[HDDS-5359] Incorrect BLOCKCOUNT and BYTESUSED in container DB - ASF JIRA

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Details

Type: Bug
Status: Resolved
Priority: Major
Resolution: Fixed
Affects Version/s: None
Fix Version/s: 1.3.0
Component/s: None
Labels:
- pull-request-available

Description

Here are default column family data of two different container replicas，

"#BCSID" -> 1354765
"#BLOCKCOUNT" -> -21
"#BYTESUSED" -> 0
"#PENDINGDELETEBLOCKCOUNT" -> 78
"#delTX" -> 1141106

"#BCSID" -> 1895040
"#BLOCKCOUNT" -> -5
"#BYTESUSED" -> 0
"#PENDINGDELETEBLOCKCOUNT" -> 106
"#delTX" -> 1146817

Update:

The BlockCount is incremented only when the Stream is closed and not when the BlockID is added to the DB. If the OutputStream was not closed properly or if, for any reason, the client starts writing to a new pipeline before the full block is written, it could lead to a Block being present in the container but the key_count (BlockCount) not being incremented for it. When a block is deleted from a container, the blockCount is also decremented. But if the blockCount is wrong to start with, it could lead to a negative value.

When a block is deleted, usedBytes is decrement in memory first after deleting a chunk. And even if the chunkFile does not exist (already deleted), the usedBytes is decremented. This could lead to usedBytes being decremented multiple times for the same chunk and causing the total usedBytes metadata in the DB to become negative. Once all the chunks in all the blocks in that iteration of BlockDeletingService task are deleted, only then is the usedBytes updated in containerDB by taking the in-memory value. This Jira proposes to first update the DB with correct usedBytes (calculated from the BlockInfo after all chunks are deleted) and then update the in-memory metadata. This is the update sequence logic followed for all other state updates.

Also, when a chunk is overwritten, then it is assumed that the size of the chunk remains the same. But it’s possible to overwrite more data into the chunk than originally present. In this case, the used_bytes should be updated with difference in the chunkSizes. (Adding this as a TODO).