Bug: HStore should try write WAL compaction marker before replacing compacted files in StoreEngine
Status: Resolved | Priority: Major | Resolution: Fixed
Created: 05/May/22 10:41
Affects Version/s: 2.5.0

On HBASE-26064, it seems we altered the order we update different places with the results of a compaction:
{noformat}
@@ -1510,14 +1149,13 @@ public class HStore implements Store, HeapSize, StoreConfigInformation,
       List<Path> newFiles) throws IOException {
     // Do the steps necessary to complete the compaction.
     setStoragePolicyFromFileName(newFiles);
-    List<HStoreFile> sfs = commitStoreFiles(newFiles, true);
+    List<HStoreFile> sfs = storeEngine.commitStoreFiles(newFiles, true);
     if (this.getCoprocessorHost() != null) {
       for (HStoreFile sf : sfs) {
         getCoprocessorHost().postCompact(this, sf, cr.getTracker(), cr, user);
       }
     }
-    writeCompactionWalRecord(filesToCompact, sfs);
-    replaceStoreFiles(filesToCompact, sfs);
+    replaceStoreFiles(filesToCompact, sfs, true);
...
@@ -1581,25 +1219,24 @@ public class HStore implements Store, HeapSize, StoreConfigInformation,
         this.region.getRegionInfo(), compactionDescriptor, this.region.getMVCC());
   }
 
-  void replaceStoreFiles(Collection<HStoreFile> compactedFiles, Collection<HStoreFile> result)
-      throws IOException {
-    this.lock.writeLock().lock();
-    try {
-      this.storeEngine.getStoreFileManager().addCompactionResults(compactedFiles, result);
-      synchronized (filesCompacting) {
-        filesCompacting.removeAll(compactedFiles);
-      }
-
-      // These may be null when the RS is shutting down. The space quota Chores will fix the Region
-      // sizes later so it's not super-critical if we miss these.
-      RegionServerServices rsServices = region.getRegionServerServices();
-      if (rsServices != null && rsServices.getRegionServerSpaceQuotaManager() != null) {
-        updateSpaceQuotaAfterFileReplacement(
-            rsServices.getRegionServerSpaceQuotaManager().getRegionSizeStore(), getRegionInfo(),
-            compactedFiles, result);
-      }
-    } finally {
-      this.lock.writeLock().unlock();
+  @RestrictedApi(explanation = "Should only be called in TestHStore", link = "",
+    allowedOnPath = ".*/(HStore|TestHStore).java")
+  void replaceStoreFiles(Collection<HStoreFile> compactedFiles, Collection<HStoreFile> result,
+    boolean writeCompactionMarker) throws IOException {
+    storeEngine.replaceStoreFiles(compactedFiles, result);
+    if (writeCompactionMarker) {
+      writeCompactionWalRecord(compactedFiles, result);
+    }
+    synchronized (filesCompacting) {
+      filesCompacting.removeAll(compactedFiles);
+    }
+    // These may be null when the RS is shutting down. The space quota Chores will fix the Region
+    // sizes later so it's not super-critical if we miss these.
+    RegionServerServices rsServices = region.getRegionServerServices();
+    if (rsServices != null && rsServices.getRegionServerSpaceQuotaManager() != null) {
+      updateSpaceQuotaAfterFileReplacement(
+        rsServices.getRegionServerSpaceQuotaManager().getRegionSizeStore(), getRegionInfo(),
+        compactedFiles, result); {noformat}
While running some large scale load test, we run into File SFT metafiles inconsistency that we believe could have been avoided if the original order was in place. Here the scenario we had:

1) Region R with one CF f was open on RS1. At this time, the given store had some files, let's say these were file1, file2 and file3;

2) Compaction started on RS1;

3) RS1 entered a long GC pause, lost ZK lock. Compaction is still running, though.

4) RS2 opens R. The related File SFT instance for this store then creates a new meta file with file1, file2 and file3.

5) Compaction on RS1 successfully completes the *storeEngine.replaceStoreFiles* call. This updates the in memory cache of valid files (StoreFileManager) and the SFT metafile for  the store engine on RS1 with the compaction resulting file, say file4, removing file1, file2 and file3. Note that the SFT meta file used by RS1 here is different (older) than the one used by RS2.

6) Compaction on RS1 tries to update WAL marker, but fails to do so, as the WAL already got closed when the RS1 ZK lock expired. This triggers a store close in RS1. As part of the store close process, it removes all files it sees as completed compacted, in this case, file1, file2 and file3.

7) RS2 still references file1, file2 and file3. It then gets FileNotFoundException when trying to open any of these files.

This situation would had been avoided if the original order of a) write WAL marker, then b) replace store files was kept.