SequenceIdentityManager.java
/*
** Module : SequenceIdentityManager.java
** Abstract : Identity manager implementation which uses a global sequence to generate new IDs
**
** Copyright (c) 2004-2024, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- --------------------------Description-------------------------------
** 001 ECF 20080805 @39306 Created initial version. Implementation of
** IdentityManager interface which retrieves new
** IDs from a global sequence.
** 002 CA 20080815 @39446 Support API change in DBUtils.
** 003 SVL 20080901 @39647 Added primary key reclamation. Implements
** IdentityPoolManager instead of IdentityManager.
** 004 ECF 20090107 @41011 Fixed server shutdown. Timer needed to be a
** daemon, it was holding up a clean shutdown of
** the server.
** 005 ECF 20090527 @42474 Fixed Context.getStatement(). It was possible to
** return a closed statement.
** 006 SVL 20090720 @43238 ProtectedTimer is used instead of Timer.
** 007 SVL 20090930 @44056 If any error has raised into
** IdentityPool.nextPrimaryKey() then stop the
** identity pool and use only sequence method for ID
** generation.
** 008 SVL 20130331 Upgraded to Hibernate 4.
** 009 ECF 20130510 Fixed sequence access.
** 010 ECF 20141222 Lazily initialize SessionFactory to avoid NPE for certain dialects.
** Replaced Apache commons logging with J2SE logging.
** 011 OM 20151208 Optimized string operations. Fixed typos in javadoc.
** 012 ECF 20160824 Greatly simplified sequence access. Do not start identity pool key
** scanning if it is configured as disabled.
** 013 ECF 20160907 Implemented key prefetch algorithm, which caches ascending keys
** prefetched from the id generator sequence, to avoid the overhead of
** a database round trip for every new key.
** 014 ECF 20200419 Removed Hibernate dependencies.
** 015 GBB 20230512 Logging methods replaced by CentralLogger/ConversionStatus.
** 016 OM 20241128 Multi-tenant runtime support: selected the proper persistence context, eventually
** based on [sharedDb] parameter.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
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** 1. No License To Use Trademarks.
**
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*/
package com.goldencode.p2j.persist.id;
import java.math.*;
import java.util.*;
import java.util.logging.*;
import com.goldencode.p2j.persist.*;
import com.goldencode.p2j.persist.dialect.*;
import com.goldencode.p2j.persist.orm.*;
import com.goldencode.p2j.util.logging.*;
/**
* Implementation of the {@link IdentityManager} interface which uses a sequence (global to a
* specific database) to produce 64-bit integer IDs which are unique across all records in that
* database.
* <p>
* Current limitations:
* <ul>
* <li>Wrapping to a negative number after we increment beyond {@code Long.MAX_VALUE} is not
* handled at this time.
* <li>Does not detect/repair fragmentation of the primary key address space for a table;
* existing gaps in primary keys are never plugged. Note that a solution for this item may
* preclude having to address the previous item.
* </ul>
*/
public final class SequenceIdentityManager
implements IdentityPoolManager
{
/** Logger */
private static final CentralLogger LOG = CentralLogger.get(IdentityManager.class.getName());
/** Range arguments passed to prefetch SQL statement */ // TODO: make configurable
private static final Integer[] PREFETCH_ARGS = new Integer[] { 1, 1000 };
/** Queue of prefetched results */
private Queue<Long> prefetched = null;
/** Identity pool used by this identity manager. */
private IdentityPool identityPool = null;
/** Persistence service object associated with this identity manager */
private Persistence persistence = null;
/** SQL statement used to prefetch multiple sequence values at once */
private String prefetchKeySQL = null;
/** SQL statement used to get next sequence value */
private String nextKeySQL = null;
/**
* Default constructor.
*/
public SequenceIdentityManager()
{
}
/**
* Specify the database for the identity manager.
* <code>DefaultIdentityManager</code> is initialized here - current
* maximum IDs for each table are retrieved.
*
* @param persistence
* Persistence service object associated with identity manager.
*/
public void setPersistence(Persistence persistence)
{
this.persistence = persistence;
Dialect dialect = persistence.getDialect();
prefetchKeySQL = dialect.getSequencePrefetchString(Persistence.ID_GEN_SEQUENCE);
// initialize prefetch queue if feature is supported by dialect
if (prefetchKeySQL != null)
{
prefetched = new LinkedList<>();
}
else
{
nextKeySQL = dialect.getSequenceNextValString(Persistence.ID_GEN_SEQUENCE);
}
}
/**
* Return the next primary key for the specified table. The pool of
* reclaimed IDs is checked first. If no reclaimed ID is available, a new
* ID is generated from the sequence.
*
* @param table
* Table for which the next primary key will be returned.
*
* @return The next primary key for the given table.
*
* @throws PersistenceException
* if there is an error determining the next primary key ID.
*/
public Long nextPrimaryKey(String table)
throws PersistenceException
{
// try to get the key from identity pool first
if (identityPool != null)
{
try
{
Long key = identityPool.nextPrimaryKey();
if (key != null)
{
return key;
}
}
catch (Throwable thr)
{
if (LOG.isLoggable(Level.SEVERE))
{
LOG.log(Level.SEVERE, "Identity pool has been stopped because of an error.", thr);
}
identityPool.stop();
identityPool = null;
}
}
// try to get key from queue of prefetched keys, filling queue if necessary
if (prefetched != null)
{
Long key = null;
synchronized (prefetched)
{
if (!prefetched.isEmpty())
{
key = prefetched.remove();
}
else
{
boolean tx = persistence.beginTransaction(Persistence.SHARED_CTX);
ScrollableResults<BigInteger> results = null;
try
{
// all tables from same logical database use the same id sequence from the shared
// physical database
results = persistence.executeSQLQuery(prefetchKeySQL, Persistence.SHARED_CTX, PREFETCH_ARGS);
if (results.next())
{
// first result will be returned
key = results.get(0, BigInteger.class).longValue();
}
while (results.next())
{
// remaining results are cached in the queue for future requests
prefetched.add(results.get(0, BigInteger.class).longValue());
}
}
finally
{
if (results != null)
{
try
{
results.close();
}
catch (PersistenceException exc)
{
if (LOG.isLoggable(Level.WARNING))
{
LOG.log(Level.WARNING,
"Error closing results [ " + prefetchKeySQL + " ]",
exc);
}
}
}
if (tx)
{
persistence.commit(Persistence.SHARED_CTX);
}
}
}
}
return key;
}
return persistence.getSingleSQLResult(nextKeySQL, Persistence.SHARED_CTX, null);
}
/**
* Inform the identity manager that the given primary keys can be reused.
*
* @param keys
* Keys for reuse.
*/
public void reclaimKeys(Long[] keys)
{
if (identityPool != null)
{
identityPool.reclaimKeys(keys);
}
}
/**
* Sets identity pool which can be used by this identity manager.
*
* @param identityPool
* Identity pool for use.
*/
public void setIdentityPool(IdentityPool identityPool)
{
if (identityPool == null)
{
return;
}
this.identityPool = identityPool;
if (!identityPool.isKeyScanningEnabled())
{
return;
}
try
{
Long sequenceValue = persistence.getSingleSQLResult(nextKeySQL, Persistence.SHARED_CTX, null);
// Set the next sequence value as a start key for the
// identity pool and add "wasted" sequence value to the pool.
identityPool.setScanStartKey(sequenceValue - 1);
identityPool.reclaimKeys(new Long[] {sequenceValue});
}
catch (PersistenceException exc)
{
if (LOG.isLoggable(Level.SEVERE))
{
LOG.log(Level.SEVERE,
"Cannot get the current sequence value. Identity pool cannot be started.",
exc);
}
}
}
}