Hash object names used as cache keys for CachingBucket

[56quarters]

What this PR does

When caching rule groups, the base64 encoded name of the rule group is used as part of the key for caching its contents. For long rule group names, this can exceed the max key length of Memcached. To solve this we use a cryptographic hash of the object name when the hashed version of the name is shorter than the full name. This is the same approach taken for postings in the store-gateway indexcache.

This has the added benefit of not invalidating most existing cache entries when rolling out this change. With the hash function picked, key generation is between 5 and 10 times slower than not hashing the key but still dramatically faster than a network operation.

Which issue(s) this PR fixes or relates to

Related #9386

Checklist

• Tests updated.
• Documentation added.
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX].
• about-versioning.md updated with experimental features.

[56quarters]

Benchmarks:

$ go test -bench=BenchmarkCachingKey ./pkg/storage/tsdb/bucketcache/...
goos: linux
goarch: amd64
pkg: github.com/grafana/mimir/pkg/storage/tsdb/bucketcache
cpu: Intel(R) Core(TM) i9-10885H CPU @ 2.40GHz
BenchmarkCachingKey/cacheKeyBuilder.iter()_recursive_keyLength=7,_bucketID=false-16             15757104                83.31 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_recursive_keyLength=44,_bucketID=false-16             2516331               564.7 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_recursive_keyLength=7,_bucketID=true-16              13092854               108.2 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_recursive_keyLength=44,_bucketID=true-16              2075427               502.0 ns/op
BenchmarkCachingKey/cacheKeyBuilder.exists()_keyLength=7,_bucketID=false-16                     25929783                55.09 ns/op
BenchmarkCachingKey/cacheKeyBuilder.exists()_keyLength=44,_bucketID=false-16                     2331666               463.0 ns/op
BenchmarkCachingKey/cacheKeyBuilder.exists()_keyLength=7,_bucketID=true-16                      15586548                73.86 ns/op
BenchmarkCachingKey/cacheKeyBuilder.exists()_keyLength=44,_bucketID=true-16                      2609112               534.3 ns/op
BenchmarkCachingKey/cacheKeyBuilder.content()_keyLength=7,_bucketID=false-16                    20508844                56.16 ns/op
BenchmarkCachingKey/cacheKeyBuilder.content()_keyLength=44,_bucketID=false-16                    2680401               438.8 ns/op
BenchmarkCachingKey/cacheKeyBuilder.content()_keyLength=7,_bucketID=true-16                     21625657                62.53 ns/op
BenchmarkCachingKey/cacheKeyBuilder.content()_keyLength=44,_bucketID=true-16                     2454789               506.2 ns/op
BenchmarkCachingKey/cacheKeyBuilder.attributes()_keyLength=7,_bucketID=false-16                 25148311                52.79 ns/op
BenchmarkCachingKey/cacheKeyBuilder.attributes()_keyLength=44,_bucketID=false-16                 2213874               462.7 ns/op
BenchmarkCachingKey/cacheKeyBuilder.attributes()_keyLength=7,_bucketID=true-16                  16169638                77.97 ns/op
BenchmarkCachingKey/cacheKeyBuilder.attributes()_keyLength=44,_bucketID=true-16                  2882824               542.0 ns/op
BenchmarkCachingKey/cacheKeyBuilder.objectSubrange()_keyLength=7,_bucketID=false-16             16226624                80.00 ns/op
BenchmarkCachingKey/cacheKeyBuilder.objectSubrange()_keyLength=44,_bucketID=false-16             2056718               528.5 ns/op
BenchmarkCachingKey/cacheKeyBuilder.objectSubrange()_keyLength=7,_bucketID=true-16              14310009                98.74 ns/op
BenchmarkCachingKey/cacheKeyBuilder.objectSubrange()_keyLength=44,_bucketID=true-16              2499112               539.1 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_keyLength=7,_bucketID=false-16                       18043245                69.51 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_keyLength=44,_bucketID=false-16                       2124430               475.1 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_keyLength=7,_bucketID=true-16                        16253055                89.75 ns/op
BenchmarkCachingKey/cacheKeyBuilder.iter()_keyLength=44,_bucketID=true-16                        2312062               605.2 ns/op
PASS
ok      github.com/grafana/mimir/pkg/storage/tsdb/bucketcache   39.470s

[dimitarvdimitrov]

nice one

[narqo]

🔥