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Counter for merge failure

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Summary:
With Merge returning bool, it can keep failing silently(eg. While faling to fetch timestamp in TTL). We need to detect this through a rocksdb counter which can get bumped whenever Merge returns false. This will also be super-useful for the mcrocksdb-counter service where Merge may fail.
Added a counter NUMBER_MERGE_FAILURES and appropriately updated db/merge_helper.cc

I felt that it would be better to directly add counter-bumping in Merge as a default function of MergeOperator class but user should not be aware of this, so this approach seems better to me.

Test Plan: make all check

Reviewers: dnicholas, haobo, dhruba, vamsi

CC: leveldb

Differential Revision: https://reviews.facebook.net/D12129
This commit is contained in:
Mayank Agarwal 2013-08-08 23:07:36 -07:00
parent f5f1842282
commit f1bf169484
9 changed files with 37 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
db/db_impl.cc
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@ -1915,7 +1915,8 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
// object to minimize change to the existing flow. Turn out this
// logic could also be nicely re-used for memtable flush purge
// optimization in BuildTable.
merge.MergeUntil(input.get(), prev_snapshot, bottommost_level);
merge.MergeUntil(input.get(), prev_snapshot, bottommost_level,
options_.statistics);
current_entry_is_merging = true;
if (merge.IsSuccess()) {
// Successfully found Put/Delete/(end-of-key-range) while merging

2
db/memtable.cc
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@ -169,6 +169,7 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
assert(merge_operator);
if (!merge_operator->Merge(key.user_key(), &v, *operands,
value, logger.get())) {
RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
*s = Status::Corruption("Error: Could not perform merge.");
}
} else {
@ -182,6 +183,7 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s,
*s = Status::OK();
if (!merge_operator->Merge(key.user_key(), nullptr, *operands,
value, logger.get())) {
RecordTick(options.statistics, NUMBER_MERGE_FAILURES);
*s = Status::Corruption("Error: Could not perform merge.");
}
} else {

2
db/memtable.h
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@ -8,10 +8,10 @@
#include <string>
#include <memory>
#include <deque>
#include "leveldb/db.h"
#include "db/dbformat.h"
#include "db/skiplist.h"
#include "db/version_set.h"
#include "leveldb/db.h"
#include "leveldb/memtablerep.h"
#include "util/arena_impl.h"

28
db/memtablelist.cc
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@ -21,17 +21,15 @@ using std::list;
// Increase reference count on all underling memtables
void MemTableList::RefAll() {
for (list<MemTable*>::iterator it = memlist_.begin();
it != memlist_.end() ; ++it) {
(*it)->Ref();
for (auto &memtable : memlist_) {
memtable->Ref();
}
}
// Drop reference count on all underling memtables
void MemTableList::UnrefAll() {
for (list<MemTable*>::iterator it = memlist_.begin();
it != memlist_.end() ; ++it) {
(*it)->Unref();
for (auto &memtable : memlist_) {
memtable->Unref();
}
}
@ -53,8 +51,7 @@ bool MemTableList::IsFlushPending(int min_write_buffer_number_to_merge) {
// Returns the memtables that need to be flushed.
void MemTableList::PickMemtablesToFlush(std::vector<MemTable*>* ret) {
for (list<MemTable*>::reverse_iterator it = memlist_.rbegin();
it != memlist_.rend(); it++) {
for (auto it = memlist_.rbegin(); it != memlist_.rend(); it++) {
MemTable* m = *it;
if (!m->flush_in_progress_) {
assert(!m->flush_completed_);
@ -184,9 +181,8 @@ void MemTableList::Add(MemTable* m) {
// Returns an estimate of the number of bytes of data in use.
size_t MemTableList::ApproximateMemoryUsage() {
size_t size = 0;
for (list<MemTable*>::iterator it = memlist_.begin();
it != memlist_.end(); ++it) {
size += (*it)->ApproximateMemoryUsage();
for (auto &memtable : memlist_) {
size += memtable->ApproximateMemoryUsage();
}
return size;
}
@ -197,9 +193,8 @@ size_t MemTableList::ApproximateMemoryUsage() {
bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s,
std::deque<std::string>* operands,
const Options& options) {
for (list<MemTable*>::iterator it = memlist_.begin();
it != memlist_.end(); ++it) {
if ((*it)->Get(key, value, s, operands, options)) {
for (auto &memtable : memlist_) {
if (memtable->Get(key, value, s, operands, options)) {
return true;
}
}
@ -207,9 +202,8 @@ bool MemTableList::Get(const LookupKey& key, std::string* value, Status* s,
}
void MemTableList::GetMemTables(std::vector<MemTable*>* output) {
for (list<MemTable*>::iterator it = memlist_.begin();
it != memlist_.end(); ++it) {
output->push_back(*it);
for (auto &memtable : memlist_) {
output->push_back(memtable);
}
}

7
db/merge_helper.cc
View File

@ -15,7 +15,7 @@ namespace leveldb {
// operands_ stores the list of merge operands encountered while merging.
// keys_[i] corresponds to operands_[i] for each i.
void MergeHelper::MergeUntil(Iterator* iter, SequenceNumber stop_before,
bool at_bottom) {
bool at_bottom, shared_ptr<Statistics> stats) {
// Get a copy of the internal key, before it's invalidated by iter->Next()
// Also maintain the list of merge operands seen.
keys_.clear();
@ -79,6 +79,8 @@ void MergeHelper::MergeUntil(Iterator* iter, SequenceNumber stop_before,
UpdateInternalKey(&key[0], key.size(),
orig_ikey.sequence, orig_ikey.type);
swap(operands_.back(), merge_result);
} else {
RecordTick(stats, NUMBER_MERGE_FAILURES);
}
// move iter to the next entry (before doing anything else)
@ -105,6 +107,8 @@ void MergeHelper::MergeUntil(Iterator* iter, SequenceNumber stop_before,
UpdateInternalKey(&key[0], key.size(),
orig_ikey.sequence, orig_ikey.type);
swap(operands_.back(), merge_result);
} else {
RecordTick(stats, NUMBER_MERGE_FAILURES);
}
// move iter to the next entry
@ -179,6 +183,7 @@ void MergeHelper::MergeUntil(Iterator* iter, SequenceNumber stop_before,
// The final value() is always stored in operands_.back()
swap(operands_.back(),merge_result);
} else {
RecordTick(stats, NUMBER_MERGE_FAILURES);
// Do nothing if not success_. Leave keys() and operands() as they are.
}
}

3
db/merge_helper.h
View File

@ -3,6 +3,7 @@
#include "db/dbformat.h"
#include "leveldb/slice.h"
#include "leveldb/statistics.h"
#include <string>
#include <deque>
@ -40,7 +41,7 @@ class MergeHelper {
// at_bottom: (IN) true if the iterator covers the bottem level, which means
// we could reach the start of the history of this user key.
void MergeUntil(Iterator* iter, SequenceNumber stop_before = 0,
bool at_bottom = false);
bool at_bottom = false, shared_ptr<Statistics> stats=nullptr);
// Query the merge result
// These are valid until the next MergeUntil call

5
db/version_set.cc
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@ -245,6 +245,7 @@ struct Saver {
std::deque<std::string>* merge_operands; // the merge operations encountered
Logger* logger;
bool didIO; // did we do any disk io?
shared_ptr<Statistics> statistics;
};
}
@ -287,6 +288,7 @@ static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
s->state = kFound;
if (!s->merge_operator->Merge(s->user_key, &v, *ops,
s->value, s->logger)) {
RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
s->state = kCorrupt;
}
} else {
@ -301,6 +303,7 @@ static bool SaveValue(void* arg, const Slice& ikey, const Slice& v, bool didIO){
s->state = kFound;
if (!s->merge_operator->Merge(s->user_key, nullptr, *ops,
s->value, s->logger)) {
RecordTick(s->statistics, NUMBER_MERGE_FAILURES);
s->state = kCorrupt;
}
} else {
@ -391,6 +394,7 @@ void Version::Get(const ReadOptions& options,
saver.merge_operands = operands;
saver.logger = logger.get();
saver.didIO = false;
saver.statistics = db_options.statistics;
stats->seek_file = nullptr;
stats->seek_file_level = -1;
@ -517,6 +521,7 @@ void Version::Get(const ReadOptions& options,
value, logger.get())) {
*status = Status::OK();
} else {
RecordTick(db_options.statistics, NUMBER_MERGE_FAILURES);
*status = Status::Corruption("could not perform end-of-key merge for ",
user_key);
}

7
include/leveldb/statistics.h
View File

@ -60,7 +60,9 @@ enum Tickers {
NUMBER_FILTERED_DELETES = 21,
TICKER_ENUM_MAX = 22
NUMBER_MERGE_FAILURES = 22,
TICKER_ENUM_MAX = 23
};
const std::vector<std::pair<Tickers, std::string>> TickersNameMap = {
@ -85,7 +87,8 @@ const std::vector<std::pair<Tickers, std::string>> TickersNameMap = {
{ NUMBER_MULTIGET_CALLS, "rocksdb.number.multiget.get" },
{ NUMBER_MULTIGET_KEYS_READ, "rocksdb.number.multiget.keys.read" },
{ NUMBER_MULTIGET_BYTES_READ, "rocksdb.number.multiget.bytes.read" },
{ NUMBER_FILTERED_DELETES, "rocksdb.number.deletes.filtered" }
{ NUMBER_FILTERED_DELETES, "rocksdb.number.deletes.filtered" },
{ NUMBER_MERGE_FAILURES, "rocksdb.number.merge.failures" }
};
/**

8
utilities/ttl/db_ttl.h
View File

@ -268,17 +268,16 @@ class TtlMergeOperator : public MergeOperator {
if (existing_value && existing_value->size() < ts_len) {
Log(logger, "Error: Could not remove timestamp from existing value.");
return false;
// TODO: Change Merge semantics and add a counter here
}
// Extract time-stamp from each operand to be passed to user_merge_op_
std::deque<std::string> operands_without_ts;
for (auto it = operands.begin(); it != operands.end(); ++it) {
if (it->size() < ts_len) {
for (const auto &operand : operands) {
if (operand.size() < ts_len) {
Log(logger, "Error: Could not remove timestamp from operand value.");
return false;
}
operands_without_ts.push_back(it->substr(0, it->size() - ts_len));
operands_without_ts.push_back(operand.substr(0, operand.size() - ts_len));
}
// Apply the user merge operator (store result in *new_value)
@ -316,7 +315,6 @@ class TtlMergeOperator : public MergeOperator {
if (left_operand.size() < ts_len || right_operand.size() < ts_len) {
Log(logger, "Error: Could not remove timestamp from value.");
return false;
//TODO: Change Merge semantics and add a counter here
}
// Apply the user partial-merge operator (store result in *new_value)