lxc-oci: support skopeo layer caching

templates/lxc-oci.in

@@ -34,6 +34,7 @@ for bin in skopeo umoci jq; do
     fi
 done
 
+LOCALSTATEDIR="@LOCALSTATEDIR@"
 LXC_TEMPLATE_CONFIG="@LXCTEMPLATECONFIG@"
 
 # Some useful functions
@@ -145,7 +146,7 @@ EOF
     return 0
 }
 
-options=$(getopt -o u:h -l help,url:,username:,password:,\
+options=$(getopt -o u:h -l help,url:,username:,password:,no-cache,\
 name:,path:,rootfs:,mapped-uid:,mapped-gid: -- "$@")
 
 if [ $? -ne 0 ]; then
@@ -157,6 +158,7 @@ eval set -- "$options"
 OCI_URL=""
 OCI_USERNAME=
 OCI_PASSWORD=
+OCI_USE_CACHE="true"
 
 LXC_MAPPED_GID=
 LXC_MAPPED_UID=
@@ -170,6 +172,7 @@ while :; do
         -u|--url)           OCI_URL=$2; shift 2;;
         --username)         OCI_USERNAME=$2; shift 2;;
         --password)         OCI_PASSWORD=$2; shift 2;;
+        --no-cache)         OCI_USE_CACHE="false"; shift 1;;
         --name)             LXC_NAME=$2; shift 2;;
         --path)             LXC_PATH=$2; shift 2;;
         --rootfs)           LXC_ROOTFS=$2; shift 2;;
@@ -195,33 +198,43 @@ if [ -n "$OCI_PASSWORD" ] && [ -z "$OCI_USERNAME" ]; then
     exit 1
 fi
 
+if [ "${OCI_USE_CACHE}" = "true" ]; then
+    if ! skopeo copy --help | grep -q 'dest-shared-blob-dir'; then
+        echo "INFO: skopeo doesn't support blob caching"
+        OCI_USE_CACHE="false"
+    fi
+fi
+
 USERNS=$(in_userns)
 
-if [ "$USERNS" != "no" ]; then
+if [ "$USERNS" = "yes" ]; then
+    if [ -z "$LXC_MAPPED_UID" ] || [ "$LXC_MAPPED_UID" = "-1" ]; then
+        echo "ERROR: In a user namespace without a map." 1>&2
+        exit 1
+    fi
+fi
+
+if [ "${OCI_USE_CACHE}" = "true" ]; then
     if [ "$USERNS" = "yes" ]; then
-        if [ -z "$LXC_MAPPED_UID" ] || [ "$LXC_MAPPED_UID" = "-1" ]; then
-            echo "ERROR: In a user namespace without a map." 1>&2
-            exit 1
-        fi
-        DOWNLOAD_MODE="user"
-        DOWNLOAD_TARGET="user"
+        DOWNLOAD_BASE="${HOME}/.cache/lxc"
     else
-        DOWNLOAD_MODE="user"
-        DOWNLOAD_TARGET="system"
+        DOWNLOAD_BASE="${LOCALSTATEDIR}/cache/lxc"
     fi
+else
+    DOWNLOAD_BASE=/tmp
 fi
 
 # Trap all exit signals
 trap cleanup EXIT HUP INT TERM
 
 if ! type mktemp >/dev/null 2>&1; then
-    DOWNLOAD_TEMP=/tmp/lxc-oci.$$
+    DOWNLOAD_TEMP="${DOWNLOAD_BASE}/lxc-oci.$$"
     mkdir -p $DOWNLOAD_TEMP
 else
-    DOWNLOAD_TEMP=$(mktemp -d)
+    DOWNLOAD_TEMP=$(mktemp -d -p "${DOWNLOAD_BASE}")
 fi
 
-# Download the image - TODO - cache
+# Download the image
 skopeo_args=("")
 if [ -n "$OCI_USERNAME" ]; then
     CREDENTIALS="${OCI_USERNAME}"
@@ -230,7 +243,13 @@ if [ -n "$OCI_USERNAME" ]; then
     fi
     skopeo_args+=(--src-creds "${CREDENTIALS}")
 fi
-skopeo copy ${skopeo_args[@]} "${OCI_URL}" "oci:${DOWNLOAD_TEMP}:latest"
+if [ "${OCI_USE_CACHE}" = "true" ]; then
+    skopeo_args+=(--dest-shared-blob-dir "${DOWNLOAD_BASE}")
+    skopeo copy ${skopeo_args[@]} "${OCI_URL}" "oci:${DOWNLOAD_TEMP}:latest"
+    ln -s "${DOWNLOAD_BASE}/sha256" "${DOWNLOAD_TEMP}/blobs/sha256"
+else
+    skopeo copy ${skopeo_args[@]} "${OCI_URL}" "oci:${DOWNLOAD_TEMP}:latest"
+fi
 
 echo "Unpacking the rootfs"
 umoci_args=("")