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Access to the Neo4j graph database through Java
/*
* Copyright (c) "Neo4j"
* Neo4j Sweden AB [http://neo4j.com]
*
* This file is part of Neo4j.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.neo4j.driver.internal.async;
import static java.util.concurrent.CompletableFuture.completedFuture;
import static org.neo4j.driver.internal.util.Futures.completedWithNull;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.atomic.AtomicBoolean;
import org.neo4j.driver.AccessMode;
import org.neo4j.driver.Bookmark;
import org.neo4j.driver.Logger;
import org.neo4j.driver.Logging;
import org.neo4j.driver.Query;
import org.neo4j.driver.TransactionConfig;
import org.neo4j.driver.async.ResultCursor;
import org.neo4j.driver.exceptions.ClientException;
import org.neo4j.driver.exceptions.TransactionNestingException;
import org.neo4j.driver.internal.BookmarkHolder;
import org.neo4j.driver.internal.DatabaseName;
import org.neo4j.driver.internal.FailableCursor;
import org.neo4j.driver.internal.ImpersonationUtil;
import org.neo4j.driver.internal.cursor.AsyncResultCursor;
import org.neo4j.driver.internal.cursor.ResultCursorFactory;
import org.neo4j.driver.internal.cursor.RxResultCursor;
import org.neo4j.driver.internal.logging.PrefixedLogger;
import org.neo4j.driver.internal.retry.RetryLogic;
import org.neo4j.driver.internal.spi.Connection;
import org.neo4j.driver.internal.spi.ConnectionProvider;
import org.neo4j.driver.internal.util.Futures;
public class NetworkSession {
private final ConnectionProvider connectionProvider;
private final NetworkSessionConnectionContext connectionContext;
private final AccessMode mode;
private final RetryLogic retryLogic;
private final Logging logging;
protected final Logger log;
private final BookmarkHolder bookmarkHolder;
private final long fetchSize;
private volatile CompletionStage transactionStage = completedWithNull();
private volatile CompletionStage connectionStage = completedWithNull();
private volatile CompletionStage resultCursorStage = completedWithNull();
private final AtomicBoolean open = new AtomicBoolean(true);
public NetworkSession(
ConnectionProvider connectionProvider,
RetryLogic retryLogic,
DatabaseName databaseName,
AccessMode mode,
BookmarkHolder bookmarkHolder,
String impersonatedUser,
long fetchSize,
Logging logging) {
this.connectionProvider = connectionProvider;
this.mode = mode;
this.retryLogic = retryLogic;
this.logging = logging;
this.log = new PrefixedLogger("[" + hashCode() + "]", logging.getLog(getClass()));
this.bookmarkHolder = bookmarkHolder;
CompletableFuture databaseNameFuture = databaseName
.databaseName()
.map(ignored -> CompletableFuture.completedFuture(databaseName))
.orElse(new CompletableFuture<>());
this.connectionContext =
new NetworkSessionConnectionContext(databaseNameFuture, bookmarkHolder.getBookmark(), impersonatedUser);
this.fetchSize = fetchSize;
}
public CompletionStage runAsync(Query query, TransactionConfig config) {
CompletionStage newResultCursorStage =
buildResultCursorFactory(query, config).thenCompose(ResultCursorFactory::asyncResult);
resultCursorStage = newResultCursorStage.exceptionally(error -> null);
return newResultCursorStage
.thenCompose(AsyncResultCursor::mapSuccessfulRunCompletionAsync)
.thenApply(cursor -> cursor); // convert the return type
}
public CompletionStage runRx(Query query, TransactionConfig config) {
CompletionStage newResultCursorStage =
buildResultCursorFactory(query, config).thenCompose(ResultCursorFactory::rxResult);
resultCursorStage = newResultCursorStage.exceptionally(error -> null);
return newResultCursorStage;
}
public CompletionStage beginTransactionAsync(TransactionConfig config) {
return this.beginTransactionAsync(mode, config);
}
public CompletionStage beginTransactionAsync(AccessMode mode, TransactionConfig config) {
ensureSessionIsOpen();
// create a chain that acquires connection and starts a transaction
CompletionStage newTransactionStage = ensureNoOpenTxBeforeStartingTx()
.thenCompose(ignore -> acquireConnection(mode))
.thenApply(connection ->
ImpersonationUtil.ensureImpersonationSupport(connection, connection.impersonatedUser()))
.thenCompose(connection -> {
UnmanagedTransaction tx = new UnmanagedTransaction(connection, bookmarkHolder, fetchSize, logging);
return tx.beginAsync(bookmarkHolder.getBookmark(), config);
});
// update the reference to the only known transaction
CompletionStage currentTransactionStage = transactionStage;
transactionStage = newTransactionStage
.exceptionally(error -> null) // ignore errors from starting new transaction
.thenCompose(tx -> {
if (tx == null) {
// failed to begin new transaction, keep reference to the existing one
return currentTransactionStage;
}
// new transaction started, keep reference to it
return completedFuture(tx);
});
return newTransactionStage;
}
public CompletionStage resetAsync() {
return existingTransactionOrNull()
.thenAccept(tx -> {
if (tx != null) {
tx.markTerminated(null);
}
})
.thenCompose(ignore -> connectionStage)
.thenCompose(connection -> {
if (connection != null) {
// there exists an active connection, send a RESET message over it
return connection.reset();
}
return completedWithNull();
});
}
public RetryLogic retryLogic() {
return retryLogic;
}
public Bookmark lastBookmark() {
return bookmarkHolder.getBookmark();
}
public CompletionStage releaseConnectionAsync() {
return connectionStage.thenCompose(connection -> {
if (connection != null) {
// there exists connection, try to release it back to the pool
return connection.release();
}
// no connection so return null
return completedWithNull();
});
}
public CompletionStage connectionAsync() {
return connectionStage;
}
public boolean isOpen() {
return open.get();
}
public CompletionStage closeAsync() {
if (open.compareAndSet(true, false)) {
return resultCursorStage
.thenCompose(cursor -> {
if (cursor != null) {
// there exists a cursor with potentially unconsumed error, try to extract and propagate it
return cursor.discardAllFailureAsync();
}
// no result cursor exists so no error exists
return completedWithNull();
})
.thenCompose(cursorError -> closeTransactionAndReleaseConnection()
.thenApply(txCloseError -> {
// now we have cursor error, active transaction has been closed and connection has been
// released
// back to the pool; try to propagate cursor and transaction close errors, if any
CompletionException combinedError = Futures.combineErrors(cursorError, txCloseError);
if (combinedError != null) {
throw combinedError;
}
return null;
}));
}
return completedWithNull();
}
protected CompletionStage currentConnectionIsOpen() {
return connectionStage.handle((connection, error) -> error == null
&& // no acquisition error
connection != null
&& // some connection has actually been acquired
connection.isOpen()); // and it's still open
}
private CompletionStage buildResultCursorFactory(Query query, TransactionConfig config) {
ensureSessionIsOpen();
return ensureNoOpenTxBeforeRunningQuery()
.thenCompose(ignore -> acquireConnection(mode))
.thenApply(connection ->
ImpersonationUtil.ensureImpersonationSupport(connection, connection.impersonatedUser()))
.thenCompose(connection -> {
try {
ResultCursorFactory factory = connection
.protocol()
.runInAutoCommitTransaction(
connection, query, bookmarkHolder, config, fetchSize, logging);
return completedFuture(factory);
} catch (Throwable e) {
return Futures.failedFuture(e);
}
});
}
private CompletionStage acquireConnection(AccessMode mode) {
CompletionStage currentConnectionStage = connectionStage;
CompletionStage newConnectionStage = resultCursorStage
.thenCompose(cursor -> {
if (cursor == null) {
return completedWithNull();
}
// make sure previous result is fully consumed and connection is released back to the pool
return cursor.pullAllFailureAsync();
})
.thenCompose(error -> {
if (error == null) {
// there is no unconsumed error, so one of the following is true:
// 1) this is first time connection is acquired in this session
// 2) previous result has been successful and is fully consumed
// 3) previous result failed and error has been consumed
// return existing connection, which should've been released back to the pool by now
return currentConnectionStage.exceptionally(ignore -> null);
} else {
// there exists unconsumed error, re-throw it
throw new CompletionException(error);
}
})
.thenCompose(existingConnection -> {
if (existingConnection != null && existingConnection.isOpen()) {
// there somehow is an existing open connection, this should not happen, just a precondition
throw new IllegalStateException("Existing open connection detected");
}
return connectionProvider.acquireConnection(connectionContext.contextWithMode(mode));
});
connectionStage = newConnectionStage.exceptionally(error -> null);
return newConnectionStage;
}
private CompletionStage closeTransactionAndReleaseConnection() {
return existingTransactionOrNull()
.thenCompose(tx -> {
if (tx != null) {
// there exists an open transaction, let's close it and propagate the error, if any
return tx.closeAsync()
.thenApply(ignore -> (Throwable) null)
.exceptionally(error -> error);
}
// no open transaction so nothing to close
return completedWithNull();
})
.thenCompose(txCloseError ->
// then release the connection and propagate transaction close error, if any
releaseConnectionAsync().thenApply(ignore -> txCloseError));
}
private CompletionStage ensureNoOpenTxBeforeRunningQuery() {
return ensureNoOpenTx("Queries cannot be run directly on a session with an open transaction; "
+ "either run from within the transaction or use a different session.");
}
private CompletionStage ensureNoOpenTxBeforeStartingTx() {
return ensureNoOpenTx("You cannot begin a transaction on a session with an open transaction; "
+ "either run from within the transaction or use a different session.");
}
private CompletionStage ensureNoOpenTx(String errorMessage) {
return existingTransactionOrNull().thenAccept(tx -> {
if (tx != null) {
throw new TransactionNestingException(errorMessage);
}
});
}
private CompletionStage existingTransactionOrNull() {
return transactionStage
.exceptionally(error -> null) // handle previous connection acquisition and tx begin failures
.thenApply(tx -> tx != null && tx.isOpen() ? tx : null);
}
private void ensureSessionIsOpen() {
if (!open.get()) {
throw new ClientException(
"No more interaction with this session are allowed as the current session is already closed. ");
}
}
/**
* The {@link NetworkSessionConnectionContext#mode} can be mutable for a session connection context
*/
private static class NetworkSessionConnectionContext implements ConnectionContext {
private final CompletableFuture databaseNameFuture;
private AccessMode mode;
// This bookmark is only used for rediscovery.
// It has to be the initial bookmark given at the creation of the session.
// As only that bookmark could carry extra system bookmarks
private final Bookmark rediscoveryBookmark;
private final String impersonatedUser;
private NetworkSessionConnectionContext(
CompletableFuture databaseNameFuture, Bookmark bookmark, String impersonatedUser) {
this.databaseNameFuture = databaseNameFuture;
this.rediscoveryBookmark = bookmark;
this.impersonatedUser = impersonatedUser;
}
private ConnectionContext contextWithMode(AccessMode mode) {
this.mode = mode;
return this;
}
@Override
public CompletableFuture databaseNameFuture() {
return databaseNameFuture;
}
@Override
public AccessMode mode() {
return mode;
}
@Override
public Bookmark rediscoveryBookmark() {
return rediscoveryBookmark;
}
@Override
public String impersonatedUser() {
return impersonatedUser;
}
}
}
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