Robust mail store

[y10k]

Revised DBM update procedure and make mailstores more robust and reduce recovery time.

The current recovery time is as follows.

• mailbox 2 has 77452 messages
• mailbox 4 has 56204 messages
• total about 134,000 messages
• total elapsed time: 994.841399 seconds (about 17 minutes)

W, [2019-04-25T23:58:30.917504 #26752]  WARN -- rims: user data recovery start: toki
I, [2019-04-25T23:58:30.917912 #26752]  INFO -- rims: test read all: meta DB
I, [2019-04-25T23:58:45.817327 #26752]  INFO -- rims: test read all: msg DB
I, [2019-04-26T00:06:47.988172 #26752]  INFO -- rims: test_read_all: mailbox DB 1
I, [2019-04-26T00:06:48.355072 #26752]  INFO -- rims: test_read_all: mailbox DB 2
I, [2019-04-26T00:06:51.601520 #26752]  INFO -- rims: test_read_all: mailbox DB 3
I, [2019-04-26T00:06:51.853118 #26752]  INFO -- rims: test_read_all: mailbox DB 4
I, [2019-04-26T00:06:54.384842 #26752]  INFO -- rims: test_read_all: mailbox DB 5
I, [2019-04-26T00:06:54.388195 #26752]  INFO -- rims: test_read_all: mailbox DB 6
I, [2019-04-26T00:06:54.569878 #26752]  INFO -- rims: test_read_all: mailbox DB 7
I, [2019-04-26T00:06:54.574507 #26752]  INFO -- rims: recovery phase 1: start.
I, [2019-04-26T00:08:36.852840 #26752]  INFO -- rims: recovery phase 1: end.
I, [2019-04-26T00:08:36.929638 #26752]  INFO -- rims: recovery phase 2: start.
I, [2019-04-26T00:13:30.333467 #26752]  INFO -- rims: recovery phase 2: end.
I, [2019-04-26T00:13:30.406764 #26752]  INFO -- rims: recovery phase 3: start.
I, [2019-04-26T00:13:30.433298 #26752]  INFO -- rims: recovery phase 3: end.
I, [2019-04-26T00:13:30.433810 #26752]  INFO -- rims: recovery phase 4: start.
I, [2019-04-26T00:13:37.010170 #26752]  INFO -- rims: recovery phase 4: end.
I, [2019-04-26T00:13:37.010808 #26752]  INFO -- rims: recovery phase 5: start.
I, [2019-04-26T00:13:37.011229 #26752]  INFO -- rims: recovery phase 5: end.
I, [2019-04-26T00:13:37.011575 #26752]  INFO -- rims: recovery phase 6: start.
I, [2019-04-26T00:13:58.327636 #26752]  INFO -- rims: recovery phase 6: end.
I, [2019-04-26T00:13:58.328012 #26752]  INFO -- rims: recovery phase 7: start.
I, [2019-04-26T00:13:58.328163 #26752]  INFO -- rims: scan mailbox: 1
I, [2019-04-26T00:13:58.328788 #26752]  INFO -- rims: scan mailbox: 2
I, [2019-04-26T00:14:34.222482 #26752]  INFO -- rims: scan mailbox: 3
I, [2019-04-26T00:14:34.314256 #26752]  INFO -- rims: scan mailbox: 4
I, [2019-04-26T00:14:59.925548 #26752]  INFO -- rims: scan mailbox: 5
I, [2019-04-26T00:14:59.926312 #26752]  INFO -- rims: scan mailbox: 6
I, [2019-04-26T00:14:59.951905 #26752]  INFO -- rims: scan mailbox: 7
I, [2019-04-26T00:14:59.952626 #26752]  INFO -- rims: recovery phase 7: end.
I, [2019-04-26T00:14:59.952858 #26752]  INFO -- rims: recovery phase 8: start.
I, [2019-04-26T00:14:59.953052 #26752]  INFO -- rims: recovery phase 8: end.
W, [2019-04-26T00:15:05.758903 #26752]  WARN -- rims: user data recovery end: toki