When a snapshot is taken, stale etcdraft WAL files should be
purged to free disk space, as well as old snapshot files.

However, we still keep several snapshot files around, in case
the latest file is corrupted, etcdraft will automatically load
an older one, until there's none left.

Change-Id: I2b8168dbc0c3e5bd56a081c104dd7dc9defbcd92
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>

This CR puts Raft snapshotting into a go routine to avoid
excessive snapshotting due to extreme small SnapshotInterval.

This is also preperation for WAL files pruning.

Change-Id: Ib43a2197c533bdc224a4bc52ff6cb418b62a0c33
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>

For etcdraft chain, if there is applied index (>0) in
block metadata, then the node is expected not to be fresh
and should have wal data.

This CR removes this constraints because that's not the
case anymore with onboarding, since one node may pull blocks
from other nodes before bootstrap chain.

Change-Id: I678db4d1d71a24e08685d9c73eee7f4bc281771f
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>

This CR adds enables etcd/raft based chain to take snapshot for
every `SnapInterval` blocks. It stores snapshot to wal and disk.
When node restarts, it loads latest snapshot and uses Term and
Index stored in it to replay WAL to memory storage.

Change-Id: Ib8c22173cd5b05b7a1b27b16e2003bdabbecf82a
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>

Prevents the etcd/raft-based orderer from writing to the production path
during tests. Instead it uses os.TempDir for WALs and snapshots.

This makes FAB-12824 #done.

Change-Id: I6bcdf5b0ac59575158e6bdb9e8d0e033f926b369
Signed-off-by: Kostas Christidis <kostas@christidis.io>

This CR refactors storage etcd/raft chain implementation
to bundle memory storage and wal together.

Change-Id: Ib0dc95497dc9a0747c365ef78d0a702382445f55
Signed-off-by: Jay Guo <guojiannan1101@gmail.com>