Make Log::Reader more robust

Summary:
This diff does two things:
(1) Log::Reader does not report a corruption when the last record in a log or manifest file is truncated (meaning that log writer died in the middle of the write). Inherited the code from LevelDB: https://code.google.com/p/leveldb/source/detail?r=269fc6ca9416129248db5ca57050cd5d39d177c8#
(2) Turn off mmap writes for all writes to log and manifest files

(2) is necessary because if we use mmap writes, the last record is not truncated, but is actually filled with zeros, making checksum fail. It is hard to recover from checksum failing.

Test Plan:
Added unit tests from LevelDB
Actually recovered a "corrupted" MANIFEST file.

Reviewers: dhruba, haobo

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16119
This commit is contained in:
Igor Canadi
2014-02-28 13:19:47 -08:00
parent a77527f2af
commit 58ca641d53
8 changed files with 74 additions and 26 deletions

View File

@@ -446,20 +446,32 @@ TEST(LogTest, BadRecordType) {
ASSERT_EQ("OK", MatchError("unknown record type"));
}
TEST(LogTest, TruncatedTrailingRecord) {
TEST(LogTest, TruncatedTrailingRecordIsIgnored) {
Write("foo");
ShrinkSize(4); // Drop all payload as well as a header byte
ASSERT_EQ("EOF", Read());
ASSERT_EQ((unsigned int)(kHeaderSize - 1), DroppedBytes());
ASSERT_EQ("OK", MatchError("truncated record at end of file"));
// Truncated last record is ignored, not treated as an error
ASSERT_EQ(0, DroppedBytes());
ASSERT_EQ("", ReportMessage());
}
TEST(LogTest, BadLength) {
const int kPayloadSize = kBlockSize - kHeaderSize;
Write(BigString("bar", kPayloadSize));
Write("foo");
// Least significant size byte is stored in header[4].
IncrementByte(4, 1);
ASSERT_EQ("foo", Read());
ASSERT_EQ(kBlockSize, DroppedBytes());
ASSERT_EQ("OK", MatchError("bad record length"));
}
TEST(LogTest, BadLengthAtEndIsIgnored) {
Write("foo");
ShrinkSize(1);
ASSERT_EQ("EOF", Read());
ASSERT_EQ((unsigned int)(kHeaderSize + 2), DroppedBytes());
ASSERT_EQ("OK", MatchError("bad record length"));
ASSERT_EQ(0, DroppedBytes());
ASSERT_EQ("", ReportMessage());
}
TEST(LogTest, ChecksumMismatch) {
@@ -510,6 +522,24 @@ TEST(LogTest, UnexpectedFirstType) {
ASSERT_EQ("OK", MatchError("partial record without end"));
}
TEST(LogTest, MissingLastIsIgnored) {
Write(BigString("bar", kBlockSize));
// Remove the LAST block, including header.
ShrinkSize(14);
ASSERT_EQ("EOF", Read());
ASSERT_EQ("", ReportMessage());
ASSERT_EQ(0, DroppedBytes());
}
TEST(LogTest, PartialLastIsIgnored) {
Write(BigString("bar", kBlockSize));
// Cause a bad record length in the LAST block.
ShrinkSize(1);
ASSERT_EQ("EOF", Read());
ASSERT_EQ("", ReportMessage());
ASSERT_EQ(0, DroppedBytes());
}
TEST(LogTest, ErrorJoinsRecords) {
// Consider two fragmented records:
// first(R1) last(R1) first(R2) last(R2)