🎉 yuuuuge performance improvements incoming :)

Fixes #477 This pull request refactors the whole cache system.

Changes

Before:

• every (cacheable) definition is cached as a separate entry
• each definition is get on demand
• each definition is set when not found
• all PSR-16 caches are supported
• APCu is recommended because given the number of get/set to the cache, all other caches are too slow

After:

• only APCu is supported: that allows a much more optimized code, less errors from users, and a more "plug and play" solution (just enable the cache, nothing to configure)
• all definitions are cached under a single cache entry
• all the definitions are get at once: huge gain
• each definition is set when not found (not optimisation here)

Things to look out for: cache stampede.

Performance comparison

Benchmark get-cache.php

Before:

• no cache used: 224ms
• APCu cache used: 181ms
• gain thanks to the cache: 19%
• profiling

After:

• no cache used: 225ms
• APCu cache used: 146ms
• gain thanks to the cache: 35%
• profiling

When you use the cache there is a 19% improvement (181 -> 146ms). Profiling

TODO

• POC
• optimize APCu calls to avoid many set in the same Container::get() call Not interesting
• test with 3rd party DI container benchmarks
• update the ContainerBuilder
• configurable cache key prefix
• the cache key should contain a hash of all sources? auto-refresh?
• decide what to do with ArrayCache
• update documentation
• changelog