s1monw commented on a change in pull request #637: LUCENE-8754: Prevent
ConcurrentModificationException in SegmentInfo
URL: https://github.com/apache/lucene-solr/pull/637#discussion_r272983458
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File path: lucene/core/src/java/org/apache/lucene/index/SegmentInfo.java
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@@ -326,7 +327,16 @@ public String getAttribute(String key) {
* value.
*/
public String putAttribute(String key, String value) {
- return attributes.put(key, value);
+ HashMap<String, String> newMap = new HashMap<>(attributes);
+ String oldValue = newMap.put(key, value);
+ // we make a full copy of this to prevent concurrent modifications to this
in the toString method
+ // this method is only called when a segment is written but the
SegmentInfo might be exposed
+ // in running merges which can cause ConcurrentModificationExceptions if
we modify / share
+ // the same instance. Technically that's an unsafe publication but IW
design would require
+ // significant changes to prevent this. On the other hand, since we expose
the map in getAttributes()
+ // it's a good design to make it unmodifiable anyway.
+ attributes = Collections.unmodifiableMap(new
HashMap<>(Objects.requireNonNull(newMap)));
Review comment:
sure
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