Bug: Full backup restore fails for empty HFiles
Status: Resolved | Priority: Major | Resolution: Fixed
Created: 27/Mar/24 15:00

A full backup restore fails if the backup contains an empty HFile, for example when all data has been deleted from a table and full compaction has run. There are several issues:
 * HFiles are read in `RestoreTool` to read the first/last key, but this fails for empty HFiles
 * In `RestoreTool`, table creation also incorrectly assumes the region contains keys
 * In `MapReduceRestoreJob`, the tool incorrectly assumes that a bulkload with no loaded entries is an error.

Example stacktrace:
{code:java}
24/03/21 18:38:09 ERROR org.apache.hadoop.hbase.backup.util.BackupUtils: java.util.NoSuchElementException: No value present
java.util.NoSuchElementException: No value present
	at java.base/java.util.Optional.get(Optional.java:143)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.generateBoundaryKeys(RestoreTool.java:440)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.checkAndCreateTable(RestoreTool.java:493)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.createAndRestoreTable(RestoreTool.java:351)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.fullRestoreTable(RestoreTool.java:211)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.restoreImages(RestoreTablesClient.java:151)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.restore(RestoreTablesClient.java:229)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.execute(RestoreTablesClient.java:265)
	at org.apache.hadoop.hbase.backup.impl.BackupAdminImpl.restore(BackupAdminImpl.java:518)
	at org.apache.hadoop.hbase.backup.RestoreDriver.parseAndRun(RestoreDriver.java:176)
	at org.apache.hadoop.hbase.backup.RestoreDriver.doWork(RestoreDriver.java:216)
	at org.apache.hadoop.hbase.backup.RestoreDriver.run(RestoreDriver.java:252)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:82)
	at org.apache.hadoop.hbase.backup.RestoreDriver.main(RestoreDriver.java:224)
24/03/21 18:38:09 ERROR org.apache.hadoop.hbase.backup.RestoreDriver: Error while running restore backup
java.lang.IllegalStateException: Cannot restore hbase table
	at org.apache.hadoop.hbase.backup.util.RestoreTool.createAndRestoreTable(RestoreTool.java:360)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.fullRestoreTable(RestoreTool.java:211)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.restoreImages(RestoreTablesClient.java:151)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.restore(RestoreTablesClient.java:229)
	at org.apache.hadoop.hbase.backup.impl.RestoreTablesClient.execute(RestoreTablesClient.java:265)
	at org.apache.hadoop.hbase.backup.impl.BackupAdminImpl.restore(BackupAdminImpl.java:518)
	at org.apache.hadoop.hbase.backup.RestoreDriver.parseAndRun(RestoreDriver.java:176)
	at org.apache.hadoop.hbase.backup.RestoreDriver.doWork(RestoreDriver.java:216)
	at org.apache.hadoop.hbase.backup.RestoreDriver.run(RestoreDriver.java:252)
	at org.apache.hadoop.util.ToolRunner.run(ToolRunner.java:82)
	at org.apache.hadoop.hbase.backup.RestoreDriver.main(RestoreDriver.java:224)
Caused by: java.util.NoSuchElementException: No value present
	at java.base/java.util.Optional.get(Optional.java:143)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.generateBoundaryKeys(RestoreTool.java:440)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.checkAndCreateTable(RestoreTool.java:493)
	at org.apache.hadoop.hbase.backup.util.RestoreTool.createAndRestoreTable(RestoreTool.java:351)
	... 10 more {code}