurations with which to develop and run Linkerd2:

  • Comprehensive: Integrated configuration using Minikube, most closely matches release.
  • Web: Development of the Linkerd2 Dashboard.

Comprehensive

This configuration builds all Linkerd2 components in Docker images, and deploys them onto Minikube. This setup most closely parallels our recommended production installation, documented at https://linkerd.io/2/getting-started/.

These commands assume a working Minikube environment.

# build all docker images, using minikube as our docker repo
DOCKER_TRACE=1 bin/mkube bin/docker-build

# install linkerd
bin/linkerd install | kubectl apply -f -

# verify cli and server versions
bin/linkerd version

# validate installation
kubectl --namespace=linkerd get all
bin/linkerd check --expected-version $(bin/root-tag)

# view linkerd dashboard
bin/linkerd dashboard

# install the demo app
curl https://run.linkerd.io/emojivoto.yml | bin/linkerd inject - | kubectl apply -f -

# view demo app
minikube -n emojivoto service web-svc

# view details per deployment
bin/linkerd -n emojivoto stat deployments

# view a live pipeline of requests
bin/linkerd -n emojivoto tap deploy voting

Go

Go modules and dependencies

This repo supports Go Modules, and is intended to be cloned outside the GOPATH, where Go Modules support is enabled by default in Go 1.11.

If you are using this repo from within the GOPATH, activate module support with:

export GO111MODULE=on

A note about Go run

Our instructions use a bin/go-run script in lieu go run. This is a convenience script that leverages caching via go build to make your build/run/debug loop faster.

In general, replace commands like this:

go run cli/main.go check

with this:

bin/go-run cli check

That is equivalent to running linkerd check using the code on your branch.

Building the CLI for development

When Linkerd2's CLI is built using bin/docker-build it always creates binaries for all three platforms. For local development and a faster edit-build-test cycle you might want to avoid that. For those situations you can set LINKERD_LOCAL_BUILD_CLI=1, which builds the CLI using the local Go toolchain outside of Docker.

LINKERD_LOCAL_BUILD_CLI=1 bin/docker-build

To build only the cli (locally):

bin/build-cli-bin

Running the control plane for development

Linkerd2's control plane is composed of several Go microservices. You can run these components in a Kubernetes (or Minikube) cluster, or even locally.

To run an individual component locally, you can use the go-run command, and pass in valid Kubernetes credentials via the -kubeconfig flag. For instance, to run the destination service locally, run:

bin/go-run controller/cmd/destination -kubeconfig ~/.kube/config -log-level debug

You can send test requests to the destination service using the destination-client in the controller/script directory. For instance:

bin/go-run controller/script/destination-client -path hello.default.svc.cluster.local:80

You can also send test requests to the destination's discovery interface:

bin/go-run controller/script/discovery-client
Running the Tap APIService for development
openssl req -nodes -x509 -newkey rsa:4096 -keyout $HOME/key.pem -out $HOME/crt.pem -subj "/C=US"
bin/go-run controller/cmd/tap --disable-common-names --tls-cert=$HOME/crt.pem --tls-key=$HOME/key.pem

curl -k https://localhost:8089/apis/tap.linkerd.io/v1alpha1

Generating CLI docs

The documentation for the CLI tool is partially generated from YAML. This can be generated by running the linkerd doc command.

Updating templates

When kubernetes templates change, several test fixtures usually need to be updated (in cli/cmd/testdata/*.golden). These golden files can be automatically regenerated with the command:

go test ./cli/cmd/... --update
Pretty-printed diffs for templated text

When running go test, mismatched text is usually displayed as a compact diff. If you prefer to see the full text of the mismatch with colorized output, you can set the LINKERD_TEST_PRETTY_DIFF environment variable or run go test ./cli/cmd/... --pretty-diff.

Web

This is a React app fronting a Go process. It uses webpack to bundle assets, and postcss to transform css.

These commands assume working Go and Yarn environments.

First time setup

  1. Install Yarn and use it to install JS dependencies:

    brew install yarn
bin/web setup

  2. Install Linkerd on a Kubernetes cluster.

Run web standalone

bin/web run

The web server will be running on localhost:7777.

Webpack dev server

To develop with a webpack dev server:

  1. Start the development server.

    bin/web dev

    Note: this will start up:

    • web on :7777. This is the golang process that serves the dashboard.
    • webpack-dev-server on :8080 to manage rebuilding/reloading of the javascript.
    • controller is port-forwarded from the Kubernetes cluster via kubectl on :8085
    • grafana is port-forwarded from the Kubernetes cluster via kubectl on :3000

  2. Go to http://localhost:7777 to see everything running.

Dependencies

To add a JS dependency:

cd web/app
yarn add [dep]

Rust

All Rust development happens in the linkerd2-proxy repo.

Docker

The bin/docker-build-proxy script builds the proxy by pulling a pre-published proxy binary:

DOCKER_TRACE=1 bin/docker-build-proxy

Dependencies

Updating protobuf dependencies

If you make Protobuf changes, run:

bin/protoc-go.sh

Updating Docker dependencies

The Go Docker images rely on base dependency images with hard-coded SHA's:

gcr.io/linkerd-io/go-deps depends on

When Go dependencies change, run the following:

go mod tidy
bin/build-cli-bin # adds back dependencies specific to `go generate` commands
bin/update-go-deps-shas

Updating ServiceProfile generated code

The ServiceProfile client code is generated by bin/update-codegen.sh, which depends on K8s code-generator, which does not yet support Go Modules. To re-generate this code, check out this repo into your GOPATH:

go get -u github.com/linkerd/linkerd2
cd $GOPATH/src/github.com/linkerd/linkerd2
bin/update-codegen.sh

Helm chart

The Linkerd control plane chart is located in the charts/linkerd2 folder. The charts/patch chart consists of the Linkerd proxy specification, which is used by the proxy injector to inject the proxy container. Both charts depend on the partials subchart which can be found in the charts/partials folder.

During development, please use the bin/helm wrapper script to invoke the Helm commands. For example,

bin/helm install charts/linkerd2

This ensures that you use the same Helm version as that of the Linkerd CI system.

For general instructions on how to install the chart check out the docs. You also need to supply or generate your own certificates to use the chart, as explained here.

Making changes to the chart templates

Whenever you make changes to the files under charts/linkerd2/templates or its dependency charts/partials, make sure to run bin/helm-build which will refresh the dependencies and lint the templates.

Build Architecture

Build Architecture

build_architecture digraph G { rankdir=LR; 
"Dockerfile-base" [color=lightblue, style=filled, shape=rect];
"Dockerfile-go-deps" [color=lightblue, style=filled, shape=rect];
"Dockerfile-proxy" [color=lightblue, style=filled, shape=rect];
"controller/Dockerfile" [color=lightblue, style=filled, shape=rect];
"cli/Dockerfile-bin" [color=lightblue, style=filled, shape=rect];
"grafana/Dockerfile" [color=lightblue, style=filled, shape=rect];
"web/Dockerfile" [color=lightblue, style=filled, shape=rect];

"_docker.sh" -> "_log.sh";
"_gcp.sh";
"_log.sh";
"_tag.sh" -> "Dockerfile-go-deps";

"build-cli-bin" -> "_tag.sh";
"build-cli-bin" -> "root-tag";

"docker-build" -> "build-cli-bin";
"docker-build" -> "docker-build-cli-bin";
"docker-build" -> "docker-build-controller";
"docker-build" -> "docker-build-grafana";
"docker-build" -> "docker-build-proxy";
"docker-build" -> "docker-build-web";

"docker-build-base" -> "_docker.sh";
"docker-build-base" -> "Dockerfile-base";

"docker-build-cli-bin" -> "_docker.sh";
"docker-build-cli-bin" -> "_tag.sh";
"docker-build-cli-bin" -> "docker-build-base";
"docker-build-cli-bin" -> "docker-build-go-deps";
"docker-build-cli-bin" -> "cli/Dockerfile-bin";

"docker-build-controller" -> "_docker.sh";
"docker-build-controller" -> "_tag.sh";
"docker-build-controller" -> "docker-build-base";
"docker-build-controller" -> "docker-build-go-deps";
"docker-build-controller" -> "controller/Dockerfile";

"docker-build-go-deps" -> "_docker.sh";
"docker-build-go-deps" -> "_tag.sh";
"docker-build-go-deps" -> "Dockerfile-go-deps";

"docker-build-grafana" -> "_docker.sh";
"docker-build-grafana" -> "_tag.sh";
"docker-build-grafana" -> "grafana/Dockerfile";

"docker-build-proxy" -> "_docker.sh";
"docker-build-proxy" -> "_tag.sh";
"docker-build-proxy" -> "Dockerfile-proxy";

"docker-build-web" -> "_docker.sh";
"docker-build-web" -> "_tag.sh";
"docker-build-web" -> "docker-build-base";
"docker-build-web" -> "docker-build-go-deps";
"docker-build-web" -> "web/Dockerfile";

"docker-images" -> "_docker.sh";
"docker-images" -> "_tag.sh";

"docker-pull" -> "_docker.sh";

"docker-pull-deps" -> "_docker.sh";
"docker-pull-deps" -> "_tag.sh";

"docker-push" -> "_docker.sh";

"docker-push-deps" -> "_docker.sh";
"docker-push-deps" -> "_tag.sh";

"docker-retag-all" -> "_docker.sh";

"go-run" -> ".gorun";
"go-run" -> "root-tag";

"linkerd" -> "build-cli-bin";

"lint";

"minikube-start-hyperv.bat";

"mkube";

"protoc" -> ".protoc";

"protoc-go.sh" -> "protoc";

"root-tag" -> "_tag.sh";

"test-cleanup";

"test-run";

"workflow.yml" -> "_gcp.sh";
"workflow.yml" -> "_tag.sh";
"workflow.yml" -> "docker-build";
"workflow.yml" -> "docker-push";
"workflow.yml" -> "docker-push-deps";
"workflow.yml" -> "docker-retag-all";
"workflow.yml" -> "lint";

"update-go-deps-shas" -> "_tag.sh";
"update-go-deps-shas" -> "cli/Dockerfile-bin";
"update-go-deps-shas" -> "controller/Dockerfile";
"update-go-deps-shas" -> "grafana/Dockerfile";
"update-go-deps-shas" -> "web/Dockerfile";

"web" -> "go-run";

} build_architecture