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CNTRLPLANE-3329: Use fuse-overlayfs for build cache instead of full copy #8568

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Merged
celebdor merged 2 commits into from
May 21, 2026
Merged

CNTRLPLANE-3329: Use fuse-overlayfs for build cache instead of full copy #8568

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141640d
ci(workflows): use EFS cache directly instead of copying
celebdor May 21, 2026
56fbf18
ci(workflows): use fuse-overlayfs for build cache instead of full copy
celebdor May 21, 2026
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19 changes: 14 additions & 5 deletions .github/actions/warm-go-cache/action.yaml
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Original file line number Diff line number Diff line change
@@ -1,13 +1,22 @@
name: 'Warm Go build cache'
description: 'Set GOCACHE and optionally warm from EFS-backed PV'
description: 'Set GOCACHE via fuse-overlayfs over the EFS-backed PV or a writable fallback'
runs:
using: composite
steps:
- shell: bash
run: |
echo "GOCACHE=/tmp/go-build-cache" >> "$GITHUB_ENV"
if [ -d /cache/go-build ]; then
mkdir -p /tmp/go-build-cache && \
mkdir -p /tmp/go-build-cache
mounted=false
if [ -d /cache/go-build ] && command -v fuse-overlayfs >/dev/null 2>&1 && [ -e /dev/fuse ]; then
mkdir -p /tmp/go-cache-upper /tmp/go-cache-work
if fuse-overlayfs -o lowerdir=/cache/go-build,upperdir=/tmp/go-cache-upper,workdir=/tmp/go-cache-work /tmp/go-build-cache; then
mounted=true
else
echo "::warning::fuse-overlayfs mount failed, falling back to copy"
fi
Comment on lines +10 to +16

@coderabbitai coderabbitai Bot May 21, 2026

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⚠️ Potential issue | 🟡 Minor | ⚡ Quick win

🧩 Analysis chain

🌐 Web query:

What is the correct syntax for fuse-overlayfs mount command with lowerdir, upperdir, and workdir options?

💡 Result:

The correct syntax for the fuse-overlayfs mount command is [1][2]: fuse-overlayfs -o lowerdir=DIR1[:DIR2...],upperdir=UPPER,workdir=WORK MOUNTPOINT Options explanation: -o lowerdir=DIR1[:DIR2...]: A colon-separated list of directories to be merged as the read-only base layers [1][3][4]. -o upperdir=UPPER: The directory where all write changes to the filesystem will be stored [1][3][4]. -o workdir=WORK: An internal working directory required by the filesystem, which must reside on the same filesystem as the upperdir [1][3][4]. MOUNTPOINT: The target directory where the merged filesystem will be accessible [1][3]. Example: fuse-overlayfs -o lowerdir=lower1:lower2,upperdir=upper,workdir=work merged_dir [2] Note that workdir must be an empty directory on the same filesystem as the upperdir [1][3]. If you omit upperdir and workdir, the filesystem will be mounted in a read-only state [5].

Citations:

🏁 Script executed:

#!/bin/bash
set -euo pipefail
sed -n '1,120p' .github/actions/warm-go-cache/action.yaml

Repository: openshift/hypershift

Length of output: 1045

Confirm fuse-overlayfs mount syntax and tighten workdir requirements.

  • The command fuse-overlayfs -o lowerdir=/cache/go-build,upperdir=/tmp/go-cache-upper,workdir=/tmp/go-cache-work /tmp/go-build-cache matches fuse-overlayfs’ documented -o lowerdir=...,upperdir=...,workdir=... MOUNTPOINT syntax, and /tmp/go-build-cache is created before the mount call.
  • To maximize mount success, ensure /tmp/go-cache-work is an empty directory before mounting (the current mkdir -p doesn’t guarantee emptiness per fuse-overlayfs’ requirement).
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In @.github/actions/warm-go-cache/action.yaml around lines 10 - 16, Ensure the
fuse-overlayfs mount uses a truly empty workdir and that the mountpoint is
created before mounting: before invoking the fuse-overlayfs command referenced
in the script (the line with "fuse-overlayfs -o
lowerdir=/cache/go-build,upperdir=/tmp/go-cache-upper,workdir=/tmp/go-cache-work
/tmp/go-build-cache"), recreate/empty /tmp/go-cache-work (e.g., remove any
contents or rm -rf and then mkdir) so it is guaranteed empty per fuse-overlayfs
requirements, and explicitly mkdir -p /tmp/go-build-cache before the mount
attempt; keep the existing mount invocation and the mounted=true fallback logic
intact.

fi
if [ "$mounted" = "false" ] && [ -d /cache/go-build ]; then
timeout 120 cp -a /cache/go-build/. /tmp/go-build-cache/ || \
echo "::warning::Failed to copy EFS cache, proceeding without cache"
echo "::warning::Failed to copy EFS cache, proceeding without cache"
fi
Comment thread
coderabbitai[bot] marked this conversation as resolved.
echo "GOCACHE=/tmp/go-build-cache" >> "$GITHUB_ENV"
1 change: 1 addition & 0 deletions Dockerfile.github-actions-runner
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,7 @@ RUN apt-get update && \
curl \
ca-certificates \
python3-pip \
fuse-overlayfs \
&& rm -rf /var/lib/apt/lists/*

ARG TARGETARCH
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