Fallback to local in-memory counter if Redis is unavailable

[VojtechVitek]

When Redis becomes unavailable:

Before

• ❌ The whole system stopped responding. It only responded with HTTP 428's very slowly (5s timeout):
• ❌ Also, during the boot time, the system used to panic with fatal error, causing the application to enter crash loop:

  panic: httprateredis: unable to dial redis host 127.0.0.1:6379
  
  goroutine 1 [running]:
  github.com/go-chi/httprate-redis.WithRedisLimitCounter(0x98?)
  	/Users/vojtechvitek/go-chi/httprate-redis/httprateredis.go:21 +0xa8
  exit status 2
  

After:

• ✅ The system is now resilient to Redis failures.
• ✅ The application can boot up no matter if Redis is available.
• ✅ Rate-limiting still works with the in-memory counter fallback.
• ❗ The rate limit is not distributed across all servers anymore. Each server instance counts its rate-limit independently, thus allowing the total of N * rate requests (where N is number of app replicas running at a time).

[c2h5oh]

One option to keep the limit roughly the same when redis is not available would be passing replica count to rate limiter so it would adjust limits to rate/N automatically

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt │
               │   sec/op   │
LocalCounter-4   1.031 ± 4%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   38.88Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.272M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │  master.txt  │
               │    sec/op    │
LocalCounter-4   852.7m ± 19%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.30Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.237M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   975.9m ± 6%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   37.07Mi ± 5%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.254M ± 1%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   879.3m ± 2%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.25Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.236M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   860.0m ± 3%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.25Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.236M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   1.019 ± 10%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   38.85Mi ± 9%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.272M ± 3%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt │
               │   sec/op   │
LocalCounter-4   1.088 ± 3%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   38.91Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.272M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt │
               │   sec/op   │
LocalCounter-4   1.017 ± 6%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   38.94Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.273M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   861.2m ± 3%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.29Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.237M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │ master.txt  │
               │   sec/op    │
LocalCounter-4   864.1m ± 1%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.29Mi ± 0%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.237M ± 0%

[github-actions]

Benchmark Results

goos: linux
goarch: amd64
pkg: github.com/go-chi/httprate-redis
cpu: AMD EPYC 7763 64-Core Processor                
               │  master.txt  │
               │    sec/op    │
LocalCounter-4   898.2m ± 12%

               │  master.txt  │
               │     B/op     │
LocalCounter-4   35.25Mi ± 1%

               │ master.txt  │
               │  allocs/op  │
LocalCounter-4   1.236M ± 0%