[PATCH] TermInfosReader, SegmentTermEnum Out Of Memory Exception
----------------------------------------------------------------
Key: LUCENE-436
URL: http://issues.apache.org/jira/browse/LUCENE-436
Project: Lucene - Java
Issue Type: Improvement
Components: Index
Affects Versions: 1.4
Environment: Solaris JVM 1.4.1
Linux JVM 1.4.2/1.5.0
Windows not tested
Reporter: kieran
Attachments: FixedThreadLocal.java, lucene-1.9.1.patch,
Lucene-436-TestCase.tar.gz, TermInfosReader.java,
ThreadLocalTest.java
We've been experiencing terrible memory problems on our production
search server, running lucene (1.4.3).
Our live app regularly opens new indexes and, in doing so,
releases old IndexReaders for garbage collection.
But...there appears to be a memory leak in
org.apache.lucene.index.TermInfosReader.java.
Under certain conditions (possibly related to JVM version,
although I've personally observed it under both linux JVM
1.4.2_06, and 1.5.0_03, and SUNOS JVM 1.4.1) the ThreadLocal
member variable, "enumerators" doesn't get garbage-collected when
the TermInfosReader object is gc-ed.
Looking at the code in TermInfosReader.java, there's no reason why
it _shouldn't_ be gc-ed, so I can only presume (and I've seen this
suggested elsewhere) that there could be a bug in the garbage
collector of some JVMs.
I've seen this problem briefly discussed; in particular at the
following URL:
http://java2.5341.com/msg/85821.html
The patch that Doug recommended, which is included in lucene-1.4.3
doesn't work in our particular circumstances. Doug's patch only
clears the ThreadLocal variable for the thread running the
finalizer (my knowledge of java breaks down here - I'm not sure
which thread actually runs the finalizer). In our situation, the
TermInfosReader is (potentially) used by more than one thread,
meaning that Doug's patch _doesn't_ allow the affected JVMs to
correctly collect garbage.
So...I've devised a simple patch which, from my observations on
linux JVMs 1.4.2_06, and 1.5.0_03, fixes this problem.
Kieran
PS Thanks to daniel naber for pointing me to jira/lucene
@@ -19,6 +19,7 @@
import java.io.IOException;
import org.apache.lucene.store.Directory;
+import java.util.Hashtable;
/** This stores a monotonically increasing set of <Term,
TermInfo> pairs in a
* Directory. Pairs are accessed either by Term or by ordinal
position the
@@ -29,7 +30,7 @@
private String segment;
private FieldInfos fieldInfos;
- private ThreadLocal enumerators = new ThreadLocal();
+ private final Hashtable enumeratorsByThread = new Hashtable();
private SegmentTermEnum origEnum;
private long size;
@@ -60,10 +61,10 @@
}
private SegmentTermEnum getEnum() {
- SegmentTermEnum termEnum = (SegmentTermEnum)enumerators.get();
+ SegmentTermEnum termEnum = (SegmentTermEnum)
enumeratorsByThread.get(Thread.currentThread());
if (termEnum == null) {
termEnum = terms();
- enumerators.set(termEnum);
+ enumeratorsByThread.put(Thread.currentThread(), termEnum);
}
return termEnum;
}
@@ -195,5 +196,15 @@
public SegmentTermEnum terms(Term term) throws IOException {
get(term);
return (SegmentTermEnum)getEnum().clone();
+ }
+
+ /* some jvms might have trouble gc-ing enumeratorsByThread */
+ protected void finalize() throws Throwable {
+ try {
+ // make sure gc can clear up.
+ enumeratorsByThread.clear();
+ } finally {
+ super.finalize();
+ }
}
}
TermInfosReader.java, full source:
======================================
package org.apache.lucene.index;
/**
* Copyright 2004 The Apache Software Foundation
*
* 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.
*/
import java.io.IOException;
import org.apache.lucene.store.Directory;
import java.util.Hashtable;
/** This stores a monotonically increasing set of <Term, TermInfo>
pairs in a
* Directory. Pairs are accessed either by Term or by ordinal
position the
* set. */
final class TermInfosReader {
private Directory directory;
private String segment;
private FieldInfos fieldInfos;
private final Hashtable enumeratorsByThread = new Hashtable();
private SegmentTermEnum origEnum;
private long size;
TermInfosReader(Directory dir, String seg, FieldInfos fis)
throws IOException {
directory = dir;
segment = seg;
fieldInfos = fis;
origEnum = new SegmentTermEnum(directory.openFile(segment +
".tis"),
fieldInfos, false);
size = origEnum.size;
readIndex();
}
public int getSkipInterval() {
return origEnum.skipInterval;
}
final void close() throws IOException {
if (origEnum != null)
origEnum.close();
}
/** Returns the number of term/value pairs in the set. */
final long size() {
return size;
}
private SegmentTermEnum getEnum() {
SegmentTermEnum termEnum = (SegmentTermEnum)
enumeratorsByThread.get(Thread.currentThread());
if (termEnum == null) {
termEnum = terms();
enumeratorsByThread.put(Thread.currentThread(), termEnum);
}
return termEnum;
}
Term[] indexTerms = null;
TermInfo[] indexInfos;
long[] indexPointers;
private final void readIndex() throws IOException {
SegmentTermEnum indexEnum =
new SegmentTermEnum(directory.openFile(segment + ".tii"),
fieldInfos, true);
try {
int indexSize = (int)indexEnum.size;
indexTerms = new Term[indexSize];
indexInfos = new TermInfo[indexSize];
indexPointers = new long[indexSize];
for (int i = 0; indexEnum.next(); i++) {
indexTerms[i] = indexEnum.term();
indexInfos[i] = indexEnum.termInfo();
indexPointers[i] = indexEnum.indexPointer;
}
} finally {
indexEnum.close();
}
}
/** Returns the offset of the greatest index entry which is less
than or equal to term.*/
private final int getIndexOffset(Term term) throws IOException {
int lo = 0; // binary search indexTerms[]
int hi = indexTerms.length - 1;
while (hi >= lo) {
int mid = (lo + hi) >> 1;
int delta = term.compareTo(indexTerms[mid]);
if (delta < 0)
hi = mid - 1;
else if (delta > 0)
lo = mid + 1;
else
return mid;
}
return hi;
}
private final void seekEnum(int indexOffset) throws IOException {
getEnum().seek(indexPointers[indexOffset],
(indexOffset * getEnum().indexInterval) - 1,
indexTerms[indexOffset], indexInfos[indexOffset]);
}
/** Returns the TermInfo for a Term in the set, or null. */
TermInfo get(Term term) throws IOException {
if (size == 0) return null;
// optimize sequential access: first try scanning cached enum
w/o seeking
SegmentTermEnum enumerator = getEnum();
if (enumerator.term() != null // term is at or
past current
&& ((enumerator.prev != null && term.compareTo(enumerator.prev) > 0)
|| term.compareTo(enumerator.term()) >= 0)) {
int enumOffset = (int)(enumerator.position/
enumerator.indexInterval)+1;
if (indexTerms.length == enumOffset // but before end of
block
|| term.compareTo(indexTerms[enumOffset]) < 0)
return scanEnum(term); // no need to seek
}
// random-access: must seek
seekEnum(getIndexOffset(term));
return scanEnum(term);
}
/** Scans within block for matching term. */
private final TermInfo scanEnum(Term term) throws IOException {
SegmentTermEnum enumerator = getEnum();
while (term.compareTo(enumerator.term()) > 0 && enumerator.next
()) {}
if (enumerator.term() != null && term.compareTo(enumerator.term
()) == 0)
return enumerator.termInfo();
else
return null;
}
/** Returns the nth term in the set. */
final Term get(int position) throws IOException {
if (size == 0) return null;
SegmentTermEnum enumerator = getEnum();
if (enumerator != null && enumerator.term() != null &&
position >= enumerator.position &&
position < (enumerator.position + enumerator.indexInterval))
return scanEnum(position); // can avoid seek
seekEnum(position / enumerator.indexInterval); // must seek
return scanEnum(position);
}
private final Term scanEnum(int position) throws IOException {
SegmentTermEnum enumerator = getEnum();
while(enumerator.position < position)
if (!enumerator.next())
return null;
return enumerator.term();
}
/** Returns the position of a Term in the set or -1. */
final long getPosition(Term term) throws IOException {
if (size == 0) return -1;
int indexOffset = getIndexOffset(term);
seekEnum(indexOffset);
SegmentTermEnum enumerator = getEnum();
while(term.compareTo(enumerator.term()) > 0 && enumerator.next
()) {}
if (term.compareTo(enumerator.term()) == 0)
return enumerator.position;
else
return -1;
}
/** Returns an enumeration of all the Terms and TermInfos in the
set. */
public SegmentTermEnum terms() {
return (SegmentTermEnum)origEnum.clone();
}
/** Returns an enumeration of terms starting at or after the
named term. */
public SegmentTermEnum terms(Term term) throws IOException {
get(term);
return (SegmentTermEnum)getEnum().clone();
}
/* some jvms might have trouble gc-ing enumeratorsByThread */
protected void finalize() throws Throwable {
try {
// make sure gc can clear up.
enumeratorsByThread.clear();
} finally {
super.finalize();
}
}
}
