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fix(client): Concatenate string instead of using fmt.Sprintf #132145

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fix(client): Concatenate string instead of using fmt.Sprintf #132145

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@inkel inkel commented Jun 6, 2025

What type of PR is this?

/kind feature

What this PR does / why we need it:

In the bearerAuthRoundTripper used in the client, every call to RoundTrip will add the Authorization: Bearer %s header to each request. The value of this header was built using fmt.Sprintf, doing virtually the same as concatenating strings; using fmt.Sprintf for this simple operation incurs in minor overhead from having to call a function, and performs an additional allocation.

I've made a small benchmark for this and when run against current master and this branch, the results are significant for this function:

goos: darwin
goarch: arm64
pkg: k8s.io/client-go/transport
cpu: Apple M1 Pro
                          │ bart.base.log │           bart.concat.log            │
                          │    sec/op     │    sec/op     vs base                │
BearerAuthRoundTripper-10    361.3n ± 31%   295.5n ± 11%  -18.21% (p=0.000 n=20)

                          │ bart.base.log │          bart.concat.log          │
                          │     B/op      │    B/op     vs base               │
BearerAuthRoundTripper-10      768.0 ± 0%   752.0 ± 0%  -2.08% (p=0.000 n=20)

                          │ bart.base.log │          bart.concat.log           │
                          │   allocs/op   │ allocs/op   vs base                │
BearerAuthRoundTripper-10      6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=20)

Considering this method is likely used in many installations, the gains, while small, adds up to bigger savings.

Which issue(s) this PR fixes:

Special notes for your reviewer:

Note that I mention a benchmark, this wasn't include in my changes because I couldn't find a similar one in the codebase, but I can add it in this PR. The benchmark is very simple:

func BenchmarkBearerAuthRoundTripper(b *testing.B) {
	rt := &testRoundTripper{}
	req := &http.Request{}
	bart := NewBearerAuthRoundTripper("test", rt)
	b.ReportAllocs()
	for b.Loop() {
		bart.RoundTrip(req)
	}
}

Does this PR introduce a user-facing change?

NONE

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

@inkel
Concatenate string instead of using fmt.Sprintf
92a0e42 
The call to `fmt.Sprintf` does virtually the same as concatenating the
strings, but incurs in minor overhead from having to call a function,
and performs an additional allocation.

I've made a small benchmark for this and when run against current
`master` and this branch, the results are significant for this
function:

    goos: darwin
    goarch: arm64
    pkg: k8s.io/client-go/transport
    cpu: Apple M1 Pro
                              │ bart.base.log │           bart.concat.log            │
                              │    sec/op     │    sec/op     vs base                │
    BearerAuthRoundTripper-10    361.3n ± 31%   295.5n ± 11%  -18.21% (p=0.000 n=20)

                              │ bart.base.log │          bart.concat.log          │
                              │     B/op      │    B/op     vs base               │
    BearerAuthRoundTripper-10      768.0 ± 0%   752.0 ± 0%  -2.08% (p=0.000 n=20)

                              │ bart.base.log │          bart.concat.log           │
                              │   allocs/op   │ allocs/op   vs base                │
    BearerAuthRoundTripper-10      6.000 ± 0%   5.000 ± 0%  -16.67% (p=0.000 n=20)

Considering this method is likely used in many installations, the
gains, while small, adds up to bigger savings
@k8s-ci-robot k8s-ci-robot added do-not-merge/needs-kind Indicates a PR lacks a `kind/foo` label and requires one. release-note-none Denotes a PR that doesn't merit a release note. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. kind/feature Categorizes issue or PR as related to a new feature. size/XS Denotes a PR that changes 0-9 lines, ignoring generated files. do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. needs-priority Indicates a PR lacks a `priority/foo` label and requires one. and removed do-not-merge/needs-kind Indicates a PR lacks a `kind/foo` label and requires one. labels Jun 6, 2025
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@k8s-ci-robot k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Jun 6, 2025
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Hi @inkel. Thanks for your PR.

I'm waiting for a kubernetes member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: inkel
Once this PR has been reviewed and has the lgtm label, please assign aojea for approval. For more information see the Code Review Process.

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@k8s-ci-robot k8s-ci-robot added sig/api-machinery Categorizes an issue or PR as relevant to SIG API Machinery. and removed do-not-merge/needs-sig Indicates an issue or PR lacks a `sig/foo` label and requires one. labels Jun 6, 2025
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ffromani commented Jun 6, 2025

/ok-to-test

@k8s-ci-robot k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Jun 6, 2025
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cici37 commented Jun 10, 2025

/triage accepted

@k8s-ci-robot k8s-ci-robot added triage/accepted Indicates an issue or PR is ready to be actively worked on. and removed needs-triage Indicates an issue or PR lacks a `triage/foo` label and requires one. labels Jun 10, 2025
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