fix(azure): default endpoint_suffix to blob.core.windows.net

[pujitha24]

Motivation:
After commit da2ad99 switched Cortex's Azure bucket client to Thanos'
objstore, block-storage-dependent components (alertmanager, ruler,
store-gateway, compactor, etc.) hang on startup when endpoint_suffix
is left empty, failing with DNS errors and no clear message, e.g.:

Get "https://<account>./<container>?restype=container": dial tcp:
lookup <account>. on 192.168.5.3:53: no such host

Root cause: Cortex builds the Thanos azure.Config struct directly in
pkg/storage/bucket/azure/bucket_client.go and calls
NewBucketWithConfig, which bypasses Thanos' parseConfig/DefaultConfig
that would otherwise seed Endpoint with "blob.core.windows.net". Because
Cortex's own azure.endpoint-suffix flag defaulted to "", the resulting
FQDN was <account>., which is invalid.

Approach:
Default the azure.endpoint-suffix flag to "blob.core.windows.net",
matching Thanos' DefaultConfig. This restores the pre-da2ad99
out-of-the-box behavior for Azure public cloud while still allowing the
value to be overridden for sovereign/government clouds. The
connection-string / Azurite path is unaffected because Thanos never reads
Endpoint when a connection string is set.

Test config default and generated config docs are updated to match.

Validation:
go build ./...
go test -tags "netgo slicelabels" ./pkg/storage/bucket/...
make doc BUILD_IN_CONTAINER=false # regenerated config docs
All passed.

Fixes #5449

Signed-off-by: Pujitha Paladugu 10557236+pujitha24@users.noreply.github.com

[Copilot]

Pull request overview

This PR fixes a regression in Cortex’s Azure object storage configuration by defaulting endpoint_suffix to the Azure public cloud value (blob.core.windows.net). This prevents Cortex from constructing an invalid FQDN (<account>.) when Cortex directly instantiates Thanos’ azure.Config and bypasses Thanos’ internal defaulting logic.

Changes:

• Default azure.endpoint-suffix flag to blob.core.windows.net.
• Update the Azure config default test to match the new flag default.
• Update generated configuration docs and add a changelog entry documenting the behavior change.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
pkg/storage/bucket/azure/config.go	Changes the CLI flag default for Azure endpoint-suffix to a valid public cloud suffix.
pkg/storage/bucket/azure/config_test.go	Updates the default-config assertion to include the new Endpoint default.
docs/configuration/config-file-reference.md	Updates the documented default for endpoint_suffix across relevant Azure config blocks.
docs/blocks-storage/store-gateway.md	Updates the documented default for endpoint_suffix in store-gateway config docs.
docs/blocks-storage/querier.md	Updates the documented default for endpoint_suffix in querier config docs.
CHANGELOG.md	Documents the Azure defaulting bugfix and its impact.

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[friedrichg]

Thanks!

[friedrichg]

@pujitha24 modified cortex-config-schema.json should be included in the PR

[pujitha24]

@friedrichg good catch — I'd missed regenerating the schema. I ran go run -tags slicelabels ./tools/doc-generator -json-schema and committed the updated schemas/cortex-config-schema.json, which now adds "default": "blob.core.windows.net" to the endpoint_suffix field in all four Azure sections. This matches the generator output exactly and should clear the failing "Check Generated Documentation" lint step.

On the Copilot note about the connection-string help-text wording: that phrasing predates this PR and isn't related to the defaulting bugfix, so I've left it out of scope here rather than expanding this change.