HBASE-29831: Fix for NPE in region replication #7629
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charlesconnell
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guluo2016
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Jan 16, 2026
| if (useCache && locations.size() == 1) { | ||
| if (tableDescriptors.get(tableName).getRegionReplication() > 1 && retries <= 3) { | ||
| TableDescriptor td = tableDescriptors.get(tableName); | ||
| if (td != null && td.getRegionReplication() > 1 && retries <= 3) { |
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I noticed through idea's smart suggestions that retries <= 3 seems is unnecessary.
And I analyzed it and it's true
After removing it, there are 3 main cases, and none lead to an infinite loop:
- case 1
First loop: useCache && locations.size() == 1 && RegionReplication > 1 is true.
Set useCache = false and continue.
Second loop: The logic will proceed and eventually return or break.
- case2
First loop: useCache && locations.size() == 1 is true but RegionReplication > 1 is false.
Go to subsequent logic.
If !Bytes.equals(primaryLocation.getRegionInfo().getEncodedNameAsBytes(), encodedRegionName) is false: break (loop ends).
If !Bytes.equals(primaryLocation.getRegionInfo().getEncodedNameAsBytes(), encodedRegionName) is true and useCache is true: set useCache = false and continue. Second loop will then return or break.
- case3
First loop: useCache && locations.size() == 1 is false.
Go to subsequent logic.
If useCache is alread false: return or break.
If useCache is true : similar to case 2, it will either break or retry once (setting useCache=false), then finish.
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Is it possible to add a unit test for this? Thanks |
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The RegionReplicaSinkWriter.append() method checks table descriptors to determine if a table has region replication enabled (to decide whether to bypass the location cache). When a table is dropped concurrently, tableDescriptors.get(tableName) returns null, and the subsequent call to getRegionReplication() throws a NullPointerException.
This race condition can occur in the following scenario:
Since RegionReplicaReplicationEndpoint handles replica updates for all tables on a RegionServer, a single dropped table crashes the entire endpoint. This stops replica updates for all regions (including those from unrelated tables) hosted by that RegionServer until it is restarted.