mirror of
https://github.com/go-gitea/gitea
synced 2024-11-09 11:44:27 +00:00
132 lines
7.0 KiB
Markdown
132 lines
7.0 KiB
Markdown
---
|
|
date: "2023-04-27T15:00:00+08:00"
|
|
title: "Design of Gitea Actions"
|
|
slug: "design"
|
|
sidebar_position: 40
|
|
draft: false
|
|
toc: false
|
|
menu:
|
|
sidebar:
|
|
parent: "actions"
|
|
name: "Design"
|
|
sidebar_position: 40
|
|
identifier: "actions-design"
|
|
---
|
|
|
|
# Design of Gitea Actions
|
|
|
|
Gitea Actions has multiple components. This document describes them individually.
|
|
|
|
## Act
|
|
|
|
The [nektos/act](https://github.com/nektos/act) project is an excellent tool that allows you to run your GitHub Actions locally.
|
|
We were inspired by this and wondered if it would be possible to run actions for Gitea.
|
|
|
|
However, while [nektos/act](https://github.com/nektos/act) is designed as a command line tool, what we actually needed was a Go library with modifications specifically for Gitea.
|
|
So we forked it as [gitea/act](https://gitea.com/gitea/act).
|
|
|
|
This is a soft fork that will periodically follow the upstream.
|
|
Although some custom commits have been added, we will try our best to avoid changing too much of the original code.
|
|
|
|
The forked act is just a shim or adapter for Gitea's specific usage.
|
|
There are some additional commits that have been made, such as:
|
|
|
|
- Outputting execution logs to logger hook so they can be reported to Gitea
|
|
- Disabling the GraphQL URL, since Gitea doesn't support it
|
|
- Starting a new container for every job instead of reusing to ensure isolation.
|
|
|
|
These modifications have no reason to be merged into the upstream.
|
|
They don't make sense if the user just wants to run trusted actions locally.
|
|
|
|
However, there may be overlaps in the future, such as a required bug fix or new feature needed by both projects.
|
|
In these cases, we will contribute the changes back to the upstream repository.
|
|
|
|
## Act runner
|
|
|
|
Gitea's runner is called act runner because it's based on act.
|
|
|
|
Like other CI runners, we designed it as an external part of Gitea, which means it should run on a different server than Gitea.
|
|
|
|
To ensure that the runner connects to the correct Gitea instance, we need to register it with a token.
|
|
Additionally, the runner will introduce itself to Gitea and declare what kind of jobs it can run by reporting its labels.
|
|
|
|
Earlier, we mentioned that `runs-on: ubuntu-latest` in a workflow file means that the job will be run on a runner with the `ubuntu-latest` label.
|
|
But how does the runner know to run `ubuntu-latest`? The answer lies in mapping the label to an environment.
|
|
That's why when you add custom labels during registration, you will need to input some complex content like `my_custom_label:docker://centos:7`.
|
|
This means that the runner can take the job which needs to run on `my_custom_label`, and it will run it via a docker container with the image `centos:7`.
|
|
|
|
Docker isn't the only option, though.
|
|
The act also supports running jobs directly on the host.
|
|
This is achieved through labels like `linux_arm:host`.
|
|
This label indicates that the runner can take a job that needs to run on `linux_arm` and run it directly on the host.
|
|
|
|
The label's design follows the format `label[:schema[:args]]`.
|
|
If the schema is omitted, it defaults to `host`.
|
|
So,
|
|
|
|
- `my_custom_label:docker://node:18`: Run jobs labeled with `my_custom_label` using the `node:18` Docker image.
|
|
- `my_custom_label:host`: Run jobs labeled with `my_custom_label` directly on the host.
|
|
- `my_custom_label`: Same as `my_custom_label:host`.
|
|
- `my_custom_label:vm:ubuntu-latest`: (Example only, not implemented) Run jobs labeled with `my_custom_label` using a virtual machine with the `ubuntu-latest` ISO.
|
|
|
|
## Communication protocol
|
|
|
|
As act runner is an independent part of Gitea, we needed a protocol for runners to communicate with the Gitea instance.
|
|
However, we did not think it was a good idea to have Gitea listen on a new port.
|
|
Instead, we wanted to reuse the HTTP port, which means we needed a protocol that is compatible with HTTP.
|
|
We chose to use gRPC over HTTP.
|
|
|
|
We use [actions-proto-def](https://gitea.com/gitea/actions-proto-def) and [actions-proto-go](https://gitea.com/gitea/actions-proto-go) to wire them up.
|
|
More information about gRPC can be found on [its website](https://grpc.io/).
|
|
|
|
## Network architecture
|
|
|
|
Let's examine the overall network architecture.
|
|
This will help you troubleshoot some problems and explain why it's a bad idea to register a runner with a loopback address of the Gitea instance.
|
|
|
|
|
|
|
|
There are four network connections marked in the picture, and the direction of the arrows indicates the direction of establishing the connections.
|
|
|
|
### Connection 1, act runner to Gitea instance
|
|
|
|
The act runner must be able to connect to Gitea to receive tasks and send back the execution results.
|
|
|
|
### Connection 2, job containers to Gitea instance
|
|
|
|
The job containers have different network namespaces than the runner, even if they are on the same machine.
|
|
They need to connect to Gitea to fetch codes if there is `actions/checkout@v4` in the workflow, for example.
|
|
Fetching code is not always necessary to run some jobs, but it is required in most cases.
|
|
|
|
If you use a loopback address to register a runner, the runner can connect to Gitea when it is on the same machine.
|
|
However, if a job container tries to fetch code from localhost, it will fail because Gitea is not in the same container.
|
|
|
|
### Connection 3, act runner to internet
|
|
|
|
When you use some actions like `actions/checkout@v4`, the act runner downloads the scripts, not the job containers.
|
|
By default, it downloads from [github.com](http://github.com/), so it requires access to the internet. If you configure the `DEFAULT_ACTIONS_URL` to `self`, then it will download from your Gitea instance by default. Then it will not connect to internet when downloading the action itself.
|
|
It also downloads some docker images from Docker Hub by default, which also requires internet access.
|
|
|
|
However, internet access is not strictly necessary.
|
|
You can configure your Gitea instance to fetch actions or images from your intranet facilities.
|
|
|
|
In fact, your Gitea instance can serve as both the actions marketplace and the image registry.
|
|
You can mirror actions repositories from GitHub to your Gitea instance, and use them as normal.
|
|
And [Gitea Container Registry](usage/packages/container.md) can be used as a Docker image registry.
|
|
|
|
### Connection 4, job containers to internet
|
|
|
|
When using actions such as `actions/setup-go@v5`, it may be necessary to download resources from the internet to set up the Go language environment in job containers.
|
|
Therefore, access to the internet is required for the successful completion of these actions.
|
|
|
|
However, it is optional as well.
|
|
You can use your own custom actions to avoid relying on internet access, or you can use your packaged Docker image to run jobs with all dependencies installed.
|
|
|
|
## Summary
|
|
|
|
Using Gitea Actions only requires ensuring that the runner can connect to the Gitea instance.
|
|
Internet access is optional, but not having it will require some additional work.
|
|
In other words: The runner works best when it can query the internet itself, but you don't need to expose it to the internet (in either direction).
|
|
|
|
If you encounter any network issues while using Gitea Actions, hopefully the image above can help you troubleshoot them.
|