Only allocate named logger if necessary in activator

[markusthoemmes]

Proposed Changes

Allocating a named logger is somewhat expensive (~ 10 allocs) so it's worth avoiding it, especially in high-speed components like the activator.

This defers allocation of the respective named logger to error cases.

Context handler benchmark

benchmark                                                         old ns/op     new ns/op     delta
BenchmarkContextHandler/context_handler_success-sequential-16     3258          924           -71.64%
BenchmarkContextHandler/context_handler_success-parallel-16       569           175           -69.24%
BenchmarkContextHandler/context_handler_failure-sequential-16     14659         14838         +1.22%
BenchmarkContextHandler/context_handler_failure-parallel-16       10980         11384         +3.68%

benchmark                                                         old allocs     new allocs     delta
BenchmarkContextHandler/context_handler_success-sequential-16     19             7              -63.16%
BenchmarkContextHandler/context_handler_success-parallel-16       19             7              -63.16%
BenchmarkContextHandler/context_handler_failure-sequential-16     45             38             -15.56%
BenchmarkContextHandler/context_handler_failure-parallel-16       45             38             -15.56%

benchmark                                                         old bytes     new bytes     delta
BenchmarkContextHandler/context_handler_success-sequential-16     2091          592           -71.69%
BenchmarkContextHandler/context_handler_success-parallel-16       2090          592           -71.67%
BenchmarkContextHandler/context_handler_failure-sequential-16     5086          4119          -19.01%
BenchmarkContextHandler/context_handler_failure-parallel-16       4882          3715          -23.90%

Release Note

NONE

/assign @julz @vagababov

[codecov]

Codecov Report

Merging #11008 (d2c1ec2) into main (05f16c6) will decrease coverage by 0.04%.
The diff coverage is 88.88%.

@@            Coverage Diff             @@
##             main   #11008      +/-   ##
==========================================
- Coverage   87.99%   87.95%   -0.05%     
==========================================
  Files         188      188              
  Lines        9113     9113              
==========================================
- Hits         8019     8015       -4     
- Misses        839      842       +3     
- Partials      255      256       +1     

Impacted Files	Coverage Δ
cmd/activator/main.go	0.00% <0.00%> (ø)
pkg/activator/handler/context_handler.go	96.00% <100.00%> (-0.30%)	⬇️
pkg/activator/handler/handler.go	95.12% <100.00%> (+0.25%)	⬆️
pkg/reconciler/revision/reconcile_resources.go	80.95% <0.00%> (-2.39%)	⬇️
pkg/activator/net/revision_backends.go	90.41% <0.00%> (-0.92%)	⬇️

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[julz]

/lgtm

[knative-prow-robot]

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