guluo2016 commented on code in PR #6439:
URL: https://github.com/apache/hbase/pull/6439#discussion_r1828601652
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hbase-server/src/main/java/org/apache/hadoop/hbase/mob/RSMobFileCleanerChore.java:
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@@ -116,14 +120,32 @@ protected void chore() {
Set<String> regionMobs = new HashSet<String>();
Path currentPath = null;
try {
- // collectinng referenced MOBs
+ // collecting referenced MOBs
for (HStoreFile sf : sfs) {
currentPath = sf.getPath();
- sf.initReader();
- byte[] mobRefData =
sf.getMetadataValue(HStoreFile.MOB_FILE_REFS);
- byte[] bulkloadMarkerData =
sf.getMetadataValue(HStoreFile.BULKLOAD_TASK_KEY);
- // close store file to avoid memory leaks
- sf.closeStoreFile(true);
+ byte[] mobRefData = null;
+ byte[] bulkloadMarkerData = null;
+ boolean needCreateReader = false;
+ if (sf.getReader() == null) {
+ synchronized (sf) {
+ if (sf.getReader() == null) {
+ needCreateReader = true;
+ sf.initReader();
+ mobRefData =
sf.getMetadataValue(HStoreFile.MOB_FILE_REFS);
+ bulkloadMarkerData =
sf.getMetadataValue(HStoreFile.BULKLOAD_TASK_KEY);
+ // close store file to avoid memory leaks
+ sf.closeStoreFile(true);
+ }
+ }
+ }
+ // If the StoreFileReader object was created by another
thread, even if the reader
+ // has been closed now, we can still obtain the data by
HStoreFile.metataMap,
+ // because the map will not be cleared when the reader is
closed.
+ if (!needCreateReader) {
+ mobRefData = sf.getMetadataValue(HStoreFile.MOB_FILE_REFS);
+ bulkloadMarkerData =
sf.getMetadataValue(HStoreFile.BULKLOAD_TASK_KEY);
+ }
Review Comment:
Thanks for your review.
I think this way may still have the same problem.
Assume that there are two threads holding the same StoreFile object.
Let's take a look at this situation:
```java
// Time1 RSMobFileCleanerChore (Thread A) executing this code, and reader is
null
// now needCreateReader is true
boolean needCreateReader = sf.getReader() == null;
// Time2 another thread (Thread B) create the reader object
// Time3 Thread A continue to execute the code
// now reader has been created by Thread B,
// so RSMobFileCleanerChore will not create the reader object
sf.initReader();
byte[] mobRefData = sf.getMetadataValue(HStoreFile.MOB_FILE_REFS);
byte[] bulkloadMarkerData =
sf.getMetadataValue(HStoreFile.BULKLOAD_TASK_KEY);
// Time4 RSMobFileCleanerChore continue to execute the code
// because needCreateReader is true, so it will close the reader which isn't
created by itself
if(needCreateReader) {
sf.closeStoreFile(true);
}
```
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