From 5c8d62848fce778bbaf5f3990dbd242462a0e607 Mon Sep 17 00:00:00 2001
From: Satwik Sai Prakash Sahoo <sahoospsatwik@gmail.com>
Date: Fri, 31 Jul 2026 06:14:22 +0530
Subject: [PATCH] ci: cache loaded image ID to prevent redundant SDK downloads

The remote .id file on bincache is generated from `docker image inspect`
during CI at build time but `docker save` followed by `docker load` on
a different Docker daemon produce a different image ID for the same
image content. This causes `docker_image_from_buildcache()` to consider
locally loaded image as "outdated" every invocation, triggering
redundant multi-GB tarball download each time `run_sdk_container -t`
is run.

Caching the actual image ID produced by `docker load` into a local
`.local-id` file. On subsequent runs, compare against the cached ID
first before falling back to the remote .id file.

Fixes flatcar/Flatcar#2086

Signed-off-by: Satwik Sai Prakash Sahoo <sahoospsatwik@gmail.com>
---
 ci-automation/ci_automation_common.sh | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/ci-automation/ci_automation_common.sh b/ci-automation/ci_automation_common.sh
index 1ded3d1e36f..d7e22c12b04 100644
--- a/ci-automation/ci_automation_common.sh
+++ b/ci-automation/ci_automation_common.sh
@@ -235,6 +235,17 @@ function docker_image_from_buildcache() {
     if [[ -n "${local_image}" ]] ; then
         local image_id=""
         image_id=$($docker image inspect "${local_image}" | jq -r '.[].Id' | sed 's/^sha256://')
+
+        local local_id_file="${name}-${version}.local-id"
+        if [[ -f "${local_id_file}" ]] ; then
+            local cached_id=""
+            cached_id=$(cat "${local_id_file}")
+            if [[ "${image_id}" = "${cached_id}" ]] ; then
+                echo "Local image is up-to-date (cached ID match)" >&2
+                return
+            fi
+        fi
+
         local remote_id=""
         remote_id=$(curl --fail --silent --show-error --location --retry-delay 1 \
                     --retry 60 --retry-connrefused --retry-max-time 60 --connect-timeout 20 \
@@ -270,6 +281,17 @@ function docker_image_from_buildcache() {
     zstd -d -c ${tgz} | $docker load
 
     rm "${tgz}"
+
+    local loaded_image=""
+    if image_exists_locally "${name}" "${version}" ; then
+        loaded_image="${name}:${version}"
+    elif image_exists_locally "${CONTAINER_REGISTRY}/${name}" "${version}" ; then
+        loaded_image="${CONTAINER_REGISTRY}/${name}:${version}"
+    fi
+    if [[ -n "${loaded_image}" ]] ; then
+        local local_id_file="${name}-${version}.local-id"
+        $docker image inspect "${loaded_image}" | jq -r '.[].Id' | sed 's/^sha256://' > "${local_id_file}"
+    fi
 }
 # --