Hello Andrew Wong,
I'd like you to do a code review. Please visit
http://gerrit.cloudera.org:8080/14819
to review the following change.
Change subject: log: don't reopen just-closed active segments
......................................................................
log: don't reopen just-closed active segments
When we roll the log, we close the active segment before switching to the
next preallocated segment. What happens when we close the active segment?
1. We sync it.
2. We write out the (now complete) footer.
3. We close the segment file. Under the hood, this will truncate any unused
preallocated space out of the file and sync it one last time.
4. We open the closed segment file for reading. Note that this is the second
time we've opened it; we also opened it once when we last rolled the log.
5. We create a new in-memory segment reader. To avoid needless IO, we
initialize it using the in-memory header and footer, but we do end up
reloading the segment's file size from disk.
6. We replace the last segment reader in the log with the reader constructed
in step #5. Side effect: the original segment reader is now closed.
The effort to reduce IO is laudable, but we can do better by not reopening
the segment file at all: it is sufficient to inject the now complete footer
into the existing reader, and to recalculate the file size (although this is
probably only needed for tests, it was simpler to always do it).
Along the way, I cleaned up SegmentAllocator by removing its functors, which
I found difficult to follow. Instead, Log now maniupates LogReader directly,
using information passed back from SegmentAllocator functions.
Change-Id: Id2f5dd47e3be930288dcfeb1f77409fda45daac4
---
M src/kudu/consensus/consensus_queue-test.cc
M src/kudu/consensus/log-test-base.h
M src/kudu/consensus/log-test.cc
M src/kudu/consensus/log.cc
M src/kudu/consensus/log.h
M src/kudu/consensus/log_reader.cc
M src/kudu/consensus/log_reader.h
M src/kudu/consensus/log_util.cc
M src/kudu/consensus/log_util.h
M src/kudu/integration-tests/timestamp_advancement-itest.cc
M src/kudu/tablet/tablet_replica-test.cc
M src/kudu/tserver/tablet_copy-test-base.h
12 files changed, 181 insertions(+), 211 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/19/14819/1
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Id2f5dd47e3be930288dcfeb1f77409fda45daac4
Gerrit-Change-Number: 14819
Gerrit-PatchSet: 1
Gerrit-Owner: Adar Dembo <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
