chore: Replace sync.Mutex with sync.Map

[piyushroshan]

Sync.Map provides a key level locking to allow concurrent key writes.

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Benchmarks based on mutex vs sync.Map
sync.Mutex

goos: darwin
goarch: arm64
pkg: github.com/corazawaf/coraza/v3/internal/corazawaf
cpu: Apple M1 Pro
BenchmarkAddTransformationUnique-10        38994            282718 ns/op          766436 B/op          5 allocs/op
BenchmarkAddTransformationSame-10         777428              9162 ns/op             242 B/op          5 allocs/op
PASS
ok      github.com/corazawaf/coraza/v3/internal/corazawaf       19.642s

sync.Map

goos: darwin
goarch: arm64
pkg: github.com/corazawaf/coraza/v3/internal/corazawaf
cpu: Apple M1 Pro
BenchmarkAddTransformationUnique-10        32040            220037 ns/op          627028 B/op          9 allocs/op
BenchmarkAddTransformationSame-10         846592              6618 ns/op             366 B/op          9 allocs/op
PASS
ok      github.com/corazawaf/coraza/v3/internal/corazawaf       13.973s

[jcchavezs]

I think this might perform slightly better but I wonder if we could write a benchmark

[jptosso]

IMO it's a hard case to benchmark bc it requires a lot of concurrency and we cannot use gh actions for it
A sync mutex blocks read and write, and sync map just blocks at key level

[fzipi]

maybe something like https://medium.com/@nikolay.dimitrov/comparing-go-performance-of-mutex-sync-map-and-channels-for-syncing-a-map-of-counters-61810c201e17 ?

[fzipi]

Another option is to use sync.RWMutex and use RLock for the ones which are read-only.

[jcchavezs]

To be honest without evidence this being anyhow better I would not proceed with the change. sync.RWMutext an easier change to land.

[piyushroshan]

To be honest without evidence this being anyhow better I would not proceed with the change. sync.RWMutext an easier change to land.

Added the benchmark

[fzipi]

So the benchmark shows this is indeed faster for the tests. The question remains about what happens with real concurrency, but I think it will only behave better because there is no full blocking. @jcchavezs Do you want to make benchmakrs with sync.RWMutex and push them here also to compare? 🙏

[fzipi]

ping @jcchavezs

[jcchavezs]

I will do that tomorrow.

[jptosso]

LGTM

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.63%. Comparing base (a5cc4f0) to head (a79c5ae).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1197      +/-   ##
==========================================
- Coverage   81.64%   81.63%   -0.01%     
==========================================
  Files         168      168              
  Lines        9637     9634       -3     
==========================================
- Hits         7868     7865       -3     
  Misses       1519     1519              
  Partials      250      250              

Flag	Coverage Δ
coraza.rule.case_sensitive_args_keys	81.59% <100.00%> (-0.01%)	⬇️
coraza.rule.multiphase_valuation	81.63% <100.00%> (-0.01%)	⬇️
default	81.63% <100.00%> (-0.01%)	⬇️
examples+	16.44% <0.00%> (+<0.01%)	⬆️
examples+coraza.rule.case_sensitive_args_keys	81.59% <100.00%> (-0.01%)	⬇️
examples+coraza.rule.multiphase_valuation	81.52% <100.00%> (-0.01%)	⬇️
examples+memoize_builders	81.64% <100.00%> (-0.01%)	⬇️
examples+no_fs_access	80.96% <100.00%> (-0.01%)	⬇️
ftw	81.63% <100.00%> (-0.01%)	⬇️
memoize_builders	81.73% <100.00%> (-0.01%)	⬇️
no_fs_access	81.07% <100.00%> (-0.01%)	⬇️
tinygo	81.60% <100.00%> (-0.01%)	⬇️

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