# Linkerd2 Development Guide :balloon: Welcome to the Linkerd2 development guide! :wave: This document will help you build and run Linkerd2 from source. More information about testing from source can be found in the [TEST.md](TEST.md) guide. ## Table of contents - [Repo Layout](#repo-layout) - [Control Plane (Go/React)](#control-plane-goreact) - [Data Plane (Rust)](#data-plane-rust) - [Components](#components) - [Development configurations](#development-configurations) - [Comprehensive](#comprehensive) - [Publishing Images](#publishing-images) - [Go](#go) - [Web](#web) - [Rust](#rust) - [Multi-architecture builds](#multi-architecture-builds) - [Dependencies](#dependencies) - [Updating protobuf dependencies](#updating-protobuf-dependencies) - [Updating ServiceProfile generated code](#updating-serviceprofile-generated-code) - [Helm Chart](#helm-chart) - [Build Architecture](#build-architecture) - [Generating CLI docs](#generating-cli-docs) ## 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`](cli): Command-line `linkerd` utility, view and drive the control plane. - [`controller`](controller) - [`destination`](controller/api/destination): Accepts requests from `proxy` instances and serves service discovery information. - [`public-api`](controller/api/public): Accepts requests from API clients such as `cli` and `web`, provides access to and control of the Linkerd2 service mesh. - [`tap`](controller/tap): Provides a live pipeline of requests. - [`web`](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`](https://github.com/linkerd/linkerd2-proxy): Rust source code for the proxy lives in the linkerd2-proxy repo. - [`linkerd2-proxy-api`](https://github.com/linkerd/linkerd2-proxy-api): Protobuf definitions for the data plane APIs live in the linkerd2-proxy-api repo. ## 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](#comprehensive): Integrated configuration using k3d, most closely matches release. - [Web](#web): Development of the Linkerd2 Dashboard. ### Comprehensive This configuration builds all Linkerd2 components in Docker images, and deploys them onto a k3d cluster. This setup most closely parallels our recommended production installation, documented in [Getting Started](https://linkerd.io/2/getting-started/) ```bash # create the k3d cluster bin/k3d cluster create # build all docker images bin/docker-build # load all the images into k3d bin/image-load --k3d # 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 - # port-forward the demo app's frontend to see it at http://localhost:8080 kubectl -n emojivoto port-forward svc/web-svc 8080:80 # view details per deployment bin/linkerd -n emojivoto stat deployments # view a live pipeline of requests bin/linkerd -n emojivoto tap deploy voting ``` #### Deploying Control Plane components with Tracing Control Plane components have the `trace-collector` flag used to enable [Distributed Tracing](https://opentracing.io/docs/overview/what-is-tracing/) for development purposes. It can be enabled globally i.e Control plane components and their proxies by using the `--control-plane-tracing` installation flag. This will configure all the components to send the traces at `linkerd-collector.{{.Namespace}}.svc.{{.ClusterDomain}}:55678` ```bash # install Linkerd with tracing linkerd install --control-plane-tracing | kubectl apply -f - # install OpenCensus collector and Jaeger collector to collect traces linkerd inject https://gist.githubusercontent.com/Pothulapati/245842ce7f319e8bcd02521460684d6f/raw/52c869c58b07b17caeed520aa91380c2230d6e0c/linkerd-tracing.yaml --manual | kubectl apply -f - ``` *Note:* Collector instance has to be injected, for the proxy spans to show up. ### Publishing images The example above builds and loads the docker images into k3d. For testing your built images outside your local environment, you need to publish your images so they become accessible in those external environments. To signal `bin/docker-build` or any of the more specific scripts `bin/docker-build-*` what registry to use, just set the environment variable `DOCKER_REGISTRY` (which defaults to the official registry `ghcr.io/linkerd`). After having pushed those images through the usual means (`docker push`) you'll have to pass the `--registry` flag to `linkerd install` with a value matching your registry. ### Go #### Go modules and dependencies This repo supports [Go Modules](https://github.com/golang/go/wiki/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: ```bash export GO111MODULE=on ``` #### A note about Go run Our instructions use a [`bin/go-run`](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: ```bash go run cli/main.go check ``` with this: ```bash bin/go-run cli check ``` That is equivalent to running `linkerd check` using the code on your branch. #### Formatting All Go source code is formatted with `goimports`. The version of `goimports` used by this project is specified in `go.mod`. To ensure you have the same version installed, run `go install -mod=readonly golang.org/x/tools/cmd/goimports`. It's recommended that you set your IDE or other development tools to use `goimports`. Formatting is checked during CI by the `bin/fmt` script. #### Building the CLI for development The script for building the CLI binaries using docker is `bin/docker-build-cli-bin`. This will also be called indirectly when calling `bin/docker-build`. By default it creates binaries for Linux, Darwin and Windows. For Linux it creates binaries for the three architectures supported: amd64, arm64 and arm/v7. If you're using docker buildx, the build will be more efficient as the three OSes will still be targeted but the Linux build will only target your current architecture (more about buildx under [Multi-architecture Builds](#multi-architecture-builds) below). For local development and a faster edit-build-test cycle you might want to just target your local OS and architecture. For those situations you can just call `bin/build-cli-bin`. If you want to build all the controller images, plus only the CLI for your OS and architecture, just call: ```bash LINKERD_LOCAL_BUILD_CLI=1 bin/docker-build ``` #### Running the control plane for development Linkerd2's control plane is composed of several Go microservices. You can run these components in a Kubernetes 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: ```bash 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: ```bash bin/go-run controller/script/destination-client -path hello.default.svc.cluster.local:80 ``` ##### Running the Tap APIService for development ```bash 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](https://linkerd.io/2/cli/) 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: ```sh go test ./cli/cmd/... --update ``` #### Generating helm charts docs Whenever a new chart is created, or updated a readme should be generated from the chart's values.yml. This can be done by utilizing the bundled [helm-docs](https://github.com/norwoodj/helm-docs) binary. For adding additional information, such as specific installation instructions a readme template is required to be created. Check existing charts for example. ##### Annotating values.yml To allow helm-docs to properly document the values in values.yml a descriptive comment is required. This can be done in two ways. Either comment the value directly above with `# -- This is a really nice value` where the double dashes automatically annotates the value. Another explicit usage is to type out the value name. `# global.MyNiceValue -- I really like this value` ##### Using helm-docs Example usage: ```sh bin/helm-docs bin/helm-docs --dry-run #Prints to cli instead bin/helm-docs --chart-search-root=./charts #Sets search root for charts bin/helm-docs --template-files=README.md.gotmpl #Sets the template file used ``` Note: The tool searches through the current directory and sub-directories by default. For additional information checkout their repo above. ##### Markdown templates In order to accommodate for extra data that might not have a proper place in the ´values.yaml´ file the corresponding ´README.md.gotmpl´ can be modified for each chart. This template allows the standard markdown syntax as well as the go templating functions. Checkout [helm-docs](https://github.com/norwoodj/helm-docs) for more info. ##### 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](https://golang.org) and [Yarn](https://yarnpkg.com) environments. #### First time setup 1. Install [Yarn](https://yarnpkg.com) and use it to install JS dependencies: ```bash brew install yarn bin/web setup ``` 2. Install Linkerd on a Kubernetes cluster. #### Run web standalone ```bash 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. ```bash 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](http://localhost:7777) to see everything running. #### Dependencies To add a JS dependency: ```bash cd web/app yarn add [dep] ``` #### Translations To add a locale: ```bash cd web/app yarn lingui add-locale [locales...] # will create a messages.json file for new locale(s) ``` To extract message keys from existing components: ```bash cd web/app yarn lingui extract ... yarn lingui compile # done automatically in bin/web run ``` ### Rust All Rust development happens in the [`linkerd2-proxy`](https://github.com/linkerd/linkerd2-proxy) repo. #### Docker The `bin/docker-build-proxy` script builds the proxy by pulling a pre-published proxy binary: ```bash bin/docker-build-proxy ``` ### Multi-architecture builds Besides the default Linux/amd64 architecture, you can build controller images targeting Linux/arm64 and Linux/arm/v7. For that you need to have first installed docker buildx, as explained [here](https://github.com/docker/buildx). If you run `bin/docker-build` or any of the more focused `bin/docker-build-*` scripts, docker buildx will be used, as long as you have set the environment variable `DOCKER_BUILDKIT=1`. For signaling that you want to build multi-architecture images, set the environment variable `DOCKER_MULTIARCH=1`. Do to some limitations on buildx, if you'd like to do that you're also forced to signal buildx to push the images to the registry by setting `DOCKER_PUSH=1`. Naturally, you can't push to the official registry and will have to override `DOCKER_REGISTRY` with a registry that you control. To summarize, in order to build all the images for multiple architectures and push them to your registry located for example at `ghcr.io/user` you can issue: ```bash DOCKER_BUILDKIT=1 DOCKER_MULTIARCH=1 DOCKER_PUSH=1 DOCKER_REGISTRY=ghcr.io/user bin/docker-build ``` ## Dependencies ### Updating protobuf dependencies If you make Protobuf changes, run: ```bash bin/protoc-go.sh ``` ### Updating ServiceProfile generated code The [ServiceProfile client code](./controller/gen/client) is generated by [`bin/update-codegen.sh`](bin/update-codegen.sh), which depends on [K8s code-generator](https://github.com/kubernetes/code-generator), which does not yet support Go Modules. To re-generate this code, check out this repo into your `GOPATH`: ```bash 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`](charts/linkerd2) folder. The [`charts/patch`](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`](charts/partials) folder. Note that the `charts/linkerd2/values.yaml` file contains a placeholder `linkerdVersionValue` that you need to replace with an appropriate string (like `edge-20.2.2`) before proceeding. During development, please use the [`bin/helm`](bin/helm) wrapper script to invoke the Helm commands. For example, ```bash 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](https://linkerd.io/2/tasks/install-helm/). You also need to supply or generate your own certificates to use the chart, as explained [here](https://linkerd.io/2/tasks/generate-certificates/). ### Making changes to the chart templates Whenever you make changes to the files under [`charts/linkerd2/templates`](charts/linkerd2/templates) or its dependency [`charts/partials`](charts/partials), make sure to run [`bin/helm-build`](bin/helm-build) which will refresh the dependencies and lint the templates. ## Build Architecture 

build_architecture digraph G { rankdir=LR; "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"; "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-cli-bin" -> "_docker.sh"; "docker-build-cli-bin" -> "_tag.sh"; "docker-build-cli-bin" -> "cli/Dockerfile-bin"; "docker-build-controller" -> "_docker.sh"; "docker-build-controller" -> "_tag.sh"; "docker-build-controller" -> "controller/Dockerfile"; "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" -> "web/Dockerfile"; "docker-images" -> "_docker.sh"; "docker-images" -> "_tag.sh"; "docker-pull" -> "_docker.sh"; "docker-push" -> "_docker.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-retag-all"; "workflow.yml" -> "lint"; "web" -> "go-run"; } build_architecture