StaleProcedureManager.java
/*
** Module : StaleProcedureManager.java
** Abstract : Manager which should handle the work with stale persistent procedures.
**
** Copyright (c) 2020-2023, Golden Code Development Corporation.
**
** -#- -I- --Date-- --------------------------------------Description-----------------------------------------
** 001 AIL 20200622 Created initial version.
** 20200623 Made all methods static and now using the local context.
** CA 20201015 Replaced java.util.Stack with a non-synchronized custom implementation.
** 002 CA 20230713 Small optimization, use TM.getBlock() which returns the top of the stack, instead of
** TM.getBlock(0).
** 003 AL2 20240322 Moved away from Stack.iterator as it doesn't return the global scope.
*/
/*
** 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
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** Affero GPL version 3 and may not be removed by you.
**
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*/
package com.goldencode.p2j.util;
import com.goldencode.util.Stack;
import com.goldencode.p2j.security.*;
/**
* Enclosing several methods for working with stale referents.
*/
public class StaleProcedureManager
{
/** The stale procedure managers are private per each context. */
private static final ContextLocal<WorkArea> work = new ContextLocal<WorkArea>()
{
protected WorkArea initialValue()
{
return new WorkArea();
};
};
/**
* Used for marking the fact that a referent is in a stale state. It means that the referent was
* deleted, but is still able to be deleted again.
*
* @param referent
* The persistent procedure which needs to be marked as stale.
*
* @return {@code true} if the marking was done for the first time.
*/
public static boolean addStaleReferent(Object referent)
{
WorkArea wa = work.get();
boolean result = wa.pm.addStaleReferent(referent);
invalidateResource(wa, referent);
return result;
}
/**
* Invalidates the resource in terms of stale attributes. If the referent is neither active or stale,
* this method should fail. Otherwise try to delete the referent right now or postpone it to a
* suitable block.
*
* @param referent
* The persistent procedure which should be invalidated.
*
* @return <code>true</code> if the referent was invalidated, <code>false</code> if the referent was
* already deleted.
*/
public static boolean invalidateResource(Object referent)
{
return invalidateResource(null, referent);
}
/**
* Invalidates the resource in terms of stale attributes. If the referent is neither active or stale,
* this method should fail. Otherwise try to delete the referent right now or postpone it to a
* suitable block.
*
* @param wa
* The {@link WorkArea} instance. If {@code null}, a context lookup will be triggered.
* @param referent
* The persistent procedure which should be invalidated.
*
* @return <code>true</code> if the referent was invalidated, <code>false</code> if the referent was
* already deleted.
*/
public static boolean invalidateResource(WorkArea wa, Object referent)
{
if (wa == null)
{
wa = work.get();
}
if (!wa.pm.hasReferent(referent) &&
!wa.pm.hasStaleReferent(referent))
{
return false;
}
int handlingBlock = getHandlingBlock(wa, referent);
if (canDeleteNow(wa, referent, handlingBlock))
{
notifyResourceDelete(wa, referent);
}
else
{
DeferredDeletablesManager.registerAt(handlingBlock, new ExternalProgramWrapper(referent));
}
return true;
}
/**
* This should be called when a persistent procedure is deleted. This clears the contents
* stored for this specific procedure.
*
* @param referent
* The wrapper which contains the referent for which the clear should be done.
*/
public static void notifyResourceDelete(Object referent)
{
notifyResourceDelete(null, referent);
}
/**
* This should be called when a persistent procedure is deleted. This clears the contents
* stored for this specific procedure.
*
* @param wa
* The {@link WorkArea} instance. If {@code null}, a context lookup will be triggered.
* @param referent
* The wrapper which contains the referent for which the clear should be done.
*/
public static void notifyResourceDelete(WorkArea wa, Object referent)
{
if (wa == null)
{
wa = work.get();
}
wa.pm.removeStaleProcedure(referent);
}
/**
* Core method for obtaining the index of the block which is responsible with the deletion of the
* resource. This method is context dependent, thus this should be called exactly when the delete
* procedure statement is used in order to accurately detect the responsible block. This also can
* return the index of the current block if the deletion is not meant to be delayed.
*
* This is the strategy which was used in order to get the responsible block. Consider the afferent
* {@code persistentProcstack} of one procedure (the stack snapshot of the moment when the first
* global static buffer was used) and the current block stack. The handling block here is considered
* to be the first block which does not appear in both stacks. This means that when the common block
* is reached, the referent shouldn't be stale - but deleted altogether.
*
* @param wa
* The {@link WorkArea} instance. If {@code null}, a context lookup will be triggered.
* @param referent
* The resource which is used in order to detect if the deletion of it should be delayed
* or not.
*
* @return The index of the block which is responsible for deleting the resource. 0 represents
* the global scope.
*/
private static int getHandlingBlock(WorkArea wa, Object referent)
{
if (wa == null)
{
wa = work.get();
}
Stack<BlockDefinition> currentStack = wa.tm.copyStack();
Stack<BlockDefinition> persistentProcStack = wa.pm.getPersistentProcStack(referent);
if (persistentProcStack == null)
{
return currentStack.size();
}
int currentStackSize = currentStack.size();
int persistentProcStackSize = persistentProcStack.size();
for (int idx = 0; idx < currentStackSize && idx < persistentProcStackSize; idx++)
{
BlockDefinition currentBlock = currentStack.elementAt(idx);
BlockDefinition persistentProcBlock = persistentProcStack.elementAt(idx);
if (currentBlock != persistentProcBlock)
{
return idx;
}
}
if (currentStackSize <= persistentProcStackSize)
{
return currentStackSize - 1;
}
return persistentProcStackSize;
}
/**
* Check if the referent of the ExternalProcedureWrapper can be deleted now or it should be
* delayed.
*
* @param wa
* The {@link WorkArea} instance. If {@code null}, a context lookup will be triggered.
* @param referent
* The referent container which should be checked in order to detect if it need invalidation.
* @param handlingBlock
* The value of the block which is responsible for deleting this procedure. If {@code null},
* the value will be computed using the {@code getHandlingBlock}.
*
* @return <code>true</code> if the referent can be deleted now or <code>false</code> if the deletion
* should be postponed
*/
private static boolean canDeleteNow(WorkArea wa, Object referent, Integer handlingBlock)
{
if (wa == null)
{
wa = work.get();
}
Stack<BlockDefinition> persistentProcStack = wa.pm.getPersistentProcStack(referent);
if (persistentProcStack == null)
{
return true;
}
if (handlingBlock == null)
{
handlingBlock = getHandlingBlock(wa, referent);
}
return handlingBlock == wa.tm.getNestingLevel() - 1 &&
persistentProcStack.contains(wa.tm.getBlock());
}
/**
* Stores global data relating to the state of the current context.
*/
private static class WorkArea
implements Initializable
{
/** Helper to use the TM without any context local lookups. */
private TransactionManager.TransactionHelper tm = null;
/** Helper to use the ProcedureManager without any context local lookups. */
private ProcedureManager.ProcedureHelper pm = null;
/**
* Initialize the required managers.
*/
@Override
public void init()
{
tm = TransactionManager.getTransactionHelper();
pm = ProcedureManager.getProcedureHelper();
}
}
}