user-data: jinja template to render instance-data.json in cloud-config

Allow users to provide '## template: jinja' as the first line or their
#cloud-config or custom script user-data parts. When this header exists,
the cloud-config or script will be rendered as a jinja template.

All instance metadata keys and values present in
/run/cloud-init/instance-data.json will be available as jinja variables
for the template. This means any cloud-config module or script can
reference any standardized instance data in templates and scripts.

Additionally, any standardized instance-data.json keys scoped below a
'<v#>' key will be promoted as a top-level key for ease of reference in
templates. This means that '{{ local_hostname }}' is the same as using the
latest '{{ v#.local_hostname }}'.

Since instance-data is written to /run/cloud-init/instance-data.json, make
sure it is persisted across reboots when the cached datasource opject is
reloaded.

LP: #1791781

1 files changed, 15 insertions, 1 deletions

diff --git a/cloudinit/cmd/main.py b/cloudinit/cmd/main.py
index 4ea4fe7f..0eee583c 100644
--- a/cloudinit/cmd/main.py
+++ b/cloudinit/cmd/main.py
@@ -348,6 +348,7 @@ def main_init(name, args):
             LOG.debug("[%s] barreling on in force mode without datasource",
                       mode)
 
+    _maybe_persist_instance_data(init)
     # Stage 6
     iid = init.instancify()
     LOG.debug("[%s] %s will now be targeting instance id: %s. new=%s",
@@ -490,6 +491,7 @@ def main_modules(action_name, args):
         print_exc(msg)
         if not args.force:
             return [(msg)]
+    _maybe_persist_instance_data(init)
     # Stage 3
     mods = stages.Modules(init, extract_fns(args), reporter=args.reporter)
     # Stage 4
@@ -541,6 +543,7 @@ def main_single(name, args):
                    " likely bad things to come!"))
         if not args.force:
             return 1
+    _maybe_persist_instance_data(init)
     # Stage 3
     mods = stages.Modules(init, extract_fns(args), reporter=args.reporter)
     mod_args = args.module_args
@@ -688,6 +691,15 @@ def status_wrapper(name, args, data_d=None, link_d=None):
     return len(v1[mode]['errors'])
 
 
+def _maybe_persist_instance_data(init):
+    """Write instance-data.json file if absent and datasource is restored."""
+    if init.ds_restored:
+        instance_data_file = os.path.join(
+            init.paths.run_dir, sources.INSTANCE_JSON_FILE)
+        if not os.path.exists(instance_data_file):
+            init.datasource.persist_instance_data()
+
+
 def _maybe_set_hostname(init, stage, retry_stage):
     """Call set-hostname if metadata, vendordata or userdata provides it.
 
@@ -887,6 +899,8 @@ def main(sysv_args=None):
 if __name__ == '__main__':
     if 'TZ' not in os.environ:
         os.environ['TZ'] = ":/etc/localtime"
-    main(sys.argv)
+    return_value = main(sys.argv)
+    if return_value:
+        sys.exit(return_value)
 
 # vi: ts=4 expandtab