Summary:
This enables an in-process memcache client for the Rust
ContentStore/MetadataStore. For now, this implementation is lacking several
necessary optimization:
- Start-up time is always slowed down by ~0.7s, the initialization will be
moved to a background thread
- Writing data to memcache is blocking and will be moved to a background
thread too.
- Prefetching data does a roundtrip to memcache for every key, batching
memcache APIs will be added.
Compared to the existing hg_memcache_client, this implementation is both
significantly shorter and do not exhibit some of the pathological behavior of
having to flush the indexedlog for every fetched blob when used in Eden.
Reviewed By: DurhamG
Differential Revision: D19518696
fbshipit-source-id: 4725447d13e7eddd9586135c2511e13ddb921771
Any native code (C/C++/Rust) that Mercurial (either core or extensions)
depends on should go here. Python code, or native code that depends on
Python code (e.g. #include <Python.h> or use cpython) is disallowed.
As we start to convert more of Mercurial into Rust, and write new paths
entrirely in native code, we'll want to limit our dependency on Python, which is
why this barrier exists.
See also hgext/extlib/README.md, mercurial/cext/README.mb.
How do I choose between lib and extlib (and cext)?
If your code is native and doesn't depend on Python (awesome!), it goes here.
Otherwise, put it in hgext/extlib (if it's only used by extensions) or
mercurial/cext (if it's used by extensions or core).
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