tree dd62ebf8749543da8023466bd434c2a1cff5d874
parent 1c73715511bbfffdd760318674b482c59dea3189
author Pasha Kuznetsov <pasha@tydbits.com> 1544751911 -0800
committer Sijie Guo <sijie@apache.org> 1544751947 +0800
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Issue #1884: (@W-5697664@) dir_*_usage stats are reported as 0 ...

for read-only bookies after a restart

### Motivation

Fixing the Issue #1884:

When a read-only bookie is restarted it keeps reporting `dir_*_usage`
stats as `0` until it becomes writable again.

This is caused by the `LedgerDirsMonitor.check` only updating
`diskUsages` if there are any writable dirs, or if the total usage
goes below the low water mark, otherwise relying on previously filled
values which are `0` after a bookie is restarted.

### Changes

* Change the `LedgerDirsMonitor.check` to update `diskUsages`
  even when there are no writable dirs.
* Add new `testLedgerDirsMonitorStartReadOnly` testing this scenario.
* Simplify previous tests checking read-only since `diskUsages`
  are now updated regardless if a bookie is in read-only mode.

jvrao reddycharan

Reviewers: Sijie Guo <sijie@apache.org>, Charan Reddy Guttapalem <reddycharan18@gmail.com>

This closes #1885 from pasha-kuznetsov/issue-1884-dir-usage-ro-restart, closes #1884

(cherry picked from commit 1b2138fd4ecdbc4dfec00709b51e1367dfd49654)
Signed-off-by: Sijie Guo <sijie@apache.org>