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Replace per-operation backend read lock with a scalable shared-access gate #680

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Replace per-operation backend read lock with a scalable shared-access gate #680

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1bf1eb5
Replace per-operation backend read lock with a scalable shared-access…
vharseko Jul 3, 2026
b0a4eb5
Convert the remaining hasSubordinates shared-lock site to the access …
vharseko Jul 3, 2026
e540fb6
Keep draining shared accesses when the exclusive locker is interrupted
vharseko Jul 4, 2026
a9f7ecc
Make the shared-access gate drain provably exact via a same-slot stri…
vharseko Jul 4, 2026
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62 changes: 33 additions & 29 deletions opendj-server-legacy/src/main/java/org/opends/server/backends/pluggable/BackendImpl.java
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
*
* Copyright 2007-2010 Sun Microsystems, Inc.
* Portions Copyright 2013-2016 ForgeRock AS.
* Portions Copyright 2025 3A Systems, LLC
* Portions Copyright 2025-2026 3A Systems, LLC
*/
package org.opends.server.backends.pluggable;

Expand All @@ -29,7 +29,7 @@
import java.util.Set;
import java.util.SortedSet;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.LongAdder;

import org.forgerock.i18n.LocalizableException;
import org.forgerock.i18n.LocalizableMessage;
Expand Down Expand Up @@ -93,9 +93,13 @@ public abstract class BackendImpl<C extends PluggableBackendCfg> extends LocalBa
/** The root container to use for this backend. */
private RootContainer rootContainer;

// FIXME: this is broken. Replace with read-write lock.
/** A count of the total operation threads currently in the backend. */
private final AtomicInteger threadTotalCount = new AtomicInteger(0);
/**
* A count of the total operation threads currently in the backend. Bumped
* twice per operation by all worker threads, so it uses LongAdder to avoid
* contending on a single cache line; it is only read when waiting for the
* backend to become quiescent.
*/
private final LongAdder threadTotalCount = new LongAdder();
/** The base DNs defined for this backend instance. */
private Set<DN> baseDNs;

Expand Down Expand Up @@ -130,14 +134,14 @@ private EntryContainer accessBegin(Operation operation, DN entryDN) throws Direc
{
throw new DirectoryException(ResultCode.UNDEFINED, ERR_BACKEND_ENTRY_DOESNT_EXIST.get(entryDN, getBackendID()));
}
threadTotalCount.getAndIncrement();
threadTotalCount.increment();
return ec;
}

/** End a Backend API method that accesses the EntryContainer. */
private void accessEnd()
{
threadTotalCount.getAndDecrement();
threadTotalCount.decrement();
}

/**
Expand All @@ -147,7 +151,7 @@ private void accessEnd()
*/
private void waitUntilQuiescent()
{
while (threadTotalCount.get() > 0)
while (threadTotalCount.sum() > 0)
{
// Still have threads accessing the storage so sleep a little
try
Expand Down Expand Up @@ -252,7 +256,7 @@ public void closeBackend()
}

// Make sure the thread counts are zero for next initialization.
threadTotalCount.set(0);
threadTotalCount.reset();

// Log an informational message.
logger.info(NOTE_BACKEND_OFFLINE, cfg.getBackendId());
Expand Down Expand Up @@ -340,7 +344,7 @@ public ConditionResult hasSubordinates(DN entryDN) throws DirectoryException
throw de;
}

container.sharedLock.lock();
container.beginSharedAccess();
try
{
return ConditionResult.valueOf(container.hasSubordinates(entryDN));
Expand All @@ -351,7 +355,7 @@ public ConditionResult hasSubordinates(DN entryDN) throws DirectoryException
}
finally
{
container.sharedLock.unlock();
container.endSharedAccess();
accessEnd();
}
}
Expand All @@ -362,7 +366,7 @@ public long getNumberOfEntriesInBaseDN(DN baseDN) throws DirectoryException
checkNotNull(baseDN, "baseDN must not be null");

final EntryContainer ec = accessBegin(null, baseDN);
ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
return ec.getNumberOfEntriesInBaseDN();
Expand All @@ -374,7 +378,7 @@ public long getNumberOfEntriesInBaseDN(DN baseDN) throws DirectoryException
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -401,7 +405,7 @@ public long getNumberOfChildren(DN parentDN) throws DirectoryException
throw de;
}

ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
return ec.getNumberOfChildren(parentDN);
Expand All @@ -412,7 +416,7 @@ public long getNumberOfChildren(DN parentDN) throws DirectoryException
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -421,7 +425,7 @@ public long getNumberOfChildren(DN parentDN) throws DirectoryException
public boolean entryExists(final DN entryDN) throws DirectoryException
{
EntryContainer ec = accessBegin(null, entryDN);
ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
return ec.entryExists(entryDN);
Expand All @@ -432,7 +436,7 @@ public boolean entryExists(final DN entryDN) throws DirectoryException
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -441,7 +445,7 @@ public boolean entryExists(final DN entryDN) throws DirectoryException
public Entry getEntry(DN entryDN) throws DirectoryException
{
EntryContainer ec = accessBegin(null, entryDN);
ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
return ec.getEntry(entryDN);
Expand All @@ -452,7 +456,7 @@ public Entry getEntry(DN entryDN) throws DirectoryException
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -462,7 +466,7 @@ public void addEntry(Entry entry, AddOperation addOperation) throws DirectoryExc
{
EntryContainer ec = accessBegin(addOperation, entry.getName());

ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
ec.addEntry(entry, addOperation);
Expand All @@ -473,7 +477,7 @@ public void addEntry(Entry entry, AddOperation addOperation) throws DirectoryExc
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -484,7 +488,7 @@ public void deleteEntry(DN entryDN, DeleteOperation deleteOperation)
{
EntryContainer ec = accessBegin(deleteOperation, entryDN);

ec.sharedLock.lock();
ec.beginSharedAccess();
try
{
ec.deleteEntry(entryDN, deleteOperation);
Expand All @@ -495,7 +499,7 @@ public void deleteEntry(DN entryDN, DeleteOperation deleteOperation)
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -506,7 +510,7 @@ public void replaceEntry(Entry oldEntry, Entry newEntry, ModifyOperation modifyO
{
EntryContainer ec = accessBegin(modifyOperation, newEntry.getName());

ec.sharedLock.lock();
ec.beginSharedAccess();

try
{
Expand All @@ -518,7 +522,7 @@ public void replaceEntry(Entry oldEntry, Entry newEntry, ModifyOperation modifyO
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand All @@ -538,7 +542,7 @@ public void renameEntry(DN currentDN, Entry entry, ModifyDNOperation modifyDNOpe
throw new DirectoryException(ResultCode.UNWILLING_TO_PERFORM, WARN_FUNCTION_NOT_SUPPORTED.get());
}

currentContainer.sharedLock.lock();
currentContainer.beginSharedAccess();
try
{
currentContainer.renameEntry(currentDN, entry, modifyDNOperation);
Expand All @@ -549,7 +553,7 @@ public void renameEntry(DN currentDN, Entry entry, ModifyDNOperation modifyDNOpe
}
finally
{
currentContainer.sharedLock.unlock();
currentContainer.endSharedAccess();
accessEnd();
}
}
Expand All @@ -559,7 +563,7 @@ public void search(SearchOperation searchOperation) throws DirectoryException, C
{
EntryContainer ec = accessBegin(searchOperation, searchOperation.getBaseDN());

ec.sharedLock.lock();
ec.beginSharedAccess();

try
{
Expand All @@ -571,7 +575,7 @@ public void search(SearchOperation searchOperation) throws DirectoryException, C
}
finally
{
ec.sharedLock.unlock();
ec.endSharedAccess();
accessEnd();
}
}
Expand Down
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