From a2dfdfa699bf13ed6fa488e86a5445c720a20a23 Mon Sep 17 00:00:00 2001
From: Avi Deitcher <avi@deitcher.net>
Date: Tue, 24 Sep 2024 15:58:48 +0300
Subject: [PATCH] Switch to v4 of actions/cache; add documentation about it;
 explicitly check runner arch.

Does the following three things in one file:

1. Switch to v4 of actions/cache. That action has a nasty bug in that it depends on the absolute path to the directory being cached. That means that if you save on one runner type and restore on another, it will fail the restore. Not 100% clear that v4 fixes it.
2. Add documentation about why we use actions/cache in the way we do, rather than separate actions/cache/save.
3. For `eve` job, we would assume the runner is amd64, which will not hold forever. Instead, explicitly check it.

Signed-off-by: Avi Deitcher <avi@deitcher.net>
---
 .github/workflows/build.yml | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 96e03f86c3..39781877ce 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -63,8 +63,11 @@ jobs:
           # the following weird statement is here to speed up the happy path
           # if the default server is responding -- we can skip apt update
           $APT_INSTALL || { sudo apt update && $APT_INSTALL ; }
+      # The next step explicitly use actions/cache, rather than actions/cache/save at the end.
+      # If we rerun a job without changing the sha, we should not have to rebuild anything.
+      # Since the cache is keyed on the head sha, it will retrieve it.
       - name: update linuxkit cache if available
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: ~/.linuxkit/cache
           key: linuxkit-${{ matrix.arch }}-${{ github.event.pull_request.head.sha }}
@@ -120,6 +123,21 @@ jobs:
           username: ${{ secrets.RELEASE_DOCKERHUB_ACCOUNT }}
           password: ${{ secrets.RELEASE_DOCKERHUB_TOKEN }}
 
+      - name: Arch Runner is Matrix
+        id: arch_runner_equals_matrix
+        run: |
+          RUNNER_ARCH=${{ runner.arch }}
+          [ "$RUNNER_ARCH" = "X64" ] && RUNNER_ARCH="amd64"
+          [ "$RUNNER_ARCH" = "ARM64" ] && RUNNER_ARCH="arm64"
+          [ "$RUNNER_ARCH" = "X86" ] && RUNNER_ARCH="i386"
+          [ "$RUNNER_ARCH" = "ARM" ] && RUNNER_ARCH="arm"
+          MATCHED="false"
+          [ "$RUNNER_ARCH" = "${{ matrix.arch }}" ] && MATCHED="true"
+          # report for good measure
+          echo "runner_arch=${RUNNER_ARCH}"
+          echo "matrix_arch=${{ matrix.arch }}"
+          echo "matched=${MATCHED}"
+          echo "matched=${MATCHED}" >> "$GITHUB_OUTPUT"
       # the next three steps - cache_for_docker, load images, and cache_for_packages -
       # having nothing to do with the content of the final eve image. Instead, it is because we are running
       # on amd64, and we need some of the tools in order to compose the final eve image for the target arch.
@@ -128,7 +146,7 @@ jobs:
       # load them into docker, and then clear the cache so we can load the cache for the target arch.
       - name: update linuxkit cache for runner arch so we can get desired images
         id: cache_for_docker
-        uses: actions/cache/restore@v3
+        uses: actions/cache/restore@v4
         with:
           path: ~/.linuxkit/cache
           key: linuxkit-amd64-${{ github.event.pull_request.head.sha }}
@@ -137,14 +155,14 @@ jobs:
         run: |
           make cache-export-docker-load-all
       - name: clear linuxkit cache so we can load for target arch
-        if: ${{ matrix.arch != 'amd64' }}  # because our runner arch is amd64; if that changes, this will have to change
+        if: ${{ steps.arch_runner_equals_matrix.outputs.matched != 'true' }}
         run: |
           rm -rf ~/.linuxkit
       # With the "load into docker" complete, now we can restore the packages into the cache for the target arch (as opposed to the runner arch)
       - name: update linuxkit cache for our arch
         id: cache_for_packages
-        if: ${{ matrix.arch != 'amd64' }}  # because our runner arch is amd64; if that changes, this will have to change
-        uses: actions/cache/restore@v3
+        if: ${{ steps.arch_runner_equals_matrix.outputs.matched != 'true' }}
+        uses: actions/cache/restore@v4
         with:
           path: ~/.linuxkit/cache
           key: linuxkit-${{ matrix.arch }}-${{ github.event.pull_request.head.sha }}