Revise Europa Docs - Core Concepts - It all starts with a plan
Thank you Tanguy for the "fresh pair of eyes" perspective. Thank you Tom for the link suggestions. Supersedes https://github.com/dagger/dagger/pull/1847 Signed-off-by: Gerhard Lazu <gerhard@lazu.co.uk>
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Gerhard Lazu
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@ -5,15 +5,19 @@ displayed_sidebar: europa
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# It all starts with a plan
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A CI/CD pipeline declared in Dagger starts with a plan, specifically `dagger.#Plan`
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## Plan structure
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This plan is the entrypoint for everything that runs within a pipeline. The simplest plan will usually:
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A config declared in Dagger starts with a plan, specifically `dagger.#Plan`
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- interact with the client filesystem to read (e.g. source code) or write files (e.g. build output)
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- read environment variables
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- declare a few actions, e.g. deps, test & build
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Within this plan we can:
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This is our **Getting Started** example app plan structure:
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- interact with the `client` filesystem
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- read files, usually the current directory as `.`
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- write files, usually the build output as `_build`
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- read `env` variables, such as `NETLIFY_TEAM` in our example
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- declare a few `actions`, e.g. `deps`, `test` & `build`
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This is our **Getting Started** todoapp plan structure:
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```cue file=../tests/core-concepts/plan/structure.cue.fragment
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```
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@ -21,53 +25,87 @@ This is our **Getting Started** example app plan structure:
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When the above plan gets executed via `dagger do build`, it produces the following output:
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```shell
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[✔] client.filesystem.".".read 0.0s
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[✔] actions.deps 1.1s
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[✔] actions.test.script 0.0s
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[✔] actions.test 0.0s
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[✔] actions.build.run.script 0.0s
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[✔] actions.build.run 0.0s
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[✔] actions.build.contents 0.0s
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[✔] client.filesystem.build.write 0.1s
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[✔] client.filesystem.".".read 0.0s
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[✔] actions.deps 1.1s
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[✔] actions.test.script 0.0s
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[✔] actions.test 0.0s
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[✔] actions.build.run.script 0.0s
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[✔] actions.build.run 0.0s
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[✔] actions.build.contents 0.0s
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[✔] client.filesystem."./_build".write 0.1s
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```
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Since these actions have run before, they are cached and take less than 1 second to complete.
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Since these actions have run before, they are cached and take less than 2 seconds to complete.
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While the names used for the actions above - `deps`, `test` & `build` - are short & descriptive,
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While the names used for the actions above - `deps`, `test` & `build` - are short and descriptive,
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any other names would have worked. Put differently, action naming does not affect plan execution.
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In the example above, the `deps` action is an instance of the docker package build definition.
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Lastly, notice that even if the `deploy` action is defined, we did not run it.
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Similar to Makefile targets, we have the option of running specific actions.
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This is written as `deps: docker.#Build`
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We ran the `dagger do build` command, which only runs the `build` action (and all its dependent actions).
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This Dagger property enables us to keep the entire CI/CD config in a single file, while keeping the integration execution separate from the deployment one.
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Separating CI & CD concerns becomes essential as our pipelines grow in complexity, and we learn about operational and security constraints specific to our systems.
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Default definition configuration - `docker.#Build` in this case - can be modified via curly brackets, e.g.
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## Packages & imports
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In order to understand the correlation between actions, definitions and packages, let us focus on the following fragment from our **Getting Started** todoapp config:
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```cue
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deps: docker.#Build & {
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package todoapp
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import (
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"dagger.io/dagger"
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"universe.dagger.io/netlify"
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)
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dagger.#Plan & {
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// ...
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actions: {
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// ...
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deploy: netlify.#Deploy & {
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// ...
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}
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// ...
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}
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}
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```
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We start by declaring the package name, `package todoapp` above.
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Next, we import the packages that we use in our plan.
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The first import is needed for the `dagger.#Plan` definition to be available.
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The second import is for `netlify.#Deploy` to work.
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:::info
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Which other imports we are missing?
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Look at all the actions in the plan structure at the top of this page.
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Now check all the available packages in [universe.dagger.io](https://github.com/dagger/dagger/tree/v0.2.0/pkg/universe.dagger.io).
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:::
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We now understand that the `deploy` action is the deploy definition from the netlify package, written as `deploy: netlify.#Deploy`
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Each definition has default values that can be modified via curly brackets. This is what that looks like in practice for our deploy action:
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```cue
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// ...
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deploy: netlify.#Deploy & {
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contents: build.contents.output
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site: client.env.APP_NAME
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token: client.env.NETLIFY_TOKEN
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team: client.env.NETLIFY_TEAM
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}
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// ...
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```
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We can build complex pipelines efficiently by referencing any definition, from any package in our actions.
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This is one of the fundamental concepts that makes Dagger a powerful language for CI/CD.
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Before we can use a package in a plan, we need to declare it at the top of the pipeline configuration, like this:
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This is one of the fundamental concepts that makes Dagger a powerful language for building CI/CD pipelines.
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```cue
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import (
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"universe.dagger.io/docker"
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)
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```
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Since we are using the plan definition from the dagger package - `dagger.#Plan` - we also need to declare it at the top of the pipeline configuration:
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```cue
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import (
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"dagger.io/dagger"
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"universe.dagger.io/docker"
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)
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```
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If you want to learn more packages in the context of CUE, the config language used by Dagger configs, check out the [Packages](1215-what-is-cue.md#packages) section on the **What is CUE?** page.
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:::tip
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Now that we understand the basics of a Dagger plan, we are ready to learn more about how to interact with the client environment.
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This will enable us to configure plans just-in-time, save build artefacts, and perform other interactions with the environment within which Dagger runs.
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We can read the env (including secrets), run commands, use local sockets, etc.
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:::
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@ -1,3 +1,8 @@
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// ...
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// A plan has pre-requisited that we cover below.
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// For now we focus on the dagger.#Plan structure.
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// ...
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dagger.#Plan & {
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client: {
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filesystem: {
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@ -22,5 +27,8 @@ dagger.#Plan & {
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// ...
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}
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}
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deploy: netlify.#Deploy & {
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// ...
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}
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}
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}
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@ -1,4 +1,4 @@
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package netlify
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package todoapp
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import (
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"dagger.io/dagger"
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@ -23,12 +23,12 @@ dagger.#Plan & {
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contents: dagger.#FS
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exclude: [
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"README.md",
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"build",
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"netlify.cue",
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"_build",
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"todoapp.cue",
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"node_modules",
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]
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}
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build: write: contents: actions.build.contents.output
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"./_build": write: contents: actions.build.contents.output
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}
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env: {
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APP_NAME: string
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@ -50,8 +50,6 @@ dagger.#Plan & {
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contents: client.filesystem.".".read.contents
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dest: "/src"
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},
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// bash.#Run is a superset of docker.#Run
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// install yarn dependencies
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bash.#Run & {
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workdir: "/src"
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mounts: {
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