--nosync development flag

[crawshaw]

Background

I regularly spin up a single-node etcd in unit tests and read/write many keys. Experiments with tmpfs on linux suggest that most of the time in my tests is spent writing to disk. Unfortunately macOS does not have a tmpfs, and standard dev/CI environments do not have one configured so typically the tests are slow, dominated by ephemeral etcd writes.

Proposal

Add an unsafe --nosync flag to etcd that disables fsync.

The implementation is straightforward as the underlying bbolt already exposes options for this, NoSync and NoFreelistSync, it's a matter of plumbing them through.

I would be happy to implement this if the idea is generally acceptable.

[gyuho]

implementation is straightforward as the underlying bbolt already exposes options for this, NoSync

Yeah think it can be exposed as an unsafe option --unsafe-no-sync?

etcd also writes WAL (no option to disable).