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Fix DNS resolution performance regression during cloud-init local #6665

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Fix DNS resolution performance regression during cloud-init local #6665

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aa4be53
Fix DNS resolution performance regression during cloud-init local
drzee99 Jan 10, 2026
44c23e7
Merge branch 'canonical:main' into fix-dns-resolution-performance
drzee99 Jan 19, 2026
5ec0eae
Fixed linting issues
Jan 19, 2026
470ef62
Merge branch 'canonical:main' into fix-dns-resolution-performance
drzee99 Jan 27, 2026
f860f87
Revert "Fixed linting issues"
drzee99 Jan 27, 2026
7d9192c
Fixed linting issue with correct user id for commit
drzee99 Jan 27, 2026
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1 change: 0 additions & 1 deletion cloudinit/sources/DataSourceEc2.py
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Original file line number Diff line number Diff line change
Expand Up @@ -77,7 +77,6 @@ class DataSourceEc2(sources.DataSource):
metadata_urls = [
"http://169.254.169.254",
"http://[fd00:ec2::254]",
"http://instance-data.:8773",
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@holmanb holmanb Jan 12, 2026

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The ec2 datasource is used by various other clouds besides just ec2 - and unfortunately not all clouds are known, so this change poses a risk.

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@drzee99 drzee99 Jan 12, 2026 •
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That is confusing. There should be a separate Data Source implementation for each provider. Even if some are same/similar to allow for future changes a cloud provider may implement.

That being said.

It is possible to override the metadata_urls ref: https://cloudinit.readthedocs.io/en/latest/reference/datasources/ec2.html

IMHO the default should be the ones that are provided by the named Data Source (in this case EC2). If this breaks other cloud providers that use the same path, then they should create an config setting for the metadata_url as pr. documentation to add the relevant metadata_urls.

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@holmanb holmanb Jan 22, 2026

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To be sure that I understand: You are saying that breaking clouds is justified because the code is confusing and there is a workaround that involves manual modifications to the image, right?

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@drzee99 drzee99 Jan 26, 2026 •
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The DataSource is named DataSourceEC2.py - EC2 is explicitly referring to Amazon Web Services EC2 service (in fact "Amazon EC2" is a registered trademark). Thus it should IMHO adhere to what ever is standard for Amazon EC2 at the current point in time.

It is fair that other clouds have implemented similar things, but they should either have their own data sources OR there should be a generic data source (DataSourceGeneric,py). They should not rely on that Amazon EC2 keeps doing things the same way. What if EC2 changes fundamentally "tomorrow"?

This change in DataSourceEC2.py is not important and I'm happy to back it out.

The important change to resolve the issue is that the check for IP addresses is made earlier in is_resolveable() so we do not unnecessarily go into the "Detect DNS Redirection check" when we don't even have a proper network and just try to query the metadata service (the result from this query is used to setup the network).

]

# The minimum supported metadata_version from the ec2 metadata apis
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10 changes: 6 additions & 4 deletions cloudinit/util.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1295,6 +1295,12 @@ def is_resolvable(url) -> bool:
global _DNS_REDIRECT_IP
parsed_url = parse.urlparse(url)
name = parsed_url.hostname

# Early return for IP addresses - no DNS resolution needed
with suppress(ValueError):
if net.is_ip_address(parsed_url.netloc.strip("[]")):
return True

if _DNS_REDIRECT_IP is None:
badips = set()
badnames = (
Expand All @@ -1319,10 +1325,6 @@ def is_resolvable(url) -> bool:
LOG.debug("detected dns redirection: %s", badresults)

try:
# ip addresses need no resolution
with suppress(ValueError):
if net.is_ip_address(parsed_url.netloc.strip("[]")):
return True
result = socket.getaddrinfo(name, None)
# check first result's sockaddr field
addr = result[0][4][0]
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