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Send platform as a query parameter on container create - #607
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ls-todd-lunter merged 2 commits intoOct 24, 2026
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/containers/create takes `platform` as a query parameter. Docker::Container.create
forwarded only `name` to the query string and dumped everything else into the
request body, so a caller asking for a platform got it placed in the body, where
the daemon accepts and silently ignores it:
QUERY={"name" => "dapi-plat"}
requested linux/amd64 on an arm64 host -> got arm64
Nothing raised. The container simply came up on the wrong architecture, which is
the worst way for this to fail.
Pull the query keys out into CREATE_QUERY_KEYS and route both name and platform
through it. With the fix the daemon actually sees the parameter, and asking for a
platform the local image does not provide now reports that:
image with reference alpine:latest was found but does not provide
the specified platform (linux/arm64)
Not a breaking change: `platform` previously had no effect wherever it was
placed, so no caller can be relying on the old behaviour.
ls-todd-lunter
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Oct 27, 2026
* Declare base64 as a runtime dependency so the gem loads on Ruby 3.4+ (#605) * Replace multi_json with the json standard library and drop the multi_json dependency (#613) * Keep the build context inside the build directory: symlinks are archived as symlinks rather than followed, and .dockerignore patterns can no longer reach outside the directory (#611) * Send platform as a query parameter on Container.create (#607) * Honor stdout: false and stderr: false in Container#exec (#609) * Request an HTTP upgrade when attaching to stdin so the attach no longer hangs (#610) * Memoize Connection#rootless? when the daemon is not rootless (#608) * Add gemspec metadata (source_code_uri, bug_tracker_uri, rubygems_mfa_required) and build the gem file list without git (#615) * Fix and update README examples and streaming read_timeout docs (#606, #585, #592) * Fix CI, test through Ruby 4.0 and Docker 28 and 29, and remove Travis, Code Climate and unmaintained test image leftovers (#604, #605, #614, #616)
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/containers/createtakesplatformas a query parameter.Docker::Container.createforwarded onlynameto the query string and dumped everything else into the request body, so a caller asking for a platform got it placed in the body — where the daemon accepts and silently ignores it.The bug
Nothing raised. The container just came up on the wrong architecture. This is why kitchen-dokken bypasses the gem entirely and posts to
/containers/createby hand.The fix
Pull the query keys into
CREATE_QUERY_KEYSand route bothnameandplatformthrough it.Verification
The query parameter now reaches the daemon:
And the daemon acts on it. With only the amd64 variant of alpine present locally, asking for arm64 is now correctly rejected instead of silently starting an amd64 container:
Two specs cover it — one asserting
platformreaches the query string, one asserting it is absent from the body. Both were confirmed to fail before the change:62 examples across the container, exec, network, volume and top-level specs pass with the change.
Compatibility
Not a breaking change —
platformpreviously had no effect wherever it was placed, so nothing can be relying on the old behaviour.CI will be red until #605 lands; this branch is off master, where the workflow is currently broken for unrelated reasons.