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TransactionStateMachine.java
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TransactionStateMachine.java
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/*
* Copyright (c) 2002-2018 "Neo Technology,"
* Network Engine for Objects in Lund AB [http://neotechnology.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 <http://www.gnu.org/licenses/>.
*/
package org.neo4j.bolt.v1.runtime;
import java.time.Clock;
import java.util.Optional;
import java.util.regex.Pattern;
import org.neo4j.bolt.security.auth.AuthenticationResult;
import org.neo4j.bolt.v1.runtime.bookmarking.Bookmark;
import org.neo4j.bolt.v1.runtime.spi.BoltResult;
import org.neo4j.bolt.v1.runtime.spi.BookmarkResult;
import org.neo4j.cypher.InvalidSemanticsException;
import org.neo4j.function.ThrowingAction;
import org.neo4j.function.ThrowingConsumer;
import org.neo4j.graphdb.TransactionTerminatedException;
import org.neo4j.internal.kernel.api.security.LoginContext;
import org.neo4j.internal.kernel.api.exceptions.KernelException;
import org.neo4j.kernel.api.KernelTransaction;
import org.neo4j.kernel.api.exceptions.Status;
import org.neo4j.kernel.api.exceptions.TransactionFailureException;
import org.neo4j.kernel.impl.query.QueryExecutionKernelException;
import org.neo4j.values.virtual.MapValue;
import static org.neo4j.function.ThrowingAction.noop;
public class TransactionStateMachine implements StatementProcessor
{
private static final Pattern BEGIN = Pattern.compile("(?i)^\\s*BEGIN\\s*;?\\s*$");
private static final Pattern COMMIT = Pattern.compile("(?i)^\\s*COMMIT\\s*;?\\s*$");
private static final Pattern ROLLBACK = Pattern.compile("(?i)^\\s*ROLLBACK\\s*;?\\s*$");
final SPI spi;
final MutableTransactionState ctx;
State state = State.AUTO_COMMIT;
TransactionStateMachine( SPI spi, AuthenticationResult authenticationResult, Clock clock )
{
this.spi = spi;
ctx = new MutableTransactionState( authenticationResult, clock );
}
public State state()
{
return state;
}
private void before()
{
if ( ctx.currentTransaction != null )
{
spi.bindTransactionToCurrentThread( ctx.currentTransaction );
}
}
@Override
public StatementMetadata run( String statement, MapValue params ) throws KernelException
{
before();
try
{
ensureNoPendingTerminationNotice();
state = state.run( ctx, spi, statement, params );
return ctx.currentStatementMetadata;
}
catch ( TransactionFailureException ex )
{
state = State.AUTO_COMMIT;
throw ex;
}
finally
{
after();
}
}
@Override
public void streamResult( ThrowingConsumer<BoltResult, Exception> resultConsumer ) throws Exception
{
before();
try
{
ensureNoPendingTerminationNotice();
state.streamResult( ctx, resultConsumer );
}
finally
{
after();
}
}
/**
* Rollback and close transaction. Move back to {@link State#AUTO_COMMIT}.
* <p>
* <b>Warning:</b>This method should only be called by the bolt worker thread during it's regular message
* processing. It is wrong to call it from a different thread because kernel transactions are not thread-safe.
*
* @throws TransactionFailureException when transaction fails to close.
*/
@Override
public void reset() throws TransactionFailureException
{
state.terminateQueryAndRollbackTransaction( ctx );
state = State.AUTO_COMMIT;
}
private void after()
{
spi.unbindTransactionFromCurrentThread();
}
@Override
public void markCurrentTransactionForTermination()
{
KernelTransaction tx = ctx.currentTransaction;
if ( tx != null )
{
tx.markForTermination( Status.Transaction.Terminated );
}
}
@Override
public void validateTransaction() throws KernelException
{
KernelTransaction tx = ctx.currentTransaction;
if ( tx != null )
{
Optional<Status> statusOpt = tx.getReasonIfTerminated();
if ( statusOpt.isPresent() )
{
if ( statusOpt.get().code().classification().rollbackTransaction() )
{
ctx.pendingTerminationNotice = statusOpt.get();
reset();
}
}
}
}
private void ensureNoPendingTerminationNotice()
{
if ( ctx.pendingTerminationNotice != null )
{
Status status = ctx.pendingTerminationNotice;
ctx.pendingTerminationNotice = null;
throw new TransactionTerminatedException( status );
}
}
@Override
public boolean hasTransaction()
{
return state == State.EXPLICIT_TRANSACTION;
}
@Override
public void setQuerySource( BoltQuerySource querySource )
{
this.ctx.querySource = querySource;
}
enum State
{
AUTO_COMMIT
{
@Override
State run( MutableTransactionState ctx, SPI spi, String statement,
MapValue params ) throws KernelException
{
if ( BEGIN.matcher( statement ).matches() )
{
ctx.currentTransaction = spi.beginTransaction( ctx.loginContext );
Bookmark bookmark = Bookmark.fromParamsOrNull( params );
if ( bookmark != null )
{
spi.awaitUpToDate( bookmark.txId() );
ctx.currentResult = new BookmarkResult( bookmark );
}
else
{
ctx.currentResult = BoltResult.EMPTY;
}
return EXPLICIT_TRANSACTION;
}
else if ( COMMIT.matcher( statement ).matches() )
{
throw new QueryExecutionKernelException(
new InvalidSemanticsException( "No current transaction to commit." ) );
}
else if ( ROLLBACK.matcher( statement ).matches() )
{
ctx.currentResult = BoltResult.EMPTY;
return AUTO_COMMIT;
}
else
{
if ( statement.isEmpty() )
{
statement = ctx.lastStatement;
}
else
{
ctx.lastStatement = statement;
}
if ( spi.isPeriodicCommit( statement ) )
{
BoltResultHandle resultHandle = executeQuery( ctx, spi, statement, params, noop() );
ctx.currentResultHandle = resultHandle;
ctx.currentResult = resultHandle.start();
ctx.currentTransaction = null; // Periodic commit will change the current transaction, so
// we can't trust this to point to the actual current transaction;
return AUTO_COMMIT;
}
else
{
ctx.currentTransaction = spi.beginTransaction( ctx.loginContext );
BoltResultHandle resultHandle = execute( ctx, spi, statement, params );
ctx.currentResultHandle = resultHandle;
ctx.currentResult = resultHandle.start();
return AUTO_COMMIT;
}
}
}
/*
* In AUTO_COMMIT we must make sure to fail, close and set the current
* transaction to null.
*/
private BoltResultHandle execute( MutableTransactionState ctx, SPI spi, String statement, MapValue params )
{
return executeQuery( ctx, spi, statement, params, () -> closeTransaction( ctx, false ) );
}
@Override
void streamResult( MutableTransactionState ctx,
ThrowingConsumer<BoltResult, Exception> resultConsumer ) throws Exception
{
assert ctx.currentResult != null;
resultConsumer.accept( ctx.currentResult );
ctx.currentResult.close();
closeTransaction( ctx, true );
}
},
EXPLICIT_TRANSACTION
{
@Override
State run( MutableTransactionState ctx, SPI spi, String statement, MapValue params )
throws KernelException
{
if ( BEGIN.matcher( statement ).matches() )
{
throw new QueryExecutionKernelException(
new InvalidSemanticsException( "Nested transactions are not supported." ) );
}
else if ( COMMIT.matcher( statement ).matches() )
{
closeTransaction( ctx, true );
long txId = spi.newestEncounteredTxId();
Bookmark bookmark = new Bookmark( txId );
ctx.currentResult = new BookmarkResult( bookmark );
return AUTO_COMMIT;
}
else if ( ROLLBACK.matcher( statement ).matches() )
{
closeTransaction( ctx, false );
ctx.currentResult = BoltResult.EMPTY;
return AUTO_COMMIT;
}
else
{
if ( statement.isEmpty() )
{
statement = ctx.lastStatement;
}
else
{
ctx.lastStatement = statement;
}
if ( spi.isPeriodicCommit( statement ) )
{
throw new QueryExecutionKernelException( new InvalidSemanticsException(
"Executing queries that use periodic commit in an " +
"open transaction is not possible." ) );
}
else
{
ctx.currentResultHandle = execute( ctx, spi, statement, params );
ctx.currentResult = ctx.currentResultHandle.start();
return EXPLICIT_TRANSACTION;
}
}
}
private BoltResultHandle execute( MutableTransactionState ctx, SPI spi, String statement, MapValue params )
{
return executeQuery( ctx, spi, statement, params,
() ->
{
if ( ctx.currentTransaction != null )
{
ctx.currentTransaction.failure();
}
} );
}
@Override
void streamResult( MutableTransactionState ctx,
ThrowingConsumer<BoltResult,Exception> resultConsumer ) throws Exception
{
assert ctx.currentResult != null;
resultConsumer.accept( ctx.currentResult );
ctx.currentResult.close();
}
};
abstract State run( MutableTransactionState ctx,
SPI spi,
String statement,
MapValue params ) throws KernelException;
abstract void streamResult( MutableTransactionState ctx,
ThrowingConsumer<BoltResult, Exception> resultConsumer ) throws Exception;
void terminateQueryAndRollbackTransaction( MutableTransactionState ctx ) throws TransactionFailureException
{
if ( ctx.currentResultHandle != null )
{
ctx.currentResultHandle.terminate();
ctx.currentResultHandle = null;
}
if ( ctx.currentResult != null )
{
ctx.currentResult.close();
ctx.currentResult = null;
}
closeTransaction( ctx, false);
}
/*
* This is overly careful about always closing and nulling the transaction since
* reset can cause ctx.currentTransaction to be null we store in local variable.
*/
void closeTransaction( MutableTransactionState ctx, boolean success ) throws TransactionFailureException
{
KernelTransaction tx = ctx.currentTransaction;
ctx.currentTransaction = null;
if ( tx != null )
{
try
{
if ( success )
{
tx.success();
}
else
{
tx.failure();
}
if ( tx.isOpen() )
{
tx.close();
}
}
finally
{
ctx.currentTransaction = null;
}
}
}
}
private static BoltResultHandle executeQuery( MutableTransactionState ctx, SPI spi, String statement,
MapValue params, ThrowingAction<KernelException> onFail )
{
return spi.executeQuery( ctx.querySource, ctx.loginContext, statement, params, onFail );
}
/**
* This interface makes it possible to abort queries even before they have returned a Result object.
* In some cases, creating the Result object will take as long as running the query takes. This way, we can
* terminate the underlying transaction while the Result object is created.
*/
interface BoltResultHandle
{
BoltResult start() throws KernelException;
void terminate();
}
static class MutableTransactionState
{
/** The current session security context to be used for starting transactions */
final LoginContext loginContext;
/** The current transaction, if present */
KernelTransaction currentTransaction;
Status pendingTerminationNotice;
/** Last Cypher statement executed */
String lastStatement = "";
/** The current pending result, if present */
BoltResult currentResult;
final Clock clock;
/** A re-usable statement metadata instance that always represents the currently running statement */
private final StatementMetadata currentStatementMetadata = new StatementMetadata()
{
@Override
public String[] fieldNames()
{
return currentResult.fieldNames();
}
};
BoltQuerySource querySource;
BoltResultHandle currentResultHandle;
private MutableTransactionState( AuthenticationResult authenticationResult, Clock clock )
{
this.clock = clock;
this.loginContext = authenticationResult.getLoginContext();
}
}
interface SPI
{
void awaitUpToDate( long oldestAcceptableTxId ) throws TransactionFailureException;
long newestEncounteredTxId();
KernelTransaction beginTransaction( LoginContext loginContext );
void bindTransactionToCurrentThread( KernelTransaction tx );
void unbindTransactionFromCurrentThread();
boolean isPeriodicCommit( String query );
BoltResultHandle executeQuery( BoltQuerySource querySource,
LoginContext loginContext,
String statement,
MapValue params,
ThrowingAction<KernelException> onFail );
}
}