GitHub Action to cache a directory via rsync

.envrc.example

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+use flake

.gitignore

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+/.envrc
+/node_modules/

README.md

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+# OpenMS CI Tools
+
 Scripts used in the OpenMS CI/CD system.
+
+## Actions
+
+To build the actions:
+
+```sh
+npm ci
+npm run build
+```
+
+### Cache via rsync
+
+Push/pull a directory via rsync.
+
+To use, put something like this in your workflow YAML:
+
+```yml
+- uses: OpenMS/ci-tools/actions/rsync-cache@XXXX
+  with:
+    name: vcpkg-cache
+    path: ${{ github.workspace }}/.vcpkg-cache
+    key: ${{ runner.os }}-${{ runner.arch }}-${{ matrix.compiler }}
+    ssh_key: ${{ secrets.ARCHIVE_RRSYNC_SSH }}
+    ssh_host: ${{ secrets.ARCHIVE_RRSYNC_HOST }}
+    ssh_port: ${{ secrets.ARCHIVE_RRSYNC_PORT }}
+    ssh_user: ${{ secrets.ARCHIVE_RRSYNC_USER }}
+```

actions/rsync-cache/action.yml

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+name: "Cache via rsync"
+description: "Cache a directory to a private server using rsync"
+inputs:
+  name:
+    description: "A name to use for the sub-directory on the remote server"
+    required: true
+  path:
+    description: "An absolute path to a directory that should be cached"
+    required: true
+  key:
+    description: "A cache key, which is essentially a sub-directory name on the remote server"
+    required: true
+  ssh_key:
+    description: "The contents of an SSH private key"
+    required: true
+  ssh_host:
+    description: "The host name of the remote server"
+    required: true
+  ssh_port:
+    description: "The port to use for SSH"
+    required: false
+  ssh_user:
+    description: "The remote SSH user"
+    required: true
+runs:
+  using: 'node24'
+  main: dist/restore.js
+  post: dist/commit.js
+  post-if: "success()"

actions/rsync-cache/src/commit.js

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+import Rsync from "./rsync.js";
+import * as core from "@actions/core";
+
+async function main() {
+  try {
+    const rsync = new Rsync();
+    await rsync.push();
+  } catch (error) {
+    core.setFailed(error.message);
+  }
+}
+
+main();

actions/rsync-cache/src/restore.js

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+import Rsync from "./rsync.js";
+import * as core from "@actions/core";
+
+async function main() {
+  try {
+    const rsync = new Rsync();
+    await rsync.pull();
+  } catch (error) {
+    core.setFailed(error.message);
+  }
+}
+
+main();

actions/rsync-cache/src/rsync.js

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+import fs from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+import * as core from "@actions/core";
+import * as github from "@actions/github";
+import * as exec from "@actions/exec";
+import * as io from "@actions/io";
+
+export default class Rsync {
+  constructor() {
+    // Cache settings:
+    this.name = core.getInput("name", {required: true});
+    this.path = core.getInput("path", {required: true});
+    this.key = core.getInput("key", {required: true});
+
+    // SSH settings:
+    this.ssh_key_dir = os.homedir() + "/.ssh"
+    this.ssh_key_file = this.ssh_key_dir + "/private.key";
+
+    this.ssh_key = core.getInput("ssh_key", {required: true});
+    this.ssh_host = core.getInput("ssh_host", {required: true});
+    this.ssh_port = core.getInput("ssh_port", {required: false});
+    this.ssh_user = core.getInput("ssh_user", {required: true});
+    this.ssh_dir = `${this.ssh_user}@${this.ssh_host}:${this.name}/${this.key}/`;
+
+    this._validate();
+    this._set_vars();
+  }
+
+  // Ensure all our settings look good.
+  _validate() {
+    if (!this.ssh_port) {
+      this.ssh_port = "22"
+    }
+
+    if (!path.isAbsolute(this.path)) {
+      throw new Error(`path to cache must be absolute: ${this.path}`)
+    }
+  }
+
+  // Prepare some variables.
+  _set_vars() {
+    // The SSH command line.
+    const ssh_command = [
+      "ssh",
+      "-i", this.ssh_key_file,
+      "-p", this.ssh_port,
+      "-o", "StrictHostKeyChecking=accept-new",
+    ].join(" ")
+
+    // The base rsync command:
+    this.command = "rsync"
+    this.args = [
+      "-e", ssh_command,
+      "--progress",
+      "--human-readable",
+      "--archive",
+      "--verbose",
+      "--compress",
+
+      // We need this so we can create sub-directories, one for each
+      // cache key (OS, architecture, compiler, etc.)
+      "--mkpath",
+    ];
+  }
+
+  // Run rsync with extra arguments and return its exit code.
+  async run(additional_arguments=[]) {
+    await io.mkdirP(this.path);
+    await io.mkdirP(this.ssh_key_dir);
+    await fs.writeFile(this.ssh_key_file, this.ssh_key, 'utf8');
+    await fs.chmod(this.ssh_key_file, 0o600);
+
+    // Run rsync.
+    const options = {ignoreReturnCode: true};
+    const exit_code = await exec.exec(this.command,
+      [...this.args, ...additional_arguments], options);
+
+    // Remove the key file.
+    await fs.unlink(this.ssh_key_file);
+
+    // Let callers decide what to do with the exit code.
+    return exit_code;
+  }
+
+  // Pull the cache from the remote server.
+  async pull() {
+    const rsync_args = [
+      this.ssh_dir, // FROM
+      this.path,    // TO
+    ];
+
+    const exit_code = await this.run(rsync_args);
+
+    if (exit_code != 0) {
+      core.notice(`Cache ${this.name}: error fetching remote cache`);
+    }
+  }
+
+  // Push the cache to the remote server.
+  async push() {
+    const rsync_args = [
+      "--delete-before",
+      this.path,    // FROM
+      this.ssh_dir, // TO
+    ];
+
+    const exit_code = await this.run(rsync_args);
+
+    if (exit_code != 0) {
+      core.notice(`Cache ${this.name}: error pushing to remote cache`);
+    }
+  }
+}

flake.nix

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+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+  };
+
+  outputs =
+    inputs:
+    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+      systems = [
+        "x86_64-linux"
+        "aarch64-darwin"
+        "x86_64-darwin"
+      ];
+
+      perSystem =
+        { pkgs, ... }:
+        {
+          devShells.default = pkgs.mkShell {
+            nativeBuildInputs = with pkgs; [
+              nodejs_24
+              shellcheck
+              shfmt
+            ];
+          };
+        };
+    };
+}