fix(nodes): omit tailLines for file log queries - #1279
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Kubelet resolves file paths under /var/log and rejects log options for file queries. Keep tailing for services while allowing file queries to succeed, and publish corrected tool examples. Fixes: containers#1262 Constraint: Kubelet only accepts tailLines for service-style queries. Rejected: Forward tailLines for every query | kubelet returns 406 for files Confidence: high Scope-risk: narrow Directive: Keep file-query detection aligned with kubelet path semantics. Tested: go test -p 1 -count=1 ./...; make lint; make build Not-tested: Full race suite could not link all packages within local disk. Signed-off-by: ychampion <ychampion@users.noreply.github.com>
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@2uasimojo mind reviewing this one? |
2uasimojo
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Jul 30, 2026
2uasimojo
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2uasimojo
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This looks right to me based on the issue. Couple questions inline.
| // Query parameters for tail | ||
| if tailLines > 0 { | ||
| // The kubelet only supports tailLines for service log queries. | ||
| if tailLines > 0 && !strings.ContainsAny(query, `/\`) { |
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Do you think we should at least warn when ignoring an input parameter? (I'm actually curious why we don't just error.)
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| if req.URL.Query().Get("tailLines") != "2" { | ||
| w.WriteHeader(http.StatusNotAcceptable) | ||
| return | ||
| } | ||
| logContent = "Line 4\nLine 5\n" |
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I'm not fully understanding how this test is structured, but this seems tightly coupled to the test case by requiring an exact tailLines value. Would it be too painful to do something like (pseudo):
logLines = "Line 1\nLine 2\nLine 3\nLine 4\nLine 5\n".Split("\n")
switch tailLines, err := atoi(req.URL.Query().Get("tailLines")) {
case (err != nil, tailLines <= 0): // Is zero acceptable?
w.WriteHeader(http.StatusNotAcceptable) // invalid numeric input
return
case tailLines > len(logLines):
tailLines = len(logLines)
fallthrough
default:
logContent = logLines[len(logLines)-tailLines:].Join("\n") // Possible off-by-one; I didn't try too hard :)
}
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Summary
tailLinesfor file-based node log queries/var/logand cover service/file behaviorWhy
The kubelet rejects options on file queries, so
nodes_logreturned 406 whenever a file path was used withtailLines. The existing examples also double-prefixed/var/log.Fixes #1262.
Validation
go test -p 1 ./pkg/mcp -run 'TestNodes/TestNodesLog' -count=1go test -p 1 -count=1 ./...make lintmake build