openstack: avoid unneeded metadata probe on non-openstack platforms

OpenStack datasource is now discovered in init-local stage. In order to
probe whether OpenStack metadata is present, it performs a costly
sandboxed dhclient setup and metadata probe against http://169.254.169.254
for openstack data.

Cloud-init properly detects non-OpenStack on EC2, but it spends precious
time probing the metadata service also resulting in a confusing WARNING
log about 'metadata not present'. To avoid the wasted cycles, and
confusing warning, get_data will call a detect_openstack function to
quickly determine whether the platform looks like OpenStack before trying
to setup network to probe and crawl the metadata service.

LP: #1776701

1 files changed, 15 insertions, 0 deletions

diff --git a/doc/rtd/topics/datasources/openstack.rst b/doc/rtd/topics/datasources/openstack.rst
index 0ea89943..421da08f 100644
--- a/doc/rtd/topics/datasources/openstack.rst
+++ b/doc/rtd/topics/datasources/openstack.rst
@@ -7,6 +7,21 @@ This datasource supports reading data from the
 `OpenStack Metadata Service
 <https://docs.openstack.org/nova/latest/admin/networking-nova.html#metadata-service>`_.
 
+Discovery
+-------------
+To determine whether a platform looks like it may be OpenStack, cloud-init
+checks the following environment attributes as a potential OpenStack platform:
+
+ * Maybe OpenStack if
+
+   * **non-x86 cpu architecture**: because DMI data is buggy on some arches
+ * Is OpenStack **if x86 architecture and ANY** of the following
+
+   * **/proc/1/environ**: Nova-lxd contains *product_name=OpenStack Nova*
+   * **DMI product_name**: Either *Openstack Nova* or *OpenStack Compute*
+   * **DMI chassis_asset_tag** is *OpenTelekomCloud*
+
+
 Configuration
 -------------
 The following configuration can be set for the datasource in system