org.neo4j.kernel.api.query.QueryTransactionStatisticsAggregator Maven / Gradle / Ivy
Show all versions of neo4j-kernel Show documentation
/*
* Copyright (c) "Neo4j"
* Neo4j Sweden AB [https://neo4j.com]
*
* This file is part of Neo4j.
*
* Neo4j is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see
* NOTE: The logic for computing the statistics of the commit phase assumes that for
* a given transaction sequence number, the two methods
* recordStatisticsOfTransactionAboutToClose and recordStatisticsOfClosedTransaction
* are called in sequence.
*/
public interface QueryTransactionStatisticsAggregator {
/**
* Record the page cache statistics of a transaction that is about to close.
*/
void recordStatisticsOfTransactionAboutToClose(long hits, long faults, long transactionSequenceNumber);
/**
* Record the page cache statistics of a transaction that has closed.
*/
void recordStatisticsOfClosedTransaction(
long hits, long faults, long transactionSequenceNumber, CommitPhaseStatisticsListener listener);
/**
* Get the total page hits of closed transactions.
*/
long pageHitsOfClosedTransactions();
/**
* Get the total page faults of closed transactions.
*/
long pageFaultsOfClosedTransactions();
/**
* Get the page hits of closed transaction commits.
*/
long pageHitsOfClosedTransactionCommits();
/**
* Get the page faults of closed transaction commits.
*/
long pageFaultsOfClosedTransactionCommits();
/**
* Get a consistent execution statistics snapshot of closed transactions excluding commits.
*/
@VisibleForTesting
ExecutionStatistics statisticsOfClosedTransactionsExcludingCommits();
/**
* Get a consistent execution statistics snapshot of closed transaction commits.
*/
@VisibleForTesting
ExecutionStatistics statisticsOfClosedTransactionCommits();
/**
* An of {@link QueryTransactionStatisticsAggregator} that uses volatile fields for read visibility
* but only supports a single writer thread to record statistics.
*/
class DefaultImpl implements QueryTransactionStatisticsAggregator {
private volatile long pageHitsOfClosedTransactionsExcludingCommits;
private volatile long pageFaultsOfClosedTransactionsExcludingCommits;
private volatile long pageHitsOfClosedTransactionsIncludingCommits;
private volatile long pageFaultsOfClosedTransactionsIncludingCommits;
private volatile long pageHitsOfClosedTransactionCommits;
private volatile long pageFaultsOfClosedTransactionCommits;
@Override
public void recordStatisticsOfTransactionAboutToClose(long hits, long faults, long transactionSequenceNumber) {
// We only have one thread writing to these fields. Ignore transactionSequenceNumber.
//noinspection NonAtomicOperationOnVolatileField
pageHitsOfClosedTransactionsExcludingCommits += hits;
//noinspection NonAtomicOperationOnVolatileField
pageFaultsOfClosedTransactionsExcludingCommits += faults;
}
/**
* A transaction executing part of this query is closing; record its page cache statistics (including commit).
*/
@Override
public void recordStatisticsOfClosedTransaction(
long hits, long faults, long transactionSequenceNumber, CommitPhaseStatisticsListener listener) {
// We only have one thread writing to these fields
//noinspection NonAtomicOperationOnVolatileField
pageHitsOfClosedTransactionsIncludingCommits += hits;
//noinspection NonAtomicOperationOnVolatileField
pageFaultsOfClosedTransactionsIncludingCommits += faults;
pageHitsOfClosedTransactionCommits =
(pageHitsOfClosedTransactionsIncludingCommits - pageHitsOfClosedTransactionsExcludingCommits);
pageFaultsOfClosedTransactionCommits =
(pageFaultsOfClosedTransactionsIncludingCommits - pageFaultsOfClosedTransactionsExcludingCommits);
listener.onRecordedStatisticsOfCommitPhase(
pageHitsOfClosedTransactionCommits,
pageFaultsOfClosedTransactionCommits,
transactionSequenceNumber);
}
public long pageHitsOfClosedTransactions() {
return pageHitsOfClosedTransactionsExcludingCommits + pageHitsOfClosedTransactionCommits;
}
public long pageFaultsOfClosedTransactions() {
return pageFaultsOfClosedTransactionsExcludingCommits + pageFaultsOfClosedTransactionCommits;
}
public long pageHitsOfClosedTransactionCommits() {
return pageHitsOfClosedTransactionCommits;
}
public long pageFaultsOfClosedTransactionCommits() {
return pageFaultsOfClosedTransactionCommits;
}
@Override
public ExecutionStatistics statisticsOfClosedTransactionsExcludingCommits() {
return new Stats(
pageHitsOfClosedTransactionsExcludingCommits, pageFaultsOfClosedTransactionsExcludingCommits, 0);
}
@Override
public ExecutionStatistics statisticsOfClosedTransactionCommits() {
return new Stats(pageHitsOfClosedTransactionCommits, pageFaultsOfClosedTransactionCommits, 0);
}
}
/**
* An implementation of {@link QueryTransactionStatisticsAggregator}
* that supports concurrent writer threads to record statistics.
*/
class ConcurrentImpl implements QueryTransactionStatisticsAggregator {
private final Map pageStatsExcludingCommits = new ConcurrentHashMap<>();
private final AtomicReference statsOfClosedTransactionsExcludingCommits =
new AtomicReference<>(new Stats(0, 0, 0));
private final AtomicReference statsOfClosedTransactionCommits =
new AtomicReference<>(new Stats(0, 0, 0));
public ConcurrentImpl() {}
public ConcurrentImpl(QueryTransactionStatisticsAggregator statistics) {
var hitsIncluding = statistics.pageHitsOfClosedTransactions();
var faultsIncluding = statistics.pageFaultsOfClosedTransactions();
var hitsOfCommits = statistics.pageHitsOfClosedTransactionCommits();
var faultsOfCommits = statistics.pageFaultsOfClosedTransactionCommits();
var hitsExcluding = hitsIncluding - hitsOfCommits;
var faultsExcluding = faultsIncluding - faultsOfCommits;
var statsExcludingCommits = statsOfClosedTransactionsExcludingCommits.get();
var statsOfCommits = statsOfClosedTransactionCommits.get();
statsExcludingCommits.hits = hitsExcluding;
statsExcludingCommits.faults = faultsExcluding;
statsOfCommits.hits = hitsOfCommits;
statsOfCommits.faults = faultsOfCommits;
}
@Override
public void recordStatisticsOfTransactionAboutToClose(long hits, long faults, long transactionSequenceNumber) {
// NOTE: We assume that only one thread is recording statistics for a given transaction sequence number.
var stats = pageStatsExcludingCommits.get(transactionSequenceNumber);
if (stats == null) {
pageStatsExcludingCommits.put(
transactionSequenceNumber, new Stats(hits, faults, transactionSequenceNumber));
} else {
stats.hits += hits;
stats.faults += faults;
}
updateStats(statsOfClosedTransactionsExcludingCommits, hits, faults, transactionSequenceNumber);
}
@Override
public void recordStatisticsOfClosedTransaction(
long hits, long faults, long transactionSequenceNumber, CommitPhaseStatisticsListener listener) {
// NOTE: We assume that only one thread is recording statistics for a given transaction sequence number.
var excludingCommitsStats = pageStatsExcludingCommits.remove(transactionSequenceNumber);
if (excludingCommitsStats == null) {
throw new IllegalStateException(
"Expected to find recorded page cache statistics for transaction sequence number "
+ transactionSequenceNumber + " on thread "
+ Thread.currentThread().getName());
}
var hitsDuringCommit = hits - excludingCommitsStats.hits;
var faultsDuringCommit = faults - excludingCommitsStats.faults;
listener.onRecordedStatisticsOfCommitPhase(hitsDuringCommit, faultsDuringCommit, transactionSequenceNumber);
updateStats(
statsOfClosedTransactionCommits, hitsDuringCommit, faultsDuringCommit, transactionSequenceNumber);
}
private static void updateStats(
AtomicReference stats, long hits, long faults, long transactionSequenceNumber) {
Stats current;
Stats updated = new Stats(0, 0, transactionSequenceNumber);
do {
current = stats.get();
updated.hits = current.hits + hits;
updated.faults = current.faults + faults;
// Keep the highest observed transaction sequence number
var currentSequenceNumber = current.transactionSequenceNumber;
if (currentSequenceNumber > transactionSequenceNumber) {
updated.transactionSequenceNumber = currentSequenceNumber;
}
} while (!stats.weakCompareAndSetVolatile(current, updated));
}
@Override
public long pageHitsOfClosedTransactions() {
return statsOfClosedTransactionsExcludingCommits.get().hits + statsOfClosedTransactionCommits.get().hits;
}
@Override
public long pageFaultsOfClosedTransactions() {
return statsOfClosedTransactionsExcludingCommits.get().faults
+ statsOfClosedTransactionCommits.get().faults;
}
@Override
public long pageHitsOfClosedTransactionCommits() {
return statsOfClosedTransactionCommits.get().hits;
}
@Override
public long pageFaultsOfClosedTransactionCommits() {
return statsOfClosedTransactionCommits.get().faults;
}
@Override
public ExecutionStatistics statisticsOfClosedTransactionsExcludingCommits() {
return statsOfClosedTransactionsExcludingCommits.get();
}
@Override
public ExecutionStatistics statisticsOfClosedTransactionCommits() {
return statsOfClosedTransactionCommits.get();
}
}
class Stats implements ExecutionStatistics {
long hits;
long faults;
long transactionSequenceNumber;
Stats(long hits, long faults, long transactionSequenceNumber) {
this.hits = hits;
this.faults = faults;
this.transactionSequenceNumber = transactionSequenceNumber;
}
@Override
public long pageHits() {
return hits;
}
@Override
public long pageFaults() {
return faults;
}
@Override
public long getTransactionSequenceNumber() {
return transactionSequenceNumber;
}
}
@FunctionalInterface
interface CommitPhaseStatisticsListener {
void onRecordedStatisticsOfCommitPhase(long pageHits, long pageFaults, long transactionSequenceNumber);
CommitPhaseStatisticsListener NO_OP = (pageHits, pageFaults, transactionSequenceNumber) -> {};
}
}