Merge "Lock around extract-image downloads and extracts"

elements/redhat-common/bin/extract-image

@@ -14,11 +14,12 @@ CACHED_IMAGE=$4
 
 CACHED_TAR=$DIB_IMAGE_CACHE/$BASE_IMAGE_TAR
 DIB_LOCAL_IMAGE=${DIB_LOCAL_IMAGE:-""}
+TAR_LOCK=$CACHED_TAR.lock
 
+function extract_image() {
     if [ -n "$DIB_OFFLINE" -a -f "$CACHED_TAR" ] ; then
         echo "Not checking freshness of cached $CACHED_TAR."
     else
-
         if [ -z "$DIB_LOCAL_IMAGE" ]; then
             echo "Fetching Base Image"
 
@@ -89,9 +90,20 @@ else
         else
             echo "Using cached tar from $CACHED_TAR"
         fi
-
     fi
+
     # Extract the base image (use --numeric-owner to avoid UID/GID mismatch between
     # image tarball and host OS e.g. when building Fedora image on an openSUSE host)
     echo "Extracting base root image from $CACHED_TAR"
     sudo tar -C $TARGET_ROOT --numeric-owner -xzf $CACHED_TAR
+}
+
+(
+    echo "Getting $TAR_LOCK: $(date)"
+    # Wait up to 20 minutes for another process to download
+    if ! flock -w 1200 9 ; then
+        echo "Did not get $TAR_LOCK: $(date)"
+        exit 1
+    fi
+    extract_image
+) 9> $TAR_LOCK