Hello Alexey Serbin, Andrew Wong,
I'd like you to do a code review. Please visit
http://gerrit.cloudera.org:8080/14822
to review the following change.
Change subject: log_index: use RWFiles for IO
......................................................................
log_index: use RWFiles for IO
To use LogIndex in FileCache, we need to do one of two things:
1. Add an mmap-based file abstraction to Env, to be used by LogIndex.
2. Rework LogIndex to use RWFile instead of memory mappings.
This patch implements option #2. Why? Because although memory mappings can
be used for zero copy IO, the LogIndex wasn't doing that, and more
importantly, failures during memory mapped IO are communicated via UNIX
signals, making it practically impossible for an application of Kudu's
complexity to recover from a WAL disk failure surfaced during log index IO,
a feature that is being actively worked on in KUDU-2975.
IO through mmap is identical to IO through RWFile (i.e. pwrite/pread) for
all other intents and purposes:
- Both can use ftruncate to grow the file's size while keeping it sparse.
- Both maintain holes in file sections that aren't written.
- Both go through the page cache for reads and writes.
- Both allow pages to be dirty before writing them out asynchronously.
Change-Id: I75c0476bbd9be55657291c85488b9121e04a91de
---
M src/kudu/consensus/log-test.cc
M src/kudu/consensus/log.cc
M src/kudu/consensus/log_index-test.cc
M src/kudu/consensus/log_index.cc
M src/kudu/consensus/log_index.h
5 files changed, 71 insertions(+), 95 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/22/14822/1
--
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: I75c0476bbd9be55657291c85488b9121e04a91de
Gerrit-Change-Number: 14822
Gerrit-PatchSet: 1
Gerrit-Owner: Adar Dembo <[email protected]>
Gerrit-Reviewer: Alexey Serbin <[email protected]>
Gerrit-Reviewer: Andrew Wong <[email protected]>
