Metadata caching in bucket (#2579)

* Added caching for Iter.

Signed-off-by: Peter Štibraný <[email protected]>

* Added cache for Exists call for meta-files.

Signed-off-by: Peter Štibraný <[email protected]>

* Added cache for reading block metadata files.

Signed-off-by: Peter Štibraný <[email protected]>

* Make caching bucket configurable with different caches for different type of objects.

Signed-off-by: Peter Štibraný <[email protected]>

* Fixed tests.

Signed-off-by: Peter Štibraný <[email protected]>

* Added caching for ObjectSize. Enabled caching of index.

Signed-off-by: Peter Štibraný <[email protected]>

* Lint feedback.

Signed-off-by: Peter Štibraný <[email protected]>

* Use single set of metrics for all operations.

Signed-off-by: Peter Štibraný <[email protected]>

* Constants.

Signed-off-by: Peter Štibraný <[email protected]>

* Use operation specific config. Generic configuration is only for user.

Signed-off-by: Peter Štibraný <[email protected]>

* Fix typo, make lint happy.

Signed-off-by: Peter Štibraný <[email protected]>

* Simplify constants.

Signed-off-by: Peter Štibraný <[email protected]>

* Simplify caching configuration.

Signed-off-by: Peter Štibraný <[email protected]>

* Refactor cache configuration.

Configuration is now passed to the cache when created.

Signed-off-by: Peter Štibraný <[email protected]>

* Review feedback.

Signed-off-by: Peter Štibraný <[email protected]>

* Fix operationRequests and operationHits for getRange.

Signed-off-by: Peter Štibraný <[email protected]>

* Make codec for Iter results configurable.

Signed-off-by: Peter Štibraný <[email protected]>

* Added header.

Signed-off-by: Peter Štibraný <[email protected]>

* Renamed "dir" config to "blocks-iter".

Signed-off-by: Peter Štibraný <[email protected]>

* Bump default values for meta exists/doesntExist ttls.

Signed-off-by: Peter Štibraný <[email protected]>

* Removed example how cache could be configured for index.

Signed-off-by: Peter Štibraný <[email protected]>

* Address review feedback.

Signed-off-by: Peter Štibraný <[email protected]>

* Get now implements streaming reader, and buffers object in memory.

Signed-off-by: Peter Štibraný <[email protected]>

* Added test for partial read.

Signed-off-by: Peter Štibraný <[email protected]>

* Removed unused function.

Signed-off-by: Peter Štibraný <[email protected]>

Author: pstibrany