"socket.getaddrinfo" of "metadata.google.internal" fails on GCE

This bug was originally filed in Launchpad as [LP: #1837106](https://bugs.launchpad.net/cloud-init/+bug/1837106)

Launchpad details

affected_projects = []

assignee = None

assignee_name = None

date_closed = None

date_created = 2019-07-18T19:40:41.411272+00:00

date_fix_committed = None

date_fix_released = None

id = 1837106

importance = medium

is_complete = False

lp_url = https://bugs.launchpad.net/cloud-init/+bug/1837106

milestone = None

owner = pkashsurya

owner_name = Prakash Surya

private = False

status = triaged

submitter = pkashsurya

submitter_name = Prakash Surya

tags = []

duplicates = []

_Launchpad user **Prakash Surya(pkashsurya)** wrote on 2019-07-18T19:40:41.411272+00:00_

When booting an Ubuntu 18.04 based image on GCE, we see the following messages in the log:

2019-05-30 00:05:27,818 - util.py[DEBUG]: Resolving URL: http://metadata.google.internal/computeMetadata/v1/ took 0.001 seconds
2019-05-30 00:05:27,818 - DataSourceGCE.py[DEBUG]: http://metadata.google.internal/computeMetadata/v1/ is not resolvable
2019-05-30 00:05:27,818 - util.py[DEBUG]: Crawl of GCE metadata service took 0.013 seconds
2019-05-30 00:05:27,818 - DataSourceGCE.py[WARNING]: address "http://metadata.google.internal/computeMetadata/v1/" is not resolvable

Further, the contents of "/run/cloud-init/instance-data.json" doesn't have any meaningful data.

What I've found is that, read_md() in DataSourceGCE.py will call util.is_resolvable_url() on the address "http://metadata.google.internal/computeMetadata/v1/", which results is calling socket.getaddrinfo() for "metadata.google.internal", and it's this socket.getaddrinfo() call that fails.

This failure appears to be due to the fact that "cloud-init.service" does not ensure it waits for DNS (i.e. "systemd-resolved.service") to be working before it runs. I say this because:

1. If I add "After=systemd-resolved.service" to the "cloud-init.service" definition, this failures goes away.

2. If I run "cloud-init init" after the system has booted up (i.e. after enough time has passed, such that DNS is working), the failure doesn't occur.